US3276518A

US3276518A - Process for extracting liquid bitumens from an underground deposit

Info

Publication number: US3276518A
Application number: US215493A
Authority: US
Inventors: Schlicht Erika Marie; Lange Hans
Original assignee: Deutsche Erdoel AG
Current assignee: Wintershall Dea Deutschland AG
Priority date: 1961-08-08
Filing date: 1962-08-06
Publication date: 1966-10-04
Anticipated expiration: 1983-10-04
Also published as: DE1199718B

Description

www12 XR Oct. 4, 1966 Filed Aug. 6. 1962 G. SCHLICHT ETAL PROCESS FOR EXTRACTING LIQUID BITUMENS FROM AN UNDERGROUND DEPOSIT 2 Sheets-Sheet 1 Inra/vraies GUN THE@ `SCHL/CAW, dsasad [Lega/ represen/hm) ERI/(A MAR/E SCHL/awr YHANS Af/6E Oct. 4, 1966 G. scr-:LICHT E'rAL 3,276,518

PROCESS FOR EXTRACTING LIQUID BITUMENS FROM AN UNDERGROUND DEPSIT 2 Sheets-Sheet 2 fd m a7 FIG!! n. I s r v u.-.....-....\ n... d.. ....,..D.:....... un. ..1 .r1 Z .VH ...Il .nv f v n .n u C represen ra'va Gw msn ScHL/L'Hv; deceased,

kyEr/kd Mdr/'c Schl/'chf legal H4 Ns LA NG: BY MW y zum 1 ATTORNEYS Filed Aug.V

The present invention relates to the extraction of liquid bitumens, more particularly, to a primary extraction process for extracting liquid bitumens from underground deposits wherein the pressure of the deposit is greater than the bubble pressure of the liquid bitumen. y

`In order to extract liquid bitumens from underground deposits many processes have been devised to treat the deposit tofacilitate the extraction of the bitumen. Some processes are based ondecreasing the viscosity of the bitumen by heating the deposit through the use of various heating media. Many oi these processes are carried out by using-one bore throughwhich a medium is introduced and an adjacent bore from which the bitumen is extracted. 25

" The heating medium, such as a gas or water, is added to the underground deposit in such a way -that the underground circulation of this medium in the deposit from the introduction bore to the extraction bore is at an angle of about degrees with respect to the direction in which v the deposit is being exploited.

.Many of these secondary extraction processes include the introduction of water through one bore and flowing the water underground through the deposit to an adjacent bore from which the water andthe bitumens are extracted.

. Other processes wherein a heating medium is used which does not originate from the deposit and which may comprise hot water or steam is introduced into the deposit through one bore, tlowed underground through the del posit and withdrawn through an extraction bore together .Y with theA bitumens.

Other processes include the positioning of electrical heating arrangements in boreholes, so as to heat the adjacentdeposits and render them viscous, whereby the deposits can then be flowed to an extraction bore. Since the heat is transferred from theA bore to the deposit only l by conduction, the eiciency and capacity of such a heating arrangement is limited and is insuticient to produce the necessary quantities of heat for heating large portionsv of the deposit. .-.i Y A" Other methods propose the addition of gases, such as CO2, or chemicals tothe deposit or adding these chemicals tothe water used for lioodingth'e deposit.

In the aforementioned processes difficulties are encountered when littlel or no consideration i's given to the action of the introduced medium, such as a gas or liquid, with respect-to"theunderground deposit of the bitumen. One

i source of diiculty is the failure to pay careful attention to theditference in viscosity between the water and the bitumens in the deposit. Further diiculties arise when ,these media are introduced through bores which are positioned from the extraction bores along the direction in which the deposit is to be extracted. When the junction surface between a liquid bitumen, such as oil, and the waterI used for ushing bitumen is moving toward the extraction boreholes and 'care is not taken to maintain a uniformity in this junction surface, there is the everpresent risk that channels are formed from the yaction of this water in the underground deposit, particularly when the permeability of the deposit is changing. It is virtually impossible to uniformly treat the junction zone beited States arent "ice tween the oil and water with any of the known processes, since these processes cannot be readily controlled.

It is therefore the principal object of the present invention to provide a more effective process for the extraction f of vliquid bitumens from underground deposits.

In order to carry out the present process a series of boreholes are drilled into an underground deposit of liquid bitumens and extending in the direction of the deposit. The boreholes are drilled to the lowest point of the deposit in a direction proceeding to the highest point of the deposit which is the direction in which the bitumens are to be extracted. Water is introduced into the deposit through the boreholes in the deepest part of the deposit and the bitumens are extracted from the deposit from boreholes in a higher part of the deposit. Boreholes positioned between the ooding and extracting boreholes are used forgtreating the liquid bitumens. The contents of the deposit are circulated between one of these latter bores in a closed pipe system wherein the bitumen is brought aboveground, heated, perhaps treated with a chemical substance and introduced into a return borehole f to the underground deposit. lt is also possible to heat the bitumen in the. return-borehole. vThe contents of the deposit then circuate underground from one borehole to Substances which are known per se vare added to the bitumens to reduce the surface tensions between the junction surfaces of the oil and water, as this junction surface approaches the treating bores.

The liquid bitumens are generally circulated several times between the treating boreholes, in order to transfer, v suicient heat to the surrounding rock formation in order to heat the same. j

During this process water is added to the ooding boreholes to maintain a suicient pressure on the underground liquid bitumens, so that this pressure remains above the bubble pressure of the liquid bitumen. In the event the 40 pressure is decreased below the bubble pressure, gaseous bubbles will form in the individual pores of the rock storing the liquid bitumen and will'accordingly make the deposit compressible. creasingly dilicult to transfer heat from the 'borehole into the deposit and thus large portions of heat will be rendered ineffective.

bitumen begin to escape at that temperature of the under *A A ground deposit. I Other objects and advantages of the lpresent invention will be apparent upon reference to the accompanying drawing which schematically illustrates the manner in which the present process is'carried out.

An understanding of the invention may be facilitated by an inspection of the drawings wherein:

FIGURE l schematically illustrates a top plan view of a portion of an underground deposit of liquid bitumens;

FIGURE 2 schematically illustrates a vertical cross section of FIGURE 1, showing the variations in temperature as different sections of the deposit are being treated;

FIGURE 3 illustrates a vertical cross section of a portion of an underground deposit of liquid bitumens showthe otherv in -a direction which forms'an angle ot from As a result, itwill become in-v The bubble pressure of the liquidbitumen is considered that point at which gases in the trated in the drawings, with particular reference to FIG- f URES i and 4. This portion of the underground deposit can be divided into 3 sections indicated by I, l1 and III. Section I is the water or flooding Section and represents kthe deepest or lowest part of the underground deposit.

The boreholes l4 extend downwardly into this water section.

The extraction section III is positioned in the highest'- l-portiou of the deposit and has .a plurality of boreholes 3 extending downwardly thereinto.

The treating section II is positioned between the water These samples taken from the leading boreholes will give accurate indications since the oil must be circulated section I and the extracting section III and has a plu rality of boreholes therein whose specific functions will be presently described.

As the extraction of the deposit proceeds the boreholes of section I will be moved in the direction of the extraotion which is represented by the arrow c.

During the extraction process water is introduced into the boreholes 4 in section I to maintain a pressure on the liquid bitumens of the underground deposit. The liquid bitumens, such as oil, are then withdrawn from the boreholes 1 which are designated as withdrawing or leading the. viscosity of the oil. The oil is then returned to the deposit downwardly through treating borehole 2.

The flow of the oil aboveground from leading borehole 1 to treating borehole 2 is eected through a closed heatscaled pipeline which is provided with a suitable pumping arrangement for increasing the pressure of the oil. The

circulation of the oil aboveground between

boreholes

1 and 2 is in the direction of solid arrow a and underground the oil tlows from treating borehole 2 to leading borehole i in 4the direction of the dashed arrow b. The

leading bores 1 are so positioned with respect to the adjacent treating bores 2 that these directions of llow form an angle of from 45 to 90 with respect to the general direction of extraction as indicated bythe arrow c. This produces a uniformly high zone of heat between the leading and treating bores which zone moves in the direction of c until it reaches the next series of boreholes,

where the zone is again formed, if necessary, to continue the extracting process.

As the contents of the deposit, i.e. the oil, is circulated between boreholes 1 and-2 the oil is extracted from the i extracting borehole 3 and simultaneously with this extraction ood water. is added through the ooding bores 4 in order to maintain the pressure on the oil within the deposit. A pressure on the oil is maintained which is greater than the bubbling pressure of the oil.

The heated oil is circulated through the

boreholes

1 and 2. As the junction of the oil and water, as indicated at 5, proceeds in the direction of the arrow c and approaches the leading boreholes 1, substances are then added to the circulating oil for improving this oil-water junction. These substances are addedv to decrease the interfacial and surface tensions between the contacting surfaces of the oil and the water. The approach of the voil-water junction 5 vis indicated by samplings taken from the leading bores 1. The rst .traces of water in the oil as revealed in the samplings taken from the leading boreholes 1 will indicate the approaching of the oil-water junction 5. By the adding of these substances which will vary in quantity and composition according to the analysis of the sample the oil will be more readily extracted from the rock formations adjacent the oil-water boundary 5 and is more easily freed from the water.

through the leading and treating boreholes several times in order to sufciently heat the underground rock'formations bearing the oil. These rock formations have a p0- rosity of -about 25% and it is therefore necessary to circulate a quantity of heated oil which is from 2-6 times :i

the quantity of the liquid contained in the rock formations. Circulating of this quantity of heated oil will transfer suicient heat to the rock formations to release the oil therefrom. Thus it is apparent that the circulating oil will pass several times by the point from which the sam-V p'le is taken.

After the oil-water junction 5 has passed the leading hores 1 and the samples indicate that nothing but water had seen discharged from the leading boreholes, the leading bores are then employed as the flooding boreholes.

Whenthe leading boreholes are now used as the ilooding boreholes the entire extraction process is moved to the next boreholes in the direction of arrow c and repeated.

Also after the oil-water junction 5 has passed the leading boreholes 1 as shown in the drawing, the substances may then be added to the flooding water in order to improve the interfacial and surface tensions between the contacting :oil and water surfaces.

The most essential factor for the satisfactory extraction of oil from the deposit according to the present invention is the ratio of the viscosity of the oil to that of the water. If the viscosity of the water is close to thatof the oil or even greater than the viscosity of the oil, the

removal of the oil from the deposit can be more easily and rapidly achieved. The viscosity of the aqueous phase can be increased in the usual way by adding suitable and known chemicals. By way of example, carboxymethylcellulose or cement may be added to the saltwater. However, more satisfactory results are obtained by the addition of substances which increase the viscosity of the water and simultaneously decrease the specific gravity thereof as, for example, emulsions of oilin water (5 to 20% of oil,in water) which emulsions can readily be prepared from the llooding water and the crude oil contained in the deposit.

The yield of oil from the deposit can be further increased by adding CO2 in a known manner to the circulating medium consisting of oil and water. Concentrations of CO2 from 15-30% are preferable. 'The carbon dioxide mitted to the moving ooding water..

By the application of these substances as described above, the relationship between the viscosities of the oil and water is improved to increase the speed by lwhich the extraction of the oilis carried out. The presence of these substances in the oil and water will preclude the formation of channels in the deposits between the oil and water. However, when the speed of ow of the oil through the deposit is increased the friction is also correspondingly increased and accordingly losses in Vpressure will arise. In order to compensate for these pressure losses the flooding water is increasingly looded through the bores which are positioned in the flooding water section just after the oil-water junction has passed.

The entire deposit is divided into treating sections which may be treated separately according to the present invention. The length of such a treating section is indicated by B and is defined by the distance between successive lead-4 ing bores. The width of the treating section is indicated at A and is defined by twice the space between two leading bores of a. series. The series ofbores positioned in the direction of arrow c of section II can be treated only posit are. treated. The -variation of the temperature in the present treating section, i.e. that-defined by A and B is shown at 6, and 7 indicates the graduallyincreasing temperature in the treating section which has become incorporatedinto the flooded section I. Curve 8 shows the heat in' the next successive treating section which heat is introduced primarily by the heat exchange between the heated ooding water and the circulating oil.

Thus itcan be seen that the process according to t-he present invention provides for thoroughly and continuously extracting the contents or"l an underground deposit of liquid bitumens step by step wherein the process can be closely controlled according to conditions encountered in the deposit'.` The important conditions are encountered primarily in the area of the oil-water junction surface. The'deposit' is partially heated by one treating section after the other with the contents of the deposit serving asl the heating medium. The Iheating of the deposit decreases theviscosity of the oil and establishes a better relationship between the viscosities of the oil and water,

so as to enable a more rapid' and complete extraction ofthe oil from the deposit.` 'Ilheheated contents of the deposit are circulated between neighboring boreholes of the treatment section'lL While'the heated contents are circulated under pressure a closed pipe system aboveground, a substance isintroducedinto the heated contents to either ohangethe physical properties or adapt them tov given conditions as indicated by periodic samples taken from the -circulating oil. In addition to the rapid and complete extraction [of the liquid bitumens from the deposit, losses are reduced by avoiding the formation of water channels in the deposit.z

The -ehiciency of the process can be further improved by preventing excessive losses of heat trom the circulating oil.' This can be'accomplished by insulating the pipelines positioned in the treating and leadingboreholes with 'insulation' and the walls of the boreholes the pipelines withinl the boreholes are provided vwith spacers'which center the pipelines within'the boreholes and subdivide the `length of the borehole into smaller sections.

Tofurther assist in thecomprehension of the present invention, a specific operating example of this process will next be described in'detail.

A parainicpetroleum deposit sealed under a pressure of l'l3'atrnospheres was exploited. The rocks of the de- VposiVconSiSted of an'oi-l sand having a porosity of 25% and an average permeability of 600 millidarcys. The deposit`was located in an anticline in an ascending depth ranging from lOOIto 3,100 m. and was about 30 m. thick, Its extension in length was 4,000 m. and its average width 1,500m.

The deposit was developed by rows of bores, whereby v ofa diameter' ofv 1.6 81 mm. into which an ascending tube having a diameter of 77.8 mm. was mounted. This tube was provided with an insulation layer having a thickness of 20 mm. and surrounded with a thin-wailed plastic casing. The air between the exterior casing and the ascending tube was displaced lby CO, and then partially evacuated. Aboveground the bore tubes were connected with a closed intermediate container and a pump. The two rows of bores adjacent ooding section I served as so-called treatment section. In adjacent bores of a transverse row each second bore served as a treating bore- All of the other bores served as leading bores. Oil was extracted through the leading bores under a pressure maintained therein and pressed through the neighboring treating bores again into the deposit where it was heated. A nuclear reactor served as a source of heat.

The process was started by introducing underpressure 10 m/h. of flushwater into the first row of the iiushingbores and extracting 9 m.3/h. of oil from the extraction bores. 6 m.3/h. of oil was simultaneously extracted through the leading bores aboveground and reintroduced by means of the pump at a pressure of 60 atmospheres above the closing pressure through the neighboring treatthrough the leading bores proceeded, the circulating quantity of oil was slowly increased simultaneously with thea-"- quantity of the tlush rwater and that or' the extracted oil.

After a circulation of 120 days a decrease in the viscosity of the circulating oil was observed, conditioned by the temperature. After another days the discharged oil reached the desired temperature. First traces of water indicated that the oil-water junction zone was approaching the first row of bores of the treating section. 20% by volume of- CO2 were then added to the oil prior to its entering the treating bore. When the circulating medium discharged from the leading bores contained more than 50% of water, the mixture of oil and water arriving through the circulation was emulsilied in addition to the carbon dioxide. A

The discharge of pure water from the leading bores after another 60 days indicated that the oil-water junction zone had passed by the first row of bores orfthe treating section. Thereafter the circulation through the first rows of bores of the treating section was stopped and said bores then used as ushing bores.

The water emerged after 26o-350 days from the new row of bores in the treating section, so that the next row H4-50 m? per day and one quarterof the iield has been l exploited after 3 years. yThe oil yield ofthe deposit is 30% higher than in case the usual ushing and extraction process without a treating section had been applied.

It will be understood that this inventionv is susceptible to modification in order to adapt it to dilerent usages and conditions, 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 the process of extracting liquid bitumens from underground deposits the pressure of which exceeds the bubble pressure of the liquid bitumens, the steps of forming a plurality of bores into the underground deposit of. liquid bitumens in the direction of exploitation of thedeposit, extracting the liquid bitumens from bores into the highest portions of the deposit, ooding water through other bores into the deepest portions of the deposit simultaneously with the extracting of the liquid bitumens to maintain a pressure on the liquid bitumens which is greater than the `bubble pressure thereof, withdrawing liquid bitumens derived from the deposit from bores in an intering a plurality of lbores into the underground deposit of liquid bit-umeus in the direction of exploitation of the deposit, extracting the liquid bitumens from bores into the highest .Lwrtions of the deposit, flooding water through other bores into the deepest portions of the deposit simultaneously with .the extracting of the liquid bitumens to maintain a pressure on the liquid bit-umeus which is greater than the bubble pressure thereof, withdrawing liquid bitumens from bores between the flooding extracting hores, and heating the withdrawn bitumens and recirculating the so heated bitumens through other bores located between said ooding and extracting bores into the deposit to heat the same, and adding substances to the water to improve the extraction qualities of the liquid bitumens as the junction between the water and the liquid bitumens passes the withdrawing bores.

3. In the process'of extracting liquid bitumens from underground .deposits the pressure of which exceeds the bubble pressure of the liquid bitumens, the steps of Y forming a plurality of hores into the underground deposit of liquid bitumens in the direction of exploitation of the deposit, extracting the liquid bitumens from extracting bores into the highest portions of the deposit, ooding water through flooding bores into the deepest portions of the deposit simultaneously with the extracting of the liquid bitumens to maintain a pressure on the liquid bitumens whichv is greater than the bubble pressure thereof, withdrawing liquid bitumens fnom leading bores between said flooding and extracting bores, and heating the withdrawn bitumens and recirculating .the so heated bitumens through treating bores located between said flooding ,and extracting bores into the deposit to heat the same, said leading and treating bores having walls and pipelines passing therethrough defining spaces therebetween, and introducing CO2 into said spaces to insulate against heat losses from the heated liquid bitumens.

4. In the process as claimed in claim 3 wherein the CO2 is maintained at a pressure less than atmospheric.

5. In the process of extracting liquid bitumens from underground deposits wherein the pressure exceeds the bubble pressure of the gases dissolved, in the liquid bi- I maintaining a pressure on said liquid bi-tumens higher than the bubble pressure of the gases dissolved in the liquid bitumens, circulating the contents of said deposit without production therefrom in a circulating section of said deposit defined by leading bores and treating bores located between said flooding bores and said extraction bores said circulating the contents comprising withdrawing a portion of said contents through said leading bores, heating said portion of said contents and recirculating said portion of said contents through said treating bores where-by said contents are heated, the viscosity of said liquid bitumens is lowered and said liquid bitumens are advanced in the direction of said extraction bores.

6. The process as defined in claim 5, wherein said contents are brought to the surface through said leading bores and said contents are again returned to said deposit through said treating bores without separation of any of the components of said contents with closed circulating between said treating bores and said leading bores whereby heat is distributed throughout said deposit.

7. In the process of extracting liquid bitumens from underground deposits wherein the pressure exceeds the bubble pressure of the gases dissolved in the liquid bitumens, the steps of forming a plurality of bores into an underground deposit of liquid bitumens in the direction of the highest portion of the deposit, extracting said i liquid bitumens from extraction bores positioned in a section of the highest portion of said deposit, ooding water through ooding bores positioned in a section of the deepest portion of said deposit whereby an oil-water Contact surface results between said water and said liquid bitumens and simultaneously with said extracting of the liquid bitumens maintaining a pressure on said liquid bitumens higher than the bubble pressure of the gases dissolved in the liquid bitumens, circulating the contents 'i of said deposit without production therefrom in a circulating section of said deposit defined by leading oores and treating bores located between said flooding bores and said extraction bores said circulating the content-s comprising withdrawing a portion of said contents through said leading bores, heating said portion of said contents, adding swbstances to said liquid bitumens to improve said oil-water contact surface as said oil-water contact surface approaches said leading bores, adding substances to said water to improve said oil-water contact surface as said oil-water contact surface passes said leading bores and recirculating said portion of said contents through said treating bores whereby said contents are heated, the viscosity of said liquid bitumens is lowered and said liquid bitumens are advanced in the direction of said extraction bores.

- 8. In the process of extracting liquid bitumens from underground deposits the pressure of which exceeds the bubble pressure of the liquid bitumens, the steps of forming a plurality of 'bores into the underground deposit of liquid bitumens, extracting the liquid rnitumens from bores into the highest portions of the deposit, llooding water th-uough other bores into the deepest portions of the deposit simultaneously with the extracting of the liquid bitumens to maintain a pressure on the liquid 'bitumens which is greater than the bubble pressure thereof, withdrawing liquid bitumens derived from the deposit from bores in an intermediate zone between the ooding and extracting bores, heating the withdrawn bitumens and reci-rcuiating the so heated bitumens through 'other bores located 'between said ooding and extract' mg bores into the deposit to heat the same, said recir culating continued to heat the deposit in the intermediate zone to release substantially-al1 the liquidbitumens from said deposit whereby substantially all of said liquid bitumens is recoverable.

References Cited bythe Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner.

S. J. NOVOSAD, Assistant Examiner,

Claims

8. IN THE PROCESS OF EXTRACTING LIQUID BITUMENS FROM UNDERGROUND DEPOSITS THE PRESSURE OF WHICH EXCEEDS THE BUBBLE PRESSURE OF THE LIQUID BITUMENS, THE STEPS OF FORMING A PLURALITY OF BORES INTO THE UNDERGROUND DEPOSIT OF LIQUID BITUMENS, EXTRACTING THE LIQUID BITUMENS FROM BORES INTO THE HIGHEST PORTIONS OF THE DEPOSITS, FLOODING WATER THROUGH OTHER BORES INTO THE DEEPEST PORTIONS OF THE DEPOSIT SIMULTANEOUSLY WITH THE EXTRACTING OF THE LIQUID BITUMENS TO MAINTAIN A PRESSURE ON THE LIQUID BITUMENS WHICH IS GREATER THAN THE BUBBLE PRESSURE THEREOF, WITHDRAWING LIQUID BITUMENS DERIVED FROM THE DEPOSIT FROM BORES IN AN INTERMEDIATE ZONE BETWEEN THE FLOODING AND EXTRACTING BORES, HEATING THE WITHDRAWN BITUMENS AND RECIRCULATING THE SO HEATED BITUMENS THROUGH OTHER BORES LOCATED BETWEEN SAID FLOODING AND EXTRACTING BORES INTO THE DEPOSIT TO HEAT THE SAME, SAID RECIRCULATING CONTINUED TO HEAT THE DEPOSIT IN THE INTERMEDIATE ZONE TO RELEASE SUBSTANTIALLY ALL THE LIQUID BITUMENS FROM SAID DEPOSIT WHEREBY SUBSTANTIALLY ALL OF SAID LIQUID BITUMENS IS RECOVERABLE.