US3581821A

US3581821A - Cryothermal process for the recovery of oil

Info

Publication number: US3581821A
Application number: US823306A
Authority: US
Inventors: Sigmund L Ross
Original assignee: Petra Flow Inc
Current assignee: Petra Flow Inc; SHUFFMAN ROSE
Priority date: 1969-05-09
Filing date: 1969-05-09
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01
Also published as: AU1492770A

Abstract

A process for the recovery of oil, particularly the secondary recovery of oil is disclosed. The process is based on a series of steps involving the use of cryogenic fluids and the application of high thermal energy to a complex of elongated holes drilled in an oil production formation. Major steps include: establishing a complex of elongated holes arranged in a predetermined geometric pattern which penetrate the oil production formation; injecting pressurized, superheated steam into the holes; fracturing the oil production formation using cryogenic techniques; and recovering the mobilized oil.

Description

United States Patent [72] Inventor Sigmund L. Ross Bronx, N.Y. [21} Appl. No. 823,306 [22] Filed May 9, 1969 [45] Patented June 1,1971 [73] Assignee Petra-F low Inc. New York, N .Y.

[54] CRYO-THERMAL PROCESS FOR THE RECOVERY OF OIL 14 Claims, 16 Drawing Figs.

[52] US. Cl 166/245, 166/263, 166/271, 166/272 [51] Int. Cl ..E2lb43/24, E2 1 b 43/25 [50] Field of Search 166/303, 302, 308, 268, 272, 271, 274, 263, 245

[56] References Cited UNITED STATES PATENTS 3,042,114 7/1962 Willman 166/272 w13,5s1,s21

3,100,528 8/1963 Plummer et a1 166/303 3,129,758 4/1964 Closmann 166/271X 3,273,640 9/1966 Huntington l66/303X 3,276,518 10/ l 966 Schlicht et al. 166/272 3,284,281 11/1966 Thomas".. 166/303X 3,353,598 11/1967 Smith 166/272X 3,393,741 7/1968 Huitt et al. 166/308 3,434,544 3/1969 Satter et al 166/303 Primary Examiner-Stephen J Novosad Allorneysl(enyon & Kenyon and Reilly, Carr & Chapin CRYOGENIC THERMAL ENERGY GENERATOR FLUID INPUT 42 CONDENSER CRYOGENIC FLUID OUTPUT PATENTJ'ED JUN nan sum 1 or 3 FIG.

SUPERHEATER STEAM GENERATOR FIG. 2b

FIG. 20'

FIG. 2e

INVENTOR SIGMUND L. ROSS FIG. 2d

BY M W ATTORNEYS mm JUN nan SHEET 2 0F 3 PRESS o l WELL FIG. 3c

FIG. 3d

2/ WELL I v .7 QL PR R Q I i I g PRESSURE I WELL RESSURE WELL ATTORNEYS PATENTED JUN 1 Ian sum 3 or 3 FIG. 6

CRYOGENIC FLUID INPUT THERMAL ENERGY GENERATOR GAS CONDENSER CRYOGENIC FLUID OUTPUT SIGMUND L. ROSS INVENTOR BYbry w ATTORNEYS CRYO-THERMAL PROCESS FOR THE RECOVERY OF OIL This invention relates to oil recovery processes and, more particularly, to improved processes for the recovery of oil using thermal and cryogenic techniques.

When oil production from a producing well ceases using primary recovery techniques, it is known that additional oil still exists in the stratigraphic trap. Resort is then made to secondary recovery means which employs the general feature of forcing movement of the oil which is present in the formation to a point from which recovery is possible.

Basic methods for the secondary recovery of oil include the following as applied to the oil-bearing field: a) fire flooding, b) water flooding, v) steam flooding, d) gas injection, and e) excavation and retorting. Methods through d employ procedures which will force the oil in place to migrate either directly or'by reducing the viscosity of the oil. The latter is particularly important with regard to highly viscous oils.

Steam flooding has been used in convention techniques to supply force :and to reduce viscosity. The injected steam tends to raise the temperature of the petroleum reservoir. The resulting thermal expansion of the in place petroleum in connection with gas pressure created by steam distillation of a portion of the petroleum forces the oil deposit to move or migrate to a relief zone. Usually this relief zone is the invasion hole drilled into the formation up through which the oil rises.

There are three zones created by conventional steam injection: first, a steam zone near the well bore; second, a hot water condensate zone where the steam condenses; and third, a water and condensate zone where the water and condensate reach the ambient temperature of the reservoir. The heat energy imparted to the deposit must be large enough to drive through two lower temperature zones to get to the deposit. In addition, the heat energy drive must be sufficient to penetrate the dirt and condensed water film covering the walls of the cavity which theinjected steam creates.

In practice, the use of the conventional steam-flooding technique starts with the invasion of a pay zone formation and is continued ata distinct level. The resultant cavity will eventually become so large that the steam is not able to retain its initial heat before reaching the cavity walls. This results in excessive condensation on the cavity walls and increasing difficulty in heating the cavity. The long periods required to stage a field using this technique also make it uneconomical as well as inefficient.

The present invention obviates many of the disadvantages of the conventional steam-flooding operation and provides additional steps which make oil recovery techniques, particularly with regardto secondary oil recovery, highly efficient and economical.

An object of this invention, therefore, is to improve the recovery ofoil using novel thermal techniques.

An additional object is to aid recovery of oil by the use of geometrically'arranged and spaced hole formations.

Another object of this invention is to assist in the recovering of oil by the useof cryogenic methods.

A further object is to provide oil recovery process which is efficient and economical using selected combinations of the above steps.

In accordance with the invention, a method for recovering oil from a formation containing oil in a nonflowable state comprises establishing a complex of elongated holes arranged in a predetermined geometric pattern which penetrate an oil production formation. The method further includes injecting pressurized, superheated steam into at least one of the holes, fracturing the oil production formation using cryogenic fluids and recovering the mobilized oil.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings, and the scope of the invention will be pointed out in the appended claims.

In the drawings:

FIG. 1 illustrates a partly sectioned vertical view of an arrangement for providing pressurized superheated steam to a bore hole;

FIG. 2 a--f shows an elevation view of embodiments of a steam jet nozzle for use with this invention;

FIG. 3 a--f has illustrated plan views of the preferred geometric hole arrangements for use with this invention;

FIG. 4 is a plan view of the five-hole pattern in more detail; and

FIG. 5 is a vertical sectional view of the oil formation using the five-hole arrangement of FIG. 4; and

FIG. 6 illustrates a partially schematic and partial plan view of the steam stimulation-pressure well technique as implemented.

GENERAL DESCRIPTION OF THE INVENTION Although the following cryothermal process of secondary oil recovery and its variations are to be described in general terms, it must be recognized that this technique will vary according to the characteristics of the in place petroleum as sell as the nature of the formation where the petroleum is found.

A major feature of the process is the injection of pressurized, superheated steam into a complex of elongated bore holes. Generally the number of holes will be 10 or less and will be spaced between 75 feet minimum and 600 feet maximum of each other from center to center of the holes. The complex of holes is in specific geometric formation.

The use of superheated steam provides significant advantages over nonsuperheated steam. First, a moderate amount of superheat greatly increases the volume of the steam. The quantity of water required for a given amount of heat energy is therefore greatly reduced. Second, thermal conductivity of superheated steam is less than that of saturated steam, therefore, less heat is lost through pipe walls and more heat energy is delivered to the pay zone. Third, considerably more heat may be extracted from superheated steam for the same amount of fuel used.

The high temperature superheated steam is introduced into the hole complex under veryhigh pressure to create thermal expansion in the oil, to lower the viscosity ofthe oil, to liberate the hydrocarbon gases from the in place petroleum, and to flash much of the connate water present in the formation into additional steam. All of the above combine to generate a force to mobilize the in place oil. In addition, pressure is rapidly built up in the hole which densifies the pay zone immediately adjacent the hole. The degree of densification of the stimulation well, in that region wherein the heat is being introduced, improves the local thermal conductivity, thus permitting more heat energy to bring about in place petroleum migration.

Under certain conditions, the pressurized, superheated steaming alone will cause the oil adjacent the hole to move into the hole where it is carried up and out. The pressurized gases, which rise up the hole above the point at which the steam is energizing, create a pressure differential within the hole which also tends to pull out the oil in place.

A second feature of theprocess is the use of a cryogenically produced oxidizing liquid such as liquid oxygen (lox) in addition to the pressurized, superheated steam to provide additional heat energy to the pay load. Certain formations have faults or cracks which will tend to siphon off some of the injected steam, which detrimentally lower the pay zone temperature. If this occurs, liquid oxygen may be mechanically introduced into the pay zone. The effect of an oxidizing agent such as liquid oxygen being subjected to intense heat and pressure and contacting organic combustible material such as grease, oil, tar asphalt and kerosene is to deflagrate or rapidly oxidize. The material so exposed will burn fiercely and will raise the temperature of the pay zone considerably, as well as the shaft of the elongated hole. The heat generated by the lox oxidation will also flash the connate water in the interstices of the pay zone into additional steam. Secondarily, the deflagration will effectively contribute to fracturing the pay. zone region of the formation. To reiterate, the purpose of the lox is to accelerate the heat stimulation process. Fracturing may occur as a result of this high heat energy level by the mechanism of isotropic or anisotropic expansion. After its initial use, the lox will be used whenever the bore holes of the stimulation wells drops below the temperature of the injected superheated steam.

The hot bore hole produced by the superheated, pressurized steam and the lox injection has further advantageous effects on oil recovery. First, the lighter hydrocarbons become gaseous and expand, which, on rising upwards expands further because of the reduction of ambient pressure on it. This tends to increase the pressure differential in the hole. Any bubbles of gas present in individual oil droplets tend to expand the oil, further destroying any cohesive property of the oil on sand graines and other detritus.

In addition, the existence of temperature differentials as well as pressure differentials at different levels in the bore hole, effectively create a fractionating distillation column tending to break out additional chemical elements which may be present in the oil.

It should be emphasized that both pressurized, superheated steam and the lox injection may be applied to all or selected holes of the hole complex mentioned earlier. This will largely be determined by the nature of the oil in place, the type of formation and the geographical features of the terrain.

A third feature of this process is the use of cryogenic freezing of moisture or fluid in the pay zone region. This may be accomplished by application of a cryogenic fluid to one or a number of the holes if there is sufficient moisture in the soil of the pay zone (e.g. more than percent moisture content). If the moisture content is not this high, a fluid, preferably water, is injected in the desired hole or holes. Then the cryogenic fluid or solid is inserted which rapidly freezes the water. Liquid nitrogen is a preferred freezing agent although pressurized CO may also be effective.

The fluid in the hole is quick frozen. If it is water, it expands and swells and laterally, and to some extent vertically, displaces the pay zone in the region of the hole. The effect of this is to collapse the pores of the formation which squeezes the trapped oil and water in the interstices of the formation. Additionally, the connate water is frozen and expanded. A third effect is to improve, locally, the thermal conductivity of the pay zone both by freezing and by densifieation. The effect of the swelling in a central well, when coupled with the heat and pressure in adjacent or flanking well is to figuratively put the formation through a wringer and the petroleum literally wrung out.

The effect ofimproving local thermal conductivity is important if there is a desire to directionalize the heat flow in the pay zone. In addition to extracting the pay zone oil directly from the superheated hole, it may be desired to use certain of the extreme holes as stimulation holes (i.e. inject the high energy thermal sources there), and other extreme holes, preferably on the other side of the formation, as production holes (i.e. remove the oil there). The heat energy and pressure will cause migration of the oil from the stimulation holes to the production holes from which the oil will be removed. If the thermal conductivity of the formation were increased in the direction of migration of the oil, it would accelerate the migration process by directing the flow of heat from the stimulation holes to the production holes. To this effect, the rapid freezing of a central or pressure hole between stimulation and production holes will be advantageous.

It may be desirable to use pressurized nitrogen gas in addition to and in conjunction with the quick freezing of the pressure well to create additional fracturing and better mobilization of oil.

The cryogenic technique may be used at any stage of the overall secondary oil recovery process as seems advantageous.

DETAILED DESCRIPTION OF THE INVENTION A more detailed discussion of specific embodiments of the invention will now be described.

Referring first to FIG. I, a particular arrangement for injecting the pressurized steam is shown. A water pump 10 draws water through a suction line and supplies the water to a steam generator 11. The steam output is then supplied to a superheater 12 which provides the additional heat energy necessary to superheat the steam to the desired temperature, The pressure of the superheated steam will be controlled by the rate of conversion of water to superheated steam. The pump 10, steam generator 11 and superheater 12 may be provided on a mobile unit. The pressurized, superheated steam is directed through a flexible metal hose 13 which is guided by an overhead support 14. The metal superheated steam line 13, preferably created from stainless steel, is connected to a steam lance 14 which has a head 16 to which a plurality of nozzles 23 is attached. The steam lance 14 is inserted in a predrilled hore hole in tight formations or may be used to bore its own holeby virtue of the high pressure coming from the lance head 16. The diameter of the bore hole must be such as to accept a minimum 10 inches casing I9. The casing 19 must accommodate the steam lance l4 and the oil takeup pipe 20. Pipe 20 has attached to it pressure 21 and temperature 22 indicators which help to determine the nature of the bore hole and pay zone and the appropriate moment for oil removal. Pipe 20 is connected to storage tanks (not shown).

Although the superheated steam injection is similar whether oil is to be removed from the same hole or will be removed from a different hole, FIG. 1 is illustrative of oil removal from the steam-simulated hole.

The head 16 is shown in more detail in FIG. 2 a-f. FIG. 2a shows a cross section of a jet nozzle 23 which is the heart of head 16. The nozzle 23 is shown to have an interior venture arrangement for optimizing the pressure of the steam. FIGS. 2b2f show various arrangements and orientations of the nozzle as it is attached to head 16. In FIG. 2b, a single nozzle 23 is downwardly directed. FIG. 2c shows a single nozzle at to the vertical attached using a rounded elbow. FIG. 2d illustrates a straight tee arrangement for achieving a 90 nozzle attachment which has the capability of adding an additional downward-directed nozzle. FIG. 2e indicates just such a connection by two 90 oriented nozzles attached to steam head 16.

The preferred arrangement is 2]". This arrangement has flve nozzles 23 connected to the steam head 16. One nozzle 23a is directed vertically downward and the others, 2312, 23c, 23d and 23 e, are arranged concentrically and symmetrically in a horizontal plane. Other arrangements of nozzles 23 may also prove advantageous.

The steam slams out of jet nozzles 23 at a speed between a mach 2 and mach 4. The steam lance may thus be used to drill its own hole in loose formations.

As the steam pipe starts down the bore hole, it jets out a continuous flow of steam. The only time steaming is interrupted is when additional lengths of pipe are added. As the steam lance enters the pay zone, the descent of the lance is preferably interrupted and the region of the pay zone will be subjected to a period of steaming for approximately 15 minutes. Then the lance will continue its descent, stopping every 20 feet in soft formations and 10 feet in tight formations. The descent of the lance will continue until the bottom of the pay zone is reached. At this point, the lance will be raised some 3 feet and steaming will continue and will not be interrupted until the temperature of the bore hole drops below a certain level (e.g. 250 F. less than the injected steam) at which point some other step such as lox application, will be used or the process discontinued as to this pay zone area.

Typically, in the initial steaming operation, if the temperature of the bore falls below this prescribed level, the injection of liquid oxygen will then commence. If the bore hole is large enough, the lox will merely be dropped down the hole at intermittent intervals. In the event the bore hole is not large enough to contain'both the steam line and the lox container, steam injection will be interrupted and the steam line will be valved off, disconnected and removed. Then glass containers, about one liter in volume, filled with lox and stoppered with a gas escape tube in place are intermittently dropped down the hole. The containers will burst open striking the bottom of the hole and spattering the lox which had not escaped through the gas relief tube around the region of the hole. The lox, in coming into contact with the heated petroleum flashes into flame, developing intense heat. A

In certain instances, this high localized heat may cause the silica portion of the sands in the pay zone to fuse. In this event, methyl alcohol, chilled to an appropriate temperature, to minus 60 F. for example, and under a predetermined pressure, 300 p.s.i.g. pressure for example, is released through a pipe down the bore hole to impact and splatter on the extremely hot fused silica. Thermal shock follows which shatters the silica, thereby creating a path for subsequently applied super heated steam.

Referring now to FIG. 3, shown are preferred arrangements of geometric hole formations for three to holes. The number of holes will vary depending on the size and nature of the formation. The holes are to be used in applying the superheated steam and lox steps of the invention and the appropriate holes for directionalizing the oil flow using the pressure well technique are indicated as well.

Regarding the pressure hole or well step, reference is now made to FIG. 4. In that figure, a particular arrangement of five wells is shown to indicate the operation of the pressure well technique and the limits of the regions of influence of applied thermal energy.

The first two wells 25, 26, stimulation wells, are drilled in line. The third well 27 is spaced equidistant between the first two 25, 26 and at the same distance from the first two along a line normal to wells 25 and 26. Wells 28 and 29 are located similar to wells 25 and 26 and equidistant from well 27 along a line normal to wells 28 and 29. The center well is called the pressure well, while wells 4 and 5 are called the production wells. The approximate regions of influence of each well are shown by the larger circles surrounding each of the wells.

Well 27 is typically to be filled with water to a point some 10 feet above the pay zone of the formation. Tanks containing liquid nitrogen are lowered into the water. The liquid nitrogen tanks preferably have a quick-opening device to be controlled from the surface which rapidly expels the liquid nitrogen into the water. The water then quick freezes and fractures the formation as previously described. An alternate approach is to circulate either liquid nitrogen or another suitable cryogenic fluid through a closed pipe in the bore hole. It may be desirable to use pressurized nitrogen gas in conjunction with the icecreating pressures to provide additional pressures to the pay zone to further fracture the formation and mobilize the oil.

The pay zone in the vicinity of pressure well 27 is fractured which squeezes out some trapped oil and directionalizes the flow of heat from the stimulation wells 25 and 26 to the production wells. The in place petroleum will follow the least resistant thermal path and the newly created fissures from the stimulation wells 1 and 2 to the production wells 28 and 29.. The oil will then fill the bore holes of wells 28 and 29 flowing up to the surface and out. Certain highly viscous oils may require application of heat to the production wells bore zone to increase the rapidity of flow.

After the pressure well-freezing has been applied, the superheated steam is further applied to the stimulation wells. When this is done, the well opening on the surface is closed by a collar. In the collar is welded a threaded pipe nipple.

The purpose of the nipple is to regulate the pressure buildup in the stimulation wells; in addition, it permits the attachment of a secondary heat line which may convey escaping heat energy into the bore holes of the production wells to facilitate oil flow as mentioned above.

Referring now to FIG. 5, the injection profile of the fivewell approach using the center pressure well is shown, including the direction of heat flow. Also indicated are the limits of the local primary heat influence. Note that the depths of the wells are sloped toward the production wells to take advantage of natural drainage.

A preferred embodiment for implimenting the pressure well technique is shown for a five-well arrangement in FIG. 6. A thermal energy generator 30 supplies the pressurized, superheated steam to a main steam line 31. The main steam line 31 is connected to the

stimulation wells

32 and 33 which would typically be closed by a collar with an attached nipple as previously mentioned.

Secondary heat lines

37 and 38 are attached to the nipples in the stimulation collars and connect to the

production wells

34 and 35. The output oil lines from the production wells connect to line 51 which is brought to oil storage tanks 45. The gaseous portions of the production well output are forced out of the storage tanks 45 as the tanks fill up. The gas enters gas vent line 43 or auxiliary gas feed line 41. If the gas is transmitted through gas vent line 43, it is condensed in gas condenser 39 by the circulation of cryogenic fluids. The distilled gases are collected in distillate storage tank 40. The distillate may be drawn off by output line 43. The auxiliary gas feed line 41 disposes of the gas in some other predetermined manner. Thus, all portions of the oil well out put are collected and may be used.

Extensions to a second well complex is shown by

wells

47, 48 and 49. In this case, well 47 will be the pressure well and

wells

48 and 49 will be the production wells. Similarly, a third and additional complexes may be added by adding three additional wells, e.g. 50, 51,52 to the existing complex.

It should be also noted that if fracture zone exists in the formation, it may not be necessary to use a center pressure well. Also, it may not prove necessary to directionalize the heat flow in an existing formation. What will determine if all or part of the above process is used are the following general criteria: I) permeability of the formation pay zone; 2) porosity of the pay zone; 3) the percentage of oil, water or gas in place; 4) reservoir pressure (if any); 5) type of formation of the pay zone; and 6) the Terrastatic pressure confining the pay zone.

The following are examples of how the invention may be used in a particular oil-bearing formation. The examples were chosen to indicate multistep application of the invention.

Example 1 Conditions: Pay zone formation is located on the forward slope of an anticline. Depth is 1,672 feet down. Permeability of the formation is 46 millidarcies. Percentage of porosity of the formation is 34.4. Of this 34.4 percent, 27 percent is oil and 56 percent is water, the rest being gas. API gravity is 24.

Process: Construct the five-well complex as shown in FIG. 4. The wells are generally drilled to the depth shown in FIG. 5 taking advantage of natural drainage. Fill the center well with water from the bottom to a point 10 feet above the pay zone or 10 feet up into the rock mass capping the oil sands. Lower tanks filled with liquid nitrogen into the water and quickly release the liquid nitrogen to rapidly freeze the water, thereby trapping the nitrogen tanks in place.

Apply the superheated steam to the bore holes of both stimulation wells. Position the jet nozzles of the steam line approximately 1 inch from the face of the formation at the bottom of the pay zone. The nozzle is directed horizontal and tangent to the radius of influence of densification peripheral to the pressure well. Inject superheated steam at 950 p.s.i.g. and 950 F. into the stimulation wells. The effective rate of steam flow per second is l'k pounds (by weight).

Continue steaming for 24 hours, with a collar closure including pipe nipples around the bore holes.

After 24 hours, disconnect the steam line and remove it from the bore hole.

Drop liquid oxygen in liter glass containers down the bore hole at the rate of one every l5 minutes. Continue for 1 hour.

After lox application, reconnect the steam lines and continue steaming for 7 days. Resume lox treatment during the 7 days only if the bore hole temperature drops below the temperature of the steam.

After the 7 days, test the trapped tanks in the pressure well to determine whether they can be hauled up. (If they can, it means that sufficient heat has migrated to the center well and wholly or partially melted the ice.) After hauling up the tanks, check the water in the bore hole for gas infusion, for oil presence and for temperature. If the temperature is substantially above freezing, stop steaming, disconnect the steam lines and begin dropping lox at minute intervals for 2 hours in the stimulation wells. Reconnect the steam lines and resume steaming for another 7 days. During this second 7 day interval continue checking the pressure well every 6 hours for temperature, oil show and gas infusion.

Once the entrapped tanks are removable and there are oil and/or gas infusions, it means the heat energy is migrating effectively. When the temperature of the center well reaches half that of the stimulation wells, the producing wells are quick frozen to improve the thermal conductivity of that area by the techniques already described.

If the oil in the pay zone is more viscous between the pressure well and the producing well, than between stimulation well and pressure well, apply superheated steam to the production wells using steam lines and jet nozzles for a period of 2 hours at the same pressure and temperature as that existing in the stimulation wells.

lf additionally necessary, remove steam lines, pump in water under high pressure of an amount in gallons equal to the pay zone depth and follow with liquid nitrogen to improve the directionalized heat flow toward the production wells.

Eventually the oil will begin to surge up the production wells.

Example 2 Given the same conditions as example 1 and following similar procedures, if at the end of the second 7-day period, the middle well temperature has not risen substantially to at least half the temperature of the stimulation wells, it means that the migrating heat energy has been stopped by a permeability barrier or fault.

Then steam or pump the water out of the center well. Connect a secondary steam line to the pipe nipple on the stimulation wells and insert in the center well. After 3 hours, remove the steam line and pour some crude oil down the well so that it covers the pay zone but does not penetrate due to its viscosity. Drop lox down the center bore hole at 15-minute intervals for an hour. Then an insulated line is used to apply methyl alcohol chilled to a temperature of approximately 60 F. and forced under pressure (300 p.s.i.g.) down the center hole. The purpose, of course, is to apply thermal shock to fracture the formation and break through the fault. This procedure may be repeated if necessary.

Eventually, oil or gas infusion will be visible in the center hole and the process described in example 1 should be continued.

Example 3 In a syncline geographic situation (trough), the general fivewell implementation will use four stimulation wells and a center producing well without a central pressure well. The general procedures of example 1 should then be followed.

As indicated by the foregoing examples, the exact process depends on the nature of the terrain and the response of the pay zone to the applied steps.

While general reference has been made to the use of the present invention with regard to secondary recovery of oil, no limitation precludes use of any or all of the steps of this invention to primary oil recovery as well.

Accordingly, while there have been described what are considered to be the preferred embodiments of this invention, it Wlll be ObVlOUS to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim is:

l. A method for recovering oil from a formation containing oil in a nonflowable state comprising the steps of establishing a complex of elongated holes arranged in a predetermined geometric pattern which penetrate an oil production formation;

injecting pressurized, superheated steam into at least one of said holes;

fracturing the oil production formation using cryogenic recovering the mobilized oil.

2. A method as described in claim 1, which further includes the step of injecting liquid oxygen into at least one of said elongated holes.

3. A method as described in claim 1, wherein said fracturing step is accomplished by adding a liquid to at least one of the wells and rapidly freezing said liquid by the introduction of liquid nitrogen.

4. A method as described in claim 3 wherein said liquid is water.

5. A method as described in claim 3 which also includes use of pressurized nitrogen gas to fracture the formation.

6. A method as described in claim 1, wherein said recovery of oil is from the holes wherein said superheated steam is applied.

7. A method as described in claim 1, wherein said steam is injected into predetermined ones of said holes and said oil is recovered from different predetermined ones ofsaid holes.

8. A method as described in claim 1 wherein said elongated holes include at least one stimulation hole and at least one production hole and said steam is injected into said stimula' tion holes and said oil is recovered from said production holes.

9. A method as described in claim 8 which further includes a pressure hole which is used for the fracturing step to apply the cryogenic substances.

10. A method as described in claim 9 which includes the steaming of stimulation holes as described with a collar closure at the top of the hole to seal the hole.

11. A method as described in claim 9 which includes inserting a predetermined quantity of water in the pressure hole, and rapidly circulating the cryogenic fluid by way of pipes passing through water to freeze the water.

12. A method as described in claim 9 which includes inserting a predetermined quantity of water in a pressure hole and inserting tanks of liquid nitrogen in the pressure hole to rapidly freeze the water.

13. A method for recovering oil from a formation containing oil in a nonflowable state comprising the steps of establishing a complex of elongated holes arranged in a predetermined geometric pattern which penetrate an oil production formation, said holes including at least one stimulation hole, at least one pressure hole and at least one production hole;

injecting pressurized, superheated steam into at least one stimulation hole;

injecting liquid oxygen into at least one stimulation hole;

introducing water into said pressure well and rapidly freezing said water with liquid nitrogen; and

recovering the mobilized oil from at least one production hole.

14. A method as described in claim 13 wherein the soil adjacent said pressure well is densitied and reduced in temperature below 32 F., thereby substantially increasing its thermal conductivity.

UNI'IED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,581,821 Dated June 1., 1971 lnventor( Sigmund L. ROSS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet [73] "Petra-Flow Inc. New York, N. Y. should read Oscar Shuffman, Scarsdale N. Y.

Signed and sealed this 15th day of June 1971 (SEAL) Attest:

EDWARD I I.FLETCHER,JR. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

Claims

2. A method as described in claim 1, which further includes the step of injecting liquid oxygen into at least one of said elongated holes.
3. A method as described in claim 1, wherein said fracturing step is accomplished by adding a liquid to at least one of the wells and rapidly freezing said liquid by the introduction of liquid nitrogen.
4. A method as described in claim 3 wherein said liquid is water.
5. A method as described in claim 3 which also includes use of pressurized nitrogen gas to fracture the formation.
6. A method as described in claim 1, wherein said recovery of oil is from the holes wherein said superheated steam is applied.
7. A methOd as described in claim 1, wherein said steam is injected into predetermined ones of said holes and said oil is recovered from different predetermined ones of said holes.
8. A method as described in claim 1 wherein said elongated holes include at least one stimulation hole and at least one production hole and said steam is injected into said stimulation holes and said oil is recovered from said production holes.
9. A method as described in claim 8 which further includes a pressure hole which is used for the fracturing step to apply the cryogenic substances.
10. A method as described in claim 9 which includes the steaming of stimulation holes as described with a collar closure at the top of the hole to seal the hole.
11. A method as described in claim 9 which includes inserting a predetermined quantity of water in the pressure hole, and rapidly circulating the cryogenic fluid by way of pipes passing through water to freeze the water.
12. A method as described in claim 9 which includes inserting a predetermined quantity of water in a pressure hole and inserting tanks of liquid nitrogen in the pressure hole to rapidly freeze the water.
13. A method for recovering oil from a formation containing oil in a nonflowable state comprising the steps of establishing a complex of elongated holes arranged in a predetermined geometric pattern which penetrate an oil production formation, said holes including at least one stimulation hole, at least one pressure hole and at least one production hole; injecting pressurized, superheated steam into at least one stimulation hole; injecting liquid oxygen into at least one stimulation hole; introducing water into said pressure well and rapidly freezing said water with liquid nitrogen; and recovering the mobilized oil from at least one production hole.
14. A method as described in claim 13 wherein the soil adjacent said pressure well is densified and reduced in temperature below 32* F., thereby substantially increasing its thermal conductivity.