Thermal oil recovery

Dec. 27, 1966

3,294,167

J. V. VOGEL

THERMAL OIL RECOVERY

Filed April 13, 1964

Sheets-Sheet 1

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FIG. I

HEAT PRODUCED

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FIG. 2 inventor:

by:

JOHN V. VOGEL

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HIS AGENT

Dec. 27, 1966

3,294,167

J. V. VOGEL

THERMAL OIL RECOVERY

Filed April 13, 1964

Sheets-Sheet 3

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FIG. 3

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FIG. 4 inventor: JOHN V. VOGEL

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HIS AGENT

J. V. VOGEL

THERMAL OIL RECOVERY

Dec. 27, 1966

Filed April 13, 1964

3,294,167

Sheets-Sheet 3

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FIG. 5 inventor: JOHN V. VOGEL

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3,294,167

Patented Dec. 27, 1966

United States Patent Office

3,294,167 THERMAL OIL RECOVERY

John V. Vogel, Houston, Tex., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware

Filed Apr. 13,1964, Ser. No. 359,200

Claims. (CI. 166—11)

This invention relates to a method of recovering oil from underground formations and pertains more particularly to a method of driving oil from a first formation by thermal means, said first formation being positioned adjacent a second formation from which oil had been previously recovered by thermal means or methods.

It is well known that heat can be employed to recover hydrocarbons from underground formations through wells drilled in the underground petroleum deposits. Various methods have been developed over the years for the primary or secondary recovery of oil from underground formations by thermal means. The manner in which the hydrocarbons are recovered often depends upon the temperature to which they are heated and/or whether or not combustion takes place. Thus, hydrocarbons can be removed from an underground formation by heating the formation to a temperature sufficient to reduce the viscosity of the hydrocarbon to a mobile condition whereby, upon reduction of pressure, the heated oil may flow back into the heat injection well, or alternatively may be driven to a second well, commonly known as a production well, by thermal drive means. At higher temperatures of heating, pyrolysis of the hydrocarbons may take place with the resulting products being driven through the formation and collected at the production well. Such action may take place during in situ combustion wherein the air and the fuel are injected in a formation and burned to heat the formation, or where merely air is injected into the formation at a temperature sufficient to promote underground combustion within the formation. Pyrolysis can also be caused to occur without in situ combustion by heating the underground formation with a hot heat-carrying medium such as steam, water, hydrocarbon liquids or vapors, and other liquids, gases or vapors.

In any of the well-known thermal production methods of underground formations, a substantial amount of heat is retained in the now depleted or substantially depleted underground hydrocarbon-bearing formations. In addition, those formations forming the cap and base rocks, that is, the formations above and below the former oilbearing formation, absorb significant amounts of heat and stay hot for many months.

In some oil fields, especially those containing low grade and low viscosity oils which must be heated before it is possible to recover them from an underground formation, a primary consideration of the economic feasibility of recovering such an oil would be the cost of heating the oil-bearing formation.

It is therefore a primary object of the present invention to provide a method of recovering hydrocarbons from an underground formation by use of the thermal recovery method.

A further object of the present invention is to provide a method of recovering oil from an underground formation wherein a thermal recovery method is employed utilizing a hot fluid which has been heated by previously forcing it through a heat-bearing underground formation from which hydrocarbons, sulfur or other materials have previously been extracted.

Another object of the present invention is to produce two adjacent oil-bearing underground formations by thermal recovery means wherein first one formation is heated and the oil therein recovered therefrom and sub10 sequently the second formation is heated by heat retained in the first formation so that the oil can subsequently be recovered from the second formation.

These and other objects of the invention will be understood from the following description taken with reference to the drawing, wherein

FIGURE 1 is a diagrammatic view showing two adjacent oil fields or oil-bearing formations taken in longitudinal section and provided with a pair of wells each for carrying out the method of the present invention; and

FIGURES 2, 3, 4 and 5 are diagrammatic views showing other arrangements of heating equipment for carrying out the method of the present invention in adjacent oil-bearing formations which are shown in longitudinal section.

In accordance with the method of the present invention, hydrocarbons may be recovered from a subsurface formation by providing communication through a well between the surface of the earth and a first subsurface formation containing hydrocarbons, recovering hydrocarbons from said first subsurface formation by a thermal recovery method, completing the thermal recovery method in the first formation in a manner whereby a substantial amount of heat remains in the first formation, providing communication between the heated first subsurface formation and a second subsurface formation containing hydrocarbons, forcing fluid into and out of the heated first subsurface formation whereby the temperature of the fluid is increased, conveying the fluid from out of the heated first subsurface formation and into a second subsurface formation to heat the hydrocarbons therein, and producing the hydrocarbons from the second subsurface formation.

As shown in FIGURE 1, a first subsurface formation 11, originally containing hydrocarbons, is in communication with the surface 12 of the earth through a pair of wells 13 and 14 which are preferably lined by well casing closed at the top and open or perforated at the bottom whereby a fluid may be forced down well 13, through the formation 11 and up well 14.

In the vicinity of the first subsurface formation 11, a second subsurface formation 21 containing hydrocarbons exists. This second subsurface hydrocarbon-containing formation 21 is also in communication with the surface o fthe earth through one or more wells 22 and 23 which are open or perforated at the bottom so that fluid may enter the hydrocarbon formation 21. In FIGURE 1 the wells 13 and 22 may be considered input wells while the wells 14 and 23 may be considered output wells. The output well 14 of the first subsurface formation 11 is in fluid communication with the input well 22 of the second subsurface formation 21 which contains hydrocarbons. If the two subsurface formations are relatively close to each other, the output well 14 may be connected to the input well 22 by a pipeline 24 which may be provided, if desired, with pumps (not shown) in order to convey any fluid in the pipeline a considerable distance.

FIGURE 1 of the drawing illustrates the method of the present invention wherein hydrocarbons have been recovered to a substantial degree from the first subsurface formation 11 by any suitable thermal recovery method wherein a substantial amount of heat is left in the first formation 11. Thus, with the pipeline 24 not being connected to well 22, air or a combination of air and fuel may be injected down well 13 to carry out an in situ combustion within the formation 11 so as to drive the hydrocarbon products therein out of the formation through the output well 14. Instead of carrying out an underground combustion in the first formation 11, a thermal fluid drive may be carried out wherein steam or hot water or a combination of both, or any other heat-carrying

3,294,167 fluid, is injected down well 13 to reduce the viscosity of the hydrocarbons in the formation 11 and/or to pyrolyze them and cause them to be produced from output well 14.

After the thermal recovery method in the subsurface formation 11 has been completed, the output well 14 is connected by means of pipeline 24 or any other suitable means to the input well 22 in communication with the second subsurface hydrocarbon-bearing formation 21 which represents an oil field independent of formation 11 and located some distance therefrom in which thermal recovery of the hydrocarbons is to be carried out. In carrying out the method of the present invention, a cold heat-absorbing medium is pumped through pipe 15 and down injection well 13 into the hot depleted formation 11. The injected medium or fluid may flow either through naturally permeable rock or through artificially induced fractures in the formation 11. It is not necessary that the injected fluid or medium contact all portions of the hot rock of the formation in order to recover heat therefrom. Heat will flow by conduction from the hot rock to cooler portions of the formation in immediate contact with the heat-absorbing medium. After absorbing heat from the rock in the first formation 11, the hot medium is led back to the surface through output well 14 and then transported through pipe 24 to input well 22 of the undepleted hydrocarbon-bearing formation 21. In some oil fields the depleted hot first formation furnishes all the heat required to heat the fluid sufficiently to carry out the thermal recovery method of the second undepleted formation 21. If more heat is required within the second formation 21, additional heat may be supplied to the fluid in pipeline 24 by any suitable means, as by a heater 26 positioned in the line. Alternatively, heat may be supplied to the underground formation 21 as necessary from other suitable sources well known to the art. If desired, partial combustion of the material in the second subsurface formation 21 may be carried out.

It is not necessary that the depleted first underground formation 11 and the second undepleted underground formation 21 be in different fields, formations or strata, or that they be separated by faults or impermeable structures, such as a salt dome. The two fields or formations 11 and 21 may, in fact, simply be portions of one continuous large deposit.

Any of several fluids may be employed as the heatabsorbing medium for use in accordance with the present invention. Various media may include, but are not limited to liquids, gases, and vapors, such as water, steam, hydrocarbon liquids, hydrocarbon gases or vapors, air, nitrogen, carbon dioxide, carbon monoxide, and other gases.

It is not essential to the basic invention that the same fluid or medium be injected into the hydrocarbon-bearing or undepleted formation as was used to absorb heat from the hot depleted formation. Thus, one fluid or medium could be used to absorb heat from the hot depleted formation and the heat picked up by the fluid could then be transferred by means of well-known heat-exchanged devices to another heat-carrying medium for injection into the undepleted or hydrocarbon-bearing formation. This modification of the method is illustrated in FIGURE 2 of the drawing showing a hot depleted formation 31 in the vicinity of a hydrocarbon-bearing undepleted formation 34. Input and output wells 32 and 33, respectively, are in communication between the earth surface and the hot depleted formation 31 while input and output wells 35 and 36, respectively, are in communication with the oil-bearing formation 34 to be depleted. The output well 33 of the first formation 31 is connected by pipeline 37 to a heat-exchange device 38 while a second fluid in the heat exchange device 38 is led therefrom through pipe 39 down the input well 35 into the second formation 34 to be subjected to thermal recovery methods for hydrocarbons. For example, water could be injected through input well 32 into the hot depleted deposit 31 where it absorbs heat and is vaporized to steam which is led to the surface through discharge well 33 and thence into the heat exchanger 38. In the heat exchanger 38, the steam gives up its heat to evaporate or heat a second fluid, for ex5 ample a hydrocarbon liquid, which is then injected through pipeline 39 into the input well 35 and thence into the oil-bearing formation 34. The heated oil in the formation 34 is then driven out the discharge well 36.

The method of the present invention may be carried out jO in either a continuous or intermittent manner. In either case it is not essential to the process that two wells be used for conveying a fluid into and out of a hot depleted formation in order to absorb the heat therefrom.

FIGURE 5 illustrates an example where only one well is 15 used in the hot depleted formation and another in the formation to be depleted. A cold heat-absorbing medium is pumped into well 85 down through insulated pipe 86 past a packer 87 and into a hot depleted formation 88. The injected medium or fluid may flow either through 20 naturally permeable rock or through artificially induced fractures up through formation 88 from which it absorbs heat. It is led back to the surface through annulus 89 and brought out outlet 90. The hot medium or fluid is then led or pumped through line 91 to well 92 in a second 25 formation 95, which is to be depleted. The hot fluid is led down insulated pipe 93 past packer 94 and into formation 95 from which it causes the thermal recovery of products which are carried up to the surface through annulus 96 and through outlet 97.

³⁰ FIGURE 4 illustrates an intermittent operation in which a cold fluid could be injected down pipe 41 of well 42 past packers 43, 44 and 45 and into a hot depleted formation 46. During this period a valve 47 in a conduit 48, which is in communication between the lower hot depleted ³5 formation 46 and an upper oil-bearing undepleted formation 49, is closed. After the fluid injected into the hot formation 46 is at the desired pressure and temperature, valve 50 in line 41 would be closed and valve 47 in conduit 48 would be opened to allow the hot fluid from formation ⁴⁰ 46 to flow up conduit 48 into the oil-bearing formation 49 to be heated. At this time valves 51 and 52 at the wellhead would be closed. After the hydrocarbons in the upper formation 49 had been heated to a temperature sufficient to reduce their viscosity, they would flow into 45 the well 42 above the packer 44 and be removed therefrom, as by a pump 53 of any type well known to the art. While the oil-bearing formation 49 is illustrated as being above the hot depleted formation 46 in FIGURE 4, it is readily apparent that it could just as well be below 50 the hot depleted formation 46 and a suitable piping arrangement made to heat the oil-bearing formation.

The method of the present invention may be employed in various arrangements of wells which are in communication with one or more or the formations needed 55 in carrying out the method of the present invention. In FIGURE 3 an oil-bearing undepleted formation is illustrated as being positioned above a hot depleted formation 62. One well 63 is in communication between the surface of the earth with both of the formations 61 and 60 62 whereby a cold fluid is injected through pipe 64 past a casing packer 65 and into the lower hot formation 62 while at the same time hot oil may be produced up the annulus 66 between the pipe 64 and the casing 63. A second well 67 passes through both formations 61 and 65 62 and is in communication with both so that hot fluid from the lower formation 62 may be led upwardly to the upper oil-bearing formation 61 to heat the formation and drive oil therefrom. The second well 67 is either closed at the top or is provided with a packer 68 just above the 70 upper oil-bearing formation 61.

If desired, an intermediate well 69 may be provided in communication between the upper oil-bearing zone 61 and the earth surface. Thus, a cold fluid would be injected through pipe 64 down into the hot depleted for75 mation 62 and thence along the formation to the output

3,294,167 well 67 which would lead the heated fluid into the upper oil-bearing formation 61. The oil in the formation 61 would be driven therefrom through the intermediate production well 69, or would be driven into well 63 above the packer 65 and thence upwardly through the annulus 5 66 to be discharged through pipe 70 at the top of the well.

The method of the present invention of using the heat in a depleted formation may be used in any other method which requires the injection of a hot heat-carrying medium or fluid into a formation. These methods may be contin- io uous or intermittent. They may be one well or multiwell methods and may include, but are not limited to, steam soak, steam drive, hot water flood, hot solvent drive, underground pyrolysis, etc. The method may also be used to pre-heat a formation before utilizing an in situ 15 combustion recovery method.

By using the method of the present invention a high overall efficiency of heating formations and recovering hydrocarbons therefrom by thermal recovery method is achieved with savings of up to 60% in the cost of heat- 20 ing and depleting an oil-bearing reservoir. Where water is used as the heat absorbing medium, another advantage is enjoyed by eliminating any need for treating the water used in the drive or flood. Thus, impure water can be injected into a hot depleted formation where it is vaporized 25 with the impurities carried by the water being left underground where they do not contaminate the oil-bearing formation to be treated.