RU2718665C1 - Development method of low-permeability reservoir - Google Patents

Abstract

FIELD: soil or rock drilling.

SUBSTANCE: invention can be used for development of low-permeability reservoirs, where drilling of horizontal wells with multistage hydraulic fracturing of formation (MHFF) is performed and it is necessary to maintain formation pressure. Method includes drilling of wells with horizontal section, multistage hydraulic fracturing of formation (MHFF) in horizontal sections of wells with arrangement of ports, determination of production well, in which watering of the product by more than 15 % per month, determination of pick-up on ports in at least one injection well adjacent to production well, in which watering of the product by more than 15 % per month, stopping the injection well, which resulted in production watering in the production well, cutting off at least one side barrel from the main borehole in this injection well, arrangement of ports in the side barrel of the injection well in zones closer to ports of the main hole of the injection well, at which intake capacity is less than 60 % of maximum intake capacity per one port of the main barrel of injection well, than to ports with capacity above said threshold, pumping of working fluid into side barrel of injection well at choke restriction or at stopping of main bore of injection well.

EFFECT: technical result consists in improvement of productivity of production wells with horizontal sections, in particular in increasing extraction of hydrocarbons (oil recovery) formations during development of low-permeability reservoirs.

15 cl, 7 dwg

Description

The invention can be used to develop low-permeability reservoirs, where horizontal drilling with multistage hydraulic fracturing (MHF) is used and it is necessary to maintain reservoir pressure.

To increase productivity, horizontal sections of multi-fracturing wells are usually oriented in the direction of minimum horizontal stress. When using the claimed method, horizontal sections can also be located towards maximum horizontal stress (stress).

A known method of developing an oil reservoir according to patent RU 2613713 (publication date: 03/21/2017, IPC ЕВВ 43/00, ЕВВ 43/26). A method of developing an oil reservoir, in accordance with which in the reservoir are drilled and alternated through one row, placing at a distance from each other, rows of horizontal production wells and rows of horizontal injection wells. In this case, the horizontal wells of the production wells and the horizontal wells of the injection wells are positioned in the direction of the minimum horizontal stress in the formation so as to ensure the propagation of hydraulic fractures perpendicular to the direction of the horizontal wells. At least two hydraulic fracturing ports are installed in casing strings of injection and production wells located at a distance from each other and providing communication between the wells and the formation. Common signs of the claimed technical solution with the known method is the drilling of horizontal production wells (production wells with horizontal sections), horizontal injection wells (injection wells with horizontal sections), hydraulic fracturing (multi-stage hydraulic fracturing), installation of at least two hydraulic fracturing ports ( with installation of ports).

The disadvantage of this method is the low productivity of producing wells as a result of uneven and in some areas low injectivity of injection wells. As a result, with an uneven distribution of the waterflooding profile across the ports, maximum oil recovery is not ensured.

A known method of developing an oil reservoir according to patent RU 2394981 (publication date: 07/20/2010, IPC ЕВВ 43/20, Е21В 7/06). A method for developing an oil reservoir includes drilling a reservoir with vertical and / or inclined wells, taking products through production wells and injecting a working agent through injection wells, drilling in production wells from a vertical or inclined sidetrack, and taking products from both trunks. When drilling a sidetrack, the sidetracking interval is selected below the zones of absorption and intense water showings, below the zones of shedding of unstable rocks, below the level of fluid in the well. The lateral trunk is drilled in the range of dense, impermeable, masonry-free formations. Common features of the claimed method and the known method of developing a deposit are drilling wells with deposits, product selection through production wells and pumping a working agent through injection wells, drilling a side well, product selection.

The disadvantage of this method is the lack of oil recovery and, as a consequence, the low productivity of producing wells due to the lack of uniform distribution of the working fluid in the formation through injection wells.

The technical result is to increase the productivity of producing wells with horizontal sections, in particular, to increase the hydrocarbon recovery (oil recovery) of the reservoirs when developing low-permeability reservoirs.

Low permeability reservoirs are oil fields with a low oil recovery coefficient. The oil recovery factor of facilities with low permeability reservoirs currently does not exceed 6%.

The technical result is achieved through the application of a method of developing a low permeability reservoir, in which they carry out:

drilling of wells with a horizontal section;

multi-stage hydraulic fracturing (MHF) in horizontal sections of wells with port placement; depletion of wells;

starting the working fluid in injection mode in at least one of the wells (injection well);

control of watering production in wells operating in production mode (production wells);

determination of the producing well in which the product was flooded by more than 15% per month;

conducting geophysical surveys and determining injectivity at ports in at least one injection well adjacent to the producing well, in which production was irrigated by more than 15% per month;

shutting off the injection well, which led to the flooding of production in the producing well;

killing at least one sidetrack (WBC) from the main trunk in a given injection well;

placement of ports in the side well of the injection well in areas closer to the ports of the main well of the injection well, at which the injectivity is less than 60% of the maximum injectivity at one port of the main well of the injection well than to ports with an injectivity higher than the specified threshold;

injection of the working fluid into the lateral well of the injection well during plastering or when the main well of the injection well stops.

Thus, the technical result is achieved by ensuring the alignment of the waterflood profile in the formation during drilling of the side well of the injection well and the installation of ports to further increase water flooding in areas with insufficient injectivity of the main well of the injection well.

When plucking the main well of the injection well, the waterflood profile is leveled due to the total distributed work of the main and side shafts of the injection well. At the same time, the flow rate of the working fluid along the main trunk is reduced, which allows to reduce the water cut of the product through the main trunk port, which ensures maximum throttle response, for example as a result of auto-hydraulic fracturing.

When the main well of the injection well stops, the previously created waterfront (profile) in the reservoir is supplemented by the operation of the sidetracking ports located in the zones of insufficient water flooding, thereby shifting the waterflood front in these zones to the producing well.

Drilling wells can be perpendicular to the maximum reservoir stress. Horizontal sections of wells (production and injection) can be located mutually in parallel.

The ratio of the number of injection wells to the number of production wells may be in the range from 1: 1 to 1: 3.

The ratio of the number of producing wells to the number of injection wells can be in the range from 1: 1 to 1: 3. Preferably, the ratio is 1: 2 production wells to injection wells, respectively.

Injection wells may be alternated through one, two, or three production wells.

Production wells may be alternated through one, two, or three injection wells.

The distance between the horizontal sections of the wells can be in the range from 700 m to 1500 m.

After at least one sidetracking from the main injection wellbore to the injection of the working fluid into the sidetrack of the injection well is performed, the sidetrack of the injection well may be drilled.

Field-geophysical studies can be carried out in the injection well adjacent to the producing well, by which the product is flooded, i.e. located closer to the producing well than other injection wells.

When implementing the method, the water cut (degree of water cut) of the product as a result of a breakthrough from the injection well into the producing well can be determined using pressure sensors.

When implementing the method in areas of further port placement in the lateral well of the injection well, a multi-stage hydraulic fracturing is performed.

Wells (production or injection) can be cased or uncased.

The method of developing low permeability reservoirs is illustrated by the figures:

in FIG. 1 - stage of well operation for depletion;

in FIG. 2 - stage of starting the working fluid in the injection mode in two wells (injection wells);

in FIG. 3 - the stage of cutting one sidetrack (WBC) from the main well of the injection well and flooding through it;

in FIG. 4 - a system for maintaining reservoir pressure (RPM) on the example of a production well GS 1D and an injection well GS 1H;

in FIG. 5 - pickup distribution by ports (P1, P2, P3, P4, P5) of the main injection wellbore;

in FIG. 6 - dynamics of changes in flow rate, injectivity and water cut (watering) of the injection well GS 1N and the production well GS 1D;

in FIG. 7 - pickup distribution by ports (P1, P2, P3, P4, P5) of the main well of the injection well after geological and technical measures (geological and technical measures).

In this case, geological and technical measures are understood to mean sidetracking of the injection well and waterflooding.

A method of developing a low permeability reservoir is as follows.

Produce drilling wells with a horizontal section (Fig. 1). The length of the horizontal section of the wells is on average 1000 m. It is recommended that the horizontal sections of the wells be located at a distance of at least 500 m from each other. Multistage hydraulic fracturing is performed in the horizontal sections of the wells with port placement. Next, the wells are operated for depletion until the oil production rate falls below 1 ton / well port with multi-stage fracturing (Fig. 1). After conducting wells for depletion, the working fluid is launched in injection mode into at least one well. In FIG. 2 it can be seen that well 1 is put into the injection mode, and the second well is operating in the operating mode (production well 2).

In FIG. Figure 4 shows the field development site, in which two wells are indicated: the production well GS 1D and the injection well GS 1N. Five ports were made at the injection well. When the GS 1H well is operating in the injection mode, the port pick-up distribution looks like that shown in FIG. 5.

The pick-up at port P5 is 40% of the total injectivity of the main well of the injection well, at port P4 - 25%, at port P3 - 10%, at port P2 - 15%, at port P1 - 10%.

In FIG. Figure 6 presents the results of an analysis of the development of the injection well GS 1H and the production well GS 1D over several years.

The degree of watering of the product may be more than 15%, i.e. 20%, 25%, etc.

When monitoring the water cut (water cut) of production in wells operating in the production mode (production wells), it was found that the increase in water cut (B) of production in October is 18% (Fig. 6). The reaction to a change in the regime of GS 1D is visible in a month - an increase in the liquid rate and oil rate.

When establishing the water cut of the production in the production well GS 1D above 15%, field and geophysical surveys are carried out in the neighboring injection well GS 1H, located closer than other injection wells (not shown in Fig.). As a result of field geophysical studies, the zone of breakthrough of the working fluid into the production well GS 1D is determined. In the above embodiment, at the site of the port P5 of the GS 1H well, the maximum injectivity of the injection well is 40% of the total injectivity. After determining the most “loaded” port of the injection well through which the breakthrough occurs, the injection well GS 1H is stopped.

Subsequently, sidetracking 3 (ZBS) is carried out (Fig. 3) from the main well of the injection well GS 1H and the sidetrack 3 is drilled if there is an influx of oil in the production of the well with sidetracking (Fig. 4). At the same time, the ports P1 ', P2', P3 'are located in the lateral well of the GS 1H injection well in areas as close as possible (located closer) to the ports (P1, P2, PZ) of the main well of the GS 1H injection well, at which the injectivity is less than 60 % of the maximum injectivity at one port P5 of the main well of the injection well. In FIG. Figure 5 shows that the maximum throttle response is provided at port P5 and is 40%. In this case, in the zone close to the ports where the injectivity is less than 24% (i.e. 60% of 40%), it is necessary to install the ports on the side well of the GS 1H well. In the above example, these ports are ports: P1, P2, and P3, because on them the pick-up is 10%, 15% and 10%, respectively.

In this example, the injection of the working fluid into the lateral well of the injection well GS 1H is carried out when the main stem of the injection well GS 1H is inserted. The results of the equalized injectivity at the ports of the injection well GS 1H are presented in FIG. 7.

In FIG. 7 it is seen that the distribution of injectivity after conducting the declared geological and technical measures ensured an increase in injectivity at the tail of the injection well with a decrease in injectivity at ports, which most likely cause waterlogging of the product in the producing well.

As a result, it is seen that while preventing water cut of the product when using the invention, an increase in injectivity at previously less involved ports of injection well 1 is ensured. Consequently, by aligning the formation waterflooding profile 4 from injection well 1, productivity in the adjacent producing well 2 is increased (Fig. 2, Fig. . 3).

The main and side shafts of the injection well are preferably cased (with casing strings), because in this case, a more accurate distribution of injectivity along the injection wellbore is provided.

Thus, by equalizing the injectivity of the injection wells when installing ports in the lateral wells in areas with minimal injectivity of the main injection well, the oil recovery in the production wells is enhanced.

Claims (26)

1. The method of developing a low permeability reservoir, which carry out: - drilling wells with a horizontal section; - multistage hydraulic fracturing (hydraulic fracturing) in horizontal sections of wells with port placement; - depletion of wells; - starting the working fluid in the injection mode in at least one of the wells (injection well); - control of watering production in wells operating in the production mode (production wells); - determination of the producing well in which the product was flooded by more than 15% per month; - conducting field geophysical studies and determining injectivity at ports in at least one injection well adjacent to the producing well, in which production was irrigated by more than 15% per month; - stop the injection well, which led to the flooding of production in the producing well; - cutting off at least one lateral wellbore from the main wellbore in a given injection well; - placement of ports in the lateral well of the injection well in areas closer to the ports of the main well of the injection well, at which the injectivity is less than 60% of the maximum injectivity at one port of the main well of the injection well than to ports with an injectivity higher than the specified threshold; - injection of the working fluid into the lateral well of the injection well during plastering or when the main well of the injection well is stopped. 2. A method for developing a low permeability reservoir according to claim 1, wherein the drilling of the wells is perpendicular to the maximum formation stress. 3. A method for developing a low permeability reservoir according to claim 1, wherein the horizontal sections of the wells are arranged in parallel. 4. The method of developing a low permeability reservoir according to claim 1, wherein the ratio of the number of injection wells to the number of production wells is in the range from 1: 1 to 1: 3, respectively. 5. The method of developing a low permeability reservoir according to claim 1, wherein the ratio of the number of producing wells to the number of injection wells is in the range from 1: 1 to 1: 3, respectively. 6. A method of developing a low permeability reservoir according to claim 4, wherein the injection wells are alternated through one, two or three production wells. 7. A method for developing a low permeability reservoir according to claim 5, wherein the producing wells are alternated through one, two or three injection wells. 8. A method for developing a low permeability reservoir according to claim 1, wherein further determining the water cut of the product as a result of a break from the injection well into the producing well using pressure sensors. 9. The method of developing a low permeability reservoir according to claim 1, wherein the distance between the horizontal sections of the wells is in the range from 700 to 1500 m 10. The method of developing a low-permeability reservoir according to claim 1, wherein the sidetracking of the injection wellbore is carried out at an equidistant distance from the horizontal section of the main injection wellbore and the horizontal section of the producing well. 11. A method for developing a low-permeability reservoir according to claim 1, wherein in the areas of further port placement in the lateral well of the injection well, a multi-stage hydraulic fracturing is performed. 12. A method for developing a low permeability reservoir according to claim 1, wherein after cutting at least one lateral wellbore from the main injection wellbore to pumping the working fluid into the lateral wellbore, the lateral well is injected. 13. The method of developing a low-permeability reservoir according to claim 1, wherein field and geophysical surveys are carried out in at least one injection well adjacent to the production well, in which the product is flooded, while being closer to the production well than other injection wells. 14. The method of developing a low permeability reservoir according to claim 1, wherein the wells are cased. 15. The method of developing a low permeability reservoir according to claim 1, wherein the wells are uncased.

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