CN100540844C

CN100540844C - Be used to control the method for sand fallout

Info

Publication number: CN100540844C
Application number: CNB02821417XA
Authority: CN
Inventors: 柯蒂斯·L·博尼; 迪安·威尔伯格; 马修·J·米勒
Original assignee: Prad Research and Development Ltd
Current assignee: Services Petroliers Schlumberger SA; Prad Research and Development Ltd
Priority date: 2001-09-11
Filing date: 2002-09-10
Publication date: 2009-09-16
Anticipated expiration: 2022-09-10
Also published as: EA005718B1; EA200400421A1; WO2003023177A2; CN1639445A; AU2002333819A1; WO2003023177A3

Abstract

In the subsurface formations pressure break or unite the method that causes sand fallout in the pressure break of carrying out and the gravel pack, by transferring a filter cake in early days in processing procedure, inject proppant particulates slurry then, injecting in proppant particulates slurry then utilizes one or more filter cake degradation agent and optional filter cake degradation agent assistant to destroy said filter cake with chemical mode when proceeding, thereby make leak-off increase, proppant concentration in the crack increases, so the proppant sand fallout.Comprise also in this method that the additional bridge joint that uses promotes material, these bridge joints promote that material can use separately, also can be used in combination with filter cake degradation.

Description

Be used to control the method for sand fallout

Technical field

The present invention relates to increase the fluid flow that flows into or flow out missile silo.More particularly, the present invention relates to promote fluid to flow in the pit shaft (wellbore) from the rock stratum.Especially, in the fracturing process that the present invention relates to after gravel pack or pressure break and operation of gravel pack, carry out, crack size, shape, position and method for quality that control is produced by water conservancy pressure break (traditional or utilize flexible pipe (coiled tube)).

Background technology

Fracturing, gravel pack or the operation of finishing pressure break and gravel pack in an operation are widely used in promoting from the stratum exploitation to hydrocarbons, water or other fluid.These operations relate at fracturing process pumping " proppant (proppant) " slurries (be used for after the crack forms natural materials or synthetic materials that the crack is strutted) or at gravel-packing process pumping " gravel ".In high permeability formation, the purpose that fracturing is handled normally forms the crack of short and wide high flow conductivity, so that in order to avoid near (bypass) injury zone the pit shaft that causes during drilling well and/or the completion (completion), thereby guarantee between rock stratum and pit shaft, to form good connection, can be used for making fluid to flow into the interior surface area of pit shaft thereby increase.Gravel also can be natural or synthetic material, and this material can be identical with proppant, also can be different from proppant.Gravel pack is used to prevent " sand ".Said sand is meant those any particulate materials from the stratum that can be carried in the mining equipment, for example earth.Gravel pack is a kind of anti-sand method that is used to prevent formation sand production, in this anti-sand method, in pit shaft, place a steel sieve tube (screen), and the gravel that filling is prefabricated in annular space with specific dimensions, can stop up subsurface equipment or ground installation so that prevent those, and the reservoir sand that reduces flow passes through, thereby.The main purpose of gravel pack is that the stratum is stablized, and makes simultaneously the infringement that capacity of well caused is reached minimum.

Sometimes, do not having to finish gravel pack under the situation of screen casing.The stratum of high osmosis usually concreteness is very poor, therefore, need carry out sand control.So, in the single continuous operation of carrying out with gravel pack (pressure break and filling), usually unite and adopted the fracturing processing, utilize this fracturing to handle and produce short and wide crack.For brevity, in the following description, we may only mention in fracturing, the pressure break of carrying out and gravel pack (pressure break and filling) or the gravel pack any one in an operation, and still, the meaning is meant the whole of above-mentioned these operations.

Proppant or gravel do not wish to take place to the filling of pit shaft on the top of payzone.If this phenomenon that takes place of not wishing has taken place, so, just must clean pit shaft, so that can carry out other various downhole operations such as place tool etc., so that can exploit best by convection cell.In addition, if this operation sand fallout is too late or do not carry out, promptly, if the crack continues to increase, make the length in crack and/or highly exceeded needed and desired value, so, just can not produce the best filling and the flaw size and the shape of expectation, thereby also just can not productivity gain, can not prevent the backflow (flowback) of proppant or sand, this situation is very disadvantageous.

Just as said, wish to produce short and wide crack.Yet, utilize conventional frac treatment can not obtain short and wide crack.The most frequently used method that is used for expressly forming short and wide crack is to cause end sand fallout (TSO) during pumping operation.In the sand fallout of end, because fluid leak-off (leak-off) is in the stratum, therefore, terminal solid concentration becomes very big in the crack, so that slurries are no longer mobile.These proppant particulates slurry that concentrate are just stopped up the crack (plug), and prevent that the crack continuation from increasing.After forming sand fallout, pumping proppant/fluid slurry again in the stratum makes the crack become wideer, and puts into the proppant that the per unit surface area has big concentration in the crack.The equipment of these processing depends on the understanding to mechanical property accurately, permeability, reservoir pressure and the fluid saturation on processed stratum.Before carrying out most of these processing, carry out little frac treatment (being known as " data pressure break " or " little pressure break " sometimes), so that these characteristics are measured, and the stratum is to the reaction of these fracturings processing.Usually in work is carried out, these Treatment Design are made amendment, so that adopt these new information.Important design parameters has: the size in prepad fluid (pad) size, stage (stage) and number, in each follow-up phase proppant or gravel concentration, fluid character, in the character of used additive of each stage.Usually finish this Treatment Design and modification by means of obtainable computer model in the industry.

Prepad fluid is meant the fluid that does not contain proppant, and before comprising some stages of reinstating proppant or gravel, this fluid that does not contain proppant is pumped, so that begin to form a crack and make fracture extension.This prepad fluid also has another kind of effect usually, forms a covering layer on the surface in formation crack, and this covering layer is known as " filter cake ".This filter cake has reduced the fluid flow (having influenced " efficient " (description of face as follows) of work) that flow into from the crack in the stratum.Filter cake can be made by some thickening agents, these thickening agents normally, for example, polymer.For that purpose, filter cake also can be made by some interpolation materials are added in the fluid that is used to form filter cake, especially under the very big situation in the hole of fracture faces.In this use, the material that is optionally added is commonly referred to as fluid loss additive or FLA.

In the fracturing process, especially in low permeability formation, wish to have long as far as possible crack (so that form big as far as possible fracture faces, so that fluid flow in the crack, and finally flow in the pit shaft), in order to obtain the crack of long water conservancy diversion, avoid employing can cause the operator scheme of end sand fallout usually.If before whole Design Treatment liquid is pumped, the situation of end sand fallout in this fracturing operation, occurs, and this situation can be learnt by the rising of hydraulic pressure, so, pump rate will be lowered, or, the processing most probable is stopped, thereby this processing is considered to invalid.We will not wish that the fracturing work design and the work execution that have the end sand fallout and the end sand fallout does not take place are called " traditional " pressure pressure break this.

On the other hand, wish to have the end sand fallout sometimes.Have in hope that the common design feature that adopts usually relates to such certain methods in the special circumstances of end sand fallout, these methods guarantee that for speed that the fluid filter loss is injected with respect to proppant and the amount be very high.This can by utilize little prepad fluid, utilize seldom or do not have fluid loss additive, in the method for the proppant of handling that utilizes higher concentration more in early days, pumping more slowly and utilize the method that those of ordinary skill is known in pressure/gravel pack field in pressure break and combination to realize.

Unfortunately, although during handling, show in many even most of hope has the processing of end sand fallout (TSO) by pressure bomb collected data pressure break information, pressure instantaneous value the sand fallout of said end does not take place.Fluid still can flow at the end in crack, and terminal continuation the in crack increases in the entire process process, so, in the crack, do not reach the proppant concentration of expectation.Therefore, form long and thin crack, so, the fracture condudtiviy that can not obtain to expect.Usually, when wishing the end sand fallout, must cause the end sand fallout by reducing pump rate or increasing proppant concentration.

Can not realize that suitable end sand fallout has two chief reasons.First reason is that for proppant volume, the crack may be too big.A) when prepad fluid too big, or b) when efficient too high, or c) when the ratio of proppant volume and slurry volume in work design is enough high, will not take place to realize suitable end sand fallout.(when the characteristic by fluid and matrix or when adding fluid loss additive the fluid leak-off is controlled to an acceptable low degree, " efficient " of fracturing operation is high; When the leak-off degree was high, efficient was just low, thereby the necessary very a large amount of fluid of pumping so that produce the flaw size and the shape of expectation, and is placed the proppant or the gravel of ormal weight.) second reason be that for proppant, crack width may be too big, thereby can not form bridge joint in the crack.This may be because initial designs bad (for example bad in the design of selection proppant diametrically) or width increase the value that has surpassed expectation.

Up to now, except more must getting well the work design, the main method of handling these problems is aimed at the selection of convection cell fluid loss control agent and uses the working stage of these fluid loss control agents to select the aspect to be optimized, if especially subject matter is the too big situation in crack for proppant volume.

In fracturing process, utilize fiber to control proppant backflow.In this case, add fiber with optium concentration, so that the control proppant backflow, but the flow conductivity in not appreciable impact crack.If utilize glass fiber, for example, this concentration is approximately about 1% of proppant weight.Under the situation that glass fiber is normally used, especially in the stratum of hypotonicity, in pump period, this concentration is not enough to cause bridge joint (bridging).Sometimes, when fluid viscosity was very low, fiber also was used to help the conveying of proppant.In these are handled, intentionally go to avoid the end sand fallout usually; By the design of careful preliminary treatment work,, keep low proppant concentration especially to the selection of pump time.For example, in these processing procedures, in traditional work design, lead volume increases, so that guarantee to produce enough crack widths before proppant/fiber slurry enters the crack.

Because the true nature on stratum is unknown and changes that therefore, to a great extent, the ability that successfully obtains the end sand fallout is very uncertain.Be ideally, can obtain certain methods makes just can cause the end sand fallout when the sand fallout of needs end, and cause the end sand fallout to depend on the feature of the work of operator under controlling (especially fluid and and the chemical property of used fluid fluid loss additive) more, rather than depend on the variability of the unknown on stratum.Therefore, need some more reliable methods to guarantee that desired end sand fallout meeting takes place, have greater flexibility aspect the design end sand fallout processing so that allow.

Summary of the invention

The present invention relates to following content:

1. 1 kinds of methods that form the end sand fallouts in the wellbore treatments process of item, this method comprises: inject proppant particulates slurry with the pressure that is higher than fracture pressure in load fluid, comprise that also the bridge joint that adds capacity in said slurries promotes material so that slurries produce sand fallout.

2. 1 kinds in the method for subsurface formations being carried out form in the stimulation treatment process sand fallout, and this method comprises: inject proppant particulates slurry with the pressure that is higher than fracture pressure in load fluid, so that form one or more cracks, this method may further comprise the steps:

D) inject the prepad fluid fluid, this prepad fluid fluid is used to form filter cake;

E) inject one or more first slurry stage, this first slurry stage comprises the proppant in the load fluid;

F) when injecting one or more second slurry stage, utilize the filter cake degradation agent to make filter cake degradation, second slurry stage wherein comprises the proppant in the load fluid.

3. methods according to item 2, wherein, filter cake is that these materials are by one or more are formed in the following material: can water-soluble polymer, crosslinked can water-soluble polymer, fluid loss additive, and their mixture.

Item 4. methods according to

item

2 or 3, wherein, the filter cake degradation agent is selected from following this listed group material: oxidant, enzyme, acid and their mixture.

Item 5. arbitrary methods according to item 2 to 4, wherein, the prepad fluid fluid comprises a kind of in material of this group of listing below, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for included filter cake degradation agent, do not comprise that the filter cake degradation agent assistant at it gets final product; One or more first slurry stage comprise in this group material of listing below a kind of, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for the filter cake degradation agent that has in included or the prepad fluid, do not comprise that the filter cake degradation agent assistant at it gets final product; One or more second slurry stage comprise a kind of in material of this group of listing below, and this group material is: filter cake degradation agent, filter cake degradation agent assistant, and their mixture.

Item 6. arbitrary methods according to item 2 to 5, wherein, prepad fluid fluid and one or more first slurry stage all comprise: fluid loss additive, the first filter cake degradation agent, be used for the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent wherein has more activity than the first filter cake degradation agent under treatment conditions; And one or more second slurry stage, this second slurry stage comprises the second filter cake degradation agent.

7. arbitrary methods according to item 2 to 6, wherein, filter cake comprises polymer, and this polymer is subjected to enzymatic and degraded oxidation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

Item 8. arbitrary methods according to item 2 to 7; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

The item 9. arbitrary methods according to item 2 to 8, wherein, one or more prepad fluid fluids, one or more first slurry stage, one or more second slurry stage comprise a kind of bridge joint and promote material.

The item 10. arbitrary methods according to aforementioned item, wherein, wellbore treatments is selected from: then carry out gravel pack after the fracturing, fracturing, and unite fracturing and the gravel pack of carrying out.

The item 11. arbitrary methods according to aforementioned item wherein, were placed into the position to sand control screen before wellbore treatments.

Item 12. arbitrary methods according to aforementioned item, wherein, the fluid composition of said slurries is selected from this group material of listing below, and this group material is: emulsion, foam, energized fluids.

13. 1 kinds in the method for subsurface formations being carried out form in the stimulation treatment process sand fallout, and this method comprises: inject proppant particulates slurry with the pressure that is higher than fracture pressure in load fluid, comprise that also adding bridge joint in said slurries promotes material.

In one embodiment, when the end sand fallout takes place in expectation, just cause the end sand fallout by adding bridge joint accelerator to proppant particulates slurry.In another embodiment, bridge joint accelerator (bridging-promoting agents) is some fibre, these fibers are added to proppant particulates slurry to be higher than the concentration of controlling typical concentrations that is used for refluxing, and these fibers are being added in early days of handling, so that cause the proppant bridge joint, and cause the end sand fallout in pump period.Another one embodiment of the present invention expressly causes the end sand fallout by the bridge joint accelerator in the early stage use high concentration of increasing production (stimulation) processing.An alternative embodiment of the invention be by in the combined treatment of volume increase/gravel pack especially in fracturing/gravel-packing process, use the bridge joint accelerator of high concentration expressly to cause the end sand fallout in early days handling.Another one embodiment of the present invention is by in volume increase/gravel pack Combined Treatment of using annular screen casing (annular screen), specially causes the end sand fallout the early stage use high concentration bridge joint accelerator of handling.An alternative embodiment of the invention is except the bridge joint accelerator of handling early stage use high concentration, utilizes processing parameter is carried out suitable selection, with increase the possibility of end sand fallout takes place, thereby causes the end sand fallout.Some embodiment in addition are more such methods formerly, promptly in these methods, are handling later stage interpolation bridge joint accelerator.An embodiment in addition is a kind of proppant particulates slurry, and this proppant particulates slurry comprises enough bridge joint accelerator, can make these slurries carry out sand fallout when being injected in the crack with these bridge joint accelerator of box lunch.

Another one embodiment of the present invention is a kind of like this method, promptly, during the stratum is increased production, by support pressure break, by forming filter cake, when being injected into proppant in the crack, utilize one or more filter cake degradation agent to make filter cake degradation then, thereby form sand fallout.In certain embodiments, filter cake is to be made by the thickening agent of the load fluid that is used for slurries, or is made by fluid loss additive (fluid loss additive), or form jointly by said thickening agent and fluid loss additive.In certain embodiments, the filter cake degradation agent can be oxidant, enzyme, acid or their mixture.Another one embodiment is a kind of method that forms sand fallout in stratum stimulation treatment process, stimulation treatment wherein comprises to be higher than fracture pressure the slurries of proppant is injected in the load fluid, so that form one or more cracks, this method comprises: inject the prepad fluid fluid that is used to form filter cake; Inject one or more first slurry stage that comprise the proppant of load fluid, utilize the filter cake degradation agent to come filter cake is degraded, inject one or more second slurry stage that comprise the proppant of load fluid simultaneously.In other embodiment of this method, said prepad fluid fluid comprises one or more in fluid loss additive, filter cake degradation agent, filter cake degradation agent assistant and their mixture, as long as for included filter cake degradation agent, do not comprise that the filter cake degradation agent assistant at it gets final product; One or more first slurry stage comprise one or more in fluid loss additive, filter cake degradation agent, filter cake degradation agent assistant and their mixture, as long as for included degradation agent, in first slurry stage, do not comprise assistant, perhaps in prepad fluid, do not have filter cake degradation agent assistant at its filter cake degradation agent; Said one or more second slurry stage comprises one or more in filter cake degradation agent, filter cake degradation agent assistant and their mixture.In a further embodiment, prepad fluid fluid and one or more first slurry stage include fluid loss additive, the first filter cake degradation agent and are used for the filter cake degradation agent assistant of the second filter cake degradation agent, under treatment conditions, the said second filter cake degradation agent has more activity than the first filter cake degradation agent; Said one or more second slurry stage comprises the second filter cake degradation agent.In a further embodiment, filter cake comprises polymer, and this polymer is vulnerable to the degraded of enzymatic and oxidation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises and be used for enzyme that polymer is degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises and be used for oxidized compound that polymer is degraded; For the second filter cake degradation agent, the second filter cake degradation agent assistant is present in one or more prepad fluid fluids, in one or more first slurry stage, one or more second stage, and is tertiary amine.In another embodiment; filter cake comprises the solid particle compound of theobromine dissolving, and the second filter cake degradation agent is present in outer or a plurality of second slurry stage, and comprises a kind of acid; under treatment conditions, this acid can be partly dissolved the solid particle compound of said theobromine dissolving at least.In a further embodiment, one or more prepad fluid fluids, one or more first slurry stage, one or more second slurry stage comprise that bridge joint promotes material.In a preferred embodiment, filter cake comprises polymer, and under treatment conditions, this polymer is vulnerable to enzymatic and oxidant degraded; The first filter cake degradation agent is present in the said prepad fluid, and comprises a kind of enzyme, and this kind of enzyme is degraded to the said polymer; The second filter cake degradation agent is present in one or more slurry stage, and comprises a kind of oxidized compound, and this oxidized compound is degraded to said polymer; Be used for the second filter cake degradation agent, the second filter cake degradation agent assistant is present in one or more prepad fluid fluids, is present in one or more first slurry stage, and is present in one or more second slurry stage, and be a kind of tertiary amine; At least a portion in said one or more first slurry stage comprises bridge joint and promotes material.In other embodiment, before handling, place a sand control screen.In a further embodiment, said processing is the Combined Treatment of pressure break/gravel pack.Additional embodiments of the present invention provides some to cause the method for end sand fallout in processing procedure, if do not adopt these methods among the present invention then be to be difficult to cause the end sand fallout, or it is very expensive or efficient is not high, or even can not cause the end sand fallout, will provide the additional mode that is used to control processing for the operator like that.

Description of drawings

Fig. 1 has expressed to have fluid loss additive and not to have typical fluid filtrate volume data under the fluid loss additive situation.

Fig. 2 has fluid loss additive and does not have the degree of depth schematic diagram of leak-off fluid permeability in the stratum under the fluid loss agents situation.

Fig. 3 has expressed dynamic filtrate volume and the functional relation of fluid viscosity and time in some experiments of two kinds of various combinations that use fluid loss additive, filter cake degradation agent and filter cake degradation agent assistant.

Fig. 4 expressed in an experiment, stop to add fluid loss additive and do not have the filter cake degradation agent or the situation of filter cake degradation agent assistant under dynamic filtrate volume and fluid viscosity and the functional relation between the time.

Fig. 5 is a schematic diagram, has expressed and has added the effect that formation produced to the crack of fluid loss additive, fiber, filter cake degradation agent and filter cake degradation agent assistant.

The description of preferred embodiment

In order to help to understand the end sand fallout specially that in the pressure break/gravel-pack operations process of fracturing and associating, is produced by the work design, can be referring to M.Economides andK.notle, eds., Reservoir Stimulation, 3rd edition, John Wiley﹠amp; Sons, Ltd, New York (2000) pp 10-21 to 10-24; And F.L.Monus, F.W.Broussard, J.A.Ayoub and W.D.Norman, " Fracturing Unconsolidated Sand FormationsOffshore Gulf of Mexico, " SPE 24844, (1992).We find that we can produce such a case,, in this case, by in two characteristics that change slurries one or two, make that the slurries in the crack no longer are flowable that is.By adding the immobilization material except that proppant, make solid can be changed (altered), thereby make that making slurries when not adding said material no longer is that flowable concentration of slurry is compared, slurries are flowable no longer just in lower concentration, or, can increase the fluid leak-off, thereby make the concentration of solid increase, perhaps the both is.We have found such certain methods, that is, and and by promoting control of material ground expressly to produce sand fallout in the crack to the manipulation of the composition that injects fluid and/or by the bridge joint that adds such as fiber etc.When reason that can not sand fallout is that this method is to form a filter cake earlier, reduces the filter cake size or increases its permeability at reasonable time then because for proppant volume during the too big cause in crack, it is effective especially that a kind of method is arranged.Our used term filter cake degradation comprises the permeability that reduces the big or small of filter cake or increase filter cake by at least a portion cracking of at least a composition that makes filter cake or dissolving.This can finish like this, for example, by utilizing one or more suitable decomposition agents (breaker) or lytic agent (dissolver) to make filter cake cracking or dissolving at work, we claim that wherein decomposition agent and lytic agent are the filter cake degradation agent, sometimes this filter cake degradation agent has additional decomposition agent or lytic agent assistant, and we claim that this decomposition agent or lytic agent assistant are filter cake degradation agent assistant.Decomposition agent or lytic agent can be delayed, and for example utilize retarding agent or by encapsulated it are delayed.When for proppant volume, when the crack is too big, in whole work or at least, add one or more decomposition agents or lytic agent at the prepad fluid and/or the commitment of working.

When can not sand fallout being because for the proppant of bridge joint during the too wide cause in crack, some other method is then effective especially.One of them example is, by in the after-stage of work, adding a suitable decomposition agent, sometimes this decomposition agent also has the decomposition agent assistant, perhaps adds the efficient in the after-stage that multiple decomposition agent or a kind of better decomposition agent be reduced in work in the after-stage of work.In this embodiment, at prepad fluid or in early days can be in the driving phase without decomposition agent.When the resistance of filter cake fluid flow mainly is because in this fluid or the polymer in the fluid loss additive (FLA) when causing, these decomposition agents are effective.

If the resistance of filter cake fluid flow mainly is owing to during the material of calcium carbonate in the fluid loss additive or the dissolving of one or more other theobromine, by add acid in after-stage filter cake is dissolved.

Another method is to add fiber or other material (be known as bridge joint and promote material) to proppant, so that help bridge joint, this method can be used separately also and can be used in combination with top a kind of substantially method that filter cake is carried out cracking or dissolving.Sand fallout is from bridge joint, and just, the solid in the crack stops to move, and liquid then can continue to flow; Given position in the crack, the important parameter that influences bridge joint tendency are the volumetric concentrations of granular size and distribution of shapes, crack width and proppant in the slurries.Add bridge joint and promote that material has a direct impact bridge joint; Specially destruction to filter cake during handling can influence proppant concentration.

These relate to, and filter cake is carried out cracking and dissolving and adds the method for fiber can be side by side or the use that is combined continuously.These methods can also be used to expressly form wideer crack (these cracks have bigger fracture condudtiviy).These methods can also be used as a kind of changing its course (diversion) form, that is to say, the operator can expressly make the increase in a crack and filling stop, and causes a new crack under the situation that does not have zone isolation (zonal isolation).These methods can be in whole cracks or only destroy said fluid loss additive (FLA) in the parts in crack.By quickening leak-off; selectively by helping bridge joint; the operator can determine and control the when and where that produces sand fallout and (thereby avoid producing the result who does not expect of sand fallout; can avoid very slowly the result with the inefficiency sand fallout, also can avoid the result of the generation sand fallout in the pit shaft on the stratum).

These important conceiving with unification that relate to the method for filter cake degradation are the degradeds that comprise filter cake, put down a filter cake in early days in processing, inject proppant particulates slurry then, then when proppant particulates slurry continues injection, make filter cake generation chemical change by the filter cake degradation agent, thereby leak-off is increased, the proppant concentration in the crack is increased, thereby make the proppant sand fallout.According to these factors, the reactivity of (for example pH value of temperature and load fluid) employed one or more filter cake degradation agent under treatment conditions for example, the planned time that thickness of the filter cake that deposits (for example being subjected to the viscosity of load fluid and the influence of in-place permeability) and other work design parameters are for example worked, the size in crack, the granular size of proppant, the time of adding various chemical substances will change.For example, the pump time of prepad fluid must long enough and/or is contained enough fluid loss additives, so that guarantee to produce required filter cake.Filter cake degradation can not can not too promptly begin too soon so that sand fallout resulted from before it is supposed to produce.On the contrary, filter cake degradation can not can not begin too slowly too lately, so that sand fallout produces to such an extent that produce too late or not.Usually in a plurality of stages, finish the interpolation of proppant.In each stage, inject the proppant of specific concentrations, injection length continues a specific time quantum.Continuous stages has the proppant concentration of continuous increase usually.Proppant concentration can also be changed in slope (ramped) mode smoothly, that is to say, proppant concentration increases continuously during the filling proppant stage.In order to help to describe, typical work will be divided into prepad fluid stage and two groups of proppant slurry stage.In the prepad fluid stage, the crack is begun to be formed, and filter cake is put down.In first group of stage, the crack is increased.In second group of stage, produce sand fallout, and use the proppant pack crack.Just as said, some further features of work can influence the time of adding chemical substance strongly.If prepad fluid must be very little, the engineering of transferring filter cake just can continue in the whole or commitment in first group of stage.If the filter cake degradation agent is worked lentamente, even can begin in the stage to add at prepad fluid, so, degraded can begin in first group of stage.If the filter cake degradation agent is worked very apace, so, can only in second group of stage, begin to add.The filter cake degradation agent that can use reagency to increase gradually, or, can be simultaneously or use the filter cake degradation agent that the heterogeneity of filter cake is degraded continuously.If the filter cake degradation agent does not have enough reagencies, so just can add filter cake degradation agent assistant.Can before or after adding the filter cake degradation agent, add said filter cake degradation agent assistant, and add by this way, promptly, make and only in second group of stage, just have filter cake degradation agent and filter cake degradation agent assistant jointly, or, in second group of stage, add filter cake degradation agent and filter cake degradation agent assistant together.In all prepad fluids and some stages, can add a kind of bridge joint accelerator.In scope of the present invention and design, according to such as the availability of the availability of chemical substance and material, equipment and the factors such as ability, cost of adding chemical substance and material, those of ordinary skill in volume increase field, stratum can be designed such processing to be permitted different ways, that is, this handle can produce the have specific final argument crack of (for example size and flow conductivity).

Preferably, the present invention implements like this, at first consider information, design the design scheme of an optimization then, be used for making the well capacity maximum according to these data and standard about the standard aspect of well, stratum, obtainable fluid, successful fracturing yield increasing.This design scheme comprises injects a certain amount of prepad fluid and a certain amount of fracturing fluid through selecting through selecting.Usually finish like this, that is, utilize FRACTURING DESIGN and assessment software to analyze, wherein, barometric gradient and fracture length and the algorithm that highly makes progress, complete leak-off information, the effect of repeatedly fluid injection and its variations in temperature combine.For fracturing or gravel pack or both combinations, utilize polymer (normally crosslinked) or utilize viscoelastic surfactant (viscoelastic surfactant) structure (" VES structure ") to be used in aqueous fluid prepad fluid or that be used to form slurries by multiviscosisty with boron, zirconium or titanium compound, wherein, the utilization specific surfactant that can form the micelle (micelles) of suitable size and shape just can form said viscoelastic surfactant structure.Can adopt any fracturing fluid or gravel placement fluids among the present invention, as long as they can be compatible with proprietary material of the present invention (fluid loss additive, fiber, decomposition agent, decomposition agent assistant) energy, and can get final product with the result fit of stratum, proppant and expectation.Therefore, said fluid can for example be water base or oil based fluids, acidity or alkaline fluids, and these fluids can comprise one or more polymer, viscoelastic surfactant or gel oil.Polymer can be crosslinked.These methods of the present invention can be used for original work design, or said work can design under the situation that does not have the end sand fallout, then, need can determine the end sand fallout term of execution of work, so, said work is made amendment.(notice that in this manual, we usually are called end sand fallout (TSO) to the sand fallout in any crack, still, the meaning of end sand fallout is meant the sand fallout that produces in the crack, and is not the sand fallout that must produce in the end in distance pit shaft crack farthest; Crucial is in time of expectation and position is not to produce said sand fallout in pit shaft)

We are meant a kind of like this fracturing by terminology used here " conventional pressure break ", promptly in this fracturing, do not want to produce and also do not wish to produce the end sand fallout.The meaning of our used term " end sand fallout " is meant and is not in pit shaft but in the crack but is not must be away from the sand fallout in the end, crack of pit shaft.In conventional pressure break, be to avoid those may cause the operator scheme of end sand fallout.If in conventional fracturing operation, run into the end sand fallout, before whole Design Treatment was pumped, this can derive from the increase of pumping pressure, so, can to running parameter for example pump rate or proppant concentration make change so that reduce to take place the possibility of end sand fallout as possible.Yet this processing usually is stopped, and is considered to a kind of failure.

Prepad fluid of the present invention comprises load fluid and multiviscosisty polymer or viscoelastic surfactant.It can contain some other additive that is generally used in these fluids in addition, as long as the composition of prepad fluid does not cause damage to stratum or fracturing fluid.In the present invention, the fluid that is used as prepad fluid can comprise usually such as materials such as anti-corrosion additive, friction reducer (friction reducer), earth stabilizing agent, antisludging agent (scaleinhibitor), biocides.

Load fluid provides a kind of medium, is used for other composition is transported in the stratum.Preferably, said load fluid is water or salt solution.Organic salt or the inorganic salts or the mixture that can comprise selection are as long as they can be compatible with the composition in prepad fluid, fracturing fluid, stratum and the formation fluid.Usually utilization contain the potassium chloride (KCl) of 1%～7% weight or ammonium chloride approximately solution as the base fluid in fracturing fluid and the prepad fluid (base liquid) so that make earth stable, and prevent that earth from expanding.Sometimes, can adopt other salt solution or seawater.Organic cation salt for example tetramethyl ammonium chloride is a kind of effective salt, and its percentage by weight is about 0.2～0.5, but is not limited thereto.

Usually, if polymer is used to make fluid to become sticky, so, this polymer is can be water-soluble.Commonly used effectively can comprise by water-soluble polymer: the polymer of polyvinyl, PMAm, cellulose ether, polysaccharide, sulfonated oil (lignosulfonate), amine, alkali metal, and their alkaline earth salt.Some concrete examples that typically can water-soluble polymer are: acrylic acid-acrylamide copolymer, acrylic acid-methacrylamide copolymer, polyacrylamide, the polyacrylamide of partial hydrolysis, the PMAm of partial hydrolysis, polyvinyl alcohol, polyvinyl acetate, polyalkylene oxide (polyalkyleneoxide), carboxycellulose, the carboxyalkyl hydroxy ethyl cellulose, hydroxyethylcellulose, galactomannans (for example guar gum), the galactomannans of replacement is (for example, hydroxypropyl guar, carboxyl methyl hydroxypropyl guar and carboxyl methyl melon you), by the heteroglycan that fermentation obtained of starch derived carbohydrate (for example, and their ammonium and alkali metal salt xanthans).Preferably can comprise hydroxyethylcellulose by water-soluble polymer, starch, sclerosis glucan, the galactomannans of galactomannans and replacement.

Originally measure leak-off by the rock-like of selecting the leak-off parameter of expectation, utilize to have the sample and the formation samples of expectation fluid or be similar to the stratum, and just can determine best polymer concentration.Leak-off is limited by three terms: " spurt loss (spurt) ", it is meant that the last filter cake that forms in surface (face) in the crack stops fluid quick leak-off originally before, and square feet to measure gallon/100, the leak-off that takes place after forming for the leak-off that takes place subsequently or even filter cake, and this leak-off can and be built the parameter that wall tendentiousness (wall-building propensity) controls by viscosity and is: wall building leakoff coefficent Cw and viscosity control leakoff coefficent Cv.If there is not the wall building material to exist, Cw is inapplicable.If have low, limited Cw, so, Cv is inapplicable.Cw and Cv measure with feet per minute clock 1/2." spurt loss volume ", the preferred value of Cw and Cv are respectively 0 to about 5, about 0.001 to about 0.05 and about 0.001 to about 0.05; Preferred value is 0 to about 2, about 0.001 to 0.008 and about 0.001 to 0.008; Most preferred value is 0 to 1, about 0.001 to 0.003 and about 0.001 to 0.003.The value of these parameters (and their represented agendas) can significantly change, as long as produce suitable filter cake at reasonable time.Provided a kind of experimental technique that is used for determining these values in the article below, this article is: Navarrete, R.C., Caweizel, K, E., andConstien, V.G.: " Dynamic Fluid Loss in Hydraulic Fracturing Under RealisticShear Conditions in High Permeability Rocks ", SPE Production andFacilities, pp138-143 (August, 1996).

Any fluid based on viscoelastic surfactant can both be used, and in the prepad fluid process and/or after the prepad fluid, said prepad fluid and stratum, formation fluid, any additives can both be compatible.At U.S. Pat 5551516, US5964295; US5979555; US5979557; US6140277; Some especially effectively some fluids have been described among the US6258859.Decomposition agent also can be used for viscoelastic surfactant.

In the present invention those partly or mainly by in the certain methods of filter cake being carried out suitable destruction of regularly locating or reduction, prepad fluid and/or proppant carrying stage preferably also comprise one or more fluid loss additives, so that form suitable filter cake.If they do not comprise the polymeric material that can form suitable filter cake, for example, if utilize viscoelastic surfactant to make pad of frac and/or load fluid multiviscosisty, so, prepad fluid and/or proppant carrying stage must comprise the fluid loss additive that one or more are used to form suitable filter cake.Fluid loss additive for example can be, but be not limited to can water-soluble polymer or crosslinked can water-soluble polymer.If make prepad fluid and/or be loaded with the fluid multiviscosisty of proppant with polymer or cross-linked polymer, so, fluid loss additive can be identical or different polymer or cross-linked polymer.Load fluid is carried out the amount that the required amount of multiviscosisty can be enough, perhaps can be added more so that form suitable filter cake.Fluid loss additive also can be a solid, for example asbestos, pearl starch, calcium carbonate (calcite), granulated mica, plastic grain, solid wax or wax-polymer beads, solid can oil dissolving resin particle, undissolvable salt, the salt that can slowly dissolve (for example, sodium chloride, prerequisite are that load fluid and formation water have high ionic strength) and their mixture.Fluid loss additive must comprise at least a such composition, promptly, this composition can cleaved or degraded (for example, the enzyme of polymer oxidation or crosslinked natural polymer degraded) or dissolved (for example dissolve calcium carbonate with acid, or come wax or resin are dissolved with solvent).

The present invention implements like this, promptly, normal then at first by experiment conventional computer simulation and modeling, determine fluid loss additive and decomposition agent or decomposition agent (being preferably with the decomposition agent assistant) or lytic agent (as acid) the best amount and determine the stage that should comprise this tittle so that make filter cake the expectation when and where generation cracking and dissolving.The those of ordinary skill that carries out in the volume increase field on missile silo and stratum can utilize the understanding to chemical substance and condition (especially related time and temperature) easily to realize these.This process can be finished like this, for example, does by regulating chemistry and/or work pumping design or both, comprises the employing iterative manner, adopts simulation up to the result who predicts expectation usually.We claim these to be used to make the material of filter cake and/or fluid loss additive cracking or dissolving to be " filter cake degradation agent ".In certain embodiments, can not add fluid loss additive, filter cake can only form by thickening agent.In other embodiment, for example, when utilizing viscoelastic surfactant to make the fluid multiviscosisty, filter cake can be formed by one or more fluid loss additives fully.In a preferred embodiment, prepad fluid and selectable first proppant are taken the decomposition agent assistant (for example, can be catalyzer) that sand (proppant-laden) stage comprises first decomposition agent and is used for second decomposition agent.Stage subsequently comprises second decomposition agent.These decomposition agents and decomposition agent assistant can be solid or liquid, and can be delayed (for example by encapsulated).Interstage can comprise two kinds of decomposition agents or two kinds of decomposition agents add the decomposition agent assistant that is used for second decomposition agent, or only comprises second decomposition agent and its decomposition agent assistant.Therefore, when second decomposition agent contact filter cake, filter cake has comprised a kind of decomposition agent assistant that is used for second decomposition agent.So each stage of work (prepad fluid, early stage proppant stage, the proppant stage in later stage) can comprise fluid loss additive, different decomposition agent, be used for the various combinations of the decomposition agent assistant of different decomposition agents.The decomposition agent assistant can its to the decomposition agent of onset be used before, in, or be pumped afterwards.The material that is used to form filter cake will be positioned at prepad fluid or thickening agent (polymer or cross-linked polymer) or the fluid loss additive that adds all the time.Decomposition agent is not must be present in the prepad fluid, and is especially enough high so that take place at least under the situation of some natural degradations in temperature.Similarly, if formed gratifying filter cake, so, fluid loss additive is not to be present in all stages of containing proppant or the stage that some contain proppant.All these methods are opposite (counter) with common practice all, and in these methods, expectation keeps hydraulic efficiency highly as far as possible, up to finishing volume increase.

If (for example pass through to a composition, this composition is a calcium carbonate, but be not limited to calcium carbonate) dissolving and filter cake is degraded, so, these just can be by in suitable one or more stages, polymer, cross-linked polymer or viscoelastic surfactant (all that be in the prior art and and combine with sour) in utilize acid to finish.Suitable acid can be any acid that calcium carbonate is dissolved of being used for well known in the prior art, such as, but be not limited to: inorganic acid, the mixture of example hydrochloric acid, hydrofluoric acid and these two kinds of acid.Also can adopt organic acid, for example just be not limited to: formic acid, acetate, fluoboric acid, citric acid, these organic acids can be used in combination with inorganic acid, also can use separately.Can utilize add material for example chelating agent improve the dissolving power of acid.For example but and be confined to: amino poly-carboxylic acid, as second (support) ethylenediamine tetraacetic acid (EDTA) (ethylenediamine tetraacetic acid), diethyl pentetic acid (diethylenetriaminepentaacetic acid) and their mixture.

Usually the way that adopts during this way of coming dissolving filter cake in pressure break duration of work utilization acid and the conventional pressure break is opposite, is not to be desirably in duration of work to remove filter cake in traditional way.For example, the known method that has some to be used for acid fracturing, prepad fluid and souring stage are (alternated) that hockets.Each prepad fluid stage all comprises a kind of fluid loss additive or polymer or emulsion that is used to form filter cake, and formed filter cake blocking-up is transferred to before not by a part of matrix of acid attack by the matrix of acid attack (matrix) zone (perhaps being formed with hole in this zone) and acid.In this application, do not wish that filter cake removed by acid.

Usually it is desirable to, filter cake is degraded, so that reduce the infringement on fracture faces " top layer ", and the feasible fluid amount of flow that flows into the crack from matrix makes finally that to maximum the fluid flow that flows into pit shaft reaches maximum.Although this degraded is very slow, but it is normally abiogenous, be to pass through thermal process, or by in typical slurry fluids to the dissolving of filter cake, or undertaken by physical process, this especially since reverse flow (the reversal of flow) (during handling, fluid flows out the crack and flows into the stratum, when beginning to exploit, said fluid just flows out the stratum and flows into the crack) cause.Formerly do not adopt the filter cake degradation agent to cause during fracturing is handled filter cake degradation very fast.Because utilize the method among the present invention specially to make filter cake degradation, thereby can make that degraded is faster, like this, just accelerate the speed of fluid exploitation greatly.

At present, a kind of method that prevents the end sand fallout be work design for the bridge joint of feasible size for used proppant the crack too wide.On the contrary, a kind ofly be used to promote that the method for end sand fallout is to add a kind of material, this material helps maybe can promote bridge joint, and can stop moving of proppant in the crack.We have found that, some material can promote or help the bridge joint (realizing by the interactional degree that improves significantly and strengthen between the particle) of proppant particles and the mobile of proppant in the crack stopped when being added in the proppant particulates slurry with enough concentration.We are called these materials " bridge joint-promotion material " or bridge joint-accelerator.We have found that at a duration of work, no matter whether said work is end sand fallout design, can promote that material causes the end sand fallout by the bridge joint that adds right quantity to proppant particulates slurry.Although we will be that example is described embodiments of the invention with the fiber,, other material also can be used as bridge joint accelerator, for example, spicule (needles), fibrillation, platelet, irregular particle, thin slice, band, especially aspect ratio are greater than about 3 material, most preferably aspect ratio is greater than about 300 material, but also do not limit to these materials.Any organic and inorganic, material natural or that synthesize all is fit to, as long as they can reduce the flowability of fluid/proppant slurry when dehydration (dewater).Aspect ratio is a preferable material greater than 3 material approximately, and this is because these materials can make proppant pack (proppant pack) have bigger permeability.In U.S. Pat 5330005, US5439055, US5501275 discloses particularly suitable material among the US5782300, quote these patent documentations as a reference at this, but said material also is not limited to these.In single processing, can while or continuous the use more than a kind of bridge joint promotion material.The material that is used to make bridge joint accelerator is not key variables, as long as mobile reduce agent and chemical reaction do not take place with other composition that uses this flowability to reduce in the fluid of agent, and it is stable in using their environment that this flowability reduces agent, and mobile reduce agent and contain that the slurries that flowability reduces agent can be handled by obtainable equipment, mixing and pumping get final product.Following description still, should be known in that adding bridge joint promotes that the notion of material and filter cake formation/degraded can be by while or continuous combination mainly based on utilizing bridge joint to promote the method for material to be used as promoting the method for end sand fallout.

In traditional fracturing, utilize fiber to prevent proppant backflow, that is to say, proppant is remained in the crack, thereby can not make these proppants be come out by exploitation with fluid.This refluxes with regard to the hydro carbons that allows stronger (higher rate) fracturing fluid and exploited, and the backflow of proppant can not take place.The proppant that is covered with resin is used to identical purpose, and still, fiber is better usually.At M.Economides and K.Nolte, eds., ReservoirStimulation, 3rd edition, John Wiley﹠amp; Sons, Ltd, New York (2000) pp.11-30 and 11-31; U.S. Pat 5330005; US5439055; US5501275; Described among the US5782300 and used fiber by this way.

Using fiber so that in traditional fracturing, in the control proppant backflow, select those selected parameters according to the thing that expectation takes place in the crack after finishing processing.Concentration with the best is added fiber, so that control proppant backflow, but influences the flow conductivity in crack indistinctively.If the employing glass fiber, so, suitable concentration is 1% of proppant weight.Under the condition that adopts usually, in pump period, this concentration is not enough to produce bridge joint.In fact, in traditional fracturing, expressly select fibre concentration, so that can not increase the bridge joint tendency in pump period.In most common fracturing situation, fiber is added to the final stage of processing, thereby makes that the proppant of close pit shaft mixes mutually with fiber.Really, in these that prevent proppant backflow are handled, most critical be that near the crack area the pit shaft is handled.In traditional fracturing, sometimes, all proppants are taken the sand stage and are all handled with fiber; When proppant backflow is the problem of most critical, or when fiber was used to reduce the friction pressure purpose, this can finish at Jing Zhonglai.Yet in these were handled, fibre concentration was linear scale with respect to proppant concentration and changes (that is to say that if the amount of proppant is doubled, so, fibre concentration just is doubled, etc.).In typical design scheme, early stage proppant stage, proppant and fibre concentration are very low; And do not expect to produce sand fallout, if produce sand fallout, that neither be caused by these fibers.

Sometimes, add fiber in the whole process that traditional fracturing is handled, this is because the cause of Another reason: help the conveying of proppant, for example, when fluid viscosity is very low.By designing preliminary treatment work meticulously, select pump time especially meticulously, thereby in these are handled, avoid the end sand fallout.For example, in these were handled, with respect to common work design, lead volume was increased, so that guarantee to produce enough crack widths before proppant/fiber slurry enters the crack.In addition, in the analog operation design, fibre concentration is carefully followed the tracks of, and reminds engineers too early to form the possibility of sand fallout.At last and since in these designs in all stages the interpolation of fiber be vital for the conveying of proppant, therefore, all stages must comprise fiber.

Therefore, when not expecting to form the end sand fallout, utilize fiber to control proppant backflow, it is characterized in that two cardinal principles: first, in traditional FRACTURING DESIGN, it is enough low usually to be used to control the reflux amount of required fiber, thereby makes and can not produce the end sand fallout.The second, although in the entire process process, will add fiber sometimes,, for the control that refluxes, (or afterbody (tailed in)) interpolation fiber when processing finishes usually, normally operating process last 10% in add said fiber.This is to have stake because of the physical characteristic apart from the nearest proppant pack of pit shaft, and must be controlled, so that prevent proppant backflow.In conventional pressure break, utilize fiber to help the proppant conveying and be characterised in that careful work design and monitoring, so that prevent the end sand fallout.In each case, when not expecting to produce the end sand fallout, can be by the pattern of intrinsic use fiber, or design by careful work and to prevent to produce the end sand fallout as much as possible.

From describe this lighted, and except embodiment 5, when we mentioned " percentage fiber ", the meaning was meant " percentage by weight of liquid in the slurries ".For brevity, suppose that fluid density used in the fracturing fluid is about 8.4 pounds of per gallons.Proppant silt carrying capacity commonly used is to contain in the slurries of 1 gallons of fluid to carry 8 pounds of proppants.This will be described to 8 pounds of proppants that added, or 8PPA.In this case, if add fiber with 1% the amount that equals liquid weight, so, the amount of fiber will be 0.5 for the percentage that accounts for whole slurry weight.Therefore, when the percentage by weight that the scale of fiber is shown as based on liquid, they are different with the percentage based on slurry weight, and this depends on the amount of proppant.

Processing of the present invention can utilize common equipment, chemical substance, personnel, the mode identical with conventional process implemented in the oil field, still, if said equipment does not have the function of adding fiber, the equipment that makes will improve said equipment so, so that can add fiber.In U.S. Pat 5501275 and US5782300, described some and be used to add the method for fiber.Preferably, adding the method for fiber implements like this, promptly, proppant with fiber is added in the proppant before fluid mixes, before fluid and mixed with proppants, add in the fluid, or added fiber slurry in certain stage before slurries are pumped into the down-hole, but the present invention also is not limited thereto.Although when adding proppant, fiber is added in the fluid greatly usually,, can before work, be pre-mixed these compositions, also can they be mixed in the down-hole.

In a kind of preferable methods, even processing is designed to do not having under the situation of fiber, also can increase the possibility of end sand fallout, and afterwards in " data pressure break " or " small pressure break ", initial Treatment Design scheme is carried out some additional modifications, so that further increase the possibility of end sand fallout, afterwards, this Treatment Design scheme just is modified at fluid and is comprising the fiber of high concentration.When proppant concentration from about 0 to about 8PPA the time, the fiber of high concentration is added the early stage driving phase that arrives this processing at least.Be to particular importance, guarantee the fiber of high concentration was added in some stages, in these stages, proppant concentration for approximately from 0.5 to about 6PPA.Usually in whole work, all add fiber.The increase of the solid concentration that causes because of leak-off helps the increase of fiber and proppant concentration usually, when fiber and proppant concentration increase when surpassing a threshold, will produce sand fallout.Can reduce the flowability of proppant particulates slurry owing to add the fiber of high concentration, even slurries can not be flowed, in traditional fracturing, normally will avoid this situation to take place.In the present invention, then to expressly add.If do not need the control of sand control or proppant backflow, so, after the end sand fallout has produced, just can continue to add fiber.

Even do not having under the situation of fiber, said processing also need not originally just be designed to increase the possibility of end sand fallout.Promote material so that the generation sand fallout, said processing can have traditional design scheme except adding enough bridge joints such as fiber.In addition, the fiber interpolation is not must be early stage what work yet.The mode that constantly increases with fibre weight is added fiber (little by little or step by step) till producing sand fallout, or work later stage suddenly add fiber with sufficiently high concentration, so that generation sand fallout, or adding fiber in the mode that fibre weight constantly increases, this is also within the scope of the invention.Increase the concentration of the proppant in the slurries and/or increase injection rate, and add fiber in conjunction with the mode with the fibre weight of continuous increase, or begin to add fiber after the not fibrous slurries of pumping, this way also within the scope of the invention.Because when leak-off was very big, the tendentiousness that produces sand fallout was bigger, therefore, these methods of the present invention are more favourable when leak-off is very low.Yet the present invention also can use having finished under any condition that pressure break comprises pressure break/gravel pack.For example, the optium concentration that for example selection of in-place permeability or one or more fluid loss control agents of the factor that influences leak-off (if with) can the required fiber of influence, but not in the optium concentration that is confined to this required fiber (or concentration profile).

Volume increase/gravel pack and specially end sand fallout and combination can finish in every way.More nonrestrictive examples comprise following described example.In first method, at first form a crack that has the end sand fallout, then, pit shaft is cleaned, and screen casing is placed, and carries out gravel pack then and handles.In the second approach, before handling, place screen casing and special tool.Sand fallout crack, end is formed, and by set of tools (tool set) filling, thereby the prepad fluid and the slurries of injection enter in the crack, but do not enter annular space; Regulate said instrument then, make slurries enter annular space.Pump rate is lowered usually, to guarantee the filling of annular space.In the third method, do not adopt gravel and screen casing, but adopt other technology to prevent that proppant or sand from being exploited out.Said technology for example is: added fiber in proppant before fracturing operation just finishes, perhaps use the proppant that is covered with resin.Fiber also can use with screen casing with the proppant that is covered with resin.

These methods among the present invention and fluid also can be used in the volume increase method, and these volume increase methods are commonly referred to as " water-pressure break " or " hydraulic pressure splits " or " level and smooth hydraulic pressure splits ".In water-pressure break,, use thickening agent and the proppant economized as far as possible to produce hydraulic fracture usually in order to reduce cost.This is by utilizing very high pump rate and very high slurries cumulative volume to realize.As usual, in traditional water-pressure break, purpose is generally used for forming long as far as possible crack, but, if the operator wants to stop the increase of length, and the increase of beginning width, so, can add the proppant of fibre plate (a slug of fiber) or fiber and high concentration.

Can add fiber or other bridge joint and promote that material causes the end sand fallout with enough high concentrations.Yet, in other embodiment, when using bridge joint to promote material, can not be to add bridge joint in the mode of the end sand fallout among enough generation the present invention to promote material.The density of fiber, proppant and fluid all can change, and therefore, the amount of fiber will be enough high, cause the end sand fallout with activation, and this can carry out separately, also can carry out in conjunction with the filter cake degradation agent, and this depends on the concrete selection to fiber, proppant and fluid.Be described with regard to liquid, aqueous and preferred fiber of the present invention below, synthetic organic polymer fiber has quite low density, is about 1 to 1.5 gram/cubic centimetre.Yet, also can use the fiber of bigger density, for example by making such as inorganic material such as glass or potteries; Density that these fibers have is bigger for the twice of synthetic organic polymer fibre density.When using with the filter cake degradation agent, the fiber volume of the amount of the fiber in liquid/fiber/proppant slurries that generation end sand fallout is required and the fiber/proppant mixture of every volume is the most closely related.Therefore, the amount of described fiber should be at the density of related concrete composition and be conditioned below.The density of fiber is big more, and required weight concentration is just high more.In addition, aspect ratio, length, all can influence the amount (being expressed as the percentage by weight of liquid in the slurries) of the fiber in causing the required liquid of end sand fallout/fiber/proppant slurries with respect to the fibre diameter of proppant diameter.When fibre diameter reduces or fibre length or aspect ratio when increasing, then need lower fiber weight percentage (being expressed as the percentage by weight of liquid in the slurries).This adjusting belongs to those of ordinary skills' conventional ability.At U.S. Pat 5330005, US5439055; US5501275; Described some particularly suitable fibers and other material among the US5782300, but the present invention is not limited to these fibers and material, quotes these patent documentations as a reference at this.

We alleged " fiber " can be any fibrous material, natural organic fiber for example, comminuted plants material, (non-limiting example has synthetic organic fibre, polyester, poly aromatic acid amides (polyaramide), polyamide, novoloid or novoloid formula polymer), fibriilar synthetic organic fibre, glass fiber, carbon fibre, ceramic fibre, inorfil, wire and their mixture.Preferably, the length of fibrous material is about 2 to about 30 millimeters, and diameter is about 5 to about 100 microns, most preferably is, length is about 2 to about 30 millimeters, and diameter is about 10 to about 100 microns.It is circular that fiber cross sections needs not to be, and it is straight that fiber needs not to be.If use fibriilar fiber, so, the diameter of individual filaments (fibrils) can be more much smaller than fibre diameter described above.

Have been found that the percentage by weight at liquid is the concentration of the synthetic organic polymer fiber between about 1 to about 2, the slurries that contain fiber work as the fracturing fluid of standard, and can utilize the oil field pumping and the mixing apparatus of standard to handle.Utilize down well tool to test, it can not block outlet (ports).Adding fiber to early stage proppant stage will can not make the execution of said processing become complicated significantly.

Yet along with fracturing fluid/fiber/proppant mixture enters into the stratum, proppant and fiber will concentrate, and this is because the cause of fluid leak-off.When higher concentration, fiber has increased the tendentiousness of the bridge joint of slurries greatly.When make fibre concentration be increased to about 4 during to about 5 percentage by weights owing to leak-off, slurries have the appearance of wet pulp (wet pulp).Show that in the laboratory with in the test of workshop the percentage of the synthetic organic polymer fiber in the liquid is about 4 to about groove that can block 6 to 12 mm wides at 5 o'clock.Therefore, when fiber and proppant concentrated because of the fluid leak-off in the crack, because the existence of supporting agent/fibre blend, slurries had very big bridge joint tendentiousness, and can form sand fallout.

Help cause the end sand fallout if use fiber, so, when developing into, filter cake degradation make hydraulic efficiency approximately less than for example 20% the time, fiber is usually at least in first proppant stage, and concentration is selected to so, that is, the fiber/proppant slurries have been filled solid (pack off) (no longer being flowable), thereby cause the end sand fallout.It should be noted that, in certain methods of the present invention, cause the amount of the required fiber of end sand fallout can be less than normally used in fracturing process so that under the situation that does not cause the end sand fallout, prevent the amount of proppant backflow fiber, this is because in these methods of the present invention, adopt other some steps to make filter cake degradation, and increased the concentration of the fiber/proppant slurries in the crack.In other words, promote bridge joint by expressly increasing leak-off.On the other hand, the amount of used fiber also can be greater than the amount of the fiber that is generally used for preventing proppant backflow.

The amount of synthetic organic polymer fiber is preferably in from about 0.5 scope to about 2 percentage by weights and is conditioned, so that solve the variation of hydraulic efficiency.The synthetic organic polymer fiber that it has been generally acknowledged that 0.5 percentage by weight is not high concentration, and it can not form sand fallout.Yet, an object of the present invention is to utilize the fibre concentration that can cause sand fallout.In some cases, for example, if the fluid leakoff coefficent is quite high, hydraulic efficiency is low, and so, initial fibre concentration can be reduced to approximately that amount.So this concentration is in " normally " scope that belongs in the processing of " normally ", but for said processing, it is high.On the other hand, if hydraulic efficiency is very high, so, initial fiber concentration should be increased to surpassing commonly used 2 percent, so that cause the end sand fallout.Therefore, the scope of the synthetic organic polymer fibre concentration among the present invention for approximately from 0.5 percentage by weight to about 3 percentage by weights, preferably from about 1 percentage by weight to 2 percentage by weight.In context, " high concentration " that we are alleged, its meaning are meant so specific fibre concentration in specific liquid/fiber/proppant combination, and this concentration is enough high, so that can increase the tendentiousness of sand fallout very significantly under treatment conditions.

Although in traditional fracturing, the amount of used fiber is normally determined by the amount of used proppant, if thereby make that the amount at different stage proppants has been changed, the amount of fiber also is changed so, but, in fluid of the present invention and method, the amount of used fiber is more generally determined by the amount of used liquid, and is more generally utilized the fibre weight that is changeless percentage by weight with liquid.

Along with the increase of fiber stiffness or hardness, the tendentiousness of beginning bridge joint and formation sand fallout also just increases.Yet along with the increase of hardness, it is more difficult that fluid treatment will become.On market, be easy to obtain the fiber of various hardness or rigidity.In addition, in the pumping process, friction pressure usually reduces because of adding fiber.This is an additional advantage, especially combines with pressure break/gravel-pack operations, and wherein, fluid usually comes pumping by osculum or passage (passage), and usually osculum come by.Those of ordinary skills are by considering that different fibers in the easiness of cost or acquired, desired concn, processing, to the effect of friction pressure and the various merits and demerits of other factors, just can easily make one's options.

Although we have mentioned " end sand fallout ", but, scope of the present invention also comprises such a case: the traditional crack that utilizes traditional processing parameter to form to have desired length, then, by beginning to add filter cake degradation agent and/or filter cake degradation agent assistant in the high concentration mode and/or, thereby cause sand fallout by increased fiber concentration constantly.Also can add fiber in the prepad fluid to, to take the amount of sand in the stage suitable with adding proppant to for the amount of being added.Gravel pack normally carries out by the screen casing that is in place although carry out after pressure break,, fluid and method are applied to some do not adopt in the processing that screen casing carries out, this also is within the scope of the invention.Although we have described the present invention with regard to the exploitation of hydrocarbons,, injecting well, in the recovery well or the exploitation of being adopted in the storage well and to other fluid for example water or salt solution exploit, and utilize said fluid and method also to belong to scope of the present invention.Though we describe the present invention in the mode that adopts non-foaming fluid, the present invention also can adopt aerated fluid or energized fluids (for example, utilizing nitrogen, carbon dioxide or their mixture); Because some variations that fluid behaviour or proppant concentration can take place can be regulated fibre concentration.Should also be appreciated that fluid among the present invention and method can be used for handling formation end sand fallouts such as formed a plurality of crack, intrinsic fracture or hole (wormholes) with acid.Any method among the present invention can both utilize flexible pipe to implement.

The another one advantage of fluid among the present invention and method is: they are regulated to the parameter that the operator adds, and that is to say, they have flexibility aspect the design sand fallout processing.Therefore, do not wish to reduce lead volume the operator, the rate of pumping that slows down, reduce the proppant load or do not expect to carry out in the situation that other design changes, the operator can utilize the wherein a kind of method among the present invention.Therefore, in implementing process of the present invention, preferably said Treatment Design is become so, promptly, method in the present invention, also produce sand fallout probably, in the work design, adopt the wherein a kind of method among the present invention then, so that guarantee to form sand fallout, but, scope of the present invention also comprises following such situation: do not adopt wherein a kind of method among the present invention to design the processing that just not can produce sand fallout, increase wherein a kind of method of using among the present invention then in the work design.Scope of the present invention also comprises: design and processing of beginning pumping, said processing is carried out sand fallout in any place during not being designed to or not being desirably in processing, decision makes said processing generation sand fallout during handling then, therefore, change the design of work in corresponding place, so that adopt the wherein a kind of method among the present invention.

Should be noted that, although be not desirably in the annular space in the pit shaft, between screen casing (if any) and well bore face or generation sand fallout in preforation tunnel (perforation), but, but wish last these zone quilt fillings fully in said work.That is to say that ideal results is that (origin of sand fallout is in the crack) fallen in filter choosing in the crack, the zone that utilizes proppant/gravel to come above the filling then to be mentioned.

Any proppant (gravel) can both be used, as long as this proppant (gravel) is fit to fiber, stratum, fluid and handles desired result.These proppants (gravel) can be natural or (for example being covered by resin) synthetic, that be capped, or contain chemical substance.Can use continuously, or use proppant with different sizes and different materials more than a kind of proppant.Proppant is meant and is that the selected any granular material of specific purposes, said specific purposes can be for example to support the crack to make the crack keep opening, or gravel pack one completion, so that prevent or reduce the generation of stratum microgap.Used proppant can be identical materials with gravel and/or have identical size at identical well or different well or in handling.When these materials were placed in the crack, these materials were commonly referred to as proppant, and in these materials are placed on perforation or pit shaft the time, these materials are commonly referred to as gravel, and still in this article, term " proppant " comprises gravel.Usually, the mean particle size of used proppant is about 10 to about 100U.S. sieve mesh, and granular size is 40/60,20/40,16/20,12/20 and 8/20 material more specifically, but is not limited to these.Usually, the concentration of existing proppant arrives about 25PPA for about 1PPA in the slurries, preferably is that about 1PPA is to about 16PPA.

Can comprise that the proppant that is generally used in the prepad fluid and is used for this processing takes some additives in sand stage, as long as these additives are suitable for other the composition and the expected result of processing.These additives can comprise: antioxidant, crosslinking agent, anti-corrosion additive, retarding agent, biocide and buffer.Processed pit shaft can be vertical, inclination or level.These wells can be cased hole completion, perforation completion or barefoot completion and sieve tube completion or non-sieve tube completion.

Be suitable for that the decomposition agent in the method comprises among the present invention, but be not limited to enzyme, for example galactomannans enzyme (being used for coming the cracking polysaccharide) according to galactomannans, cracking is decided the AMS of powder, is used for the cellulase of cracking cellulose and hemicellulase such as being used for, oxidant, for example persulfate, bromate, iodate, permanganate, percarbonate, perchlorate, perborate, hypochlorite, chlorine dioxide, chlorate (being used for making polymer cracking) by oxidation, but also be not limited to these.In addition, these decomposition agents also can be wrapped up by capsule, so that postpone their release, this is well known in the art technology.It is very favourable utilizing the capsule parcel, and this is because major part or all cleaved polymer all are arranged in filter cake, and is wrapped up by capsule, that is to say that the later stage of decomposition agent in said work works.If decomposition agent is not wrapped up by capsule, so, although some decomposition agent can reflux and contact with polymer when crack pressure is released,, at least some decomposition agents can leak-offs fall and do not contact with polymer in the filter cake.The capsule parcel exists the Another reason of advantage to be, can select decomposition agent, so that selected decomposition agent can make the said polymer cracking, and can make the micelle cracking under the situation of having used viscoelastic surfactant.Capsulated favourable part is that also it makes response delay.Know all that in the art the different decomposition agent of employing can be more effective (especially to refer to temperature) under different condition.

Decomposition agent assistant (or decomposition agent activator) is as catalyzer, so that strengthen cracking process and performance thereof, especially when lower bottom hole temperature.Described some examples such as the tertiary amine of these decomposition agent assistants or contain the mixture of tertiary amine in U.S. Pat 4560486, they help the oxicracking agent.

Should be known in for the thickening agent in the load fluid is degraded, in the work design, also can comprise these decomposition agents and decomposition agent assistant.These decomposition agents and decomposition agent assistant can be used to make the decomposition agent of filter cake degradation purpose and decomposition agent assistant identical or different with those, degraded to thickening agent must be carried out after to filter cake degradation, that is to say, load fluid must can be carried proppant, till said processing is done.And must correspondingly select decomposition agent, decomposition agent assistant and selection to add the time and the concentration of these decomposition agents and decomposition agent assistant and acid or solvent.For example, during operation, can put the decomposition agent that slow adding is worked at any time, the activity of the decomposition agent that these slowly work is not enough to make during operation filter cake degradation, but it is after pumping stops, but being enough to thickening agent was degraded in the time that can contact, and irrelevant with the interpolation of filter cake degradation agent or assistant.Another example is during filter cake is put down, can include the decomposition agent assistant in injecting fluid, thereby make the decomposition agent assistant enter into filter cake; Later stage in said processing is added the decomposition agent that is used for thickening agent and filter cake, and because have the decomposition agent assistant in the filter cake, thereby make filter cake degrade faster than thickening agent.

Where the present invention can be in office implements under the situation of layer temperature, and consideration contingent any cooling (cool-down), in this case, prepad fluid and fracturing fluid and their composition, especially the micelle in prepad fluid and viscoelastic surfactant and the fracturing fluid has required characteristic, especially stability.

Embodiment 1:

Design an end sand fallout fracturing job, utilize computer and predict the result that will obtain for FracCADE software (FRACTURING DESIGN, prediction and processing monitoring of software that Schlumberger is proprietary) simulation by registration mark.Said work is the sand layers at the 200mD permeability, and 14 feet thick, and the degree of depth is 13715 feet, and static bottom-hole pressure is 9500psi, and temperature is 118 degrees centigrade.Used proppant is 20/40 purpose pottery.In 2% KCl, utilizing per thousand gallons of KCl concentration is to add 30 pounds of crosslinked melons of boron in 2% the solution since then fracturing fluid to be carried out multiviscosisty.Expressed this work design scheme in the table 1.Rate of pumping is that liquid volume is in gallon with bucket/minute measure, and proppant concentration is to measure with the proppant poundage that per gallon liquid contains, and inject time is minute to measure.

Stage No.	Pump rate	Liquid volume	Proppant concentration	Injection length
Stage No.	Pump rate	Liquid volume	Proppant concentration	Injection length	1 (prepad fluid)	15	3500	0	5.5
?2	15	1143	0.5	1.9	1 (prepad fluid)	15	3500	0	5.5
?2	15	1143	0.5	1.9	?3	15	107	0.5	0.2
?4	15	1201	1.5	2	?3	15	107	0.5	0.2
?4	15	1201	1.5	2	?5	15	1148	2.5	2
?6	15	1102	3.5	2	?5	15	1148	2.5	2
?6	15	1102	3.5	2	?7	15	1102	4.5	2.1
?8	15	1002	5.5	2	?7	15	1102	4.5	2.1
?8	15	1002	5.5	2	?9	15	1003	7.0	2.1
?10	15	950	8.5	2.1	?9	15	1003	7.0	2.1
?10	15	950	8.5	2.1	?11	15	900	10	2.1
12 (overflow (flush))	15	4669	0	7.4	?11	15	900	10	2.1

Table 1

Registration mark is that the software of FracCADE utilizes preassigned to determine when will to produce sand fallout.Twice simulation carried out in fracturing work hereto.Simulation for the first time is not add the simulation that traditional fracturing end sand fallout of fiber forms.At this work, the FracCADE software prediction goes out when proppant attempts to enter into size less than a crack of 2.5 times of the proppant diameter, or when proppant concentration is 22PPA, gets a kind of situation that their take place earlier, during this time sand fallout can take place.In simulation for the second time, synthetic organic polymer fiber is added to each proppant stage, and concentration is 0.6 volume % of liquid in the slurries.Utilizing under the situation of this fiber, the FracCADE software prediction goes out when proppant attempts to enter its size less than 3.5 times of the proppant diameter crack or when proppant concentration is 18PPA, gets one that takes place earlier, during this time can produce sand fallout.This is a low relatively fibre concentration, and therefore, this is a strict especially experiment.Result of experiment is as shown in table 2.

Running parameter	There is not fiber	Fiber is arranged
Running parameter	There is not fiber	Fiber is arranged	Supported fracture half-length (foot)	101.1	77.1
Pit shaft place support width (inch)	0.348	0.497	Supported fracture half-length (foot)	101.1	77.1
Pit shaft place support width (inch)	0.348	0.497	Average support width	0.235	0.375
Net pressure during end-of-job	649	1033	Average support width	0.235	0.375
Net pressure during end-of-job	649	1033	Efficient	0.509	0.533
Effective flow conductivity (mD-foot)	1256	1947	Efficient	0.509	0.533

Table 2

As can be seen, by adding fiber, make the crack short more wide more and have a bigger flow conductivity.By adopting fiber, increased hydraulic efficiency, and the hydraulic efficiency reflection utilizes the amount of the proppant that the load fluid of specified rate places.If there is not fiber, after 15 barrels of the stage of pumping 6, be filled with solid so at 99 feet proppants.If fiber is arranged, behind 22 barrels of the stage of pumping 4, be filled with solid at 76 feet proppants.

Embodiment 2:

Before the test of dynamic fluid leak-off, in experiment salt solution, make the core of 1.5 inch diameters saturated (2 gallons of per thousand gallon 50% tetramethyl ammonium chloride solution).Dynamic fluid leak-off device is made up of a core fixator, this core fixator is designed to make fluid to pass an end face (front end) of core, and flow in such a way, be that this mode makes some fluids meeting leak-offs in core, fluid can be injected into the other end interior (rear end) of core, thereby measures the permeability of this core; This system is controlled by automatic software.Salt solution is injected in the rear end of core, so that measure initial permeability.By making the said surface of your fluid (with 20 pounds of melon that/1000 gallons of of the fracturing fluid concentration) of borate crosslinked melon core of flowing through, and with the pressure of different about 500psi, the duration reaches 30 minutes.(this just causes some fluids to flow in the core, forms material if having filter cake in fluid, so, will form filter cake on the core surface.) utilize the shear rate during an automatic results of fracture simulation device is controlled at actual treatment.These frac treatment parameters that the experiment of dynamic fluid leak-off need be simulated in table 3, have been listed.After dynamic filtration, the mode that re-injects identical salt solution by the rear end to core is measured (regained) permeability of recovery.

Parameter	Processing costs
Parameter	Processing costs	Charge velocity	15 ppm (bpm)
Injection length	30 minutes	Charge velocity	15 ppm (bpm)
Injection length	30 minutes	Power index (n ')	0.7
Fracture height	65 feet	Power index (n ')	0.7
Fracture height	65 feet	Fracture length	75 feet
Crack width (at the pit shaft place)	0.75 inch	Fracture length	75 feet
Crack width (at the pit shaft place)	0.75 inch	Distance apart from pit shaft	1 foot

Table 3

These experiments are done under 52 ℃ of situations.Table 4 has been expressed the comparison of the laboratory result of the dynamic filtration test of simulating the crack that has or do not have fluid loss additive (concentration of said fluid loss additive is 30 pounds of per 1000 gallons of fracturing fluids of fluid loss additive).This fluid loss additive is the mixture of starch and sheet of particles.Tables of data publicly price-reduction fluid loss agents is to the influence of permeability, leak-off and the leak-off fluid permeability degree of depth in the rock stratum.These data show that at spurt loss (filter loss before filter cake forms) with for the leak-off after filter cake forms, when having used fluid loss additive, the fluid leak-off is less, final permeability is bigger, and fluid is less to the length of penetration of matrix.These results show good fluid loss additive is how to prevent or postpone sand fallout.In Fig. 1, expressed and tested 2 and 4 test result with the curve map form.These data will be used in the design of method of the present invention.It is how the scope of convection cell in from the crack leak-off to the rock stratum exerts an influence that Fig. 2 (not in scale) has schematically shown when having filter cake or not having filter cake.In Fig. 2, among the figure up, rather than below figure in, form filter cake [1] by fluid loss additive, the situation that the figure of below represents not use fluid loss additive or fluid loss additive to be removed.Therefore, if there is not filter cake, so, will from supported crack [3], go out more fluid [2] by leak-off.

Operation	Initial permeability (mD)	Final permeability (mD)	Spurt loss volume (gal/100 square feet)	Leak-off behind the spurt loss (gal/100 square feet)	Length of penetration (inch)
Operation	Initial permeability (mD)	Final permeability (mD)	Spurt loss volume (gal/100 square feet)	Leak-off behind the spurt loss (gal/100 square feet)	Length of penetration (inch)				(do not have	Fluid loss additive)
1	98	38	146	72	25				(do not have	Fluid loss additive)
1	98	38	146	72	25	2	80	10	123	58	21
		(have	Fluid loss additive)			2	80	10	123	58	21
		(have	Fluid loss additive)			3	80	47	46	19	8
4	75	35	60	17	10	3	80	47	46	19	8

Table 4

Embodiment 3:

Fig. 3 has expressed some breadboard experiments, and these experiments are used for the method that explanation utilizes the present invention in two fluid loss additive decomposition agents (filter cake degradation agent) stage.These are leak-off experiments of method identical in 52 ℃ of utilizations and example 1.As can be seen, in experiment 1, when the first semi-inclusive fluid loss additive, first decomposition agent and when being used for decomposition agent assistant (filter cake degradation agent assistant) at the second half second decomposition agents that exist, in the second half, still have fluid loss additive, the fluid leak-off does not increase in the second half.In experiment 2, when the first half with experiment 1 in first half-phase with, but the second half when not comprising fluid loss additive, the amount of fluid leak-off enlarges markedly in the second half, this shows that filter cake is by heavy damage.In pressure break, this just is interpreted as bridge joint and/or hydraulic efficiency reduces and the end sand fallout.In order to ensure this result only be not since fluid loss additive from test 2 the second half get rid of institute and cause, also carried out another laboratory experiment (referring to Fig. 4), in this experiment, all there are not decomposition agent or decomposition agent assistant in the stage in office, but, phase I comprises fluid loss additive, and second stage does not comprise fluid loss additive.Fig. 4 shows that in this case, fluid increases a little in second stage, but to compare this increase very little with the result shown in Fig. 3.This just clearly illustrates that very much, principal element is a decomposition agent, especially show the decomposition agent assistant that comprises in the phase I, these decomposition agent assistants are used for the decomposition agent assistant of the decomposition agent of second stage, and to make fluid loss additive remain into second stage be unessential.On behalf of each prepad fluid of commercial simulation process or prepad fluid, the phase I of these experiments add early stage proppant stage; The second stage of these experiments is represented the later stage proppant stage of commercial simulation process.

Embodiment 4:

Fig. 5 is used to illustrate the effect that promotes bridge joint except adding fluid loss additive by the interpolation fiber.Expressed a specific embodiment among the figure, in this embodiment, formed the filter cake that decomposition agent is contained in inside at prepad fluid, then, add some fibre to proppant stage, so that promote bridge joint, proppant stage is rearwards added other decomposition agent then.(expressed the progress along with simulation among the figure, schematic diagram A has shown the variation of the content (content) in crack from the top to the bottom to schematic diagram E; These schematic diagrames can be top view or lateral view, and are not pro rata, and the crack might not have identical size in these continuous schematic diagrames.) this order stoped the increase in crack, just filter cake removed then, this flow velocity that finally makes the fluid that must be exploited flow into the crack increases.Thickening agent in the prepad fluid, the first filter cake degradation agent, the filter cake degradation agent assistant that is used for the second filter cake degradation agent and fluid loss additive all with Fig. 2 experiment 2 in identical in the first half; Thickening agent in the load fluid is identical with thickening agent in the prepad fluid, identical in the second half in the experiment 2 among the second filter cake degradation agent and Fig. 2.In Fig. 5, " 2-4PPA " be meant and contain 2 to 4 pounds of proppants (stage of the poundage of proppant " add " or PPA) in every pound of fluid, and " 4PPA and more than " is meant from the stage that 4PPA contains proppant to the end and adds the overflow stage.

The prepad fluid of clayization comprises the first filter cake degradation agent, is used for the filter cake degradation agent assistant and the fluid loss additive of the second filter cake degradation agent.When prepad fluid is pumped (schematic diagram A) and when being positioned at the leading edge (leading edge) that increases crack [4], will form filter cake [5], so that the control leak-off, some fluids [6] leak-off is in the rock stratum.In order to form filter cake, just must the enough prepad fluids of pumping.At 2-4PPA in the stage (schematic diagram B), load fluid comprises a kind of synthetic organic polymer fiber [7] that is added to each proppant [8] stage, its concentration is about about 0.6 volume % of the fluid in the slurries, and these synthetic organic polymer fibers suppress the growth of fracture length.In the stage of back (schematic diagram C), the second filter cake degradation agent is introduced into, and under the help of (having existed) the filter cake degradation agent assistant that is used for the second filter cake degradation agent, said filter cake begins to degrade.Take the pump period (schematic diagram D) in sand stage at the later stage proppant, the second filter cake degradation agent is degraded to filter cake, makes leak-off increase gradually.Final result (schematic diagram E) is: do not have on the suitable weak point of the when and where of needs sand fallout and wide crack or filter cake is seldom arranged, and supported dose of filling well got up.Can make many kinds of modification to situation shown in these schematic diagrames, scope of the present invention also comprises, but be not limited to, the interpolation fluid loss additive adds the first filter cake degradation agent, is used for the precise time and the amount of the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent, fiber.Other some modification can comprise by different order or different combinations adds above-mentioned material.

Embodiment 5: utilize registration mark to simulate three kinds of pressure break schemes for FracCADE software (fracture design, prediction and processing monitoring of software that Schlumberger is proprietary).In these schemes, adopt the fluid loss additive identical with embodiment 3, when having the first identical filter cake degradation agent, be used for filter cake degradation agent assistant, the second filter cake degradation agent and the fiber of the second filter cake degradation agent.In three schemes, all add fluid loss additive, and the speed of adding is designed to form the filter cake that each hundred square feet of fracture faces has 2 pounds fluid loss additive.Expressed this work design in the table 5.Pump rate all is 15 barrels of per minutes; Utilization contains the crosslinked melon of 20 pounds boron in each thousand gallons of seawater you carry out clayization to prepad fluid and proppant loading stage; The overflow stage comprises identical melon that, has identical concentration in seawater, but is not crosslinked.

Stage	The fluid gallonage	The proppant poundage	The slurries barrelage	Pumping the number of minutes
Stage	The fluid gallonage	The proppant poundage	The slurries barrelage	Pumping the number of minutes	Prepad fluid	5500	0	131	8.7
0.5PPA	1000	500	24.3	1.6	Prepad fluid	5500	0	131	8.7
0.5PPA	1000	500	24.3	1.6	1.0PPA	1000	1000	24.9	1.7

2.0PPA	1000	2000	26.0	1.7
2.0PPA	1000	2000	26.0	1.7	4.0PPA	1000	4000	28.1	1.9
6.0PPA	1000	6000	30.3	2.0	4.0PPA	1000	4000	28.1	1.9
6.0PPA	1000	6000	30.3	2.0	8.0PPA	1000	8000	32.4	2.2
10.0PPA	1500	15000	51.9	3.5	8.0PPA	1000	8000	32.4	2.2
10.0PPA	1500	15000	51.9	3.5	12.0PPA	3000	36000	110.2	7.3
Overflow	3286	0	78.2	5.2	12.0PPA	3000	36000	110.2	7.3

Table 5

In

scheme

1 and 2, do not use the filter cake degradation agent, do not use filter cake degradation agent assistant yet.In scheme 2, fiber is added to the 2-4PPA stage, and adds with the speed of 0.8 weight % of proppant.In scheme 3, prepad fluid comprises the first filter cake degradation agent and is used for the filter cake degradation agent assistant of the second filter cake degradation agent, and comprises the second filter cake degradation agent from the proppant loading stage that 2PPA begins.Expressed the result of these three schemes in the table 6.

Scheme:	1	2	3
Scheme:	1	2	3	Have or not fluid loss additive in the prepad fluid?	Have	Have	Have
Filter cake degradation agent and and assistant have whether been used	Not	Not	Be	Have or not fluid loss additive in the prepad fluid?	Have	Have	Have
	Not	Not	Be	The spurt loss volume of prepad fluid (gal/ square feet)	0	0	46
Has the 2-4PPA stage added fiber?	Not	Be	Not	The spurt loss volume of prepad fluid (gal/ square feet)	0	0	46
Has the 2-4PPA stage added fiber?	Not	Be	Not	The spurt loss volume of proppant stage (gal/square feet)	0	0	99
Final supported	55.3	45.4	36.9	The spurt loss volume of proppant stage (gal/square feet)	0	0	99

Half length in crack
Half length in crack				At the final supported crack width of pit shaft	1.298	1.729	3.052

Table 6

The scheme of should be noted that comprises enough pump times, to guarantee the formation of filter cake.Prepad fluid, fracturing fluid, fracturing fluid gelatinizer, decomposition agent (filter cake degradation agent), decomposition agent assistant (filter cake degradation agent assistant), fluid loss additive, the proppant of common commercial processes amount have been adopted.From scheme 1, as can be seen, when using fluid loss additive (FLA) but adopt when destroying the measure that filter cake uses, will form long and narrow crack.When in scheme 2 when adding fiber and come the end sand fallout, just form crack short, broad.When utilizing filter cake degradation to promote the end sand fallout, just form short, the wideest crack.The good operation design scheme should be the combination of scheme 2 and scheme 3.

Specific embodiments more of the present invention described above are not to be intended to exhaustive each possible embodiment of the present invention.Those of ordinary skills can know, can make various modification to described specific embodiment here, and these modification all belong to scope of the present invention.

Claims

1. method that forms the end sand fallout in the wellbore treatments process, this method comprises: inject proppant particulates slurry with the pressure that is higher than fracture pressure in load fluid, comprise that also the bridge joint that adds capacity in said slurries promotes material so that slurries produce sand fallout.

2. one kind in the method for subsurface formations being carried out in the stimulation treatment process forming sand fallout, and this method comprises: inject proppant particulates slurry with the pressure that is higher than fracture pressure in load fluid, so that form one or more cracks, this method may further comprise the steps:

A) inject the prepad fluid fluid, this prepad fluid fluid is used to form filter cake;

B) inject one or more first slurry stage, this first slurry stage comprises that the bridge joint that proppant in the load fluid and capacity can cause the end sand fallout promotes material;

C) when injecting one or more second slurry stage, utilize the filter cake degradation agent to make filter cake degradation, second slurry stage wherein comprises the proppant in the load fluid.

3. according to the method for claim 2, wherein, filter cake is that these materials are by one or more are formed in the following material: can water-soluble polymer, crosslinked can water-soluble polymer, fluid loss additive, and their mixture.

4. according to the method for claim 2, wherein, the filter cake degradation agent is selected from following this listed group material: oxidant, enzyme, acid and their mixture.

5. according to the method for claim 3, wherein, the filter cake degradation agent is selected from following this listed group material: oxidant, enzyme, acid and their mixture.

6. according to the method for claim 2, wherein, the prepad fluid fluid comprises a kind of in material of this group of listing below, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for included filter cake degradation agent, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more first slurry stage comprise in this group material of listing below a kind of, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for the filter cake degradation agent that has in included or the prepad fluid, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more second slurry stage comprise a kind of in material of this group of listing below, and this group material is: filter cake degradation agent, filter cake degradation agent assistant, and their mixture.

7. according to the method for claim 3, wherein, the prepad fluid fluid comprises a kind of in material of this group of listing below, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for included filter cake degradation agent, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more first slurry stage comprise in this group material of listing below a kind of, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for the filter cake degradation agent that has in included or the prepad fluid, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more second slurry stage comprise a kind of in material of this group of listing below, and this group material is: filter cake degradation agent, filter cake degradation agent assistant, and their mixture.

8. according to the method for claim 4, wherein, the prepad fluid fluid comprises a kind of in material of this group of listing below, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for included filter cake degradation agent, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more first slurry stage comprise in this group material of listing below a kind of, this group material is: fluid loss additive, the filter cake degradation agent, filter cake degradation agent assistant, and their mixture, as long as for the filter cake degradation agent that has in included or the prepad fluid, do not comprise that the filter cake degradation agent assistant for this filter cake degradation agent gets final product; One or more second slurry stage comprise a kind of in material of this group of listing below, and this group material is: filter cake degradation agent, filter cake degradation agent assistant, and their mixture.

9. according to the method for claim 2, wherein, prepad fluid fluid and one or more first slurry stage all comprise: fluid loss additive, the first filter cake degradation agent, be used for the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent wherein has more activity than the first filter cake degradation agent under treatment conditions; And one or more second slurry stage, this second slurry stage comprises the second filter cake degradation agent.

10. according to the method for claim 3, wherein, prepad fluid fluid and one or more first slurry stage all comprise: fluid loss additive, the first filter cake degradation agent, be used for the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent wherein has more activity than the first filter cake degradation agent under treatment conditions; And one or more second slurry stage, this second slurry stage comprises the second filter cake degradation agent.

11. method according to claim 4, wherein, prepad fluid fluid and one or more first slurry stage all comprise: fluid loss additive, the first filter cake degradation agent, be used for the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent wherein has more activity than the first filter cake degradation agent under treatment conditions; And one or more second slurry stage, this second slurry stage comprises the second filter cake degradation agent.

12. method according to claim 6, wherein, prepad fluid fluid and one or more first slurry stage all comprise: fluid loss additive, the first filter cake degradation agent, be used for the filter cake degradation agent assistant of the second filter cake degradation agent, the second filter cake degradation agent wherein has more activity than the first filter cake degradation agent under treatment conditions; And one or more second slurry stage, this second slurry stage comprises the second filter cake degradation agent.

13. according to the method for claim 2, wherein, filter cake comprises polymer, this polymer is vulnerable to enzymatic and oxidative degradation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

14. according to the method for claim 3, wherein, filter cake comprises polymer, this polymer is vulnerable to enzymatic and oxidative degradation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

15. according to the method for claim 4, wherein, filter cake comprises polymer, this polymer is vulnerable to enzymatic and oxidative degradation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

16. according to the method for claim 6, wherein, filter cake comprises polymer, this polymer is vulnerable to enzymatic and oxidative degradation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

17. according to the method for claim 9, wherein, filter cake comprises polymer, this polymer is vulnerable to enzymatic and oxidative degradation under treatment conditions; The first filter cake degradation agent is present in the prepad fluid, and comprises the enzyme that is used to make the said polymer degraded; The second filter cake degradation agent is present in one or more second slurry stage, and comprises the oxidized compound that is used to make the said polymer degraded; The second filter cake degradation agent assistant that is used for the second filter cake degradation agent is present in prepad fluid fluid, one or more first slurry stage and one or more second slurry stage, and comprises tertiary amine.

18. method according to claim 2; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

19. method according to claim 3; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

20. method according to claim 4; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

21. method according to claim 6; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

22. method according to claim 9; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

23. method according to claim 13; wherein; filter cake comprises the solid particle compound of theobromine dissolving; the second filter cake degradation agent is present in one or more second slurry stage and comprises a kind of acid, and this acid can be dissolved the solid particle compound of at least a portion theobromine dissolving under treatment conditions.

24. according to each method in the claim 2 to 23, wherein, one or more prepad fluid fluids, one or more second slurry stage comprise a kind of bridge joint and promote material.

25. according to the method for claim 2, wherein, wellbore treatments is selected from: then carry out gravel pack after the fracturing, fracturing, and unite fracturing and the gravel pack of carrying out.

26., before wellbore treatments, sand control screen is placed into the position according to the process of claim 1 wherein.

27., wherein, before wellbore treatments, sand control screen is placed into the position according to the method for claim 25.

28. according to each method among the claim 1-23, wherein, the fluid composition of said slurries is selected from this group material of listing below, this group material is: emulsion, foam, energized fluids.

29. according to the method for claim 24, wherein, the fluid composition of said slurries is selected from this group material of listing below, this group material is: emulsion, foam, energized fluids.

30. according to each method among the claim 25-27, wherein, the fluid composition of said slurries is selected from this group material of listing below, this group material is: emulsion, foam, energized fluids.