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CA1122115A - In situ oil extraction from underground formations using hot solvent vapor injections - Google Patents

In situ oil extraction from underground formations using hot solvent vapor injections

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Publication number
CA1122115A
CA1122115A CA 341079 CA341079A CA1122115A CA 1122115 A CA1122115 A CA 1122115A CA 341079 CA341079 CA 341079 CA 341079 A CA341079 A CA 341079A CA 1122115 A CA1122115 A CA 1122115A
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CA
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Grant
Patent type
Prior art keywords
oil
solvent
vapor
formation
injection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA 341079
Other languages
French (fr)
Inventor
Paul R. Tabor
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Hydrocarbon Research Inc
Original Assignee
Hydrocarbon Research Inc
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Filing date
Publication date
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Abstract

ABSTRACT OF THE DISCLOSURE

Heavy oil or bitumen extracted and removed from underground oil bearing formations having low permeability such as tar sands by injection of hot hydrocarbon solvent vapor into a single well hole at a pressure not substantially exceeding the pressure in the formation to effectively heat and extract the bitumen. The hot solvent vapor is passed downwardly through an annular passage of concentric piping place in the well bore and is injected out through upper perforations in the casing and into the formation The hot solvent vapor condenses in the formation and drains along with recovered oil through lower perforations back into the bottom end of the inner pipe, from which the product oil and solvent mixture is pumped to above ground. The solvent is partially reclaimed from the oil product by distillation means and the solvent fraction is reheated and reinjected into the well bore for further use.
The solvent used should be matched to the characteristics of the bitumen in the tar sands formation for most effective recovery of bitumen, and contains substantially aromatic

Description

IN SITU OIL EXTRACTION USING HOT SOLVENT VAPOR IN~ECTION

B~CKGROUND OF T~IE INVENTION
___ Field o~ the Invention:
This invention pertains to -the improved recovery of heavy oil and tars from underground forma-tions containi.ng same by the injection of hot hydrocarbon vapors to heat the formation and extract the oil. It per-tains more particularly to the effective recovery of such oils from relatively impermeable formations such as tar sand by hot hydrocarbon solvent vapor injection into the formation to extract and recover the oil using a single well hole.

Description of Prior Art:
. . . _ ~
The in situ recovery of oil from underground formations is well known and there are several prior art patents in the area of oil recovery by injecting either aqueous or hydrocarbon solvent vapors into oil formations. Some of -these patents use vaporiz~d solvents such as benzene, tolu~ne/ carbon disulfide, kerosene, and a variety of other aromatic sol-vents ~ and mixtures of solvents. These known processes usually depend upon the use of two or more boreholes, one borehole used for injection of the heated solvent vapor into the formation and one or more boreholes used for recovering the oil/solvent liquids. For example, U~S. 3,608,538 to Terwilliger shows injecting hot pressurized vapor into one well at the top of an oil bearing formation to promote oil production from another adjacent well. But these prlor art systems require that the oil bearing formations have suf~icient permeability to allow lateral fluid communication between the injection and production wells. However, in many oil bearing formations, such as tar d ~

sands, the original permeability is too low to permi-t using a two well production arrangement.
Oil recovery methods using single well systems have been used for producing oil from oil shale formations, which have been previously fractured by explosive means to make them permeable, follo~ed by injecting hot gases and vapors into the formation. For example, U.S. 3,515,213 to Prats and U.S. 3,695,354 to Dilgren et al disclose shale oil recovery from such permeable shale ormations by injecting heated fluids to stimulate oil recovery from the same well. However, the prior art apparently do0s not disclose recovering heavy oils and/or tars from essentially impermeable formations by inject-ing hot hydrGcarbon sclvent vapor into an upper portion of the formation and recovering oil along with condensed solvent from a lower portion of the formation using a single well hole.
Thus, the present invention is directed to the effective recovery of heavy oils and tars by hot vapor injection using single wells, without regard to or depending on lateral fluid communication between adjacent wells, by directing the hot vapor to desired portions of the formation and recovering the liquids from a lower portion of the well.

SUMMARY OF TEIE INVENTION
This invention comprises an improved method for in situ recovery of heavy oils and tars from underground formations, and particularly for the effective recovery of bitumen from tar sands formations having low initial permeability using hot hydrocarbon solvent vapor injected into a single well hole to heat and extract the oil. The solvent is heated in a boiler and/or distillation unit at a pressure only sligh-tly exceeding that in the oil formation. The heated vapor is injected into the well hole through a rigid casing and exits the casing through upper perforations therein and passes into the formation. The vapor is prevented from continuing further down the casing by a packer set in the annular space between the casing and an inner pipe string. The hot solvent vapor condenses in the oil bearing formation, heats it and also extracts the oil or -tar (bitumen) from the formation. Extracted oil, along with condensed solventl moves generally downwardly through the formation and reenters the well casing through lower perforations. The collected liquid is pumped to above ground level through the inner pipe.
Above ground, the solvent fraction is reclaimed by evaporation in a separator and/or distillation unit. The reclaimed solvent is usually recycled to the boiler for re-heating and reinjection into the well. The remaining heavy oil from the separator or distillation unit is then ready for further treatment either at the site of for shipment to a refinery.
The hydrocarbon solvent used should be vaporizable at temperatures which will not cause appreciable cracking of either the solvent or the oil in the formation and must be miscible in the oil. The solvent vapor injected into the well should be as hot as possible, without causing significant cracking of the solvent as it passes downward through the casing, so as to enter the formation in substantially vapor form. Preferred solvents or solvent mixtures are aromatic compounds or hydrocarbon mixtures containing subs-tantial amounts o~ aromatic materials. Examples of such hydrocarbon solvents are benzene, toluene, xylenes, naphtha or other aromatic solvents having boiling range of about 200-400F.
The vapor temperature at the wellhead should be at least abou-t 400F, and preferably 500-700F. Since the oil composition to be recovered is variable from one field or formation to another, the properties of the solvent or solvent mixture used should be matched to the characteristics of the oil formation to provide for the most effective recovery of oils therefromO
In this process, the solvent vapor is injected at pres-sure not appreciably exceeding the underground formation static pressure, and preferably is at pressure only about 20~100 psig greater than the formation pressure. If the solvent vapor injection pressure appreciably exceeds the formation static - pressure, severe solvent vapor lea]~age and/or rupture of the overburden soil layer may occur, particularly if -the oil bearing formation is located near the earth surface. Further-more, high operating vapor pressures cause the solvent, which is condensed in the formation to migrate and dissolve in the heavy oil bitumen farther away from the well hole. Although some migration of solvent away from the injection port is desired, sufficien-t solvent must be a~ailable to cause the extracted oil or bitumen to flow to the well. At high operating vapor pressures, the bitumen absorbs more solvent but does not become fluid enough to flow to the well bore, which contributes to solvent loss in the formation and thus is undesirable. Thus, the forced migration of solvent away from the well bore is undesirable, as reclaiming of the solvent is therehy made more difficult.
As the hot solvent vapor contacts the oil formation or tar sand matrix, the vapor condenses and warms the formation.
At the same time, the condensed solvent dissolves and dilutes the oil. The diluted bitumen flows through the lower perfora-tions back into a sump at the bottom of the well casing, from which it is pumped to the surface for solvent separation and reclaim. As the solvent continues to leach out the oil or bitumen, the ~ormation warms and allows the oil and condensed solvent liquid to flow more easily to a lower portion of the well. It is essential that a liquid layex be maintained in the formation between the vapor injection and oil drainage points of the casing as a means of controlling vapor flow and preventing its breakthrough to the drainage points. As the bitumen is removed from the formation the permeability is increased, thereby permitting oil recovery from distances farther from the vapor injection point.
Such injection of hot solvent vapor per this invention eliminates the tendency to form water-oil emulsions and significantly improves the viscosity of -the heavy oil produced.
Also the viscosity of the recovered solvent/bitumen mixture is usually low enough to minimize or avoid sanding problems within the casing perforations. By maintaining consistent vapor flow rates and a low viscosity of the extracted liquid, the recovered liquid does not lift and transport sand grains as easily as would a more viscous liquid such as water, to cause undesirable plugging of -the casing perforations. Thus, this oil recovery process usually will not require a gravel pack placed around the lower perforations of the well casing, or screening around perforations in the inner pipe to filter out sand particles.
Use of a movable packer positioned in the annular space between the casing and inner pipe and vertically within the oil ~ormation allows improved control over this oil extraction process. After fluid communication has been established between the vapor injection point and oil removal point outside the well casing, a fluid flow channeI develops through the formation for carrying out the oil or bi-tumen. Once the fluid flow channel develops, preferential extraction of bitumen occurs along that channel. To preven-t the hot solvent vapor from flowing directly through this channel, the casing packer is preferably repositioned -to vertically separate further the vapor in~ection Level and oil removal level in the casing.
This can be accomplished preferably by initially locating the fluid injection and removal points in the lower portlon of the tar sands formation. Then as oil recovery proceeds, the point of vapor injection is progressively moved upward in the casing, usually by adding an additional packer above the existing or first one, and thereby causing vapor injection to occur at a point higher on the casing. Furthermore, if the packer is not made movable, an increase in the vapor injection pressure or a more rapid oil pumping rate could result in undesirable vapor breakthrough between the injection and recovery points external of the casing. Again, it is essential that a liquid layer be maintained between the vapor injection and oil drainage points as a means of controlling solvent 2Q vapor flow and preventing such vapor breakthrough.
By controlling location of the injection point for the hot solvent vapor, a volume of tar sand can be effectively stripped of bitumen to form a generally inverted cone shape having its apex near the bottom of the wellbore. When the oil content of the produced liquid decreases to an unfavorable level, vapor injection is stopped. After a period of time, the drainage liquid can be pumped from the well. The formation wil~ produce ~hese drainage liquids for some period of time after vapor injection has ceased, due to a combination of increased formation temperature and gravity flow of liquids.
Depending upon operating conditions, the formation and bitumen characteristics, and the solvent(s) used, oil recoveries of up to a~out 90 percent can be achieved.
The light fractions of the recovered oil provide the most convenient source for the hydrocarbon solvent vapors needed for injection and they can be conveniently obtained in the field by partial distillation of the recovered oil. In some oil formations it may be advantageous to improve the solvent power of the injected hydrocarbon vapor by adding an externally produced aromatic hydrocarbon material, such as benzene or toluene. Portable skid mounted distillation equipment is provided at the well site to accomplish this oil fractionation and blending in the field.
As recovery of oil continues from adjacent individual wells being produced, the recovered areas will ultimately inter-sect and fluid communication between adjacent wells will be established. This condition is not an essential feature of the present invention and serves only to provide a further stage for the recovery of oil and injected solvent from the formation.
As completion of the oil recovery process from a par-ticular well or wells, some quantity of condensed solvent willremain in the formation. A substantial part of this solvent can be reclaimed by injecting suitable hot fluids which are inexpensive and readily available. One procedure is to run a ; normal steam drive on the borehole, so that the steam will further warm the formation and cause an increased flow of oil and solvent into the well. However, such use of steam also fills the pore spaces with water and may inhibit flow of the remain-ing solvent to the well bore. Also, steam soaking may cause some flow restriction due to sanding problems when liquid is 3Q pumped from the weIl. As another alternative, two adjacent wells both of which have been previously operated as single well s~stems, can provide a path of communication an~ allow the injection of steam into one well and recovery o~ oil and solvent from an adjacent well. Depending upon formation characteristics, the solvents used and operating conditions, the reclaiming of solvent and its recycle for reinjection into the formation can approach 90 percent efficiency.

DESCRIPTION OF T~E DRAWI~GS
~igure 1 shows a typical oil well and hydrocarbon vapor generating equipment for hot vapor injection into and oil recovery from an oil or tar bearing formationO
Figure 2 shows a typical oil well and oil bearing formation using a movable type packer and selected vapor injection in accordance with a preferred embodiment o~ the invention.
Figure 3 is a diagram of an experimental recover~ vessel showing details of the perforated injection and drain ports in simulated tar sand formation.
Figure 4 is a graph showing the improved oil recovery obtained from hot hyd~ocarbon vapor injection into a simulated tar sands formation.
DESCRIPTION OF PREFERRED EMBODIMENTS
As illustrated by Figure 1, a borehole generally indicated at 10 is drilled through overburden 11 into an oil bearing formation 12, which may preferably be a tar sands formation such as the Athabasca tar sands located in Alberta, Canada, or the Utah tar sands of the United States. Casing 14 is inserted into borehole 10 and cemented in place within the overburden 11, at 13.

..... , ~ .
TubincJ string 16 is installed ~ithin the casing 14 and retainea in place by packer 18 installed therebetween and within the for-mation. Upper perforations 17 are provided in the ca~ing above the packer for injecting hot hydrocarbon vapor in-to the formation 12, and lower perforations 19 are provided in the casing below the packer for return of oil and solvent~ Pump 20 is provided, preferably at the lower end of tublng 16, for recovery of oil drained from the formation into sump 21 by pumping the oil to above ground in accordance with established practice in the industry.
A hydrocarbon solvent liquid at 22 is provided to a heated boiler 24 and initially vaporized at a sufficient pres-sure to force the hydrocarbon vapor through annular space 15 and upper perforations 17 into the oil bearing formation 12~
; Typically, heavy oil and tar deposits are found at depths less than about 1000 feet, requiring a vapor pressure of approximate-ly 500 psig or less. In most cases it is desirable to superheat the vapor to overcome heat losses which occur in piping the vapor to the individual well and down to the formation, and to permit condensation of the hydrocarbon vapor in the oil bear-ing formation. This could be pre~erably accomplished with a superheater passage incorporated into the boiler 24.
The hot hydrocarbon vapor passes down annular space 15 and through upper perforations 17 into the oil bearing formation 12. In the formation the hot hydrocaxbon vapor cools, condenses and reacts with the heavy oils and/or tars entrapped therein to heat and solubilize them and thereby reduce their viscosity.
The small annular space existing around the outside of casing 14 provides an initial passageway ~or the hot solvent vapor to contact the ~ormation. The resulting reduced viscosity oil flows into sump 21 at the bottom of inner tubing 16. ~rom this sump the oil is li~ted to the surface by pump 20 in accordance with well established practice in the industry.
Other type lift pumps, such as a down hole electric pump, g_ could also be used. A pump located at the bottom of the well is desirable for several reasons. It reduces the bottom hole pressure and thus promotes flow of oil to the sump 21 and tubing 16. Also, as the bottom pressure is reduced, the solvent vaporizes at a lower temperature and can more easily penetrate the formation, and therefore lowers the temperature to which the formation 12 must be heated to recover the oll.
Finally, the pump raises the pressure of the liquid mixture being purnped up through production tubing 16, thus preventing it from being boiled by the downward flowing hot vapor steam and extracting heat therefrom.
The recovered oil and condensed hydrocarbon liquid is passed to separation and/or distillation unit 26, where it is heated and some solvent vapor recovered as overhead stream 30 for reinjection as a pressurization vapor into the well casing 14. The recovered bottoms oil liquid product is withdrawn from the distillation step at 36.
After continuous operation and recovery of oil is achieved, a substantial quantity of solvent vapor ma~ be generated from khe oil distillation step 26. In such case, use of an ex~ernal hydrocarbon liquid at 22 for start-up purposes may be reduced or -terminated as desired. Alternatively, if desired, an external aromatic hydrocarbon liquid having improved solvent power such as benzene or toluene may be added at 22 as needed to improve the extraction and recovery of the heavy oils from formation 12.
Fuel for the boiler 24 and still 26 may be supplied either by combustion of an externally supplied fuel oil or gas, or by combustion of a portion of the recovered oil product 36.
Combustion of the recovered oil product would be the preferred option, unless the cost of stack gas scrubbing and environmental

2~

controls outweighed the fuel cos-t advantages of burning the crude oll.
A preferred alternatlve for oil recovery utilizing a movable packer concept is shown in Figure 2. The well casing 1~ is initially perforated at 17 and 19 and packer 18 is positioned intermediate the perforations as shown. Pressurized hot solvent vapor enters the tar sand formation 12 through the upper perforations at 17. The resulting solvent/oil mixture extracted from the formation reenters the casing 14 through the lower perforations at 19 and is pumped to above ground through inner pipe 1~. For effective recovery of oil from the entire formation, the lower perforations 19 should usually be located as close as is reliably possible to the effective lower boundary of the formation, such as at least about 3 feet and preferably 5 to 10 feet above the lower boundary of the forma-tion. These distances can be varied t:o match the physical positioning of the packer and casing perforations.
After fluid communication is established through the formation 12 between perforations 17 and 19, hot solvent vapor 2Q injection is continued until oil recovery begins to d~cline from the particular portion of the formation being produced. Packer 18 is then moved upward in the casing 14 to the point indicated "A" after the casing is reperforated at 17a. Hot solv~nt vapor injection is resumed and continues as previously described, with the vapor being injected into a new upper portion of the oil bearing formation 12. The packer 18 is similarly moved periodically upward through the well casing 14 to new position 18a and the casing is reperforated above the packer as needed to allow the 501vent vapor injection to occur progressively nearer the upper boundary of the tar sand formation. Removal of the recovered solvent/oil mixture is accomplished by pumping the liquid up through the inner tubing 16 as previously de-scribed.
An alternative procedure to moving packer 18 upward in well casin~ 1~ is to perforate the casing as indicated at 17a, position a new packer 28 at position "A", and leave the or.iginal packer 18 set within the casing 14. In this manner, a series of new packers can be positioned at higher levels in the casing 14. ~s each new packer is positioned after the casing is ~urther perforated at higher levels, the hot solvent vapor contacts a new and larger vertical portion of the tar sand formation 12.
As illustrated in Figure 2, the original path of fluid flow is from the upper perforations at 17 to the lower perfora-tions at 19. When new packer 28 is installed, the new fluid path is from perforation 17a to perforation 19. Ultimately, hot solvent vapor will enter the tar sand formation at a point ~ near the upper boundary 12a of the formation, while the result-;~ ing oil/solvent liquid mixture will reenter the casing at the lower perforations 19 near the lower boundary of the tar sand formation 12. Using this preferred procedure, substantially the entire vertical thickness of tha formation can,be effectively exposed to the action of the hot solvent vapor for extraction and reco~ery of oil therefromO
In a similar manner, the injection of hot vapor may be initiated through casing perforations and the extracted oil and solvent removed through perforations all located initially in the upper portion of an oil bearing formation. The lower or ., drain per~orations are then progressively located further down-ward in the casing, so as to expose n~w portions of the oil formation to the injected hot vapor to heat the formation and extract the oil. Using this procedure, substantially the o~

entire thickness of the forma-tion can be effectively exposed to the hot solvent vapor for extractlon and recovery of the oil.
While individual wells 10 are usually intended to be operated independently, a plurality of wells may be served by a single hydrocarbon solvent vapor supply and distillation unit.
The boiler and distillation unit will preferably be a direct fired pressure vessel mounted on a skid and capable o~ being moved from well site to well site as oil production from the individual groups of preferably three wells become exhausted.
The wells would be preferably arranged as an equilateral tri-angle pattern, with spacing of more than about 100 feet but less than 600 feet on a side.
Using the hot vapor injection method of this invention, the single wells should be produced until the stripped sand areas ~rom adjacent wells intersect, to eliminate as much as possible of the interface between heavy oil and clean sand and to promo-te maximum reclaim and reuse of solvent. Once linkage has been achieved between adjacent wells, ~arious secondary recovery techniques may be used to recover additional oil and solvent from the formation.
The operation and bene~its of this invention will be further illustrated by re~erence to the following examples and experiments, which should not be construed as limiting the scope of this inventionO

To achieve realistic conditions ~or experiments on oil recovery from heavy oil formations such as tar sands deposits having low permeability, it is essential to achieve a thoroughly compacted and nearly impermeable structure closely representative 3U of the original tar sands material in place undergroundO To provide such a simulated tar sands formation, Utah tar sand, having characteristics as described in Table 1, was hot packedinto a pressurizable vessel of 10 lnch diameter and 10 inches , CH~RACTERISTICS OF UTAH TAR SAND
_ _ Formation Location: Vernal County, Utah Tar Sand As-Received Density 2,1~4 grams/cc Water 2.40 W %
Oil 11.6 W ~ - Toluene Soluble Specific Heat __ _ Temperature C F
: 0.377 100 212 0.387 120 248 - 0.397 140 284 :~ 0.405 ~60 320 ~ 0.414 180 356 : 0.427 200 3g2 Extracted Oil ~Toluene Soluble, Toluene Free) API Gravity 8.6 Sulfur, W % 0.35 Viscosity : Centipoise F
1487 i5-~0 874 190 acuum Distiliation OF

5 ml 651 10 ml 750 20 ml 880 25 ml 940 30 ml 975- 32.46 W~
975~65.12 W%
Loss 2.42 W%

Oil-Free Sand Specific Gravity 2.363 grams/cc Compacted Bulk Density 1.56 grams/cc Screen Analysis Mesh W %
+50 26 67 70 - 1~0 18.43 100 - 140 7.96 140 - 200 4.83 20Q - 325 5.24 - 325 5.96 deep and allowed to cool; thereby closely simulating the low permeability of the sand in its original undisturbed condition.
The pressure vessel was provided with a 1/4" standard pipe nipple (.360 in. inside diameter) injection port centrally located in the top and a 1/4" standard pipe perforated drain port centrally located in the bottom as shown in Figure 3.
Using this configuration, the injected hot vapor was forced to pass outwardly through the sand formation before reaching the drain port. Approximately 22,000 grams of the tar sand material was packed into the vessel at a temperature of about ~0 250F and allowed to cool to ambient temperature. A rod was centrally located in the vessel prior to packing of the sand, then removed to provide a ~ored 5/8" diameter hole vertically through the center of the sand to simulate a well bore.
The vessel was closed with the injection pipe being inserted into the cored hole in the tar sand. The resulting simulated tar sand formation was contacted with toluene vapor introduced through the injection port at the top of the vessel at pressures up to about 50 psig and average temperatures up to about 350F. Using a cyclic pressurization mode during a 4.5 hour test, 96 grams of oil were recovered from the sand or about 4% of the oil present. In a continuous operation mode, 158 grams ~,2~

of oil were recovered in four hours or about 6.5% of that present showing still better per~ormance for the continuous vapor injection mode. In another test run under similar con-tinuous injection mode conditions with vapor heated to 380F
average temperature, 19.6 W % of the oil present was recovered.
Thus, it is apparent that using increased temperatures of the hydrocarbon vapor injected provides a corresponding increase in oil recovery from the tar sand. The area of extracted oil was generally conical shaped with the apex near the drain hole, as shown in Figure 3v Figure 4 shows a comparison of oil recovery obtained from Utah tar sand with continuous solvent liquid injection and with continuous hot solvent vapor injection over about 40 hours duration. It can be seen that the solvent vapor is appreciably more effective in recovering oil from th~ tar sand than solvent liquid, apparentl~ due to the higher temperature and greater mobility of the vapor. Also, it was unexpectedly noted that sand plugging problems (sanding) in the drain holes from the vessel were substantially reduced with solvent vapor Z0 injection as compared to steam injection.

Additional experiments were conducted using Utah tar sands hot packed into the reactor vessel as per Example 1 to simulate its original condition, with the injection of hot solvent vapor being made about 3" from the top and also about

3" from the bottom of the vessel. Figure 4 shows a comparison between injection of hot toluene solvent vapor near the top of the simulated tar sand formation and its injection nearer the bottom, without a cored intervening passageway. It can be seen that the injection of hot vapor nearer the top oE the simulated formation is more effective for recovery of bitumen, and is the preferred injection mode. Specifically/ in RunNo. 13 with top injection of toluene vapor, a total of 61~
of the oil originally in place was recovered during 43 hours of operation. In Run No. 14 with bottom injection of toluene vapor, only 57% of the oil in place was recovered in 43 hours o~ operation.

Samples from the Athahasca tar sand deposit in Canada as described in Table 2 and from a California heavy oil sand deposit were also tested in simulated formations using the new recovery method by hot hydrocarbon vapor injection per Example 2. Even using the bottom injection mode ~or hot toluene vapor, 90.7~ of the original oil in place was recovered from Athabasca tar sand, and 90.9% was recovered from the California oil sand after about 44 hours operation. In all bases, the sand in the vicinity of the bore hole was found to be stripped clean and completely free of oil This volume of completely extracted sand increased in size as the solvent vapor injection continued with an approximately constant ratio of oil extracted to solvent vapor fed. That is to say, the diameter of the circular shaped stripped area grew approximately as the square root of vapor injeckion time for constant injection rates of solvent vapor.

Solvent reclaiming is also a critical factor in the successful application of this solvent vapor injection method for oil recovery from tar sand ~ormations. It was found during these tests on simulated tar sand formation that aromatic hydrocarbon solvent dissolved readily in the heavy oil or tar, creating a mushy mixture of tar sands and solvent from which all the solvent does not flow to the drain hole. As a result, some ~2~

solvent is retained at the interface between the clean, e~trac-ted sand area and the original unaffected tar sand. It was found desirable to operate with the highest possible rate of solvent vapor injection without causing solvent vapor break-through to the oil recovery point, both to maximize production from a particular well and also to minimize the thickness of the mushy sand zone and the retention of solvent in the forma-tion. A rate o~ approximately 10 to 20 barrels of solvent evaporated per hour per well with standard 7" diameter casing lG is reasonable. At this rate, the retention of solvent will be approximately 2.2 lb. of solvent per square foot of exposed tar sand.
Following the solvent injection and recovery of oil, steam was in~ected cyclically to heat the sand and recover significant quantities of additional oil and solvent.
Although this invention has been described for the re-covery of oil from tar sand deposits, it is also applicable to the secondary recovery of heavy oils remaining in previously pumped oil fields~ While the above description discloses pre-ferred embodiments of my invention, it is recogniæed that other modifications will be apparent to those skilled in the art.It is understood, therefore, that my invention is not limited only to those specific methods, steps or combinations of same described, but covers all equivalent methods and steps that may fall within the scope of the appended claims.

Tar Sand As-Received Density, gm/cc 1.93 Water, W % 1.15 Oil (benzene-soluble), W % 15.2 Sulfur, W % 4.98 Sand, W % 83.65 Extracted Oil (Benzene-Soluble) Gravity, API 8.9 Viscosity, centipoise @1750F 315 @ l90oF lg2 @2120F 110 @230 F 70 Vacuum Distillation _ _ _ _ 5 ml 655F
10 ml 712F
20 ml 765 F
30 ml 810F
40 ml 875F
50 ml 940F
56 ml 9750F- 40.0W %
975 F+ 57.4W %
Loss, 2.6W %
Oil-Free Sand Specific Gravity, g/cc 2.59 Compacted Bulk Density, g/cc 1.59 Screen Analysis, W %
Mesh ~50 23.2 50 - 70 49.1 70 - 100 18.5 100 - 1~0 4.4 140 - 200 1.8 200 - 325 1.7 - 325 1.4

Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A method for recovering heavy hydrocarbons from an underground oil bearing formation comprising the steps of:
(a) drilling a well hole through overburden and extend-ing into the oil formation, and inserting a tubular casing into the hole;
(b) perforating the casing at upper and lower locations vertically within the formation;
(c) providing an inner pipe within the casing and position-ing a packer in the annulus between the casing and inner pipe at an intermediate level within the formation, so that the casing perforations are above and below the packer;
(d) injecting hot hydrocarbon solvent vapor into the annulus at pressure not more than about 100 psi greater than the formation pressure, so that the vapor passes outwardly through the upper perforations and into the formation to warm and extract oil from the formation;
(e) allowing the extracted oil and condensed solvent liquid to drain through perforations below the packer into the lower end of the casing and piping, then pumping the recovered oil and solvent liquid mixture out through the inner pipe to above ground;
(f) reclaiming a solvent fraction from the recovered oil and solvent mixture by distillation; and (g) reinjecting the reclaimed solvent fraction into the well hole.
2. The method of claim 1 wherein an externally provided hydrocarbon liquid is heated to generate solvent vapor for initial injection into the formation to start the oil extract and recovery.
3. The method of claim 1 wherein the hydrocarbon solvent vapor is an aromatic hydrocarbon which is at least partly derived from the recovered oil by partial distillation on site.
4. The method of claim 1 wherein an externally procured hydrocarbon is added to the recovered oil and the vapor derived by partial distillation of the mixture is injected as solvent vapor into the oil bearing formation.
5. The method of claim 1 wherein the hydrocarbon solvent vapor is substantially aromatic and selected from the group consisting of benzene, toluene, xylene, naphtha, and mixtures thereof.
6. The method of claim 1 wherein the hydrocarbon solvent is substantially toluene.
7. A method of claim 1 wherein the hot solvent vapor is introduced into the annulus at 300-700°F temperature and at pressure not more than about 50 psi greater than the formation pressure.
8. The method of claim 1 wherein the oil recovered is pumped to above ground using a downhole type pump having low suction pressure.
9. The method of claim 1 wherein the oil bearing forma-tion is tar sands containing bitumen having low initial per-meability and the solvent vapor contains an aromatic compound.
10. The method of claim 1 wherein recovered oil product is used to fire and heat the distillation step (f).
11. The method of claim 1 wherein the hot solvent vapor is injected into the formation continuously and the resulting oil and solvent mixture is recovered continuously from the well hole.
12. The method of claim 1 wherein the oil bearing formation is Utah tar sands.
13. The method of claim 1 wherein the injection of hot hydrocarbon vapor and recovery of oil and solvent is commenced at a lower portion of the oil formation, and then the vapor injection point is moved progressively upward to an upper portion of the formation, so as to extract oil successively from fresh upper portions of the formation.
14. The method of claim 1 wherein the injection of hot vapor is commenced at an upper portion of the oil formation, and then the vapor injection point is moved progressively downward to a lower portion of the formation 50 as to extract oil successively from fresh lower portions of the formation.
15. The method of claims 13 or 14 wherein oil is extracted from substantially the entire thickness of the oil formation.
16. The recovery method of claim 1 in which a single distillation unit provides hot hydrocarbon solvent vapor to two or more adjacent wells.
17. The method of claim 1 wherein the hot hydrocarbon solvent vapor is injected into multiple adjacent well holes and the resulting oil and solvent liquid mixture is recovered therefrom until the areas of stripped formation intersect, after which hot vapor injection is terminated.
18. The method of claim 1 including the additional step of injecting a heated fluid into the formation to extract additional solvent retained in the stripped oil formation.
19. The method of claim 1 wherein an additional packer is positioned above the original packer so that the vapor injection point is moved upward in the oil containing formation.
CA 341079 1978-12-29 1979-12-03 In situ oil extraction from underground formations using hot solvent vapor injections Expired CA1122115A (en)

Priority Applications (2)

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US97463078 true 1978-12-29 1978-12-29
US974,630 1978-12-29

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CA1122115A true CA1122115A (en) 1982-04-20

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Cited By (11)

* Cited by examiner, † Cited by third party
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US6662872B2 (en) 2000-11-10 2003-12-16 Exxonmobil Upstream Research Company Combined steam and vapor extraction process (SAVEX) for in situ bitumen and heavy oil production
US6708759B2 (en) 2001-04-04 2004-03-23 Exxonmobil Upstream Research Company Liquid addition to steam for enhancing recovery of cyclic steam stimulation or LASER-CSS
US6769486B2 (en) 2001-05-31 2004-08-03 Exxonmobil Upstream Research Company Cyclic solvent process for in-situ bitumen and heavy oil production
US7363973B2 (en) 2001-06-21 2008-04-29 N Solv Corp Method and apparatus for stimulating heavy oil production
US8596357B2 (en) 2006-06-07 2013-12-03 John Nenniger Methods and apparatuses for SAGD hydrocarbon production
US8602098B2 (en) 2010-02-16 2013-12-10 Exxonmobil Upstream Research Company Hydrate control in a cyclic solvent-dominated hydrocarbon recovery process
US8684079B2 (en) 2010-03-16 2014-04-01 Exxonmobile Upstream Research Company Use of a solvent and emulsion for in situ oil recovery
US8776900B2 (en) 2006-07-19 2014-07-15 John Nenniger Methods and apparatuses for enhanced in situ hydrocarbon production
US8788250B2 (en) 2007-05-24 2014-07-22 Exxonmobil Upstream Research Company Method of improved reservoir simulation of fingering systems
US8899321B2 (en) 2010-05-26 2014-12-02 Exxonmobil Upstream Research Company Method of distributing a viscosity reducing solvent to a set of wells
US9488040B2 (en) 2013-12-03 2016-11-08 Exxonmobil Upstream Research Company Cyclic solvent hydrocarbon recovery process using an advance-retreat movement of the injectant

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6662872B2 (en) 2000-11-10 2003-12-16 Exxonmobil Upstream Research Company Combined steam and vapor extraction process (SAVEX) for in situ bitumen and heavy oil production
US6708759B2 (en) 2001-04-04 2004-03-23 Exxonmobil Upstream Research Company Liquid addition to steam for enhancing recovery of cyclic steam stimulation or LASER-CSS
US6769486B2 (en) 2001-05-31 2004-08-03 Exxonmobil Upstream Research Company Cyclic solvent process for in-situ bitumen and heavy oil production
US7363973B2 (en) 2001-06-21 2008-04-29 N Solv Corp Method and apparatus for stimulating heavy oil production
US8596357B2 (en) 2006-06-07 2013-12-03 John Nenniger Methods and apparatuses for SAGD hydrocarbon production
US8776900B2 (en) 2006-07-19 2014-07-15 John Nenniger Methods and apparatuses for enhanced in situ hydrocarbon production
US8788250B2 (en) 2007-05-24 2014-07-22 Exxonmobil Upstream Research Company Method of improved reservoir simulation of fingering systems
US8602098B2 (en) 2010-02-16 2013-12-10 Exxonmobil Upstream Research Company Hydrate control in a cyclic solvent-dominated hydrocarbon recovery process
US8684079B2 (en) 2010-03-16 2014-04-01 Exxonmobile Upstream Research Company Use of a solvent and emulsion for in situ oil recovery
US8899321B2 (en) 2010-05-26 2014-12-02 Exxonmobil Upstream Research Company Method of distributing a viscosity reducing solvent to a set of wells
US9488040B2 (en) 2013-12-03 2016-11-08 Exxonmobil Upstream Research Company Cyclic solvent hydrocarbon recovery process using an advance-retreat movement of the injectant

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