CN117868759A - Shale oil reservoir radial well carbon dioxide oil displacement method and system - Google Patents
Shale oil reservoir radial well carbon dioxide oil displacement method and system Download PDFInfo
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- CN117868759A CN117868759A CN202410053067.5A CN202410053067A CN117868759A CN 117868759 A CN117868759 A CN 117868759A CN 202410053067 A CN202410053067 A CN 202410053067A CN 117868759 A CN117868759 A CN 117868759A
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 178
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 89
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 89
- 239000003079 shale oil Substances 0.000 title claims abstract description 69
- 238000011549 displacement method Methods 0.000 title claims abstract description 17
- 238000002347 injection Methods 0.000 claims abstract description 139
- 239000007924 injection Substances 0.000 claims abstract description 139
- 238000000605 extraction Methods 0.000 claims abstract description 61
- 238000006073 displacement reaction Methods 0.000 claims abstract description 31
- 238000004519 manufacturing process Methods 0.000 claims description 41
- 238000000034 method Methods 0.000 claims description 16
- 230000035699 permeability Effects 0.000 claims description 15
- 238000004891 communication Methods 0.000 claims description 6
- 230000005465 channeling Effects 0.000 claims description 5
- 238000011084 recovery Methods 0.000 abstract description 33
- 239000003921 oil Substances 0.000 description 253
- 239000010410 layer Substances 0.000 description 100
- 206010017076 Fracture Diseases 0.000 description 13
- 208000010392 Bone Fractures Diseases 0.000 description 10
- 239000010779 crude oil Substances 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 6
- 238000005553 drilling Methods 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
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- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
The invention provides a shale oil reservoir radial well carbon dioxide oil displacement method and system, wherein the oil displacement system comprises the following steps: the device comprises a first oil pipe, a second oil pipe, a third oil pipe, an oil extraction pump, an air injection pump, a carbon dioxide air source and a valve system, wherein the first oil pipe is communicated with an upper target layer through a radial horizontal well, the second oil pipe is communicated with a middle target layer through the radial horizontal well, and the third oil pipe is communicated with a lower target layer through the radial horizontal well; the inlet of the oil extraction pump and the outlet of the gas injection pump are respectively connected with the first oil pipe, the second oil pipe and the third oil pipe through a valve system, and the inlet of the gas injection pump is connected with a carbon dioxide gas source; the oil displacement method comprises the following steps: the valve system enables the first oil pipe, the second oil pipe and the third oil pipe to be respectively communicated with at most one of the oil extraction pump and the gas injection pump, and the technical problems of insufficient vertical utilization capacity of stratum and lower recovery ratio in shale oil and gas development are solved.
Description
Technical Field
The invention relates to the technical field of oil and gas field development, in particular to a shale oil reservoir radial well carbon dioxide displacement method and system.
Background
In the development of shale oil gas, compact oil gas and other unconventional oil gas resources, the conventional horizontal well fracturing technology is adopted to develop the economic benefits of shale oil gas and compact oil gas, and the investment recovery period is long. The radial horizontal well (radial well for short) is a novel drilling technology, and by means of the guiding function of a steering gear, a drill bit can complete 90-degree steering in a straight well barrel, horizontally enters a stratum in a mode of being perpendicular to the axis of the straight well barrel, and is drilled into the radial well. The hydraulic fracturing is carried out on the basis of the hydraulic fracturing, so that the radial well can be effectively guided to expand for a certain distance along the radial well direction. The radial well fracturing technology is particularly suitable for oil and gas reservoirs with low bedding development, low vertical permeability and small hydraulic fracture height, and can realize high-efficiency three-dimensional development of the oil and gas reservoirs by forming hydraulic fractures at a plurality of layers and in a plurality of directions.
However, when the reservoir permeability is small or the natural fracture development is insufficient, the conventional failure type exploitation can lead to rapid failure of the reservoir pressure, so that the higher oil and gas yield at the early stage of production is rapidly reduced along with the increase of the production time, and the too low formation pressure can lead to precipitation of light components in the formation, further reduce the development efficiency and further not fully exert the yield-increasing potential of the radial well fracturing technology.
Disclosure of Invention
The invention aims to provide a shale oil reservoir radial well carbon dioxide displacement method and system, which are used for solving the technical problems of insufficient vertical utilization capacity of a stratum and low recovery ratio in shale oil and gas development.
The above object of the present invention can be achieved by the following technical solutions:
the invention provides a shale oil reservoir radial well carbon dioxide displacement method, which adopts a shale oil reservoir radial well carbon dioxide displacement system;
the shale oil reservoir is provided with an upper destination layer, a middle destination layer and a lower destination layer which are sequentially distributed from top to bottom;
the oil displacement system comprises: the device comprises a first oil pipe, a second oil pipe, a third oil pipe, an oil production pump, an air injection pump, a carbon dioxide air source and a valve system, wherein the first oil pipe is communicated with the upper target layer through a radial horizontal well, the second oil pipe is communicated with the middle target layer through a radial horizontal well, and the third oil pipe is communicated with the lower target layer through a radial horizontal well;
the inlet of the oil extraction pump and the outlet of the gas injection pump are respectively connected with the first oil pipe, the second oil pipe and the third oil pipe through the valve system, and the inlet of the gas injection pump is connected with the carbon dioxide gas source;
the oil displacement method comprises the following steps: the valve system communicates the first, second and third tubing with at most one of the production pump and the gas injection pump, respectively.
In a preferred embodiment, the reservoir permeability of the shale reservoir is greater than 1mD, and the valve system communicates one of the first, second and third tubing with the gas injection pump and the other two with the production pump.
In a preferred embodiment, the valve system communicates the second tubing with the gas injection pump, and the first tubing and the third tubing are both in communication with the production pump.
In a preferred embodiment, the reservoir permeability of the shale reservoir is between 0.5mD and 1mD, and the valve system communicates one of the first, second and third tubing with the production pump and the other two with the gas injection pump.
In a preferred embodiment, the valve system communicates the second tubing with the production pump, and the first tubing and the third tubing are both in communication with the gas injection pump.
In a preferred embodiment, the reservoir permeability of the shale reservoir is less than 0.5mD or severe gas channeling has occurred, the flooding method comprises:
a production stage, wherein the valve system enables the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the oil extraction pump;
and in the gas injection stage, the valve system enables the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the gas injection pump.
In a preferred embodiment, a production phase is implemented, which is switched to a gas injection phase when the oil recovery speed is lower than the set oil recovery speed; and implementing the gas injection stage, and converting into a production stage after the gas injection speed is lower than the set gas injection speed.
In a preferred embodiment, the length of the radial horizontal well is 100-500 m, and the diameter is more than 20 mm; the spacing between the upper destination layer, the middle destination layer and the lower destination layer is not less than 20m.
In a preferred embodiment, the shale oil reservoir is provided with a main vertical well, the first oil pipe, the second oil pipe and the third oil pipe are all arranged in a casing of the main vertical well, and a plurality of oil casing annular spaces which are correspondingly communicated with the upper destination layer, the middle destination layer and the lower destination layer are sealed in the casing through packers;
generating hydraulic fractures in communication with the radial horizontal well by fracturing; the upper destination layer, the middle destination layer and the lower destination layer each have at least 4 of the radial horizontal wells.
The invention provides a shale oil reservoir radial well carbon dioxide displacement system which is applied to the shale oil reservoir radial well carbon dioxide displacement method;
the shale oil reservoir radial well carbon dioxide displacement system comprises: the system comprises a first oil pipe, a second oil pipe, a third oil pipe, an oil production pump, an air injection pump, a carbon dioxide air source and a valve system, wherein the first oil pipe is communicated with an upper target layer of the shale oil deposit through a radial horizontal well, the second oil pipe is communicated with a middle target layer of the shale oil deposit through a radial horizontal well, and the third oil pipe is communicated with a lower target layer of the shale oil deposit through a radial horizontal well;
the inlet of the oil extraction pump and the outlet of the gas injection pump are respectively connected with the first oil pipe, the second oil pipe and the third oil pipe through the valve system, and the inlet of the gas injection pump is connected with the carbon dioxide gas source;
the valve system includes:
the first oil extraction valve is arranged between the oil extraction pump and the first oil pipe;
the second oil extraction valve is arranged between the oil extraction pump and the second oil pipe;
the third oil extraction valve is arranged between the oil extraction pump and the third oil pipe;
the first gas injection valve is arranged between the gas injection pump and the first oil pipe;
the second gas injection valve is arranged between the gas injection pump and the second oil pipe;
the third air injection valve is arranged between the air injection pump and the third oil pipe.
The invention has the characteristics and advantages that:
according to the oil displacement method provided by the invention, carbon dioxide is injected into part of the upper target layer, the middle target layer and the lower target layer of the shale oil reservoir through the first oil pipe, the second oil pipe and the third oil pipe, and oil extraction is carried out on the other part; or, all carbon dioxide is injected simultaneously, and then all oil is extracted simultaneously, so that the combination of the crude oil extraction and the carbon dioxide injection is favorable for maintaining the pressure of a shale oil reservoir, a stable pressure field is formed in the oil reservoir, and the carbon dioxide and the crude oil form a stable displacement interface, so that the oil drainage/gas area of a reservoir is increased, the yield increasing potential of radial well oil extraction is released, the carbon dioxide injection efficiency is favorable for improving, the problem of insufficient vertical utilization capacity of a stratum is solved, and the recovery ratio is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a shale oil reservoir radial well carbon dioxide displacement system provided by the invention;
FIG. 2 is a top view of an underground portion of a shale reservoir radial well carbon dioxide displacement system provided by the invention;
FIG. 3 is a schematic illustration of an aerial portion of the shale reservoir radial well carbon dioxide flooding system shown in FIG. 1.
Reference numerals illustrate:
1. shale oil reservoirs;
2. a radial horizontal well; 3. Hydraulic fracturing; 4. A main vertical well;
6. a packer; 7. An oil jacket annulus; 8. A sleeve;
9. a first oil pipe; 10. A second oil pipe; 11. A third oil pipe;
5. a conduit shoe;
120. a valve system;
12. a first oil recovery valve; 13. A second oil recovery valve; 14. A third oil recovery valve;
15. a first gas injection valve; 16. A second gas injection valve; 17. A third gas injection valve;
18. a production pump; 19. a gas injection pump; 20. an oil-gas separator; 21. a carbon dioxide gas source;
31. a target layer is arranged on the upper layer; 32. a medium-destination layer; 33. and a lower destination layer.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Scheme one
The invention provides a shale oil reservoir radial well carbon dioxide displacement method, which adopts a shale oil reservoir radial well carbon dioxide displacement system;
the shale oil reservoir 1 is provided with an upper destination layer 31, a middle destination layer 32 and a lower destination layer 33 which are distributed in sequence from top to bottom;
as shown in fig. 1-3, the flooding system includes: the first oil pipe 9, the second oil pipe 10, the third oil pipe 11, the oil production pump 18, the gas injection pump 19, the carbon dioxide gas source 21 and the valve system 120, wherein the first oil pipe 9 is communicated with the upper destination layer 31 through the radial horizontal well 2, the second oil pipe 10 is communicated with the middle destination layer 32 through the radial horizontal well 2, and the third oil pipe 11 is communicated with the lower destination layer 33 through the radial horizontal well 2;
an inlet of the oil extraction pump 18 and an outlet of the gas injection pump 19 are respectively connected with the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 through a valve system 120, and an inlet of the gas injection pump 19 is connected with a carbon dioxide gas source 21;
the oil displacement method comprises the following steps: the valve system 120 communicates the first tubing 9, the second tubing 10 and the third tubing 11 with at most one of the production pump 18 and the gas injection pump 19, respectively.
According to the oil displacement method provided by the invention, carbon dioxide is injected into part of the upper target layer 31, the middle target layer 32 and the lower target layer 33 of the shale oil reservoir 1 through the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11, and oil is extracted from the other part; or, all carbon dioxide is injected simultaneously, and then all oil is extracted simultaneously, so that the combination of the crude oil extraction and the carbon dioxide injection is favorable for maintaining the pressure of the shale oil reservoir 1, forming a stable pressure field in the oil reservoir and enabling the carbon dioxide and the crude oil to form a stable displacement interface, thereby increasing the oil drainage/gas area of the reservoir, releasing the yield-increasing potential of the radial well oil extraction, being favorable for improving the carbon dioxide injection efficiency, solving the problem of insufficient vertical utilization capacity of the stratum and improving the recovery ratio.
In one embodiment, the shale reservoir 1 is provided with a main vertical well 4, and a first oil pipe 9, a second oil pipe 10 and a third oil pipe 11 are all arranged in a casing 8 of the main vertical well 4, and a plurality of oil casing annuluses 7 which are communicated with an upper destination layer 31, a middle destination layer 32 and a lower destination layer 33 correspondingly are sealed in the casing 8 through packers 6.
As shown in fig. 1, the lower end depths of the first oil pipe 9, the second oil pipe 10, and the third oil pipe 11 are sequentially increased to correspond to the upper destination layer 31, the middle destination layer 32, and the lower destination layer 33, respectively; inside the casing 8, a packer 6 is provided corresponding to the depth between the upper destination layer 31 and the middle destination layer 32 and the depth between the lower destination layer 33 and the middle destination layer 32, respectively, to pack the oil casing annulus 7 inside the casing 8 into at least three sections spaced up and down, the lower ends of the first, second and third oil pipes 9, 10 and 11 extend to the corresponding oil casing annulus 7, respectively, and the lower ends of the respective oil pipes are provided with conduit shoes 5, respectively. Preferably, the first tubing 9, the second tubing 10 and the third tubing 11 may be arranged side by side within the casing 8; however, the first oil pipe 9, the second oil pipe 10, and the third oil pipe 11 may be provided in a sleeved manner, for example: the second oil pipe 10 is sleeved outside the third oil pipe 11, and the first oil pipe 9 is sleeved outside the second oil pipe 10.
Further, hydraulic fractures 3 communicating with the radial horizontal wells 2 are created by fracturing, as shown in fig. 2, the upper, middle and lower destination layers 31, 32, 33 each having at least 4 radial horizontal wells 2. The hydraulic fracture 3 generated by fracturing extends in each target layer to play a role of communication, after the radial horizontal well 2 is fractured, carbon dioxide is injected to improve recovery ratio, a radial well fracturing technology is combined with a carbon dioxide injection technology, crude oil is extracted on the basis of radial well fracturing, carbon dioxide is injected to maintain pressure, a stable pressure field is formed in an oil reservoir, carbon dioxide and crude oil form a stable displacement interface, so that the oil drainage/gas area of a reservoir is increased, and the yield potential of radial well fracturing is released.
The on-off of the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11, the oil extraction pump 18 and the gas injection pump 19 is controlled by a valve system 120. In one embodiment, the valve system 120 includes: the first oil recovery valve 12, the second oil recovery valve 13, the third oil recovery valve 14, the first gas injection valve 15, the second gas injection valve 16 and the third gas injection valve 17 are arranged between the oil recovery pump 18 and the first oil pipe 9, the second oil recovery valve 13 is arranged between the oil recovery pump 18 and the second oil pipe 10, the third oil recovery valve 14 is arranged between the oil recovery pump 18 and the third oil pipe 11, the first gas injection valve 15 is arranged between the gas injection pump 19 and the first oil pipe 9, the second gas injection valve 16 is arranged between the gas injection pump 19 and the second oil pipe 10, and the third gas injection valve 17 is arranged between the gas injection pump 19 and the third oil pipe 11, so that the on-off between the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 and the oil recovery pump 18 and the gas injection pump 19 can be controlled effectively and reliably.
Further, an oil separator 20 is connected to an outlet of the oil extraction pump 18 to separate carbon dioxide from the shale oil produced. Further, the extracted shale oil is injected into the oil-gas separator 20, and the extracted carbon dioxide is injected into the ground again through the gas injection pump 19 in combination with the carbon dioxide gas source 21 after oil-gas separation.
In one embodiment, the reservoir permeability of the shale oil reservoir 1 is greater than 1mD, and the valve system 120 enables one of the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 to be communicated with the gas injection pump 19, and the other two to be communicated with the oil extraction pump 18, so that a continuous gas injection mode of 'one injection two extraction' is performed, and the oil extraction efficiency is improved.
Further, the valve system 120 enables the second oil pipe 10 to be communicated with the gas injection pump 19, the first oil pipe 9 and the third oil pipe 11 to be communicated with the oil extraction pump 18, and carbon dioxide is injected into the middle destination layer 32 positioned in the middle, so that the carbon dioxide drives oil gas of the upper destination layer 31 and the lower destination layer 33 to enter the oil sleeve annulus 7, thereby being beneficial to improving the oil extraction efficiency.
Specifically, the working process of the shale oil reservoir radial well carbon dioxide displacement system shown in fig. 1 comprises the following steps:
(1) Opening the first recovery valve 12, the second gas injection valve 16 and the third recovery valve 14, and closing the first gas injection valve 15, the second recovery valve 13 and the third gas injection valve 17;
(2) Simultaneously starting the oil extraction pump 18 and the gas injection pump 19;
(3) Carbon dioxide flows into the well through the second oil pipe 10 after being pressurized by the gas injection pump 19 from the carbon dioxide gas source 21 and the oil-gas separator 20, is transported to the middle destination layer 32 underground by the second oil pipe 10, flows into the radial horizontal well 2 from the oil sleeve annulus 7, flows into the hydraulic fracture 3 and drives oil in the upper direction and the lower direction;
(4) The oil driven upward by the carbon dioxide and the oil driven downward respectively flow into the upper destination layer 31 and the lower destination layer 33, are influenced by the ground oil extraction pump 18, are extracted to the ground through the first oil pipe 9 and the third oil pipe 11, respectively, and flow into the oil separator 20.
In another embodiment, the reservoir permeability of the shale oil reservoir 1 is between 0.5mD and 1mD, and the valve system 120 enables one of the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 to be communicated with the oil extraction pump 18, and the other two of the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the gas injection pump 19, so that a 'two-injection-one-production' type continuous gas injection mode is performed, and the oil extraction efficiency is improved.
Further, the valve system 120 enables the second oil pipe 10 to be communicated with the oil extraction pump 18, the first oil pipe 9 and the third oil pipe 11 to be communicated with the gas injection pump 19, and for the case of low reservoir permeability, the oil gas of the target layer 32 in carbon dioxide displacement enters the oil sleeve annulus 7 through simultaneously injecting carbon dioxide into the upper target layer 31 and the lower target layer 33, so that the oil extraction efficiency is improved.
Specifically, the working process of the shale oil reservoir radial well carbon dioxide displacement system shown in fig. 1 comprises the following steps:
(1) Opening the first 15, second 13 and third 17 gas injection valves and closing the first 12, second 16 and third 14 gas injection valves;
(2) Simultaneously starting the oil extraction pump 18 and the gas injection pump 19;
(3) Carbon dioxide is pressurized from a carbon dioxide gas source 21 and an oil-gas separator 20 through an air injection pump 19, flows into the well through a first oil pipe 9 and a third oil pipe 11, flows into an upper target layer 31 and a lower target layer 33 respectively, carbon dioxide flowing into the upper target layer 31 is displaced downwards, and carbon dioxide flowing into the lower target layer 33 is displaced upwards;
(4) The carbon dioxide-driven oil is collected in the middle destination layer 32, is influenced by the ground oil extraction pump 18, is extracted to the ground through the second oil pipe 10, and flows to the oil separator 20.
In another embodiment, the reservoir permeability of shale reservoir 1 is less than 0.5mD, the flooding method comprising a production stage and a gas injection stage; in the production phase, the valve system 120 puts the first tubing 9, the second tubing 10 and the third tubing 11 in communication with the production pump 18; in the gas injection stage, the valve system 120 enables the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 to be communicated with the gas injection pump 19, and a stable pressure field is formed in the oil reservoir by adopting an asynchronous gas injection mode so as to increase the oil/gas drainage area of the reservoir and release the yield potential of radial well fracturing.
Further, implementing a production stage, and converting into a gas injection stage when the oil extraction speed is lower than the set oil extraction speed; and implementing the gas injection stage, and converting into a production stage after the gas injection speed is lower than the set gas injection speed.
Specifically, the working process of the shale oil reservoir radial well carbon dioxide displacement system shown in fig. 1 comprises the following steps:
(1) In the production stage, the first oil extraction valve 12, the second oil extraction valve 13 and the third oil extraction valve 14 are opened, and the first gas injection valve 15, the second gas injection valve 16 and the third gas injection valve 17 are closed; and, the oil extraction pump 18 is turned on, and the gas injection pump 19 is turned off;
(2) The three layers of the upper destination layer 31, the middle destination layer 32 and the lower destination layer 33 are all used for oil extraction, and the extracted crude oil flows to the ground through the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 respectively;
(3) When the oil extraction rate is lower than the minimum requirement, converting into an air injection stage;
(4) Implementing the gas injection stage, opening the first 15, second 16 and third 17 gas injection valves and closing the first 12, second 13 and third 14 recovery valves; and, the oil extraction pump 18 is turned off, and the gas injection pump 19 is turned on;
(5) The three layers of the upper destination layer 31, the middle destination layer 32 and the lower destination layer 33 are all used for injecting gas, and the injected carbon dioxide flows into the stratum through the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 respectively;
(6) When the gas injection rate is lower than the minimum requirement, the production stage is switched again, namely, the steps (1) to (5) are repeated.
In the above three modes, the produced shale oil is injected into the oil separator 20 at the ground surface and further utilized; when the carbon dioxide is blown out, the produced carbon dioxide is separated from oil and gas and then is injected into the ground again in combination with the carbon dioxide gas source 21.
When severe gas channeling has occurred (i.e., more than 90% of the produced mass fraction is carbon dioxide), the above-mentioned asynchronous gas injection mode may also be adopted, and specific steps such as steps (1) to (6) in the asynchronous gas injection mode are not described herein.
The three mining modes can be mutually converted and combined, including but not limited to the production stage of the asynchronous gas injection mode, the continuous gas injection mode of 'one injection and two production' and the continuous gas injection mode of 'two injection and one production' are started again, or the production can be continued after the continuous gas injection mode of 'one injection and two production' and the continuous gas injection mode of 'two injection and one production' enter the serious gas channeling stage.
When the oil production is lower than the minimum requirement and the oil production cannot be increased through the asynchronous gas injection mode, the oil production should be stopped, and the oil well is closed.
Preferably, the length of the radial horizontal well 2 is 100-500 m, and the diameter is more than 20 mm; the spacing between the upper destination layer 31, the middle destination layer 32, and the lower destination layer 33 is not less than 20m.
Preferably, the vertical thickness of shale reservoir 1 at which the main vertical well 4 is deployed is not less than 40m.
Further, the upper destination layer 31, the middle destination layer 32 and the lower destination layer 33 are respectively drilled into 4 radial horizontal wells 2, the included angles between the radial horizontal wells 2 in the same layer are 45-90 degrees, and the included angles are 45 degrees with the direction of the maximum ground stress in the stratum, so that the hydraulic fracture 3 is gradually deflected to the direction of the maximum ground stress after being guided by the radial horizontal wells 2.
Further, the height of the hydraulic fracture 3 is controlled to 20% to 50% of the interlayer spacing to prevent premature gas channeling of carbon dioxide.
The diameter, length and spacing of the radial horizontal wells 2 should be determined according to the physical properties of the reservoir such as compressibility, permeability and oil saturation, so as to increase the guiding effect on the hydraulic fracture 3 as much as possible. The shale oil reservoir 1 is divided into a plurality of layers, and the control volume of the hydraulic fracture 3 communicated with the radial horizontal well 2 on the reservoir is expanded as much as possible. In the hydraulic fracturing process, stratum fracturing parameters, radial horizontal well 2 parameters and propping agent isopiestic fracturing parameters are designed, so that the length of the seam of the hydraulic fracture 3 is as long as possible, and the control volume in the horizontal direction is increased. The circulation flow and the pump pressure of the system are determined according to physical properties such as the pressure, permeability, oil saturation of the reservoir, the ratio of produced carbon dioxide to oil and the like, so that the condition that the reservoir gas is blown over quickly due to overlarge flow rate is avoided, the effective development time of shale oil is shortened, and meanwhile, the condition that the oil yield is too low due to overlarge flow rate is avoided.
Scheme II
The invention provides a shale oil reservoir radial well carbon dioxide displacement system which is applied to the shale oil reservoir radial well carbon dioxide displacement method;
the shale oil reservoir radial well carbon dioxide displacement system comprises: the system comprises a first oil pipe 9, a second oil pipe 10, a third oil pipe 11, an oil production pump 18, an air injection pump 19, a carbon dioxide air source 21 and a valve system 120, wherein the first oil pipe 9 is communicated with an upper destination layer 31 of the shale oil deposit 1 through a radial horizontal well 2, the second oil pipe 10 is communicated with a middle destination layer 32 of the shale oil deposit 1 through the radial horizontal well 2, and the third oil pipe 11 is communicated with a lower destination layer 33 of the shale oil deposit 1 through the radial horizontal well 2;
an inlet of the oil extraction pump 18 and an outlet of the gas injection pump 19 are respectively connected with the first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 through a valve system 120, and an inlet of the gas injection pump 19 is connected with a carbon dioxide gas source 21;
the valve system 120 includes: the first oil recovery valve 12, the second oil recovery valve 13, the third oil recovery valve 14, the first gas injection valve 15, the second gas injection valve 16 and the third gas injection valve 17 are shown in fig. 3, the first oil recovery valve 12 is arranged between the oil recovery pump 18 and the first oil pipe 9, the second oil recovery valve 13 is arranged between the oil recovery pump 18 and the second oil pipe 10, the third oil recovery valve 14 is arranged between the oil recovery pump 18 and the third oil pipe 11, the first gas injection valve 15 is arranged between the gas injection pump 19 and the first oil pipe 9, the second gas injection valve 16 is arranged between the gas injection pump 19 and the second oil pipe 10, and the third gas injection valve 17 is arranged between the gas injection pump 19 and the third oil pipe 11.
The shale oil reservoir radial well carbon dioxide displacement system provided by the invention is used for implementing carbon dioxide injection based on a radial well fracturing network, and can realize efficient and safe reservoir development. By controlling each oil extraction valve and gas injection valve in the valve system 120 through the oil displacement system, different gas injection oil extraction modes can be implemented according to the reservoir permeability of the shale oil reservoir 1, so that all or at least part of the technical effects of the gas injection method are generated, and are not described herein.
The implementation steps of the shale oil reservoir radial well carbon dioxide displacement system comprise:
(1) Selecting an upper destination layer 31, a middle destination layer 32 and a lower destination layer 33 according to the depth of the shale oil reservoir 1;
(2) Determining the burial depth of the shale oil reservoir 1, designing a drilling construction scheme, and drilling a main vertical well 4 to the bottom of the shale oil reservoir 1, wherein the depth is at least deeper than a selected lower target layer 33;
(3) A sleeve 8 is put into the main vertical well 4, and cement is injected and well cementation is carried out;
(4) Laterally windowing the sleeve 8 in the main vertical well 4 with the corresponding depth of the selected upper destination layer 31, middle destination layer 32 and lower destination layer 33, and drilling into 4 branches of the radial horizontal wells 2 which are vertical to each other;
(5) Setting a fracturing scheme, and respectively fracturing an upper target layer 31, a middle target layer 32 and a lower target layer 33 to form a hydraulic fracture 3;
(6) Lowering a first oil pipe 9, a second oil pipe 10 and a third oil pipe 11 into a casing 8 of the main vertical well 4, wherein the depth of each oil pipe corresponds to the depths of an upper destination layer 31, a middle destination layer 32 and a lower destination layer 33 respectively; a packer 6 is put into a conduit shoe 5 of each oil pipe to seal each oil pipe and an oil sleeve annulus 7, so that fluid of an air injection layer and a production layer (an upper target layer 31, a middle target layer 32 and a lower target layer 33 are air injection layers when carbon dioxide is injected, and are production layers when oil is extracted) is prevented from being communicated in a main vertical well 4;
(7) The first oil pipe 9, the second oil pipe 10 and the third oil pipe 11 are all arranged on the ground and are respectively connected with the oil extraction pump 18 and the gas injection pump 19 through a valve system 120.
The foregoing is merely a few embodiments of the present invention and those skilled in the art may make various modifications or alterations to the embodiments of the present invention in light of the disclosure herein without departing from the spirit and scope of the invention.
Claims (10)
1. A shale oil reservoir radial well carbon dioxide displacement method is characterized in that a shale oil reservoir radial well carbon dioxide displacement system is adopted;
the shale oil reservoir is provided with an upper destination layer, a middle destination layer and a lower destination layer which are sequentially distributed from top to bottom;
the oil displacement system comprises: the device comprises a first oil pipe, a second oil pipe, a third oil pipe, an oil production pump, an air injection pump, a carbon dioxide air source and a valve system, wherein the first oil pipe is communicated with the upper target layer through a radial horizontal well, the second oil pipe is communicated with the middle target layer through a radial horizontal well, and the third oil pipe is communicated with the lower target layer through a radial horizontal well;
the inlet of the oil extraction pump and the outlet of the gas injection pump are respectively connected with the first oil pipe, the second oil pipe and the third oil pipe through the valve system, and the inlet of the gas injection pump is connected with the carbon dioxide gas source;
the oil displacement method comprises the following steps: the valve system communicates the first, second and third tubing with at most one of the production pump and the gas injection pump, respectively.
2. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 1, wherein,
the reservoir permeability of the shale oil reservoir is greater than 1mD, and the valve system enables one of the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the gas injection pump, and the other two oil pipes to be communicated with the oil extraction pump.
3. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 2, wherein,
the valve system enables the second oil pipe to be communicated with the gas injection pump, and the first oil pipe and the third oil pipe are communicated with the oil extraction pump.
4. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 1, wherein,
the reservoir permeability of the shale oil reservoir is between 0.5mD and 1mD, and the valve system enables one of the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the oil extraction pump, and the other two oil pipes to be communicated with the gas injection pump.
5. The method for carbon dioxide displacement of shale oil reservoir radial well of claim 4, wherein,
the valve system enables the second oil pipe to be communicated with the oil extraction pump, and the first oil pipe and the third oil pipe are communicated with the gas injection pump.
6. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 1, wherein,
when the reservoir permeability of the shale oil reservoir is lower than 0.5mD or serious gas channeling occurs, the oil displacement method comprises the following steps:
a production stage, wherein the valve system enables the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the oil extraction pump;
and in the gas injection stage, the valve system enables the first oil pipe, the second oil pipe and the third oil pipe to be communicated with the gas injection pump.
7. The method for carbon dioxide displacement of shale oil reservoir radial well of claim 6, wherein,
the production stage is implemented, and when the oil extraction speed is lower than the set oil extraction speed, the gas injection stage is converted;
and implementing the gas injection stage, and converting into a production stage after the gas injection speed is lower than the set gas injection speed.
8. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 1, wherein,
the length of the radial horizontal well is 100-500 m, and the diameter is more than 20 mm;
the spacing between the upper destination layer, the middle destination layer and the lower destination layer is not less than 20m.
9. The method for carbon dioxide displacement of shale oil reservoir radial well according to claim 1, wherein,
the shale oil reservoir is provided with a main vertical well, the first oil pipe, the second oil pipe and the third oil pipe are all arranged in a casing pipe of the main vertical well, and a plurality of oil casing annular spaces which are correspondingly communicated with the upper target layer, the middle target layer and the lower target layer are sealed and isolated in the casing pipe through packers;
generating hydraulic fractures in communication with the radial horizontal well by fracturing; the upper destination layer, the middle destination layer and the lower destination layer each have at least 4 of the radial horizontal wells.
10. A shale reservoir radial well carbon dioxide flooding system characterized by being applied to the shale reservoir radial well carbon dioxide flooding method of any one of claims 1-9;
the shale oil reservoir radial well carbon dioxide displacement system comprises: the system comprises a first oil pipe, a second oil pipe, a third oil pipe, an oil production pump, an air injection pump, a carbon dioxide air source and a valve system, wherein the first oil pipe is communicated with an upper target layer of the shale oil deposit through a radial horizontal well, the second oil pipe is communicated with a middle target layer of the shale oil deposit through a radial horizontal well, and the third oil pipe is communicated with a lower target layer of the shale oil deposit through a radial horizontal well;
the inlet of the oil extraction pump and the outlet of the gas injection pump are respectively connected with the first oil pipe, the second oil pipe and the third oil pipe through the valve system, and the inlet of the gas injection pump is connected with the carbon dioxide gas source;
the valve system includes:
the first oil extraction valve is arranged between the oil extraction pump and the first oil pipe;
the second oil extraction valve is arranged between the oil extraction pump and the second oil pipe;
the third oil extraction valve is arranged between the oil extraction pump and the third oil pipe;
the first gas injection valve is arranged between the gas injection pump and the first oil pipe;
the second gas injection valve is arranged between the gas injection pump and the second oil pipe;
the third air injection valve is arranged between the air injection pump and the third oil pipe.
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