US2642142A - Hydraulic completion of wells - Google Patents

Description

This invention pertains to the completion of wells. More particularly the invention is concerned with an improved method of perforating casing and with the simultaneous 'perforation of casing and iracturing o the strata behind the ispezione compraron oF f Joseph B. Clark, Tulsa, Okla., assigner to Stanolind Oil-and Gas Compa-ny, Tulsa, Okla., ,a eosporation of Delaware 'Appuautn April 2o, 1949, serial 19.88.616

casing'to increase' thevproductivity of selected producing strata. v- Y In the art of completing wells, various means @have been proposed for setting casing in a well and-then selectively perfo'rating or otherwise opening up the casing to production in the various strata through which the casing has been set.

Gun perforating is one example of this type of well. completion. It has been found, howeverr that when a bullet is iii-ed through a casing and into a producing strata, the walls of the bullet hole in the strata appear to be left in a glazed condition which substantially decreases the vpermeability and productivity of the perforation and thereby retards the now of iuids into vthe well. It has also been proposed to pla-ce acid-soluble casing sections in the easingwhere- .f y be exposed to the well' by contacting this section with a suitable acid. When such sections are exposedto acid, the acid also contaetsthe iron o z steel casing and tubing, and is highly deleterious.

` suggested for selectively exposing strata through which -casing has been set in a well. In practically all cases,- however, after the casing has been perforated or the formation' otherwise exposed to the well, another service, such as hydraulic fracturing, is desirable to increase the permeability by the strata behind' the acidi'zable section may of the formation. Selective completion of a well is thus generally a long process and` is very ex.-

It is therefore an object of this intent-ion to provide an improved method of completing wells.

Another object of this invention is to provide an 'improved method of perforating casing. in a well.v .A further object of this invention is to provide l 'a methodiof selectively completing wells by a process which can simultaneously perforate casing and increase the permeability of the strata exposed by such perforation. A more specic object of this invention is to provide an apparatus and method vfor completing wells in which the. casing may be hydraulically ruptured at a. 'selected elevation in the well and the strata thereby tured.` A. still more specic-obj'ect of this invenf completingwells in which a section of' a cased i well may be isolated, 'the casing may be hydraun- ."exposed to the well may be hydraulically 'fraction' is to provide'an apparatus and method for this vdescription reference will be madeto the one way to produce a. weakened section inang. 1'

mentthecasing 9, which, as indicated, is', pref` .erably iron or steel, is provided with one or more A p'pe produces a bursting strength in air as in The grooves may `obvirmsly be milled radially` the casing where `the axial stress is not too cally ruptured at al selected elevation, the strata thereby exposed to the well may be hydraulically fractured, the fractured strata may be tested; and, if necessary, cemented without removi'zg the isolating means from the well. These and other Y objects of this invention will become more ali-l parent as the description thereof proceeds. In P accompanying drawings in which: I '1 Figure 1 is a cross-section jof a easing showing a weakened section adapted to be hydraulically ruptured, and f Figure 2 is' a diagrammatic representation-4l" 1 partially in cross-section of an alternate means 1 Q of producing a weakened casing section 'and a means for selectively perforatingthis weakened i' casing section and fracturing the adjacent strata.

This invention, in brief, may be described as an improved type of casing string which is adapl'ed to be ruptured in aA well at a selected depth and a method of completing wells includ- Y ing rupturing 'this 'casing -by applying hydraulically a stress above the'ultimate strengthof the weakened section of the casing. The invention also contemplates the rupturing of'a weakened casing section by use of a bodied fracturing uid," the bodied fracturing fluid then being injected f through the hydraulically perforated'casing into the ,strata adjacent theperforation to fracture the formation and increase the permeability of the strata adjacent the casing perforation:

The well casi-ng, which is preferably iron or 1 steel, may be -provided with. weakened sections in a. number of ways. In Figure 1, I have shovirri`- otherwise uniform casing string. In this embodigrooves i0 milled in thel outer surface. These 1f grooves may, for example. be eut .with ald" end mill axially ofthe pipe. The depth and length i 'may be varied as desired. I have found, for ex ample, that such an axial groove 2" long in 3" dieated by the table.

Table to some advantage in some..cases. Forzexample. 'it' is sometimes desirable to mill a groove around'v the periphery of the pipe near the lower end of '-1 zooo p. s. i.-

great to weaken a section which'maylater be ruptured by hydraulic pressure.

.Numerous other methods for reducing the` yield value of 'a casing string at a selected depth win be apparent. I have found' it desirable in some cases to produce a weak section in a casing string by milling a hole-or slot through the pipe completely and then filling this hole or slot with a weak material, for'exa-mple, a plastic or a .soft

metal'suchas aluminum, brass, or the like, which may be sheared out ofthe hole or slot at a pressure substantially below the yield value of the` casing at' a strong section. The slotted section may be linedwith a rupturable sleeve. indicated in Figure 2, the -weak section may be produced by placing in the casing string 9 at Also, as

selected intervals soft metal weak casu-lg joints l I, l2, I3, For example, aluminum casing joints may be inserted at intervals in the casing,` the' aluminum jointshaving' a calculated yield value in tension substantially below the yield value yof the casing string in general.

outside`of the casing, the casing is lowered into the well and landed, with the weak .sections in The depth of the groove or `the wall thickness j i as the bottom of the groovel may readily be cornputed when the bursting pressure desired is decided upon. In determini-ng the bursting pressure, the equipment available for producing the rupture and .the modulus of rupture of the strata behind the weakened section m'ust be considered.

In this connection, I have found that in sand stones and limestones, from which most oil and gas is produced, the modulus of rupture is equal to about three times the ultimate strength of the sandstone or limestone in tension. In general, it appears that the modulus of rupture of the average sandstone and limestone is between about 560-2200 p. s. i. and is quite Voften about diferential bursting pressure (internal pressurei external pressure) of the weakened casing section whenadded to the modulus of rupture'of Y the strata behind the casing atthe weakened section is a very close approximation to the rupture strength of the casing set in cement in the stra-ta. In determining the depth of a groove therefore the surface pressure required to rupture the cemented casing must be less than the pressure capacity of the-pump available for producing the rupture. Furthermore, it is generally desirableto reduce the yield value of the cas- Y.

ing at the weak section to substantially less than,

for example, to about 1/4-1/2, `to yield value of the.

casing at the strong sections so thatlwhen pressure is applied to rupture the weak section, th

strong sections will not be damaged.

In completing wells in accordance with my casing are placed in the casing string as the casing string is 'made up and lowered into the hole so that the weakened' sections will, when the casing. is landed' and cemented. be spotted at the elevation of potentially productive str-ata. Weakened casing sections'ii, i2, and i3 may thus be spotted atpotentially productive strata il, I5, and I S respectively,v aS indicated in Figure 2. Abrading means, such as well scratchers y (not shown), may be attached to the casing, preferably` throughout the producing horizons.

In'any case, it is highly desirable that the .po-

tentially productive strata be isolated behind the casing; a good cementiob at--the weakened case, ing sections in the potentially productive strata will generally not only be o! assistance in producing a. fracture in the strata. but will also isolate that fracture' from other 4'well production.

I have found empirically that the' preferred embodiment, the" weakened sections o! other potentially producing'strata i4 or I6 pene- `trated by casing string S and the-weakened c asing sections 'opposite these. strata may b e selec- `tively perforated. Alternatively the strata i5... exposed to the wellby the perforation 3 2, may be tested while itis still-isolated by the straddle g Abrading 'means should, thereiora be especially on weakened sectionsof the to remove the mud'sbeath at these elevations and produce a strong bond between the well wall andthe weakened casing.

After the casing is thus providedv ers are provided at least at intervals along the the potentially productive strata. The casing is than cemented in position by circulating a ce# ment sheath I1 around the casing shoe I8. When wall. scratchers are provided, the casing Vis moved during placement of this cement sheath l to abrade the walls and produce a strong bond i between the casing and the well walls.- as indii cated above. Thecement sheath I1 preferably extends above the highest potentially productive strata Il. The cement sheath 'may be displaced from the casing .into the annulus by following the cement with a nonfpenetrating liquid as f, yhereinafter described. While Portland or other hydraulic cement may be used to producethe ocment sheath il, -cernent sheath asused herein Y refers to a sheath of any material such as plastics, sulphur, or the like used in setting casing..

After the cement sheath hasbeen allowed to set for from 1 to 3 or more days. 'a straddlepacker 2i, adapted to be set in the casing, and

consisting of a lower packerelement 22 wlch prevents uid ow downward in the casing-and an upper packer element 23 which prevents i'u-k id -flow upward, -is lowered into the well on a tubing string 25. This straddle packer is then located in the casing -at any weakened section' i2 with the lower packer element 22 spotted'in the with M i" sections'at selected intervals and wall'scratchstrongv section ofthe casing 2 below the weakened casing joint i2. The upper packer element. 23 is spotted in the strong' casing 'section 21 above the weakened casing joint i2. A spacer 28, b etween the upper Vand lower packer elements, is connected to and communicates withthe tubing 'string 25. This spacer contains one or morev perforations 29 through which fluid injected into the isolated section 36 between the packer elements 22 .and 23. l Y

After the upper and lower packer elements Af have been" set in the strong sections of the casing, a uid such as oil or water may be niected via the tubing into isolated section 3 5. Presl sure will be built up in this isolatedsecdon by pump 3i untilv the bursting pressure of theV j l weakened casing section is reached. Whenthis f pressure is reached, the weakened section of the casing, the surrounding cement sheath I1, and l the potentially producing strata. i5 adjacent thev well fail in tension, producing 'a yperforation 32.

allowing the fluid to be injected intothe strata and the pressure in the tubing to bereaued. v i The straddle packer 'may tbemif desired. be

moved to the. elevation of one or more of the packer 2i from the remainder ofthe' wel! before the other weakened casing sections in the casingstring are ruptured." fI'oV provide a. repre- `j sentative test otrthe strata. the fluid is removed from the tubing by-a ,circulation joint above straddle 'packer 2i. by swabbing or the like, .and

the tubing by pump 3i may be discharged into f,

thicken a liquid and thereby reduce substantially its iiltrate rate'. The bodying agent may com- 5- prise, for example, a high molecular weight linear not used. Therefore, whilev aqueous liquids conthe productivity determined by owing or puxnp-- ing the well through tubing 25.

While it is desirableto isolate a weakcasing section in order to rupture that casing section-+- particularly where there is more than one weak 5 section in a casing string--I have found that these weak sections may be rupturedY without being isolated. Undersuch circumstances the j Well is preferably cleaned out by displacing the mud in the casing string with a. clean uid such l0 as oil or water., A high hydrostatic pressure is then applied to the entire casing string; and;

.since theA weak sections have a substantially lower bursting pressure than the casingr string in general, these weak sections will be ruptured 15 in the same manner as if they had been isolated 1 (as above described); and the strong sections of the casing string will not be damaged.

While my invention is adapted to exposing potenuau'y productive strate behind the casing with 20 a minimum of specialized' apparatus and services.l as above described, it is particularly adapted to l the combined process o f selectively perforating' the casing at a; weakened section and increasing the permeability of the potentially productive 3 3 strata adjacent the perforations. In this regard, I have found that if the casing section is ruptured with a strong acid,v acid may be injected into the stra-ta through the perforan to increase. the permeability of the strata adjacent the per- 3m Y foraon' Furthermore, if the casing 'section is ruptured with a bodied or non-penetrat'in'g liquid, the bodied liquid will also extend a fracture in 'the strata; at the level. of the casing rupture a substantial distance back into the formation'.A In 35 vthe preferred embodiment, therefore, I inject into the tubing 25 a viscous liquid, preferably, anoily liquidsuch as a higher alcohol, a crude oil, a refined oil such as gasoline, kerosene, naphtha., fuel oil, diesel oil, an animal oil such as lard oil or sh D oil, a vegetable' oil such ascottonseed oil, chlorinated hydrocarbons, or the like, containing a bcfiying` agent. i. e., .an agent which tends to molecule or polymer, such as salts of the'fatty acids, 4rubber or the like, which are at least partially oil soluble. While the invention not-limited to oily liquids, liquids which are miscible with o the interstitial crude oil in the formation to be fracturedare preferred since liquids immiscible with the interstitial crude oil generally tends to Areduce the permeability of thepores in the formation-to oil. That is, aqueousliquids containing a. bodying agent such as hydrated starch- 'orq water' soluble soaps produce a fracture fthe same type as the oily liquids; but, since the contamination of a. formation having low per: meability with. water tends to decrease its pernieability to oil, aqueous liquids are generally -m taining bodying agents are within the purview' of this invention, I prefer an oily liquid containing a bodying agent. Soaps produced by or from 65 am'rnonia' o'r any metal of the alkali 'metal' andy lead, nickel,- or aluminumcombined with a fatty 70 `acid produce suitable bodying agents for the lighteroily liquids. The fatty acid is vpreferably i one of the aliphatic acids carry-ing. at least one 'carboxyl group in aliphatic chain linkage, the al1- phauc cham in emrf case having preferably jat 7s ing agent which has the .ability to form hydrocarf bon gels at -ordinary temperatures. A suitable'H soap of this type can be considered ascom'pounded froni tivo distinct components. One is aluminuni laurate or a saturated fatty acid soap .containingat least ill-50% of this substance or of a. functionally related acid soap; this component is a. relatively high-melting s olid that, by itself, pro'- v duces only thin and unstable gels. The second component is analuminum soap or soaps' selected' vfrom the group including soaps of cycloaliphatic K" and unsaturated acids-that is, an aluminum'. naphthenate, oleate, oleate-iinoleate or thelike.

The combination of a'n aluminum soap of the laurate type `with-one or more soaps of the naphthenate-oleate type give a thickening or bodying.;A agent of distinctiveand superior properties not found in either component and when prepared by thev precipitation process, a solid is producedfff' y' which withstands ordinary handling and storing I have found that at about '15 F., for example,

nitrate rate and viscosity are produced .within from about 30 seconds to about 20 minutes.

I have found that from about 0.5% to about l 10% by weight, relative to the oily liquid of this hydroxy aluminum soap, preferably between about 3% and about 6%. produces a suitable gel A for fracturing most formationsinaccordance with this invention. Where the soap may be deterif'l .j v orated as by weatheringv or-contaminated as. by

moisture, it is sometimesdesirable to use even .more than. 10%. In accordance with the pre-y ferredembodiment ofA this im'ent-ion,` the oily liquid is weighed or otherwise measured and the soap isvadded in a tank as the liquid is stirred.

Sometimesthe liquid may be heated to advantage.l A flow-type mixer for the soap and the oily liquid may be used at the Well head with soap'rvhich. 1

reacts readily topr'oduce a gel in `the oily liquid.'

I have found that thegel will develop in the well.

o Therefore, since the more viscous 'gels 'are diiicultto pump, the soapfliquid dispersion may be introduced into a well before the maximum viscosity l is reached. Accordingly, `when the' gellation has proceeded to a point at which the viscosity is sufci'ent to maintain substantially all the particles of undispersed soap in suspension, the dispersion j is pumped into the well. Fluid in the tubing i ahead of the bodied fluid may be displaced into the annulus 33 before the packers 'areset or it maybe displaced through a circulation port above the stradale packercr u may be' left in ure tubing. f In any case, -a pressure herein referred to as'V the bursting pressure is builtup by pump 3|. When the casing is ruptured,.the'bodied'lluid or gel may' belnjected immediately into the formation or itv "may be. allowed' to'stand in the 'well until the maximum gellation has developed as indi'cated by' i a sample retained at the surface. By this means, Y f high viscosity liquids are available for producing conditions and which is readily soluble in the oily l fyi liquid to produce a highly viscous liquid or gel.

I a fracture'ln-the strata. !Sadjacentperforation zafter the perforation has been produced.

- vAny amount of the viscousliquid may` be injected into a formation fracture 34 depending upon thesizeof fracture desired. A ller fluid, i. e., an inert iluid such as crude oil or a refinedoil such as gasoline `or kerosene which has'noeffect upon the gel may be injected into the well after the injection of-the viscous liquid to force the viscous liquid further into the strata. When the viscous liquid reaches the' strata l5, due to its retarded tendency to lter therethrough, it not only produces a fracture in the strata, but extends thev fracture back from the well into the selected rock strata a. substantial distance.- Hard forma'- and as the sol news back into the well. f

- AS an example of the operation of my invena' tion. a. 3-inch,v l7-.57 .pou ndv A.- P I. casing section lj wasweakened-by z nillingv an axial groove 2 inches f longand. a. .124 inch deep in the outer surface. This left a minimum wall thickness atv the bot#` tom of the groove of .0Q2-inch which has'a calf tion props such as sand may be incorporated'in the gel tosupport the overlyingfrock's and .maintain a. permeable channel to the well after the Inasmuch as thisviscous. liquid tends to obi spotted in an injection' well and cemented in a. sandstone strata. A bottom-hole pressure of. v 2o struct the flow of the interstitial fluids from the fracturedv formation into the Well, it is removed therefrom after it has produced a" fracture of suitable proportions;

viscous liquid and become effective after a time delay. For example, from about 1% to about 3% 1:;

by volume of water which becomes effective severa-l hours after the viscous liquid has reached the fracture may be incorporated in the viscous liquid as, for example, by emulsication or the like. Likewise other gel breakers which become effective at the temperature of the formation A- peptizer or viscositybreaker for the' gel may be incorporated vin the the props are deposited in the fracture and held v there by the formation as the fracture ls collapsed so there is no tendency for the" props to.

flow back into the Well as the well is produced ned into the-formation. fracturewth the cous liquid; Since these liquids have only a. temporary high viscosity, i. e.. since this high viscosity is subsequently broken in the fracture.

culated bursting pressure in air of about- 2790,

p. s. i. This weakened casing section was then 3850 pounds' was then applied wtha bodied liquid. as above described, to rupture the pipe.

After the pipe ruptured, the` pressure on the bodied liquid dropped; 1000 gallons of the bodied.;`

liquid was injected. into the sand.

Fromv previous tests on an offset wellrthis .f sandstone strata is known to have a. water ins.

jection rate of substantially less .than one gal` lon perminute at 100 poundsper square inch bottom-hole pressure., After rupturingthe cas- 'ing and fracturing the formation as above dev scribed, and after breaking the bodied liquid and removing the low-viscosity liquid, this sangmay be incorporated inthe viscous liquid. In

some cases, particularly in deep wells, the heat from the formation is sufficient to reduce theviscosity or gel so that the fracturing liquid may be completely removed from the -interstis ol the formation. Among suitable materials for breaking the gel and reducingr the viscosity of soaphydrocarbon gels. I have found the water-soluble amines such as ethanolamine or similar ammoniacal compounds' and the oil soluble sulfonates tof be particularly effective. Other' suit- -able gel breakers are ammonia, alkali-oxides and hydroxides and the stronger acids. Gen- I erally about 1% breaker, based uponthe volume of the fracturing liquid, diluted with a suitable solvent such as gasoline is pumped into the well following the fracturing li'q'uid to reduce the viscosity or break the 'gel so that when the well is produced the sol will .flow out of the formation.

More vthan 1% of the breaker is sometimes required, particularly where the soa-p content is high.

While, as indicated above, the breaker ispreferably injected into the fracture through vthe well following the fracturing liquid; I have found that" some of the gels, particularly those produced by the hydroxy aluminum soaps, may be broken by contact with the interstitial fluids in most formations. Breaking the gel' .by this stone strata had a watepinjeton of 15 gallons per minute.

It will be apparent that my invention is sub. ject to a. number' ofi modifications and that it is f not limited; to the examples which are given merely for purpose of illustration. It. will. also.

be apparent that anyprocess described is not limited by the means used to weaken the casing;

and. vice versa. any time. of weakened casing' section may be ruptured by numerous embodiments of the process as hereafter claimed.

I claim: f i A 1. A method ,f completing a well comprising placing in said well a casing having a Weak section, cementing said weak section in said' well and applying internally thereto by hydrostatic pressure of a bodied liquid a vstress greaterthanthe -rcombined ultimate strength of said Weaksection and the adjacent formation whereby the strata.V adjacent said Weak section may be fractured to increase its productivity.

means is necessarily slow since" the gel must be adapted to withstand the peptization 'effect of the gel breaker for sufficient time to permit placement of the gel plus areasonable .safety factor. Thus, 4while it is not generally desirable to break the gel by the action of the interstitial iiuids dueto the necessary-delayg-'suc'h procedurev is "within the purview cfthis invention. i

As pointed out above.props, preferably sand.

are incorporated in the viscous liquid either durlng mixing or during' the time it is being injected into the well. These prop's. due tof the high suspending forces ofthe viscous liquid, are car- 2. A method of completing a well comprising v placing in said Well a casing having a weak sec-- tion, cementingsaid weak section in said well by placing Cement in the annulus above and be- 'i u' low `said opposite said weak section fromother vformationsv traversed bysaid casing, 'internally isolating said weak section from the remainder `of saidcasing,

and applying internallyl thereto b y hydrostatic pressure of a bodied liquid a stress greater than, the combined ultimate strength of said weak section and the adjacent formation. and sub.- se'quently applying to said bodied liquid apressure great'enough' to rupture. said casing and 'i fracture said formationwhereby-th'e formation at the depth of said weak'section may be frace tured to increase its productivity.

3.. A method ofcompleting a well comprising. placing in said well a casing having a weak sees tion, cementlng said weak section in said well by placing cement in the annulus above and. below said weak section to isolato the formation' opa weak section to isolate the formation.

' tially productive strata,

- posite said weakis'ection from other formations traversed by said casing. internally isolating said weak section from the remainder of said casing, applying internally theretoby hydrostatic pressure o a bodied liquid a stress suicient to rupture said casing and produce a fracturel in the lstri-ata behind said weak section, in-

whereby the permeability of said .strata is sub stantially increased.

` .4. A method of completing a well comprising placing a casing in said Well, said casing having weak sections at the depth of potentially productive' strata in said well, cementing said casing in said well by pumping cement into the an`-' nulus around said casing to an elevation above said lweak sections, internally isolating one of said weak 'sections from the remainder of said casing, applying internally of the isolated weak section by hydrostatic pressure of a bodied lid-' uid a stress greater than the combined ultimate f strength of a weak section in said casing'and the vadjacent -forma-tionand sumcient to rupture said weak section and produce a fracture in saidabitua, 1 f

jecting said bodied liquid into said racture, and reducing the viscosity of said bodied liquid,

` strata behind said weak section, injecting. said bodied liquid into said-fracture, and reducing the viscosity'of said bodied liquid whereby the permeability of said stratais increased.

5. A method according to claim 4 in which said bodiedliquid contains a propping agent.

6. A method of completing 'a wouponetraug i a plurality of potentially productive strata, irlcludinglowering into said Well a pipe containing sections ofiron or steel 'and sections of a metaly having a substantially lower tensile strength than said iron or steel, spotting said last-named sections.ai'fthe` level of saidl potentially'producannular spacesbetween said pipe and the walls of said Well'ir an amount suincient to seal the annular space above the level of said last-named sections, allowing the cementto set, placing packers in said iron or steel pipe above and be.- low one of said last-named sections to isolateA Itive stra-ta, introducing cement slurry' into the saine from other low tensile strength sections,

applying internally of the isolated sections byl hydrostatic pressure of a bodied liquid containing a propping agent a stress suicient to 'rupture said low tensile strength section of said pipe and produce a fracture in the formation behind said isolated section, and reducing the viscosity of 81 sell its riseos said bodied liquid in said fracture whereby ase lccted strata may be produced and the permeability of said selected strata, is substantially increased.

7* A method'of comiletinga well .penetrating a `plurality of potentially productive strata in.

cluding' lowering into said'ivell a pipe'containingsections ofiron or steel and sections of a metal having a substantially lower tensile strength than said iron or steel, spotting' said last-named sections at thelevel of said potenintroducing cement slurry into the annular space between said pipe andthe walls of said vwell in an amount suff icient to seal the annular space above the level of said last-named sections, allowing the' cement to set. placing .packersin s aid ironor-steel pipe.

Nuillllei Name Date Letzten Pond1oton 1 o ot. 11.1921 2.3153913 Brown' Sept. 2'4, 1940 2.2.fip9z sainirov Nov. 4. 1941 anfrage Boynton Apr.' 6.1943 2.3%44 rowers sept. 21, 19431 Benokonotem -..im July 25. 1944 :abolie below one of is produced in said formation. v

1 JOSEPHB. Ratei-fences 'cned in thoale'ofvthis .patear Containing o, propping agent a stress sufficient giwfu@ Said IOW-tensile-strength 'section or' pipe and produce a fracture inthe forma- O; behind said Isolated section, injecting said btliefd liquid inta said fracture, reducing the isity of said bodied liquid, and producing said Well i'iirough said isolated section to increase the Feylilb'bility of said potentially productive strata mld lest the productivity thereof without con-A ation from other strata penetrated by said tamiu well.

the steps oi placing a casing in said well, said casing having rupturable grooves at'the depth '3f Potentially productive formation in said well.

cenlellting said casing above and below said runf grooves, internally isolating a portionsaid casing embracing said rupturable ind 'Smm-Gam ls'llated section of casing, applyl- "ifln. blessure to said body suilicient to perforate Sold easing nt at least one of saldgrooves, co'n-V tumble 0f the www@ the tlfvplcation of pressure to said liquid' t0 llliiduce o fracture in said formation behind Said perforated casing and reducing the viscosity 0f editi low-penctiratlngllouid within said fracj tule whereby a high-permeability*channel is prol t said last-named Sections i Q lflate sume from other low-tensile-'strength- Sections.' applying internally of .the isolated sec- MOH by hydrostatic pressure of a bodied liquid 8 lil 'a method of completing awel! council-sing 'I dumm in a Mmmm o casmg pposlte said perforated y 9. The method of completing a. well comprising i' Phe steps of placing in said well a metallic casing. li'aving'a weak section opposite a potentially DlOlllbtivc formation, introducing into. the-an` nullt between said casing and the wall of said Well a cement slurry in an amount suii'icient to L 511 The said` unnulus to'a point above said weak allowing said cement slurry to set,

r introducing into said casing a quantity 0f a low-pcnctrating .gelled hydrocarbon, apply- Section. thereaito ins a hydrostatic pressure to said 'gelled hydro- I n Carbon sumoion to rupture said weak section and Dlilllee a fracture in the adjacent set cement ff and the adjacent formation, displacing adrli-tioned hydrocarbon' into the fracture in said "I b said fracture, thereafter` Woking said gelled hydrocarbon and reducing ity to substantially -the viscosity of tlie.

We lipids. and producing sold won to 'remove the l l hydlile'arbon of reduced viscosity from said for? 's mation whereby a highly permeable ow channel formation to exi-end 'UNITED armas PATENTS] f'

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