US3554282A

US3554282A - Method for improving the sweep of underground reservoirs by exploiting individual reservoir segments

Info

Publication number: US3554282A
Application number: US811926A
Authority: US
Inventors: Anthony F Altamira; Joseph Daleda
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1969-04-01
Filing date: 1969-04-01
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12
Also published as: CA919582A

Abstract

The sweep of an underground hydrocarbon formation having reservoir segments with trapped fluids therein is increased by locating wells in individual segments and injecting extraneous fluid into the formation therefrom and producing simultaneously via other wells removed from said segments, while under the influence of an active aquifer, either native or by flooding.

Description

United States Patent Inventors Anthony F. Altamira Houston, Tex.; Joseph Daleda, Montclair, NJ Appl. No. 811,926 Filed Apr. 1, 1969 Patented Jan. 12, 1971 Assignee Texaco Inc.,

New York, N.Y. a corporation of Delaware.

METHOD FOR IMPROVING THE SWEEP OF UNDERGROUND RESERVOIRS BY EXPLOITING INDIVIDUAL RESERVOIR SEGMENTS 21 Claims, 19 Drawing Figs.

U.S. Cl 166/245,

Int. Cl E2lb 43/20 Field of Search 166/245 OTHER REFERENCES Muskat, Physical Principles of Oil Production, First Edition, McGraw-Hill Book Co., me, New York (I949), (pp. 645- 650, 677, 678 and 8 I 6- 820) Primary Examiner-Stephen J. Novosad AnomeysK. E. Kavanagh and Thomas H. Whaley ABSTRACT: The sweep of an underground hydrocarbon formation having reservoir segments with trapped fluids thereinis increased by locating wells in individual segments and injecting extraneous fluid into the formation therefrom and producing simultaneously via other wells removed from said segments, while under the influence of an active aquifer, either native or by flooding.

PATENTED JAN 1 2 l9?! sum 1, BF 2 METHOD FOR IMPROVING THE SWEEP OF UNDERGROUND RESERVOIRS BY EXPLOITING.

INDIVIDUAL RESERVOIRSEGMENTS CROSS REFERENCE FIELD OF INVENTION This invention relates generally to the production of hydrocarbons from underground hydrocarbon-bearing formations, and more particularly, to a method for increasing the sweep of hydrocarbons therefrom. Y I

BACKGROUNDOF THE INVENTION In the production of hydrocarbons from permeable underground'hydrocarbon-bearing formations, it is customary to drill one or more boreholes or wells into the hydrocarbonbearing formation and produce hydrocarbons, such as oil, through designated production wells, either by the natural formation pressure or by pumping the wells. Sooner or later, the flow of hydrocarbons diminished and/or ceases, even though substantial quantities of hydrocarbons are still. present in the undergroundformations.

Frequently, many hydrocarbon-bearingformations are divided into reservoir segments, each containing traps wherein hydrocarbons have accumulated. Thesesegments in-the underground reservoir may be caused by faulting, permeability pinch outs,tar barriers and the like.

SUMMARY OF THE INVENTION It is an overall object of this invention to provide an improved recovery procedure to obtain maximum sweep of a segmented reservoirinvolving a plurality of wells located strategically, viz. by having at least one well, either injection or production, in communication with each individual reservoir segment, being under the influence of an active aquifer.

It is desirable that injection be initiated and continued either simultaneously or in turn, from wells on both-sides of thesealing fault dividing the formation into reservoir segments, when such is known to exist, until breakthrough occurs at production wells; at which time furtherv production is discontinued and the well or. wells shut in. In the-absence of a native aquifer, a water drivemay be substituted.

Other objects, advantages and features of this invention will become apparent from a consideration of the specification withreference to the figures in the accompanying drawing.

BRIEF DESCRIPTION OF TI-IE DRAWINGS FIG. la illustrates thesweep at breakthrough when the in-:

fromanadditional .well as developed from the situation as disclosed in FIG. la; l

1c illustrates the final step when the second well is converted from production to injection and the other well penetrating into an individual segment is put on production;

FIG.-.2q illustrates the sweep obtained when the production well exploiting a reservoir having segmentsdefined by a sealing fault is located away from .the injection well behind the by model study when the well at- A is produced to 'f onv thesame side of the sealing fault as the injection well atx' fault; FIG. 2b illustrates the. sweep when an additional production well is placed in operation on the'near side of the fault with respect't'o the injection well, as a modification of FIG. 2a,-

FIGHZc'iIIustrates the'finalstep' when the functions'of the several wells are changed to, achieve a greater sweep;

FIG. 3a illustrates the sweep when the production wells opposite the wells penetrating the formation on either side of a fault are produced concurrently till individual breakthrough;

FIG. 3!: discloses the sweep achieved when production is continued till breakthrough at both production wells;

FIG. 3c corresponds to FIG. 2c illustrating the final step to achieve a greater sweep;

FIG. 4a discloses the first step of an areal sweep when both wells penetrating the segments divided by a fault are injection wells and one of the oppositely located wells is put on production;

FIG. 4b illustrates the step following when the production well at breakthrough is shut in and the other oppositely located well is put on production;

FIG. 4c shows an alternative second step'of the sweep following FIG. 4a wherein the production well at breakthrough is converted to an injection well, the other well located opposite the original injection wells is put on production and the injection well nearest thereto is shut in;

FIG. 4d is another alternative second step following FIG; 40' wherein both of the original injection wells are shut in, the original production well is converted to an injection well and the remaining well is put on production till breakthrough;

FIG. 5a illustrates the sweep when the injection wells penetrating the segments separated by the fault operate simultaneously and the pair of production wells also operate simul taneously;

FIG. 5b is the converse of FIG. 5a with respect to the operating functions of the wells; J

FIGS. and 6b illustrate the steps when the injection wells are located opposite those penetrating the segments divided by the fault, the former figure being the first step of the sweep and the latter FIG., the concluding step; and

FIGS; and 7!: illustrate the steps taken to complete a sweep when a blocking fault is encountered in an inverted nine-spot pattern.

The objects of the invention are achieved by the use of production wells in combination with injection wells which are" separated from each other by a sealing fault and have more or less direct communication with the production wells.

The specification and the FIGS. of the drawings schemati cally'disclose and illustrate the practice and the advantages of ing two equal segments caused by a sealing faultI-The model studies indicate a sweep obtained in an ideal" reservo' although the recovery by an actual sweep of a particular'field' may be greater or less, depending on field parameters The results to be described were. based on the follo of experimental conditionsand'assumptionsi'fll'lh ran total fluid production rates between wells is consta'n'tfo'r given phase or step in the production "plan; I

(2) The total amount of fluid injected is equal to the ar'iiouiit' of fluid produced;

3 11: mobility ratio of the displacing todis'plaeed mildew (4) The permeability and thickness of the uniform; and

(5) Gravitationaleffects are not considered;

"Throughout the figures of the drawings, the

will be maintained as-follows:

. The solid circle indicates a production well, the crease cle indicates a shut in well, an open circle a well site, arrowed open circle indicates an injection well. V

Referring to FIG. la, there is illustrated the sweepobt'aihd breakthrough, this production well being located oppos for the extraneousdriving fluid. The sweep area amountsto 54.9 percent.

In FIG. lb, there is illustrated the increased sweep when the other oppositely located well is put on production; the original production well being shut in, to result in a sweep of 73.9 percent.

FIG. lc illustrates a sweep of 83.3 percent when the second production well is converted to an injection well and the other well penetrating the separated segment is put on production till breakthrough.

FIG. 2 2a illustrates the sweep obtained in the model used in FIG. when production is initiated and maintained at B, located above the sealing fault and the injection well at x, until breakthrough, resulting in a swept area of 62.3 percent.

In FIG. 2b, the sweep has been raised somewhat to 68.7 percent, after well B is shut in after breakthrough, by initiating and maintaining production at well A, located on the near side of the sealing fault and the injection well at x, until breakthrough thereat.

In FIG. 2c, the sweep has been increased to 80.9 percent when the production well at A in FIG. 2b is shut in and the previously shut in well at B is converted to an injection well, and the other well at y, penetrate the separated segment, is put on production till breakthrough.

In FIG. 3a, there is illustrated the sweep in the same reservoir model as in FIG. la when both production wells A'and B, located opposite the wells penetrating the segments divided by the sealing fault are produced concurrently at equal rate with the injection well at x, until the driving fluid breaks through at well A. In the second phase, as illustrated in FIG. 3b, the production well A is shown as shut in, and well His produced until breakthrough of the injection fluid, the sweep being increased to 72.8 percent.

In FIG. 30, corresponding to the situation in FIG. 2c,"the last production well is converted to an injection well and the well penetrating the other separated segment is put in production till breakthrough, to attain a sweep of 82.3 percent.

In FIGS. 40 and 4b, both the wells at and y penetrating the divided segments function as injection wells. In the former FIG., production is maintained at A till breakthrough to attain a sweep of 79.5 percent. In the latter FIG., a sweepof 88.6 percent is achieved when the former production well at A is shut in at breakthrough and the other well at B opposite the in jection wells is put on production till breakthrough.

In FIG. 4d there is illustrated a sweep of 91.1 percent when the functions of the wells shown in FIG. 4a are changed so that x and y are shut in, the production well at A is converted to an injection well, and the well at B is put on production till breakthrough.

FIG. 4c is a modification of the conditions of FIG. 4a, achieving a sweep of 90.0 percent, when the injection well at y is shut in and the closer well opposite thereto is put on production till breakthrough, the original production well being converted to an injection well.

FIGS. 5a and 5b are converse disclosures. In the former FIG., the wells penetrating the separated segments are injection wells at x and y, and the wells located opposite at A and B are production wells, operating till breakthrough to attain a sweep of 84.4 percent.

In FIG. 5b, the wells penetrating the separated segments at x and y are production wells, and the wells located opposite at A and B are injection wells. This situation results in a sweep of 87.2 percent.

FIG. 6a is the converse of FIG. 4a, with the injection wells at A and B being located opposite the wells at x and y penetrating the separated segments, with production at x alone, to achieve a sweep of 66.4 percent. Upon breakthrough and shut in at x, production is initiated and maintained till breakthrough at y to achieve a sweep of 84.9 percent.

FIGS. 7a and 7!; illustrate the application of the invention to an inverted nine-spot pattern having a sealing fault located between the central injection well and a side production well.

In FIG. 7a, following production and shut in at the side wells of the pattern following breakthrough except at P,, production is maintained at the comer wells, P, till breakthrough thereat.

In FIG. 7b, all wells suffering breakthrough are shut in, injection is shown maintained at the central. well, P (although it could be shut in) and production maintained at P, until breakthrough to achieve a greater sweep than in FIG. 7a.

Throughout the experiments. the flow of fluid through a reservoir system is governed by Darcy's Law and is assumed to be sufficiently slow for the inertia forces to be negligible (i.e. Stokes flow, with low Reynolds number), and therefore is in the direction toward decreasing pressure and proportional to the pressure gradient.

The advantages of the method disclosed above are evident. More reservoir fluids are recovered prior to breakthrough of injection fluid, and so more ultimate recovery is obtained as compared with other production methods.

Although this disclosure has illustrated the practice of this invention practice of this invention as directed to a secondary recovery operation, particularly employing driving displacement fluid, the advantages obtainable in the practice of this invention may be realized in primary hydrocarbon production wherein the location of the sealing fault is known in order that additional production wells may be employed.

We claim:

1. A method of producing formation fluids including hydrocarbons from an underground hydrocarbon-bearing formation divided into segments containing trapped fluids which comprises penetrating said formation with a first pair of wells in communication with individual segments and a second pair of wells offset in corresponding positions therefrom, injecting an extraneous fluid into said formation with said segments via a well in communication with one of said segments to displace fluids including hydrocarbons in said fonnation toward one of said second pair of wells, producing said fluids including hydrocarbons from said formation via said last mentioned well until said extraneous fluid is produced along with said formation fluids thereat, and initiating and maintaining producing fluids including hydrocarbons from said formation via the other of said second pair of wells while maintaining injecting extraneous fluid into said fonnation via the injection well.

2. In the method of producing formation fluids including hydrocarbons as defined in claim I, the first production well being closed in upon breakthrough of said extraneous fluid.

3. In the method of producing formation fluids including hydrocarbons as defined in claim 2, said first production well being closer to said injection well than the other of said second pair of wells.

4. In a method of producing formation fluids including hydrocarbons as defined in claim 3, said first production well being further from said injection well than the other of said second pair of wells.

5. In the method of producing formation fluids including hydrocarbons as defined in claim 2, the other of said second pair of wells being converted from a production well to an injection well upon breakthrough of said extraneous fluid, and thereupon initiating and maintaining producing formation fluids from the other of said first pair of wells while injecting extraneous fluid into said formation via the converted well until breakthrough thereof at the last mentioned production well.

6. In the method of producing fonnation fluids including hydrocarbons as defined in claim 1, initiating and maintaining producing formation fluids via said second pair of wells concurrently until breakthrough of said extraneous fluid at one of these production wells while continuing producing said fluids from the other production well until breakthrough thereat and thereupon converting from production to injection.

7. In the method of producing formation fluids including hydrocarbons as defined in claim 6, initiating and maintaining producing fluids from the other of said first pair of wells and injecting extraneous fluid via the converted injection well.

8. In the method of producing formation fluids including hydrocarbons as defined in claim 7, producing said formation fluids being discontinued upon breakthrough of said extraneous fluid at the production wells.

claim. 7, producing formation fluids via theproduction wells until all the production thereof comprises said extraneous fluid. j

g 10. In the in claim 1, injecting extraneous-fluidxinto said formation via said first pair of wells. I

11. In the method of producing formation fluids as defined in claim 10, converting the production well of said second pair of wells to an injection well upon breakthrough of said extraneous fluid thereat and injecting extraneous fluid into said formation therefrom until breakthrough thereof occurs at the other of said second pair of wells.

12. In the method of producing formation fluids as defined in claim 10, concurrently initiating and maintaining producing formation fluids via said second pairof wells.

13. In the method of producing formation fluids including hydrocarbons as defined in claim 1, said .extraneous fluid being an aqueous fluid.

14. In the method of producing formation fluids including hydrocarbons as. defined in claim 1, said extraneous fluid being a gas.' x i 15. A method of producing formation fluids including hydrocarbons from an underground hydrocarbon-bearing formation divided into segments by a sealing fault and. containing trapped fluids which comprises penetrating said formation with two pairs of paired wells, with a pair of offset production wells in communication with individual segments, injecting an extraneous fluid into said'formation with said segments via the other pair of said paired wells to displace fluids including hydrocarbons in said formation toward said production wells,

method of producing formation fluids as defined producing said fluids including hydrocarbons from said formation via one of said pair of production wells until said extraneous fluid is produced along with said formation fluids thereat, and maintaining producing fluids including hydrocarbons from said formation via'the other of said pair of production wells while maintaining injecting extraneous fluid into said formation via the injection wells.

16. In the method of producing formation fluids including hydrocarbons as defined in claim 15, concurrently initiating and maintaining producing formationfluids from said formation via said pair of production wells until breakthrough of said extraneous fluid thereat.

17. In the method of producing formation fluids including hydrocarbons as defined in claim 16,-producing said formation fluids via said production wells being discontinued upon breakthroughof said extraneous fluid thereat.

18. In the method of producing hydrocarbons as defined in claim 16, producing formation fluids via said production wells until all the production thereof comprises said extraneous fluid.

19. In the method of producing formation fluids including hydrocarbons as defined in claim 15, said extraneous fluid being an aqueous fluid.

20. In the method of producing formation fluids including hydrocarbons as defined in claim 15, said extraneous fluid being a gas.

21. In the method of producing formation fluids including hydrocarbons as defined in claim 1, the pairs of wells comprising part of an inverted nine-spot pattern.

Claims

2. In the method of producing formation fluids including hydrocarbons as defined in claim 1, the first production well being closed in upon breakthrough of said extraneous fluid.
3. In the method of producing formation fluids including hydrocarbons as defined in claim 2, said first production well being closer to said injection well than the other of said second Pair of wells.
4. In a method of producing formation fluids including hydrocarbons as defined in claim 3, said first production well being further from said injection well than the other of said second pair of wells.
5. In the method of producing formation fluids including hydrocarbons as defined in claim 2, the other of said second pair of wells being converted from a production well to an injection well upon breakthrough of said extraneous fluid, and thereupon initiating and maintaining producing formation fluids from the other of said first pair of wells while injecting extraneous fluid into said formation via the converted well until breakthrough thereof at the last mentioned production well.
6. In the method of producing formation fluids including hydrocarbons as defined in claim 1, initiating and maintaining producing formation fluids via said second pair of wells concurrently until breakthrough of said extraneous fluid at one of these production wells while continuing producing said fluids from the other production well until breakthrough thereat and thereupon converting from production to injection.
7. In the method of producing formation fluids including hydrocarbons as defined in claim 6, initiating and maintaining producing fluids from the other of said first pair of wells and injecting extraneous fluid via the converted injection well.
8. In the method of producing formation fluids including hydrocarbons as defined in claim 7, producing said formation fluids being discontinued upon breakthrough of said extraneous fluid at the production wells.
9. In the method of producing formation fluids as defined in claim 7, producing formation fluids via the production wells until all the production thereof comprises said extraneous fluid.
10. In the method of producing formation fluids as defined in claim 1, injecting extraneous fluid into said formation via said first pair of wells.
11. In the method of producing formation fluids as defined in claim 10, converting the production well of said second pair of wells to an injection well upon breakthrough of said extraneous fluid thereat and injecting extraneous fluid into said formation therefrom until breakthrough thereof occurs at the other of said second pair of wells.
12. In the method of producing formation fluids as defined in claim 10, concurrently initiating and maintaining producing formation fluids via said second pair of wells.
13. In the method of producing formation fluids including hydrocarbons as defined in claim 1, said extraneous fluid being an aqueous fluid.
14. In the method of producing formation fluids including hydrocarbons as defined in claim 1, said extraneous fluid being a gas.
15. A method of producing formation fluids including hydrocarbons from an underground hydrocarbon-bearing formation divided into segments by a sealing fault and containing trapped fluids which comprises penetrating said formation with two pairs of paired wells, with a pair of offset production wells in communication with individual segments, injecting an extraneous fluid into said formation with said segments via the other pair of said paired wells to displace fluids including hydrocarbons in said formation toward said production wells, producing said fluids including hydrocarbons from said formation via one of said pair of production wells until said extraneous fluid is produced along with said formation fluids thereat, and maintaining producing fluids including hydrocarbons from said formation via the other of said pair of production wells while maintaining injecting extraneous fluid into said formation via the injection wells.
16. In the method of producing formation fluids including hydrocarbons as defined in claim 15, concurrently initiating and maintaining producing formation fluids from said formation via said pair of production wells until breakthrough of said extraneous fluid thereat.
17. In the method of producing formation fluids including hydrocarbons as defined in claim 16, Producing said formation fluids via said production wells being discontinued upon breakthrough of said extraneous fluid thereat.
18. In the method of producing hydrocarbons as defined in claim 16, producing formation fluids via said production wells until all the production thereof comprises said extraneous fluid.
19. In the method of producing formation fluids including hydrocarbons as defined in claim 15, said extraneous fluid being an aqueous fluid.
20. In the method of producing formation fluids including hydrocarbons as defined in claim 15, said extraneous fluid being a gas.
21. In the method of producing formation fluids including hydrocarbons as defined in claim 1, the pairs of wells comprising part of an inverted nine-spot pattern.