RU2550642C1 - Method of oil field development with horizontal wells - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: method involves construction of horizontal producers covering the field, and horizontal injectors. Displacement agent is injected through injectors, and products are swept by producers. Horizontal production wells are arranged parallel to each other. Horizontal injector is positioned between horizontal sections parallel to them. Injection starts from bottomhole. When intake capacity of reservoirs is decreased at the bottomhole of horizontal injector to minimum profitable level, non-operating section of horizontal shaft is isolated in series in direction from the bottomhole to the beginning of horizontal injector wellbore. Horizontal producers are drilled in permeable interlayer at 3-6 m distance below the reservoir bottom and at least at 10 m distance above oil-water interface. Horizontal injector is equally spaced from horizontal sections of producers by a design pattern distance. Displacement agent is injected with reservoir pressure rise by 10-20% compared to recovery zone. After time period sufficient to recover and stabilise frontal zone of liquid injected to the reservoir, operation may return to previous intervals. Horizontal sections of producers are broached in two intervals at a distance preventing hydrodynamic connection of the wells. Products are recovered in turns. Production intervals are switched when products reach minimum profitable water cut level.EFFECT: increased oil recovery due to stabilisation of frontal zone of liquid injected to reservoir, extended application scope of horizontal wells in various field development conditions.6 dwg, 1 ex

Description

The proposed method relates to the oil industry, in particular to the field of development of oil deposits by horizontal wells.

A known method of developing an oil field (patent RU No. 2215130, IPC ⁷ ЕВВ 43/20, publ. 10/27/2003), including drilling a field with a system of vertical injection and horizontal production wells with a choice of their trajectory, injection of displacing liquid and oil production. The trajectories of horizontal production wells are determined by connecting the estimated faces of the vertical production wells according to the in-line layout. Position the beginning of the horizontal trunk in the constricting zone. The end of the trunk is located in the extreme row of production wells closest to the injection line. Spend it with multiple opening of the reservoir by entering and exiting the trunk into the reservoir. As the water front moves during the development process, the bottoms of horizontal production wells are moved to the tightening zone by phasing out the intervals of intersection of the productive formations.

The disadvantage of this method is that when it is used, oil reserves are not fully developed, since when the intersection intervals of productive formations are turned off, there is no possibility of a return to their operation. As a result of increasing the distance from the injection line to a number of production wells, the influence of the front of the injected water decreases, reservoir pressure decreases and, as a result, oil production rates and production volumes.

The closest in technical essence to the proposed one is a method of developing an oil deposit by horizontal wells (patent RU No. 2474678, IPC EV21/16, published on 02/10/2013, Bull. No. 4), which includes the construction of horizontal production wells covering the reservoir and horizontal injection wells, injection of a displacing agent through injection wells and production selection by production wells. Horizontal production wells are placed parallel to each other, and from the horizontal sections successively in different directions in more permeable sections, the branches ascending to the top of the formation are drilled. Between the horizontal sections and parallel to the horizontal sections have a horizontal injection well, in which the injection begins from the bottom. With a decrease in injectivity of the collectors at the bottom of the horizontal injection well to an extremely cost-effective, the idle section of the horizontal wellbore is sequentially isolated in the direction from the bottom to the beginning of the horizontal well of the injection well.

The disadvantage of this method is that there is no option for the re-return to operation of previously isolated sections of the horizontal trunk. The disadvantage is that with sequential isolation of the horizontal wellbore of the injection well, the remote sections of the horizontal wellbore of the producing well remain without the influence of the displacing fluid injected into the formation. As a result of incomplete impact coverage, the application of the development method will not allow to level the front of the displacement fluid advancement in the formation, which prevents the injection fluid from breaking through to the perforation intervals of horizontal production wells, and increase the oil production rates.

The technical objectives of the proposed method are to increase the technological and economic efficiency of the development of oil deposits by increasing the coefficients of coverage by the development of oil reserves and oil recovery as a result of the alignment of the front of advancement of injected displacing agents and the reuse of flooded sections of the horizontal wellbore.

The technical result is achieved by the method of developing an oil reservoir, including the construction of horizontal production wells covering the reservoir and horizontal injection wells, injection of a displacing agent through injection wells and production selection by production wells, while horizontal production wells are placed parallel to each other, between horizontal sections and parallel to horizontal sections have a horizontal injection well, in which injection begins from fight, while reducing the downhole reservoir injectivity horizontal injection well to an extremely cost-effective horizontal wellbore portion broken isolate successively in the direction from the bottom to the top horizontal section of an injection well.

New is that horizontal production wells are carried out in a permeable interlayer below the formation roof at a distance of 3-6 m and above the oil-water contact at a distance of at least 10 m, a horizontal injection well is built equidistant from the horizontal sections of the production wells at a step of the design grid, injection of displacing the agent is carried out with an increase in reservoir pressure by 10-20% compared with the selection zone, provide for the return to the previous intervals of operation after a sufficient time for restoration and alignment of the front of the injected fluid in the reservoir, the horizontal sections of the producing wells are opened in two intervals at a distance that excludes their hydrodynamic connection, and the production is taken alternately, and switching from one production interval to another is carried out until the maximum cost-effective water cut of the product is achieved.

In FIG. 1 shows a diagram of the implementation of the proposed method for the development of oil deposits (top view) in the area of three horizontal wells. In FIG. 2 shows a section through deposit AA in FIG. 1. In FIG. 3 and FIG. 4 shows a section AA of the horizontal production well of FIG. 1. In FIG. 5 and FIG. 6 shows a section BB of the horizontal injection well of FIG. one.

The inventive method is carried out in the following sequence.

Oil reservoir 1 (Fig. 1, 2) is drilled with vertical wells 2-4 (Fig. 1) on a rare grid. According to well drilling and seismic studies conducted in the field, the geological structure of the oil reservoir is being clarified. The permeability and porosity of the reservoirs are determined. Measure formation pressure in wells 2-4.

A section of reservoir 1 with oil-saturated thicknesses of more than 15 m is selected. First, at least two horizontal production wells 6, 7 and one horizontal injection well 8, which are placed parallel to each other, are built in the reservoir 1. The number of horizontal production wells 6, 7 in the area of reservoir 1 is limited by the size of the selected area, the density of the design grid, which in turn depends on the type of reservoirs, the filtration and reservoir properties of the rocks (permeability, porosity) and the amount of oil reserves. At low permeability and porosity of reservoirs, the design grid is compacted, for example, from 400 × 400 m to 200 × 200 m, the number of horizontal production wells 6, 7 and, accordingly, horizontal injection wells 8 in the area of reservoir 1 will increase.

Horizontal production wells 6, 7 are carried out in a permeable interlayer, and they are located below the top of the formation 1 (Fig. 2) at a distance of a = 3.0-6.0 m, and above the oil-water contact (WOC) at a distance of b = 10, 0 m, increasing the anhydrous period of operation of the well. Reducing the distance to the oil-water contact will lead to a breakthrough of plantar water to the horizontal sections of production wells 6, 7 (Fig. 1) as a result of differences in the viscosities of oil and produced water.

Between the horizontal sections of the production wells 6, 7, a horizontal injection well 8 is built, equidistant from the horizontal sections of the production wells 6, 7 by a distance l of the step of the design grid. The length of the horizontal injection well 8 does not exceed the length of the horizontal sections of the producing wells 6, 7.

Casing strings 9 (Fig. 3, 4) of horizontal wells 6, 7 (Fig. 1) are opened by perforation 10, 11 (Fig. 3, 4) at least in two intervals, at a distance c, excluding their hydrodynamic connection. Between these intervals, flow packers 12 are installed, which allow for interval-based selection of formation fluid.

In horizontal sections of producing wells 6, 7 (Fig. 1), tubing string 13 (Fig. 3, 4) with side openings 14 is lowered. The lower end of the tubing string 13 is plugged.

In the horizontal section of the injection well 8 (Fig. 1) lower tubing 16 (Fig. 5). At the end of the tubing 16, an in-line packer 17 is installed, which allows for the interval-wise injection of the displacing fluid into the injection well 8 (Fig. 1) in order to maintain reservoir pressure (for example, in the form of a self-sealing cuff that does not allow the displacing fluid from the bottom to the mouth).

Horizontal production wells 6, 7 are mastered and put into operation. Formation fluid begins to be taken from the most distant horizontal sections of production wells 6, 7. The number of perforation intervals 10, 11 (Fig. 3, 4) and through packers 12 depends on the length of the horizontal section and the permeability of reservoir rocks of formation 1 (Fig. 1, 2 ) The higher the permeability of the rocks, the greater the perforation and the passage packers 12 are less likely to be installed (Figs. 3, 4).

Upon reaching an extremely cost-effective water cut and a decrease in oil production, idle intervals 15 (Fig. 4) of horizontal sections of production wells 6, 7 (Fig. 1) are moved in the direction of the beginning of the horizontal well so that formation fluid is taken through perforations 11 (Fig. . 3, 4) casing 9 located between the passage packers 12 in the second interval of the formation 1 (Fig. 1). Each next interval of the horizontal section of production wells 6, 7 is mastered for selection using tubing 13 (Fig. 3, 4) and through packers 12. The use of through packers 12 in tubing 13 allows you to switch from one production interval to another when reaching the maximum cost-effective water cut of the product and return to the previous intervals of operation after a sufficient time to restore pressure and equalize the front of the injected displacing fluid in the reservoir 1 (Fig. 1).

At the same time, the idle sections 15 (Fig. 4) are sequentially isolated in the direction from the bottom to the beginning of the horizontal section with installed packers 12 (Fig. 3, 4).

After flooding the last interval 11 farthest from the bottom, the tubing 13 is moved to the bottom for selection from the first interval 10 from the bottom of the horizontal section 15 of production wells 6, 7 (Fig. 1) through holes 14 (Fig. 3).

The horizontal injection well 8 (Fig. 1) is mastered and put into operation. Initially, the injection of the displacing fluid is carried out in the bottomhole portion 18 (Fig. 5) of the horizontal section of the injection well 8 (Fig. 1).

In order to maximize the effect of the displacing agent on horizontal production wells, the displacing agent is injected with an increase in reservoir pressure by 10-20% compared to the extraction zone. This dependence was established based on the results of pilot work carried out in oil fields. The result is a stable and continuous effect on the reservoir 1, the effective use of a displacing agent, an increase in the flow rate and volumes of extracted products. With a decrease in the injectivity of the reservoir rocks at the bottom of the horizontal injection well 8 to the most cost-effective, the idle section 19 (Fig. 6) of the horizontal stem of the injection well 8 (Fig. 1) is sequentially isolated in the direction from the bottom to the beginning of the horizontal well by installing a packer-cutter 20 (Fig. 6) or cement. Then, the next interval 21 of the horizontal section of the injection well 8 (Fig. 1) is mastered under injection using tubing 16 (Fig. 5, 6) and the packer 22.

Concrete example

The implementation of this method, consider the example of a site characteristic of a massive oil reservoir of the Tournaisian layer. Oil reservoir 1 (Fig. 1, 2) is drilled with wells 2-4 (Fig. 1) along a 300 × 300 m grid. According to the data of deep drilling of wells 2-4 and 2D seismic surveys conducted in the field, the geological structure of the reservoir was clarified 1, built a structural map on the roof of the Tournaisian tier. The lower boundary for reservoir 1 is the oil-water contact (WOC) (Fig. 2).

We selected a deposit section with effective oil-saturated thicknesses of 19.6 m. The dimensions of the highlighted deposit section were 840 × 840 m, recoverable oil reserves - 330 thousand tons. Permeability was determined - 0.110 μm ² , porosity - 12.3%, oil saturation - 80.0 % The reservoir pressure is 10.4 MPa.

First, on the site of reservoir 1 (Fig. 1), two horizontal production wells 6, 7 were built at a distance of 300 m from each other and between them at a distance of 150 m one horizontal injection well 8. Horizontal wells 6-8 were placed parallel to each other in a horizontal plane . The lengths of the horizontal sections of wells 6–8 were 280–285 m.

The distance a (Fig. 2) from the top of the formation 1 (Fig. 1) to the bottom of each horizontal section of producing wells 6, 7 was 6.0 and 9.2 m. The distance b (Fig. 2) from the lowest points in the horizontal sections production wells 6 (Fig. 1) and 7 to the oil well (Fig. 2) were 12.6 and 10.4 m.

The casing strings 9 (Figs. 3, 4) were opened with perforations 10, 11 at two intervals farthest from the beginning of the horizontal sections of production wells 6, 7 (Fig. 1) at a distance of 95.0 m from each other. Columns of tubing 13 (Fig. 3, 4) with side openings 14, the lower end of which is plugged, were lowered into the horizontal sections of production wells 6, 7. Between the intervals of perforation at a distance of 110 m from the bottom, a passage packer 12 was installed.

In the horizontal section of the injection well 8 (Fig. 1) lowered tubing 16 (Fig. 5, 6). At a distance of 105 m from the bottom, a passage packer 17 was installed.

Horizontal production wells 6, 7 (Fig. 1) mastered and put into operation. The formation fluid began to be taken from the bottomhole zone 15 (Fig. 3) of the horizontal sections of production wells 6, 7 (Fig. 1). Horizontal production wells 6, 7 worked for 3 years with oil production rates of 12.0 and 10.6 tons / day. By the end of the fourth year of operation, the water cut of the product increased to 88.0 and 91.0%, and the oil production rate decreased to 1.9 and 1.2 tons / day. The tubing 13 (Fig. 3, 4) of horizontal production wells 6, 7 was moved 98.0 m in the direction of the horizontal well start so that formation fluid was taken through the perforation holes 11 (Fig. 3, 4) of the casing located between through packers 12 in the second interval of the horizontal section of production wells 6, 7 (Fig. 1). Then mastered the second interval 11 (Fig. 3, 4) of the horizontal section of production wells 6, 7 (Fig. 1) using oil tubing 13 (3, 4) and through packers 12 for oil selection.

The horizontal injection well 8 (Fig. 1) was mastered and put into operation simultaneously with the horizontal production wells 6, 7. The displacing fluid began to be pumped into the bottomhole part 18 (Fig. 5) of the horizontal injection well 8 (Fig. 1).

Horizontal injection well 8 operated in a mode with excess wellhead pressure exceeding the initial reservoir by 10.8%. The average daily injection of the displacing agent was 94.5 m ³ , over 3.5 years it decreased to 15 m ³ / day, the reservoir pressure in the reservoir area decreased by 2.8 MPa.

Due to the lack of injectivity in the first interval 18 (Fig. 5) of the horizontal section of the injection well 8 (Fig. 1), the following interval 21 (Fig. 6) of the horizontal section of the injection well 8 (Fig. 1) with a length of 85 m was mastered for injection. section 19 (Fig. 6) of the horizontal shaft was isolated by installing a packer-cutter 20. The horizontal injection well 8 (Fig. 1) was put into operation using tubing 16 (Fig. 6) and packers 20 and 22.

After 2 years of operation of the second interval of the horizontal section of the production well 6 (Fig. 1) and 2.4 years of operation of the second interval of the horizontal section of the production well 7 with an increase in water cut to 90.0% and a decrease in oil production to 2.0 and 1.6 t / day horizontal production wells 6, 7 after leveling the front of the advancement of the injected fluid in the reservoir 1 was switched to the first production interval 15 (Fig. 3).

As a result of the operation of horizontal production wells 6, 7 (Fig. 1) and horizontal injection well 8 in the area of oil reservoir 1, additional oil production in the amount of 7.5% was obtained compared to similar sections of the field due to switching from one production interval to another at achievement of extremely profitable water cut of products.

The proposed method provides leveling the front of the injected fluid into the reservoir, increasing oil recovery, expanding the field of application of horizontal wells under various development conditions of the deposits.

Claims (1)

A method of developing an oil reservoir by horizontal wells, including the construction of horizontal producing wells covering the reservoir and horizontal injection wells, injecting a displacing agent through the injection wells and selecting production by producing wells, wherein the horizontal producing wells are placed parallel to each other, between horizontal sections and parallel to horizontal sections have a horizontal injection well, the injection in which begins from the bottom, with lowering the injectivity of the collectors at the bottom of the horizontal injection well to the most cost-effective, the idle section of the horizontal well is sequentially isolated in the direction from the bottom to the beginning of the horizontal well of the injection well, characterized in that the horizontal producing wells are carried out in a permeable interlayer below the roof of the formation at a distance of 3-6 m and above water-oil contact at a distance of at least 10 m, a horizontal injection well is built equidistant from the horizontal sections of ext wells at a step distance of the design grid, injection of the displacing agent is carried out with an increase in reservoir pressure by 10-20% compared with the selection zone, provide for the return to the previous intervals of operation after a sufficient time to restore and align the front of the injected fluid in the reservoir, horizontal sections production wells are opened in two intervals at a distance that excludes their hydrodynamic connection, and the selection of products is carried out alternately, and switching from one interval another custom performed when the maximum cost-effective water production.

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