US3331438A

US3331438A - Method for in situ retorting of oil shale employing artificial barriers

Info

Publication number: US3331438A
Application number: US400413A
Authority: US
Inventors: Marion L Slusser
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1964-09-30
Filing date: 1964-09-30
Publication date: 1967-07-18
Anticipated expiration: 1984-07-18

Description

I M. LSLUSSER METHODFOR IN SITU RETORTING OFOIL SHALE EMPLOYING ARTIFICIAL BARRIERS 1 Filed Sept.- so, 1964 MANIFOLD SYSTEM MANIFOLD SYSTEM" ATTORNEY MARION L. sLusgz-rn INVENTOR.

BY M & BM

METHOD FORIN SI'IU RE'I'ORTING OI OIL SIIALE EMPLOYING ARTIFICIAL BARRIERS Marlon L. Slusser, Arlington, Tex.,' assignor'to Mobil Oil Corporation, a corporation of New York Filed Sept. 30, 1964, Ser. No. 400,413, 1t) Claims. .(Cl. 166-49) ans'mAc'r on THE DISCLOSURE This specification describes: A method for the in situ -re-' toning of a subterranean deposit of oil' shale to recover hydrocarbons, and in which method, a barrier to fluid flows is placed about that portion of the oil shaleto be retorted. More particularly, via spaced wells, a fluid with amaterial to seal openings in the deposit is injected. The

' material maybe hydraulic cement. Then, a fluidfor temporarily sealing the openings is introduced into that portion of the depositto be retorted; via the wells. This fluid may be a thixotropic clay in 'wa'ter, e.g'.,-a drilling mud.- T here-r after, the openings in that portion of the-deposit to be retorted are filled, via the wells, with a fluid capable of excluding the priorly injected fluids. This lastinjected fluid I may be water or air. Lastly, in situ retorting is carried out apart injection and production wells at increased pressures vided in a massive oil shale formation in communication with fracturesjboth natural and artificial. Approximately 9000- s.c.f.h. of air was injected into one well-and 85 vvvolume percent of the air was recovered at a 7 p.s.i.g. back pressure at-thc other well'. increasing the back pressure to 37 p.s.i.g. at the air-recovery well resulted in no air recovery as substantially all the injected-air easiest to the surrounding oil shale. formation through interconnecting fractures. I

it is obvious from the foregoing that the majority of the fluids flowing through the oil-shale between injection and production wells must be recoverable; otherwise, the

shale oil produced by retorting' cannot be recovered in acceptable quantities. This is especially important where the wells through which fluids in the oil shale are'recovered are necessarily operated at increased pressures. in one aspect, operation of these wells at an increased pressure becomes necessary to maintain a desired fluid injecin the mentioned portion of the deposit wherein fluid flows I are contained by the establishedbarrier, and hydrocarbons.

are recovered from these fluidflows.

This inve'ntion'relates to amethod forithe situ retort-F:

ing of oil shale to produce hydrocarbons which are commonly termed shale oil.

Distributed throughout the .world are massive forma tions of oil shale providing a tremendous reserve of the organic-material kerogen." The magnitude of these formations is clearly displayed in some areas by oil shale outcrops hundreds of feet in vertical extent. The organic material kerogenis convertible to shale oil by re'torting at. temperatures usually in excess of 700 F. The produced shale oil includes liquid and gaseous hydrocarbonous fractivity into the oilshaie for proper retorting conditions. In

another aspect,-it becomes necessary to operate spaced so that the recovery or production well serves as a pressure sink to facilitate the-recoveryof the produced shale oil.

This invention is directed, in an in situ-method for retorting'oil shale, toward the placing of a barrier to fluid flows about that portion otoil shale to be retorted. The

I placing of this barrier is obtained by procedural steps which are uncomplicated inlnature and employ readily obtainable materials. Furthermore, these procedural steps are compatible with the procedures, materials, and operational structures employed with'the known in situ methods for retorting oil shale. V

It is therefore an object. of the present invention to provide an insitu retorting method for recoveringhydrocarbons from oil'shale which overcomes the stated problems. Another object is to recover a major portion of the fluids flowing between an injection and a production well during the retorting of oil shale, especially at superattions. it has been proposed to retort in situ portions of, the oil'shale formations as one means for producing shale oil.

. For thisv purpose, spaced apart wells penetrating the portion to be retortedare provided. Through such wells is-- the desired retorting result effected principally by the con trolled flow of fluids through the oil'shale.

Insitu retorting may be obtained by injecting between the spacedwells fluids which apply to the oil shale by suitable mechanisms adequate heat for converting the kerogen into shale oil..The heat providing fluids may be;

combustible gases, combustion-supporting gases, and preheated ga'ses, and mixtures thereof.

For the most part, these retorting methods, tive operation, depend upon controllably flowing the heating fluids through the oil shale and moving the resulting shale oil to a point convenient for its recovery. It is this control of fluid movement in the in situ retorting of shale oil which provides severe problems to a successful employment of such methods. The problems reside in the oil shale formations being traversed by a network of fractures,- h'oth natural and artificial, which fractures are in fluid communieation'with one another at least to some degree. All fluid flows must take place through these fractures in the oil shale as it is retorted-Thus, it is apparent that the control of fluid flows through the fractures beis very-diflicult. Further, the loss of fluids via these fracfor eifecmospheric pressure levels. Yet another object is to prevent the undesired loss of fluids' flowing between injection and producing .wclls, especiallyjat superatmospheric pressure levels, exteriorly of the portionof the oil shale'being retorted. A further object of. the present invention is the limiting of fluid flows in accordance with the preceding objects by employing the injection and production wells andiother means normally used in conventional in situ retorting procedures for producing shale oil. These and other objects will be apparent to those skilled in the art when read in conjunction with the accompanying detailed description, the appended claims, and the attached drawings.

In FIGURES l and 2 of the drawings, there is illus-' .trated, in a vertical section taken. through the earth, a

portion of an oil shale formation provided with suitable structures by which the method of this invention may be practiced.

Referring particularly to FIGURES 1 and z of the vided for conveying fluids between the earth's-surface l4 and the fractures oropenings inthe interior of the oil shale 13. Such means may take the form of wells 16 and 17 spaced apart a suitable; distance within the oil shale 13, and each extending to a' suitable depth into communit ures to areas of the oil shale outside that portion being retorted increases in magnitude with every pressure increase in the fluids moving between the points. For examcation with openings in and beyond the portion of the oil shale 13 to be retorted. Extending downwardly from the earth's surface 14 to near the full depth of the wells 16 I and 17 are conduits 18 and 19, respectively. The conduits Patented July 18, 1967 ings 29.

18 and l9 arese cured within the'respective wells 16 and 17 by surrounding cement 21 or other suitable sealing material. Connected to the upper extremities of the

conduits

18 and 19 are wellhcads 22 and 23, respectively. A manifold system 24 may be disposed at the earth's surface to provide for the flow of fluids between the earths surface 14 and the openings in the interior of the oil shale 13.

The manifold system 24 may be of conventional design.

and its particular form is not important to the present invention. The

wellheads

22 and 23 are interconnected by 26 and 27,.respectively, to the manifold work of interconnecting fractures, naturalor artiflcial,,t0',

provide the principal fluid-carrying channels in the oil shale 13. A channel 28, formed of some of these fractures, provides the most direct fluid communication between the wells 16 and 17. Also, the wells 16 and 17 and the channel 28 are in fluid communication with other openings'extending outwardly into the surrounding oil shale formation 11. More particularly, such openings are those in which occurs the loss of the flowing fluids through the channel 28 in the oil shale13 at increased pressure above Any-means may be used for the injection of such fluid.

Preferably, cementing plugs 31 and 32 are disposed in the wells 16 and 17, respectively. The plugs 31' and 32 are then driven downwardly with a pressurizing fluid applied from the manifold system-24 for displacing the firstmcntioncd fluid fromthe conduits l8 and 19 in the wells l6 and 17 in substantial quantities and pressures into-the thief openings- 29. A suitable driving fluid for driving the cementing plugs 31 and 32 is WCIlCT-xHOWCVCX', other'fluids may be used. If desired, the cementing plugs 31 and 32 may be moved downwardly in the wells concurrently or scparately'whilc holding substantially the same pressure above each of such plugs. This'insures that substantially 'the same injection pressure is maintained in each ofthe wells 16 and 17. After the fluid has beendisplaced into the th'ef openings 29 and has undergone a desired conversion to the scaling material, the cementing plugs 31 I and 32 'may be removed from the

conduits

18 and 19, re-

atrnos'pheric levels between the wells '16 and 17. For pur-" poses of description, such openingsare referred to and designated'as thief openings 29, although the oil shale-13 is shown without a subtended stratum, it will bc. apparent' that the oil shale-13 obviously restsupon some support which need not be shown or described. Usually, a fluid can be circulated without any great geological loss from the-manifold system 24 through. the well .16

through the channel 28 to the well. 17 when operated at low back pressures. However, increasing the back pressurein the well 17 obviously causes increased-amounts of the injected fluid to be unrecoverably lost from the. channel 28 and the wells 16 and 17 into the thief open- In the illustrative embodiment of the method of this invention now tobe described, the thief openings 29 will be sealed to fluid flows to prevent the loss of fluids passing through the channel 28 in the oil shale 13 between the wells 16 and 17 while the channel 28 and the Wells 16 and 17 will remain open to fluid flows. A first step of this method is the injecting, into openings. of the oil shale 13, of a fluid capable of subsequently producing a material sealing such openings to fluid flow. Examples of such fluid are mixtures with water of hydraulic cement and of thixotropic clay, and mixtures thereof. Also. fluids eonvertible to plastics, and'precipitatable metal salts can spectively, by any-suitable means.

' Another step is filling the channel 28 with a fluid capable of excluding the first injected fluid from such opening. Preferably. such fluid used for filling the channel 28 is one incapable of subsequently producing a material permanently sealing openings in the oil shale 13. For example, such fluid may be water, air, 'gel-type clays and water, and mixtures thereof. Preferably, this step of filling the channel 28 is delayed until the first injected fluid begins to form the material'sealing the thief openings 29. Thereafter, the fluid capable of excluding the first injccted fluid is moved through-the wells 16 and 17 and the channel 28 from the manifold system 24. This step is clearly displayed in FIGURE 2. This excluding fluid may be circulated at any suitable pressure from the manifold system 24 through the surface conduit 26, the-well 16, through the channel 28, into' the well 17. and thence upwardly through the surface conduit 27 to return the first injected fluid tothe manifold system 24. Preferably, the circulating pressure is not'greater than the injection pressure at which the first injected fluid was introduced into the openings in the oil shale 13. Thus-sealing material is not displaced from the thief' openings 29 by the excluding fluid which preferentially will flow through the channel 28 between the wells l6and l7. However.=where there is a tendency to displace the sealing material from the thief openings 29 it is preferred to use a mixture of water and a thixotropic clay to form a gel as the excluding fluid to maintain seals inthe thief openings 29. The

' I thief openings 29 in' any event remain sealed with a sealbe used. Other fluids can be used as will be apparent to those skilled in the'art. The amount of pressure differential to be sealed against and the in situ retorting conditions are substantially determinative of the active ingredient composition of the injecting fluid. A gel-type clay and neat cement mixture with water has been found to he of utility for most purposes since the amount of cement can be varied to-produce seals of various strengths.

More particularly. the fluid is injected into the wells 16 and 17 via the manifold system 24 in suitable amounts filling the channel 28 and the thief openings 29 at least in part. Preferably. sufficicnt of the fluid for sealing the thief openings 29 is injected until the injection pressure is about that of the maximum operating pressure of the oil shale retorting procedure. As is obvious, injection of several batches of this fluid capable of providing a material sealing openings in the oil shale 13 may be necessary to fill the thief openings 29 to a desired extent. An interval is allowed before each subsequent injection to permit the priorly injected fluid to set. Also. in some cases it is found to be of particular advantage to use increasing concentrations of the active sealing ingredients during injection of the fluid.

ing material. as can be seen in FIGURE 2.

Alternatively. the excluding fluid may be moved from the manifold. system 24 simultaneously through the

surface conduits

26 and 27 to displace the first injected fluid from the wells 16 and 17 and the channel 28 into the thief openings 29. Although this practice will fill the channel 28 with the fluid for excluding the first injected fluid, there .is some danger of reopening the thief openings 29 to fluid loss. On such happening, it may be necessary to repeat the previous step if the loss of fluids into the thief openings 29 is too great. If desired, the excluding fluid here also may be a mixture of water and thixotropic clay to form a gel for reasons previously discussed.

If desired. the fluid for filling the channel 28 and excluding the first injected fluid may be a slug of water followed by air or the combustion-supporting gas to be used in the in situ combustion procedure. Alternatively, the

' combustion-supporting gas may be passed through the channel 28 to clear it of the first injected fluid or to amount of the last injected fluid that enters the Returning now to FIGURE 1, a second embodiment of the method of the present invention will be described. The structural arrangement previously described with respect to the drawings may be utilized. In this embodiment 'This fluid is injected through the channel 28 in that port'ion of the oil shale 13 residing between the wells 16 and 17 .which portion is to be retorted. Thereafter, the channel 28 is filled with afluid capable of excluding therefrom the fluid for'producinga sealing material in thethief openings 29, and lastly, follows the'carrying out'of. the

- in situ retorting procedure in that portion of the oil shale 13.between the wells 16 and 17.

, As onestep of this embodiment, a flui'd capable of subsequently producing a material temporarily sealing openings in the oil shale 13 to fluid flows is injected from the earth's surface through the channel 28. 'Anyfluid capable of producing this desired result may be used. For example, a fluid .containinga mixture of water with a thixotropic hydrated clay has been found tobe of utility. Drilling muds formed of bentonite and water are especially suitable for use. Preferably, this fluid is injected through the channel 28 in the .same rnanner as the first injected fluid,fsu ch as, hydraulic cement,.was introduced into the oil shale 13 in the first-described embodiment..Preferably, this fluid is introduced under pressure conditions similar 'to those used for carrying out the in situ retorting of the oil shale.

As another step,.a fluid capable of'subsequently producing a material sealing openings in the oil shale 13 to fluid flows is injected into the thief openings 29-00mmunicating with the wells 16 and 17. This fluid may be the same as that described for the first injected fiuidof the first embodiment. A fluid found to be of utility consistsof a mixture with water of substancessclected from the group consisting of thixotropic hydrated clay, hy draulic cement, and mixtures thereof. Preferably, such fluid is introduced under the same conditions as that fluid filling. the channel 28. This arrangement ;reduces the chann'el 28.This fluid can-be injected through the wells 16 suitable means, such as-was described for the first in- 'jected fluid inthe first embodiment. Preferably, the. wells 16 and 17 are filled with'such'fluid and the fluid displaced from these wells by cementing

plugs

31 and 32 driven downwardly by a pressured fluid applied from the manition it will be apparent that the fluid producing the relatively permanent sealing material may. be displaced into an ultimate position by a fluid producing a temporary sealing material or one-incapable of producing a sealing. material, or a combination of both. In another aspect, a material producing a temporary sealing material may be used to fill the channel 28 in that portion 'ofthe oil shale to be retorted sons to block entry of the fluid producing the relatively permanent seal whichis-introduced into the openingsin that'portion-of the oil shale not to be retorted.

Although the present invention has been described.

relative to only two spaced wells, it will be obvious to those skilled in the art that it may be applied to various patterns of wells to provide circumferential seals about distinct portions ofthe oil shale 13 to be retorted. Thus, by, this means, seals capable of, preventing losses of the operational-fluids at the pressures required for-insitu rctorting of theoil shale are formed by application'of the described steps. v

Of particular advantage in this'invention is the use of I fluids forming sealing materials in which water of hydration is essential in the forming of the sealing material. in such instances, as the in situ retorting produces elevated'temperatures at such seals, the water of hydration is-removed and the seals will fail. Inasmuch as suchsealing material as hydraulic cement has a heatcondu'ctive coeflicient much like oil shale, auniform advance of the retorting temperatures through the oil shale will produce uniform extensionsof the retorting procedure-from one. portion of the oil shale-to'another by rupturing the surrounding seals or barriers. Thus, by application of the i described steps to adjacent portions of the oil shale, sucand 17 into the interconnected thief openings '29 by any -cessive portions of the oil shale may be retorted with .con-

tinuous control of the fluid flows-by the limitations imposed through seals placed in the oil shalebeyond each portion being retorted. s

Although the present method has been described specifically applied to oil shale formations forillustrm tive purposes, it can be used in other types of earthen deposits containing hydrocarbon materials through which fluids mustflow in openings such as fractures and the like during in situ retorting procedures. One example is' the Athabasca tar sands.

From the foregoing it will be apparent that there has been provided a method well suited for satisfying all of the stated objects of this invention. Variouszchanges and alterations may be made in the. steps described for this method by those skilled in the art without departing from the spirit of the invention. It is intended that such changes and alterations under these conditionsare to be included within the scope of the followingappended claims. I

fluids-Any suitable fluid may be used; For example,

water is of utility. For this purpose, the cementing plugs.

31 and 32 are removed from the conduits l8 and 19, respectively, by any suitable means. Thereafter, such excluding fluid is passed through the wells 16 and 17 from the manifold system 24 to displace the resident fluids this fluid is circulated in the same manner as was described in the second-stepof the first embodiment. Preferably, the fluid is introduced to fill the channel 28 at somewhat less pressure than the injection pressures of either of the other injected fluids. Thus, the thief openings 29 in communication with the channel 28 and the wells -16 and 17 remain filled with a sealing material of one In either of the described embodiments of this invenfrom the wells 16 and 17 and channel 28. Preferably,

I claim:

- 1. In an in situ retorting method for recovering hydrocarbons from the subterranean deposit through well means in fluid communicationat spaced locations with openings in and beyond that portion of the deposit to be retorted, the improvement comprising the steps of:

(a) injecting from the earth's surface via the well means into openings in the deposit a fluid containing hydraulic cementand water in amounts suiiicicnt to subsequently produce a material sealing openings containing the fluid-to fluid flows, s

(b) injecting water from the earths surface via the well means into the openings in that portion of the deposit to be retorted to exclude the first-mentioned fluid therefrom, and

(c) carrying out in situ retorting with fluid flows limited to the portion of the deposit to be retorted and recoveringthe resulting hydrocarbons from these fluid flows. I

2. In the method of. claim 1, the improvement in step (b) of injecting air from the earth's surface via the well 3.' 1n the method of claim 2, the improvement of varyiitg the amounts of hydraulic cement and water contained in the injected fluid during the carrying out of step (a).

4. Inan in situ retorting method for recovering hydrocarbons from a subterranean deposit through well means in fluid communication at spaced locations with openings in and beyond that portion of the deposit to be retortcd,

the improvement comprising the steps of:

,(a) injecting from the earths surface via the well means a fluid capable .of subsequently producing a material sealing openings containing the fluid to fluid flows into openings in the deposit other than in that portion to be retorted and a fluid capable of subse- .I,'-.= quently producing a material temporarily sealingl openings containing said fluid to fluid flows during the time the first-mentioned fluid produces said'material into openings in that portion of the deposit to be retortcd,

(b) filling via the well means the openings in that portion of the deposit to be retorted with a fluid capable of excluding the priorly injected fluids from such openings, and- (c) carrying out in situ retorting with fluid flows limited to the-portion of the deposit to be retorted and recovering the resulting hydrocarbons from these fluid flows.

5. ,In an in, situ retorting method for recovering hydrocarbons from a subterranean depositthrough well means in fluid communication at spaced locations with openings in and beyond that portion of the deposit to be retortcd, the improvement comprising the steps of:

(a) injecting from the earths surface. via the well means a fluid capable of subsequently producing amaterial temporarily sealing openings containing the fluid to fluid flows into openings in that portion of the deposit to be retortcd,

(b) injecting from the earths surface via the well means of excluding the priorly injected fluids from such openings, and v (d) carryingout in situ retorting with fluid flows limited to the portion of the deposit to be retorted and recovering the resulting hydrocarbons from these fluid flows. g

6. In the method of claim 5, the improvement in step (21') wherein the fluid contains water and a thixotropic hydrated clay and in step (b) wherein the fluid contains water with a substanceselected from the group consisting of .thixotropic hydrated clay and hydraulic cement, and mixtures thereof.

7. In an in situ retorting method for recovering hydro carbons from a subterranean deposit through well means. in fluid communication at spaced locations with openings in and beyond that portion of the deposit to be retortcd, the improvement comprising the steps of:

(a) injecting from the earths surface via the well means a thixotropic hydrated clay and water mixture into openings -in that portion of the deposit to be refrom the group consisting of thixotropic hydrated clay and hydraulic cement, and mixtures thereof, into openings in the deposit other than in that portion to be retortcd,

(c) filling via the well means the openings in that'por- 1 tion of the deposit to be retorted with water'to exclude said mixtures producing sealing materials therefrom, and (d) carrying outin situ retorting with fluid flows limited to the portion ofthe deposit to be retorted and recovering the resulting hydrocarbons from these fluid flows. v

8. In an in situ retorting method for rccovcring'hydrocarbons from a subterranean deposit through well means in fluid communication at spaced locations with openings in and beyond that portion of the deposit'to be'retorted,

the improvement comprising the steps of (a) injecting at a first pressure, which pressure is about the greatest in magnitude to be employed during retorting, from the earths surface via the well means a fluid capable of subsequently producing a material temporarily sealing openings containing the fluid to fluid flows into openings in that portion of the oil shale to be retortcd,

(b) injecting at a second pressure not greater than the first pressure from the earths surface via the well means-a fluid capable of subsequently producing a material sealing openings containing said fl'uidto fluid flows into openings in the deposit other than in that portion to be retortcd, Y Y

(c) filling via the well means at a pressure loss than the second pressure the openings in that portion of the deposit to be retorted with a fluid capable of flowing to exclude thefluids producing a sealing material from such openings, and 1 a (d) carrying out in situ retorting with fluid flows limited to the portion of the deposit to be retorted and recovering the resulting hydrocarbons from these 9. In the method of claim 8, the improvement in step (a) wherein the fluid contains water'and a thixotropic clay and in step (b) wherein thefluid contains water with a substance selected from the group consisting of thixotropic clay .and hydraulic cement, and mixtures thereof. i

10. In the method of claim 8, the improvement in step (b) wherein the fluid contains water with a substance selected from the group consisting of thixotropic clay and hydraulic cement, and mixtures thereof, and the amounts of each such substance in the fluid is varied during injection into the openings in the deposit.

References Cited, UNITED STATES PATENTS 1,870,869 8/1932 Ranney et a1 299--2 2,365,039 12/1944 Andresen 166--29 2,973,813 3/1961 Parker 166- 11 3,010,512 11/1961 Hurley et a1. 166-11 3,055,423 9/1962 Parker 166-11 3,070,159 12/1962 Marx 166-25 X 3,190,355 6/1965 Clement 166-25 X 3,198,249 8/1965 Wiliman 16625 X CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, STEPHEN]. NOVOSAD,

Examiners.

Claims

1. IN AN IN SITU RETORTING METHOD FOR RECOVERING HYDROCARBONS FROM THE SUBTERRANEAN DEPOSIT THROUGH WELL MEANS IN FLUID COMMUNICATION AT SPACED LOCATIONS WITH OPENINGS IN AND BEYOND THAT PORTION OF THE DEPOSIT TO BE RETORTED, THE IMPROVEMENT COMPRISING THE STEPS OF: (A) INJECTING FROM THE EARTH''S SURFACE VIA THE WELL MEANS INTO OPENINGS IN THE DEPOSIT A FLUID CONTAINING HYDRAULIC CEMENT AND WATER IN AMOUNTS SUFFICIENT TO SUBSEQUENTLY PRODUCE A MATERIAL SEALING OPENINGS CONTAINING THE FLUID TO FLUID FLOWS, (B) INJECTING WATER FROM THE EARTH''S SURFACE VIA THE WELL MEANS INTO THE OPENINGS IN THAT PORTION OF THE DEPOSIT TO BE RETORTED TO EXCLUDE THE FIRST-MENTIONED FLUID THEREFROM, AND (C) CARRYING OUT IN SITU RETORTING WITH FLUID FLOWS LIMITED TO THE PORTION OF THE DEPOSIT TO BE RETORTED AND RECOVERING THE RESULTING HYDROCARBONS FROM THESE FLUID FLOWS.