US3163215A - Producing plural subterranean strata by in situ combustion and fluid drive - Google Patents

Description

Dec. 29, 1964 c. A. STRATTON 3,163,215

paooucms PLURAL. SUBTERRANEAN STRA'I'A BY IN SITU COMBUSTION AND FLUID DRIVE Filed Dec. 4. 1961 FIG.

INVENTOR. C.A. ST RATTON A T TORNEYS United States Patent "ice PRODUCING PLURAL SUBTERRANEAN STRATA BY IN SITU COMBUSTION AND FLUID DRIVE Charles A. Stratton, Bartlesviile, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Dec. 4, 1961, Ser. No. 156,620 5 (Ilaims. (Cl. 166-10) This invention relates to a process for the production of oil from two or more subterranean strata by in situ combustion and fluid drive.

In oil fields found in various locations, such as in the Monagas Field in Venezuela and the Danglemeyer Lease of North Texas, difl'erent oil zones having oil in diiferent viscosities are spaced apart by impermeable barriers or strata. A less'viscous' oil zone may overlie a more viscous oil zone or vice versa. Also, a more viscous oil zone may lie between adjacent less viscous oil zones from which they are separated by impermeable barriers. The less viscous oil zone may lie intermediate two or more viscous oil zones.

- Accordingly, it is an object of the invention to' provide an improved process for producing two or more spacedapart, oil-bearing strata separated by permeable layers. Another object is to provide a process for producing such strata utilizing a combination of fluid drive and in situ combustion. A further object is to provide an arrangement of apparatus in wells penetrating spaced-apart strata containing oil of different viscosities for producing said strata. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises producing hydrocarbons from an oil field including a less viscous oil-bearing stratum and a more viscous oil-bearing stratum separated by an impermeable barrier and penetrated by a pair of wells, which comprises, producing the less viscous oil-bearing stratum by fluid drive between said Wells to partially deplete same, igniting the more viscous oil-bearing stratum around one of said Wells to establish a combustion zone therein, driving the resulting combustion zone through the more viscous oil-bearing stratum toward the other well by feeding combustion-supporting gas thereto so as to produce a hot gaseous elfluent comprising hydrocarbons and combustion gases in one of said wells, passing at least a substantial portion of said hot eflluent directly from said one well through the partially depleted, less viscous oil-bearing stratum to the other Well to produce additional hydrocarbons and recovering the produced hydrocarbon from said other well.

The less viscous oil-bearing stratum may be produced by any type of fluid drive, such as miscible fluid drive, water flooding, steam drive, or other gas or liquid drive not involving in situ combustion. The more viscous oilbearing stratum is produced by either inverse or direct drive in situ combustion in a manner well known in the art. The gaseous eflluent from the in situ combustion drive is passed directly from the production Well through the partially depleted stratum containing the less viscous oil so as to produce additional oil therefrom and the hydrocarbons produced by both the in situ combustion step and the hot gas drive are recovered from one or more of the Wells in the strata.

The less viscous oil-bearing strata referred to herein includes any stratum which contains oil sufliciently fluid to be produced by fluid flood in reasonable quantity, such as to or percent of the oil in place. Oils of less than about 12 to 15 cps. are producible by fluid flooding in-sufi'icient quantity for operation of the process. The more viscous oil-bearing strata referred to herein are those containing heavy oil or semisolid to solid hydrocarbon material not producible by fluid flooding but 10- 3,163,215. Patented Dec. 29, 1964 cated in a straturn of suflicient permeability to permit moving a combustion zone therethrough by either direct or inverse injection of air. The less viscous oils usually have an API'gravity of at least 20 or 25, while the more viscous oils have an API gravity of less than about 1 2.

A more complete understanding of the invention may be obtained by reference to the accompanying drawing of which FIGURE 1 is a fragmentary section through a formation or' oil field showing one arrangement of apparatus for elfecting the invention; and FIGURE 2 is a plan view of a 5-spot well pattern for producing oil from an oil field in accordance with the invention.

Referring to FIGURE 1, a more viscous'oil-bearing stratum 10 is separated from a less viscous oil-bearingstratum 12 by animpermeable barrier 14. These strata lie between an overburden 16 and a substratum 18. All of these strata are penetrated by a pair ofouter wells 20 and anintermediate well 22. Outer Wells 20 are provided withcasing 24 andtubing string 26, Whileintermediate well 22 is provided withcasing 28 andtubing string 30.Lines 32 connect withcasing 20 and With theannulus 34 inwells 20.Tubing strings 26 are extended toat least the level ofimpermeable barrier 14 and are surrounded by packers 36 which pack ofl the annulus above and below impermeable stratum 14'. Apacker 38 may be provided aroundtubing string 30 and Well 22, if desired. The casing in each of the wells is provided with-perforations 40 which serve as means for passing fluids between the Wells and the strata as required in the process.

Referring to FIGURE 2,central well 22 is surrounded by fourcorner wells 20. .Wells 20 in FIGURE 1 may represent diagonallyopposite wells 20 in FIGURE 2 and each may also represent one of the wells in two parallel lines of wells spaced from a line ofcentral wells 22 for in-line production.

Utilizing the arrangement of apparatus shown in the drawing, less viscous oil-bearing stratum .12 is produced by fluid drive and by pumping in a conventional manner as by injecting fluid throughtubing 30 and forcingsame throughstratum 12 intowells 20 from which production is recovered by pumping or pressure lift throughtubing 26. In thisoperation lines 32 must be kept closed so that injected fluid cannot pass through stratum 10 toannulus 34 ofwells 20. After partial depletion ofstratum 12, stratum 10 is ignitedadjacent well 22 by any suitable means, and the resulting combustion zone is moved outwardly towardwells 20 by injecting combustion-supporting, o -containing gas, such as. air, throughlines 32 so as to move combustion zone 50 by inverse drive towardwells 20. The hot produced gases pass into well 22 through perforations 40 leading intostratum 12 containing residual oil. The hot gases comprising hydrocarbons, combustion gas, and steam are forced throughstratum 12 towells 20 from which they are recovered, along with additional oil produced fromstratum 12, throughtube string 26 in each of Wells 20.

It is feasible to produce a stratum containing highly viscous oiland one of low permeability by in situ com- .bustion, particularly by inverse drive as illustrated in FIGURE 1 when the stratum is not amenable to production by fluid drive. The heating of the stratum by combustion of a portion ofthe oil raises the temperature thereof to a high level, such as 800 or 900 to 1400 or 1500 F which renders the produced hydrocarbons substantially completely vaporous, thereby facilitating the drive of these vaporous hydrocarbons through the burned out, more permeable stratum behind the combustion zone. The hot vaporous effluent from the in situ combustion step provides an excellent gas fora gas drive through the partially depleted stratum containing less viscous oil.

In oil fields where stratum 10 contains oil of intermediate viscosity and sufiicient permeability is available in this stratum, the combustion zone may be driven through the stratum by direct drive. In this case, either combustion zones are establishedadjacent wells 20 and air is injected throughlines 32 or well 22 is equipped with aline 32 and a packer 36 aroundtubing 30 at the level ofstratum 14 so that air can be injected through line 32(connected with casing 28) so as to drive combustionzone 50 by direct drive through stratum into wells from which the hot gas is forced intostratum 12 by omitting packers 36 inwells 20. 'In this type of operation the arrangement of tubing and packers inwells 20 and well 22 is reversed so that produced gases are driven from stratum 10 intowells 20 from which these gases pass directly intostratum 12 and are produced throughtubing 30 which is extended below or at least to the level ofstratum 14.

Where production is effected by means of three rows of in-line wells, thesame techniques may be applied. .It is to be understood that it is not necessary to produce all of the effluent gas from the in situcombustion step in stratum 10 throughstratum 12. A portion of this hot eflluent may be passed through a third-stratum (partially depleted) lying above the stratum 10, or belowstratum 12. In the event the third stratum lies above stratum 10,

packer 38 must be placed above this third stratum. It is also feasible to simultaneously produce more than one stratum, such as 10, by in situ combustion and force all of the produced gases through one or more partially depleted strata in the same field.

Certainmodifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim: a

1. A process for producing hydrocarbons from an oil field including a first permeable stratum containing liquid oil of relatively low viscosity'and a second permeable stratum containing liquid oil of relatively high viscosity, said first and second strata being separated by" an impermeable barrier and penetrated by a pair of wells, which comprises the steps of:

(1) substantially partially depleting the oil from said first stratum by fluid drive to recover oil therefrom and render same more permeable;

(2) igniting the liquid oil along the vertical extent of said second stratum around one of said wells to establish a combustion zone coextensive vertically with stratum;

(3) driving the combustion zone of step (2) thru the second stratum by feeding combustion-supporting gas thereto thru the pores of the permeable stratum so as to sweep a full cross section of the stratum and produce a hotgaseous efliuent in one of said wells comprising a substantial proportion of oil and combustion gases; I

(4) passing at least a substantial proportion of the hot elfluent of step (3) directly from said one well thru the partially depletedstratum of step (1) to the other 7 well to produce additional oil from last said stratum;

and

(5) recovering oil produced from both strata fiom last as to move said combustion zoneby direct drive thru said second stratum.

' 4. The process of claim 1 wherein said fluid drive comprises a miscible fluid drive.

5. The process of claim 1 wherein said fluid drive comprises water flood.

References Cited in the file of this patent UNITED STATES PATENTS 2,584,605 Merriam et al Feb. 5, .1952 2,888,987 Parker June 2, 1959 2,954,218 Dew etal Sept. 27, 1960 3,034,580 Frey'et a1 May 15,1962 3,050,116 Crawford Aug. 21, .1962

OTHER REFERENCES Slobod, R. L.: A Review of Methods Used to Increase Oil Recovery, Producers Monthly, February 1958, pp. 24-31.

Claims (1)

1. A PROCESS FOR PRODUCING HYDROCARBONS FROM AN OIL FIELD INCLUDING A FIRST PERMEABLE STRATUM CONTAINING LIQUID OIL OF RELATIVELY LOW VICOSITY AND A SECOND PERMEABLE STRATUM CONTAINING LIQUID OIL OF RELATIVELY HIGH VISCOSITY, SAID FIRST AND SECOND STRATA BEING SEPARATED BY AN IMPERMEABLE BARRIER AND PENETRATED BY A PAIR OF WELLS, WHICH COMPRISES THE STEPS OF: (1) SUBSTANTIALLY PARTIALLY DEPLETING THE OIL FROM SAID FIRST STRATUM BY FLUID DRIVE TO RECOVER OIL THEREFROM AND RENDER SAME MORE PERMEABLE; (2) IGNITING THE LIQUID OIL ALONG THE VERTICAL EXTENT OF SAID SECOND STRATUM AROUND ONE OF SAID WELLS TO ESTABLISH A COMBUSTION ZONE COEXTENSIVE VERTICALLY WITH STRATUM; (3) DRIVING THE COMBUSTION ZONE OF STEP (2) THRU THE SECOND STRATUM BY FEEDING COMBUSTION-SUPPORTING GAS THERETO THRU THE PORES OF THE PERMEABLE STRATUM SO AS TO SWEEP A FULL CROSS SECTION OF THE STRATUM AND PRODUCE A HOT GASEOUS EFFLUENT IN ONE OF SAID WELLS COMPRISING A SUBSTANTIAL PROPORTION OF OIL AND COMBUSTION GASES; (4) PASSING AT LEAST A SUBSTANTIAL PROPORTION OF THE HOT EFFLUENT OF STEP (3) DIRECTLY FROM SAID ONE WELL THRU THE PARTIALLY DEPLETED STRATUM OF STEP (1) TO THE OTHER WELL TO PRODUCE ADDITIONAL OIL FROM LAST SAID STRATUM; AND (5) RECOVERING OIL PRODUCED FROM BOTH STRATA FROM LAST SAID OTHER WELL.

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