US3358759A

US3358759A - Steam drive in an oil-bearing stratum adjacent a gas zone

Info

Publication number: US3358759A
Application number: US473059A
Authority: US
Inventors: Harry W Parker
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1965-07-19
Filing date: 1965-07-19
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

Dec. 19, 1967 H. w. PARKER STEAM DRIVE IN AN OIL-BEARING STRATUM ADJACENT A GAS ZONE Filed July 19, 1965 PRODUCT 26 STEAM INVENTOR ,7 A TQRNEKS United States Patent Ofi 3,358,759 Patented Dec. 19, 1967 ice 3,358,759 STEAM DRIVE IN AN OIL-BEARING STRATUM ADJACENT A GAS ZONE Harry W. Parker, Bartlcsviile, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed July 19, 1965, Ser. No. 473,059 8 Claims. (Cl. 166-11) ABSTRACT OF THE DISCLOSURE This invention relates to a process for producing oil from an oil-bearing stratum lying adjacent a gas zone, such as a gas cap, by fluid drive.

Recovery of oil by fluid drive, and particularly by steam injection, is rapidly becoming a conventional technique in petroleum production. In oil fields in which the oilbearing stratum lies adjacent a gas zone, there is a strong tendency for the steam or other injected fluid to bypass the major portion of the oil stratum between the injection and production wells and pass into the gas zone. Even in operation in which the steam is injected into the stratum near the bottom, there is a considerable tendency for the steam to rise and pass into the gas cap a short distance from the injection well. Condensation of steam in the gas cap or other gas zone gives up its heat to the unproductive zone and results in tremendous waste of steam.

The instant invention is concerned with an improved process for producing oil from an oil stratum lying adjacent a gas zone such as a gas cap without substantial loss of injected steam or other fluid into the gas zone.

Accordingly, the principal object of the invention is to provide a process for producing oil from an oil stratum lying adjacent a gas zone. Another object is to conserve steam or other injected fluid in the production of oil from such a stratum by fluid drive. A further object is to provide a process for injecting a heating fluid such as steam deep into a stratum from an injection well in this type of stratum while conserving the injected fluid. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises fracturing an oil stratum lying adjacent a gas zone at a level remote from the gas zone thru an injection well penetrating the stratum, injecting a driving fluid such as steam into the fracture toward at least one offset production well so as to drive oil toward and into the production well(s), injecting a non-condensible gas thru the injection well into the gas zone so as to obstruct the passage of driving fluid into this zone, and recovering oil from the production well(s). In conjunction with the foregoing steps, the permeable walls of the fracture are at least partially plugged by injecting an aqueous slurry of a particulate solid plugging agent, such as clay, and the injection pressure is applied so as to extend the fracture deeper into the stratum. The extension of the fracture deeper into the stratum is usually effected with fracturing fluid free of plugging agent. After extending the fracture deeper into the stratum, the injection of steam or other driving fluid is re sumed so as to deliver the steam deeper in the stratum and extend the heated zone.

The injection of non-condensible gas into the gas zone may be effected thru the stratum adjacent the gas zone or directly into the gas zone. A convenient method of injecting the driving fluid and the non-condensible gas comprises injecting the steam into the fracture thru a tubing string extending well into the stratum being produced and packing off the annulus around the tubing between the fracture and the level at which the non-condensible gas is injected. The non-condensible gas is then injected thru the annulus into the surrounding formation above the packer. The injection of the non-condensible gas may be commenced before the injection of steam, simultaneously therewith, or shortly after the initiation of steam injection. It is also feasible to inject the non-condensible gas continuously during steam injection or periodically (intermittently). The amount of gas injected into the gas cap depends upon the extent of this zone and the well spacing.

Non-condensible gases suitable for use in the invention comprise nitrogen, air, helium, natural gas, or any normally gaseous hydrocarbon, CO or flue gas, etc. In fact, any non-condensible gas is operable and the selection of this gas will be dictated by economics. Air is the preferred gas in view of its availability and low cost.

When utilizing steam drive thru the fracture extending into the oil stratum, after an extended period of heating and driving oil toward the surrounding production wells, it is advantageous to close in the production wells while continuing the injection of steam so as to build up substantial stratum pressure, and thereafter opening the injection well to production so that the heated oil in the stratum, rendered more fluid by the heating, flows into the injection well from which it is produced in conven tional manner as by pumping. It is preferred to allow a substantial soaking period such as a period of several days after terminating steam injection and before opening the injection Well to production. After a substantial production period, steam injection is resumed and the production wells are opened to production so as to continue the healting and driving of more fluid oil into the production we s.

It is good practice to pack off the production wells around the tubing string therein at an intermediate level of the stratum to assist in directing the driving and heating fluid and the produced oil thru the stratum into the production wells. This in combination with the injection of non-condensible gases prevents substantial loss of steam to the gas zone.

The steam or other fluid drive of the invention may be effected thru a conventional ring-well pattern with a central injection well or in an in-line drive pattern from a line of injection wells to offset lines of production Wells.

Fluids utilizable in the fluid drive include light liquid hydrocarbons and mixtures thereof, air, CO or flue gas, etc. When utilizing air, ignition may be effected and the drive may principally comprise that of in situ combustion wherein hot fluidized and cracked hydrocarbons together with combustion gas sweep thru the stratum. However, steam is the preferred and most beneficial driving fluid to be used in combination with the fracturing and injection of non-condensible gas. It is also feasible to inject air into the gas zone and to conduct an in situ combustion operation in the stratum along the area thereof bounding the gas zone and driving the produced hydrocarbons into the production wells.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing which is an elevation through a formation penetrated by an injection well and a production well.

Referring to the drawing, an oil zone 10 lying below a gas cap 12 is penetrated by an injection well 14 and 0 a production well 16. A tubing string 18 extends into stratum 10 and a similar tubing string 20 extends into production well 16. Wells 14 and 16 are provided with

casing strings

22 and 24, respectively. Steam or other driving fluid is injected into well 14 through line 26. Noncondensible gas is injected into the annulus of Well 14 through line 28. When well 14 is on production, after a heating and soaking period, oil is produced through tubing 30 by conventional pumping means or gas lift. Apparatus is available for injecting steam through tubing string 18 without pulling the pump (not shown) on the end of the tubing string. This type of equipment is disclosed in US. application Ser. No. 372,553, filed June 4, 1964, by W. B. Belknap, now US. Patent No. 3,312,281.

Packer 32 packs off the annulus between the tubing and casing in well 14 and similar packer 54 positioned at an intermediate level in stratum 10 packs oif the annulus in well 16.

Casing 22 is perforated in the gas cap area at 36 for injection of non-condensible gas. Casing 24 is not perforated in the gas cap zone so as to permit building up of pressure in this area. Casing 22 is also perforated at 38 for injection of fracturing fluid to form fracture 40 and for the injection of steam or other driving fluid. The slurry of plugging agent is also injected through the tubing and through perforations 38 to line the walls of the fracture.

Perforations 42 in casing 24 below packer 34 provide for flow of oil and other fluids into production well 16 from which they are produced through tubing string 20 into production line 44.

Well 14 may represent a central well surrounded by any suitable number of production wells 16 or it may represent a line of injection wells in between parallel lines of production wells 16.

Certain modifications 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:

1. A process for producing oil from an oil-bearing stratum lying adjacent a gas-bearing zone which comprises the steps of:

(1) fracturing said stratum at a level remote from said zone through an injection well therein;

(2) injecting steam into said fracture toward at least one oifset production well so as to produce oil therein;

(3) injecting a non-condensible gas into said stratum adjacent said zone so as to obstruct the passage of steam into said zone; and

(4) recovering oil from said at least one production well.

2. The process of claim 1 including the steps of:

(5) injecting an aqueous slurry of a particulate solid plugging agent into said fracture so as to fracture deeper in said stratum; and

(6) thereafter injecting additional driving fluid into said stratum through said fracture.

3. The process of claim 1 wherein said gas-bearing zone is above said stratum and said fracture is formed in a lower section of said stratum.

4. The process of claim 3 wherein steam is injected as the driving fluid through a tubing string extending into said stratum and the surrounding annulus is packed off at an upper level of said stratum.

5. The process of claim 1 wherein air is injected into said gas-bearing zone in step (3).

6. A process for producing oil from an oil-bearing stratum lying below a gas cap which comprises the steps of:

(1) fracturing said stratum at a lower level therein through an injection well penetrating said stratum so as to form a radially extending fracture around said well;

(2) injecting steam under substantial pressure into said fracture through a tubing string extending into said stratum so as to heat the oil in the stratum above and below the fracture and drive oil into surrounding production wells;

(3) prior to injecting any substantial amount of steam in step (2), injecting a non-condensible gas into said gas cap so as to obstruct the passage of steam into said gas cap and more effectively utilize the heat in said steam in producing oil;

(4) terminating the flow of steam and injecting an aqueous slurry of clay into said fracture so as to at least partially plug the walls of said fracture and extend same deeper into said stratum; and

(5) subsequent to step (4) again injecting steam into said fracture so as to heat oil deeper in said stratum and drive additional oil into said production wells.

7. The process of claim 6 wherein the non-condensible gas in step (3) is intermittently injected during steam injection in steps (2) and (5).

8. The process of claim 6 wherein the production wells are shut-in during steam injection until substantial pressure is built up in said stratum, thereafter steam injection is terminated, after a soaking period said injection well is opened to production and oil flowing into same is produced, and steam injection is resumed with production through said production wells.

References Cited UNITED STATES PATENTS 3,159,215 12/1964 Meldau et al. 16611 X 3,167,121 1/1965 Sharp 166-11 3,259,186 7/1966 Dietz 166l 1 STEPHEN J. NOVOSAD, Primary Examiner.

Claims

1. A PROCESS FOR PRODUCING OIL FROM AN OIL-BEARING STRATUM LYING ADJACENT A GAS-BEARING ZONE WHICH COMPRISES THE STEPS OF: (1) FRACTURING SAID STRATUM AT A LEVEL REMOTE FROM SAID ZONE THROUGH AN INJECTION WELL THEREIN; (2) INJECTING STEAM INTO SAID FRACTURE TOWARD AT LEAST ONE OFFSET PRODUCTION WELL SO AS TO PRODUCE OIL THEREIN; (3) INJECTING A NON-CONDENSIBLE GAS INTO SAID STRATUM ADJACENT SAID ZONE SO AS TO OBSTRUCT THE PASSAGE OF STEAM INTO SAID ZONE; AND (4) RECOVERING OIL FROM SAID AT LEAST ONE PRODUCTION WELL.