US3349850A

US3349850A - Method for the extraction of underground bituminous deposits

Info

Publication number: US3349850A
Application number: US489776A
Authority: US
Inventors: Schlicht Erika Marie; Lange Hans
Original assignee: Deutsche Erdoel AG
Current assignee: Wintershall Dea International AG
Priority date: 1962-08-06
Filing date: 1965-08-09
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31

Description

Oct. 31, 1967 G. SCHLICHT ET AL BITUMINOUS DEPOS ITS METHOD FOR THE EXTRACTION OF UNDERGROUND Uriginal Filed Aug. 6, 1962 msbwmm IN VENTORS R SCHL/CHT GUNTHE b Erika Mar/e .Sc/r/ichl- Admin isfrafr HANS LANGE BY W i ZLL ZQ ATTORNEYS United States Patent 3,349,850 METHOD FOR THE EXTRACTION 0F UNDER- GROUND BITUMINOUS DEPOSITS Giinther Schlicht, deceased, late of Hamburg-Othmarschen, Germany, by Erika Marie Schlicht, legal representative, Hamburg-Othmarschen, Germany, and Hans Lange, Wietze, Kreis Celle, Germany, assignors t0 Deutsche Erdol-Aktiengesellschaft, Hamburg, Germany Original application Aug. 6, 1962, Ser. No. 215,494, now Patent No. 3,242,989, dated Mar. 29, 1966. Divided and this application Aug. 9, 1965, Ser. No. 489,776 4 Claims. (Cl. 166-40) ABSTRACT OF THE DISCLOSURE In a process for extracting viscous bitumens from underground deposits thereof the steps comprising:

(a) Sinking a bore into an underground deposit of viscous bitumens; and

(b) Flowing liquid bitumens heated toa temperature higher than said viscous bitumens from the bottom of said bore upwardly through said deposit thereby warming said viscous bitumens surrounding said bore to a flowable state;

(c) The improvement comprising circulating said liquid bitumens from said bottom to progressively higher points of the bore thereby increasing the flow path of said liquid bitumens through said deposit as portions of the deposit at increasing distances from said bore are heated to a flowable state.

This application is a division of application Ser. No. 215,494, filed Aug. 6, 1962, now U.S. Patent 3,242,989.

The present invention relates to the extraction of highly viscous or solidified bitumens from underground deposits, more particularly, to a method of extracting underground bituminous deposits by the application of heat.

Highly viscous or solid underground bituminous deposits have been extracted both by mining methods and by various processes involving the application of heat including gasification and dry distillation. The necessary heat for the extraction of such deposits can be introduced into the deposit in sufiicient quantities only if a circulation of the heating medium through the deposit can be achieved. The greatest difficulty in obtaining such a circulation in a deposit consists of initially establishing a suiiicient permeability in the deposit for the circulation of a liquid heating medium. It is not possible to carry out any of these extraction processes requiring the application of heat by relying solely upon the conduction of heat through the deposit in order to transfer sufficient quantities of heat into the deposit. The temperature decreases so rapidly in the direction of the heat flow that such a heat transfer is a wholly unfeasible operation.

The extraction of low-viscosity bitumens presents relatively little problem but the difiiculties increase as the viscosity of the bitumens increases. One proposed solution has been to increase the pressure of the liquid heating medium. Even when the highest possible pressure is applied over an extended period of time to such a bituminous deposit, a limit is soon. reached at which it is no longer possible to cause a highly viscous or solidified bitumen to flow.

Various processes, have been devised for treating such highly viscous or solidified bituminous deposits wherein some degree of permeability of the deposits were obtained. Such processes include the various fracture processes which can be employed in many different variations and which essentially consist of discharging a fluid under pressure from a bore into the deposit which pres V 3,349,850 Patented Oct. 31, 1967 sure is higher than the gins to break up.

In the fracture processes, liquids containing sands are employed for making passages in the deposits. The sand is for the purpose of keeping these passages open in the vicinity of the bore so as to enable the liquids to pass therethrough. Only after these preparatory processes have been carried out can the bitumens be extracted by the introduction of heat or by combustion thereof in situ. However, ditficulties may arise when part of the bituminous deposit becomes plastic and flows to close the previously formed passages. The continuation of the in situ process is thus rendered virtually impossible when almost all of the porous spaces and passages in the deposit are filled with the plastic bitumen.

It is therefore the principal object of the present invention to provide a novel and improved process for exploiting underground deposits of highly viscous or solidified bitumens.

An installation suitable for use in this process comprises three concentric tubular casings in a bore drilled 'into the ground to an underground bituminous deposit. The outer casing is provided with a plurality of passages in the wall thereof, spaced at different heights along the casing and at equal angular intervals from one another. A source of heat energy is installed in the bottom of the bore. A pump is mounted aboveground and has supply and return lines connected to the several tubular casings for the circulation of a fluid heating medium down through the bore, outwardly into the deposit, and then returning to the bore through the openings in the outer casing.

A second bore is provided spaced from the first bore and similarly comprises a plurality of concentric tubular casings and is connected to the same aboveground pump. However, the second bore is not provided with a source of heat energy and the accessory equipment for such a source.

In carrying out the process of the present invention, a liquid heating medium is pumped downwardly through a central casing into heat-exchange relationship with the heat source positioned at the bottom of the bore. The heated liquid is then discharged outwardly of the bore at the bottom thereof and flows upwardly through a porous layer immediately adjacent the lower portion of the outer surface of the outer casing of the tube. The heating medium then returns into the bore through a passage in the outer casing and flows upwardly to the aboveground pump to be recirculated again through the bore.

As the heating medium flows upwardly through the porous layer adjacent the casing, heat is transferred to the surrounding portions of the bituminous deposit.

Continued heating of the deposit reduces the heated portions of the deposit to a flowable state. Accordingly, the heating medium is circulated in increasingly longer flow paths at greater distances from the bore to continue to heat unheated portions of the deposit and reduce them to a flowable state.

In order to increase the flow path of the heating medium through the deposit, the heating medium is returned to the bore at progressively higher points along the outer casing.

After a sufiicient quantity of the bituminous deposit has been rendered flowable, water is then introduced through the casing of the bore and carries the bitumens upwardly through the bore to a processing plant where the bitumens are separated from the water according to known and conventional procedures.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying drawing wherein:

FIGURE 1 shows a vertical section through a bitumipressure at which the deposit benous deposit in which the process of the present invention is performed;

FIGURE 2 is a horizontal section through the upper portion of borehole I with the parts contained therein;

FIGURE 3 is a fragmentary vertical section of a lower portion of the same borehole with the parts contained therein.

With reference to the drawing, the arrangement of the present invention comprises boreholes I and II which are drilled downwardly through the earth from the surface indicated as 1 into an underground deposit 2 of a highly viscous or solidified bitumen.

Borehole I comprises an outer casing 3 within which there are arranged concentrically and coaxially therewith, a center casing 4 and an innner casing 5. The upper portion of the casing 3 is secured in the ground by cementing at 35 to a subsurface layer of rock 6. The lower portion of the outer face of the outer casing 3 is covered with a permeable metallic covering 7. This permeable covering 7 extends for a distance of about one third of the vertical height of the underground deposit 2.

The outer surface of the casing 3 is provided with a plurality of apertures 8, 9, and 10 to which are connected passages which open upwardly as shown in the drawing. These passages are located in the space between the outer casing 3 and the center casing 4. These openings 8, 9, and 10 are at different heights along the outer casing and are also staggered with respect to each other.

Rotary valve members 11, 12, and 13 are provided for selectively closing the passages 8, 9, and 10 respectively. These movable valves are fixedly mounted on the center casing 4 which is rotatably mounted within the bore. Thus, by rotation of the center casing 4 through predetermined angles, the passageways into the outer casing at different levels may be opened and closed in sequence.

In that portion of the outer casing 3 which is covered by the permeable covering 7, there are provided additional openings 14 for registering with the upwardly directed passageways 15 in the valve member 15 that is mounted on the rotatable center casing 4.

The source of energy for the bore comprises a nuclear reactor 16, such as a boiling-water reactor, rotatably connected to the central casing 4 by a connection 17. The nuclear reactor 16 is provided with an expansible shield 18 which is expanded outwardly when the nuclear reactor is in operation. A neutron-reflecting substance, such as ordinary water, is positioned in the space between the shield 18 and the reactor 16.

For heating a deposit, a fluid heating medium, such as the oil obtained from the deposit is supplied by an aboveground pump 21 through sup-ply conduits 22 to the upper end of the center casing 4 through a connection 23 which is stationary but permits rotation of the casing 4. The fluid medium is returned from the bore through return lines 24, which connect the outer casing 3 with an intermediate reservoir 25, which in turn is connected to the pump 21 at 26.

The process of the present the following manner:

A heating medium, such as oil from the deposit, liquid hydrocarbon or a mixture of benzene and kerosene, is pumped under pressure into the bore through supply line 22 and passes downwardly through the bore in the space between the center casing 4 and the inner casing 5. The liquid medium then passes in heatexchange relationship with the nuclear reactor 16 and is discharged from the bottom of the center casing 4 into the deposit 2. The greater the paraffin constituents having a high melting point (70 C.) in the deposit, the higher must be the temperature of the heating medium.

At the beginning of the process, the deposit is relatively solid and the liquid heating medium then flows upwardly along the outer surface of the outer casing 3 invention is carried out in through the permeable covering 7. The liquid medium then enters the aperture 10 into the space between the outer casing 3 and the center casing 4 and is returned through return line 24 and reservoir 25 to the pump 21 to be recirculated through the bore.

As the heated oil flows upwardly through the permeable layer 7, heat is transferred by conduction to the adjacent layer of the deposit The continued transfer of the heat will render this portion of the deposit permeable and eventually flowable. As the bitumen becomes less viscous and more fiowable, it is removed by the circulating heating medium. As soon as this heated portion of the deposit is removed, the heated oil comes in contact with the next adjacent layer of the deposit, which is relatively cold, and heat is again transferred from the heated oil to this relatively cold layer of a bitumen. Thus, short heat transmission paths are formed extending int-o the bituminous deposit and away from that layer of the deposit which is contacted by the heated oil, which is at a relatively high temperature. The process is characterized by heat transfer into the bituminous deposit, both by the direct contact of the heated oil with the bituminous deposit and the conduction of heat for relatively short distances into the bituminous deposit from the contacted surface thereof. The heated oil remains in close contact with the bituminous deposit because of the continuous melting of the deposit and the removal of the same by the flowing oil.

As the heated oil begins to flow at a distance away from the bore, a path is followed according to the arrows 27a. As the heating process continues, the paths of the flow of the heating medium progress outwardly to 27b and 27c. At the same time, as the path of the heating medium becomes greater, the opening 10 is closed and the opening 9 is opened by the rotation of the center casing 4 through a suflicient distance to actuate the respective valves.

In order to improve the efficiency of the process, the passages 9 and 10 are closed and the passageways 14 are open. Through the passageways 14, a highly viscous liquid, whose viscosity is not changed when heated, is forced under pressure into the deposit in the directions as indicated at 28. Such liquids include mixtures of water and carboxymethyl cellulose having a viscosity of 50-2000 centipoises, solutions containing 0.22% of carboxymethyl cellulose, or calcium aluminum silicate with water. The injection of this liquid into the deposit hastens the achievement of the permeability of the deposit further out from the bore. After this introduction of the liquid has been completed, the center casing 4 is again rotated to close the passageways 14 and the passages 9 and 10 may be opened to continue the circulation of the heating medium.

When a nuclear reactor is employed as a heating source in borehole I and has a sufiiciently high capacity, the same reactor can be used for supplying a heating medium for circulation to a second similar borehole. As seen in the drawing, borehole II is provided spaced from borehole I and is similar in all respects except for the nuclear reactor and its auxiliary structures. The corresponding components of bore hole II are indicated with the same reference numerals as the components of borehole I, but with suffixes A.

Under particular circumstances it may be desired that the oil supply to line 22A to the center casing 4A should be further heated prior to being introduced into the deposit. The circulation of the oil in this event can be obtained in the following manner:

The heated oil resulting from its passage in heat-exchange relationship with the reactor 16 is still under the high pressure of supply pump 21. A portion of the oil discharged at the bottom of central casing 4 is intro duced into the bottom of the inner casing 5 through distributors 29. This oil then flows upwardly through innor casing 5 and is discharged at 30 into a connection which introduces the heated oil into the inner casing 5A at 31. This oil then flows downwardly through inner casing 5A and is discharged as shown at 32 into the deposit. This discharge 32 is in front of the flow of oil pumped into the central casing 4A and discharged therefrom at 33.

As an alternative construction, the heated oil may be supplied from inner casing 5 into the reservoir 25 from which it is supplied to the pump 21 and introduced into borehole II through supply line 22A.

As the process employing the two boreholes continues, increasingly wider areas of the deposit are heated until the zones of the deposit heated by the individual boreholes contact each other at 34. At this point, the deposit is permeable between the two boreholes. Continued application of the process will heat portions of the deposit above the contact point 34 and between the bores. Various known heat calculations can be carried through to determine to what extent the deposit will be heated.

When sufiicient portions of the deposit have been heated as described above and the bitumens contained therein have been rendered liquid or at least flowable, the bitumens can then be extracted from the deposit. This is carried out by introducing flooding water through the inner casings 5 and 5A through the

distributors

29 and 29A into the lower portion of the deposit and then upwardly through the deposit in the direction of the arrows 33. The flooding water progressively urges the liquefied bitumens through the valve passages 9 and 9A,.10 and A into the casing 3 and 3A. The liquid bitumens can then be tapped from the supply tube 36 extending from the pump 21.

During the extraction process the circulation of the heat ing medium through the pump and supply lines to boreholes I and II can be suspended. However, the heat may be transferred together with the flooding water in a horizontal direction along the lower surface of the deposit as indicated at 37 to contact portions of the deposit which previously have not been sufficiently heated. As this flooding progresses, the resulting bitumens can be extracted through the valve passage 8 and 8A.

When the bituminous deposit is located in a rock formation which has a relatively great thickness, the treatment of the deposit by the circulation of a heating medium therethrough can be started and carried out in the lower portions thereof. In a similar manner, when the bitumens are susceptible to flow after a sufficient heating, the bitumens can be extracted by introductions of flooding water. This flooding water will absorb heat from the rock formation wherein it has been stored and transfer the heat to various portions of the deposit through which the heating medium has not been circulated. Thus, these portions of the bituminous deposit will become fiowable and can then be washed out through the various passages of the bore in a manner as previously described.

The flooding or flushing extraction is preferably carried out by a flooding water whose viscosity and density are slightly higher than for ordinary water and which also has a slightly increased surface tension.

Thus it can be seen that the present invention provides an effective process and apparatus for the extraction of highly viscous or solidified underground bituminous deposits. By the application of heat to the underground deposit in a manner as previously described, virtually the entire deposit can be rendered flowable and then extracted by the flooding of the deposit with water. At the beginnlg of the flooding operation the water is warmed but as the flooding operation continues the warming of the water may be discontinued and the flooding water may be introduced at a somewhat lower temperature.

To further assist in the comprehension of the present invention, a specific operating example of the present process will next be described in detail.

A bituminous deposit positioned in a depth of 350 m. and having a thickness of 60 m. and containing tar sands, in which the pour point of the bituminous contents is 70 C., was exploited according to the present invention.

Two bores each having a diameter of 311 mm. were drilled. The bore I was enlarged to a diameter of 520 mm. for a height of 2 m. beginning from the base of the bore, in order to provide space to accommodate the expansible shield of the reactor to be mounted therein, a 20 in. section of each bore extending upwardly from its base was undercut to a diameter of 371 mm. This undercut section Was coated with steel wool mats having a thickness of 30 mm. so that a porous layer was formed outwardly of the casing.

The casing consisted of an outer casing having a diame ter of 188 mm. and center casing with a diameter of 108 mm. Centrally arranged in the center casing was an inner casing having a diameter of 55.9 mm. The strings of casing were lowered one after the other together with the reactor. After the arrangement of the strings of casing was completed, the strings of casing were cemented into the bore beginning from the surface and extending down over a length of 200 m. The outer casing was provided in the zone of the deposit with apertures distributed over its periphery and the center casing is provided with gate valves, corresponding to each other, but which can be opened or closed, respectively, one after the other only by a rotary movement of the inner casing. The first apertures for introducing solidifying or setting means were arranged 15 m. above the base of the borehole. The first rows of apertures for admitting the circulating medium into the outer casing were positioned 0.2 m. above the porous layer. Further rows of apertures were 20 In. higher.

After the reactor was lowered onto the base of the bore, its shield was expanded to fill the space provided by the undercutting of the bore.

After the nuclear reactor was charged with normal water, free from reactor poison, as a neutron reflecting layer, the reactor was then brought to its critical state. Its capacity per hour amounts to 1,000,000 cal., and its fuel charge is calculated to deliver power for two years.

After the reactor had become critical, 15 m. /h. of light fuel oil were introduced under pressure from aboveground into the bore as a heating medium by means of the pump connected to bore I, through the center casing at a pressure of 60 atmospheres and heated to C. in the heat exchanger of the reactor. The hot oil flowed through the porous layer upwardly along the outer casing and then entered through the opened lowermost entrance aperture into the outer casing and was extracted in the upward direction. Then it was again introduced down through the center tubing by means of the pump. It was heated again in the heat exchanger and then recirculated into the deposit. After 15 days have elapsed, bore II, which did not have an individual heat energy source, was connected to the circulation system via the center casing. of bore I. After the entire system was filled up, the circulating quantity of oil was maintained constant. The pressure and the temperature as well as the quantity and the characteristic data of the oil supplied to the pump were continuously controlled. After 50 days, variations of the mentioned values indicated that the solid bituminous contents in the lower part of the deposit section surrounding the bore had liquefied to a farreaching extent and were taking part in the heat circulation. By rotating the inner casing, the lower inlet aperture into the outer casing was closed and the inlet apertures positioned 20 In. higher were opened. Bore II was subjected to the same operation.

After another 30 days, the circulation was interrupted and the inlet aperture into the outer casing closed by a corresponding rotation of the inner casing with the valves fixed thereto, and the exit aperture positioned in the lower portion were simultaneously opened. Through the lastmentioned aperture, 6 m. of cement milk were discharged at a pressure of 70 atmospheres for enlarging the heat circulation away from the bore and subsequently, after a setting had occurred, switched over again to the heat circulation. Subsequently the same operation Was carried through in bore II.

Fifty days later the circulation was switched to the uppermost inlet aperture. The progress of the heat circulation was controlled by means of a temporary interruption of the oil supply to bore II and a simultaneous throttling of the oil discharge at bore I. After another 122 days an increase in the pressure at bore II indicated that a connection had been effected between the two bores and that the bituminous portion of the deposit contents located between them had been heated and liquefied.

After a total of 343 days had elapsed, the circulation of the heating medium was stopped. Subsequently, 6 mfi/h. of prepared flooding water were supplied to the base of the bore at a pressure of 60 atmospheres and the extraction of a quantity of heated deposit oil corresponding to the quantity of supplied Water was started. Altogether 21,800 m. of oil have been extracted hitherto from the deposit and the extraction was still going on after 145 days of extraction.

Under favorable conditions in a deposit, several auxiliary bores can be concentrically arranged around the central bore being provided with the source of heat energy and connected to the latter one for providing heat circulations.

It Will be understood that this invention is susceptible to further modification and, accordingly, it is desired to comprehend such modifications Within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. In a process for extracting Viscous bitumens from underground deposits thereof the steps comprising:

(a) sinking a bore into an underground deposit of viscous bitumens; and

(b) flowing liquid bitumens heated to a temperature higher than said viscous bitumens from the bottom of said bore upwardly through said deposit thereby warming said viscous bitumens surrounding said bore to a flowable state;

2. In a process for extracting viscous bitumens from an underground deposit the steps comprising:

(a) sinking a bore into said deposit;

(b) lowering through the bore and into said deposit an outer casing having a plurality of vertically spaced apertures opening at successive levels into said deposit;

(c) lowering a central casing of smaller diameter through said outer casing;

(d) lowering a third casing of intermediate diameter through said outer casing and around said central casing, said third casing having means for selectively opening and closing said apertures;

(e) flowing liquid bitumens heated to a temperature higher than said viscous bitumens through said central casing and from the bottom of said central casing upwardly through said deposit thereby warming said viscous bitumens surrounding said bore to a flowable state; and

(f) circulating said liquid bitumens from said bottom to successively higher selectively opened apertures in said outer casing thereby increasing the flow path of said liquid bitumens through said deposit as portions of the deposit at increasing distances from said bore are heated to a flowable state.

3. The process of claim 2 further comprising:

(g) interrupting the flow of said liquid bitumens; and

(h) flowing in said outer casing a liquid having a viscosity and pressure greater than said liquid bitumens and through selectively opened lower apertures into said deposit to decrease the permeability thereof.

4. The process of claim 2 further comprising adding water to said central casing whereby the flowable portions of the deposit are removed and recovered.

References Cited vol. 57, No. 3, Jan. 19, 1959, pp. 8698.

STEPHEN J. NOVOSAD, Primary Examiner.

CHARLES E. OCONNELL, Examiner.

Claims

1. IN A PROCESS FOR EXTRACTING VISCOUS BITUMENS FROM UNDERGROUND DEPOSITS THEREOF THE STEPS COMPRISING: (A) SINKING A BORE INTO AN UNDERGROUND DEPOSIT OF VISCOUS BITUMENS; AND (B) FLOWING LIQUID BITUMENS HEATED TO A TEMPERATURE HIGHER THAN SAID VISCOUS BITUMENS FROM THE BOTTOM OF SAID BORE UPWARDLY THROUGH SAID DEPOSIT THEREBY WARMING SAID VISCOUS BITUMENS SURROUNDING SAID BORE TO A FLOWABLE STATE; (C) THE IMPROVEMENT COMPRISING CIRCULATING SAID LIQUID BITUMENS FROM SAID BOTTOM TO PROGRESSIVELY HIGHER POINTS OF THE BORE THEREBY INCREASING THE FLOW PATH OF SAID LIQUID BITUMENS THROUGH SAID DEPOSIT AS PORTIONS OF THE DEPOSIT AT INCREASING DISTANCES FROM SAID BORE ARE HEATED TO A FLOWABLE STATE.