Intelligent layered injection string for water-polymer injection wells and its operation method

Abstract

The present invention relates to an intelligent layered injection string for water-polymer injection wells, belonging to the technical field of oilfield production and injection enhancement. The layered injection string includes a double-layer oil pipe downhole, a downhole safety valve, a top packer, a cable positioning seal, a dual-medium injection working cylinder, an isolation packer, a cable insertion seal and a round plug. The dual-medium injection working cylinder is connected to the ground controller via a steel armored cable. The operation method is as follows: well cleaning; the dual-medium injection working cylinder is tested to be normal, and the string of the present invention and the steel armored cable are lowered; the string of the present invention is sealed; different media are injected according to the requirements of the reservoir; and fixed-point acidification is performed. The present invention can realize online stepless regulation of layered dual-medium injection in wells with arbitrary inclinations, and can also implement fixed-point acidification according to the requirements of the reservoir. The present invention can realize dual pipes in the same well, simultaneous injection and layering of water and polymer multi-layer sections, online stepless regulation of injection, and can also implement fixed-point acidification according to production requirements, solving many problems brought about by previous water-polymer ground injection strings.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield production and injection enhancement, and in particular relates to an intelligent layered injection string for a water-polymer injection well and an operation method thereof. Background Art

[0002] Polymer flooding primarily utilizes polymers to increase the viscosity of injected water and reduce the oil-water mobility ratio. Therefore, the viscosity of the polymer solution directly influences its effectiveness. While ensuring the injectability of the polymer solution, its viscosity within the formation is the primary factor influencing its effectiveness. As traditional water flooding methods in my country fail to meet existing oil production requirements, tertiary oil recovery (TER) technology has become a key component of my country's petroleum technology innovation, with polymer flooding being a key focus.

[0003] Offshore oilfields feature thick reservoirs with high permeability and severe heterogeneity, leading to significant conflicts between injected layers. To expand the volume swept by waterflooding and improve its recovery efficiency, polymer flooding has been implemented in some offshore waterflooding fields by adding water-soluble polymers to the injected water to increase water viscosity, reduce water permeability, improve the oil-water viscosity ratio, and increase the volumetric sweep coefficient. To meet the development requirements of reservoirs with varying physical properties and achieve refined production from multiple layers, reservoir engineers are proposing a process for injecting and producing different media in separate layers within the same well.

[0004] Some reservoirs in offshore water-flooded oil fields are severely heterogeneous. In order to expand the water-flood swept volume, improve the water-flooding oil recovery efficiency, and carry out fine-grained mining in multiple sections, the demand for layered injection technology of different displacement media in the same well has been put on the agenda.

[0005] Therefore, research on intelligent stratified injection string allocation for water-polymer injection wells can solve the stratified injection problem in the development of highly deviated wells and achieve stratified control. Summary of the Invention

[0006] In order to overcome the deficiencies in the prior art, the present invention provides an intelligent layered injection string for a water-polymer injection well and an operation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A smart layered injection string for a water-polymer injection well comprises a casing, a layered completion string and a layered injection string arranged in sequence from the outside to the inside, the layered completion string comprising a top packer, at least one isolation packer and a bottom packer arranged in the casing, an injection layer being formed between two adjacent top packers and the isolation packers; the layered injection string comprises a hydraulic control pipeline, a downhole safety valve, a cable positioning seal, a plurality of dual-medium injection working cylinders, a plurality of cable insertion seals and a round plug which are connected in sequence to a concentric oil tubing outer tube and a concentric oil tubing inner tube from top to bottom; each of the dual-medium injection working cylinders is connected to a ground controller connected to a host computer via a steel armored cable.

[0009] Furthermore, the dual-medium dispensing working cylinder includes an upper joint, an outer tube, an inner tube, a three-way valve, a flow meter and a lower joint connected in sequence from top to bottom, the upper joint and the lower joint are respectively provided with a cable upper joint and a cable lower joint for connecting to the armored cable, and double channels are axially provided in the upper joint and the lower joint, and the double channels are respectively connected to the annulus formed between the concentric oil pipe outer tube and the concentric oil pipe inner tube and the center tube, and the annulus between the outer tube and the inner tube is connected to the channel of the concentric oil pipe outer tube through the channel of the upper joint and the lower joint, The channel formed between the inner tube, the control unit cabin and the motor sealed cabin is connected to the central tube of the concentric oil pipe inner tube through the channels of the upper joint and the lower joint. The lower joint is provided with a liquid outlet and is connected to the injection layer corresponding thereto. The control unit cabin and the motor sealed cabin are provided with a control circuit board, a motor, a reducer and an adjustment mechanism. The lower end of the adjustment mechanism is connected to the valve core of the three-way valve. The valve core is controlled by the adjustment mechanism to realize the communication between the channel between the three-way valve, the outer tube and the inner tube and the channel between the inner tube, the control unit cabin and the motor sealed cabin.

[0010] Furthermore, the internal channel of the dual-medium injection working cylinder is respectively provided with a polymer injection string pressure sensor, a water injection string pressure sensor and a formation pressure monitoring sensor connected to the control circuit board, the motor and the reducer are connected to the head end of the regulating mechanism, the tail end of the regulating mechanism is connected to the head end of the three-way valve, the three-way valve is arranged in the flow regulating inner tube, and the motor and the reducer and the regulating mechanism are all arranged in the motor sealing cabin.

[0011] Furthermore, the cable positioning seal includes a positioning seal body, a positioning seal pressure cap and a positioning seal module. A positioning cable passing channel is opened on the side wall of the positioning seal body. Positioning cable sealing interfaces are provided at the upper and lower ends of the positioning cable passing channel. The positioning seal module and the top seal are sealed by plug-in connection. The positioning seal pressure cap and the positioning seal body are threadedly connected. The lower end of the positioning seal pressure cap is provided with a positioning step that cooperates with the top seal.

[0012] Furthermore, the cable insertion seal includes an insertion seal body, an insertion seal pressure cap and an insertion seal module. The side wall of the insertion seal body is provided with an insertion cable passage, and the upper and lower ends of the insertion cable passage are provided with insertion cable sealing interfaces; the insertion seal module is plugged into the isolation seal.

[0013] Furthermore, the dual-medium injection working cylinder corresponds to each injection layer respectively, and the sealing between different layers is achieved by the top seal, isolation seal, cable positioning seal and cable insertion seal. The round plug is placed at the bottom of the tubing string, and the cable positioning seal, dual-medium injection working cylinder and cable insertion seal are connected to each other through the outer layer pipe of the concentric oil tubing inner pipe.

[0014] The present invention has the following beneficial effects over the prior art:

[0015] The present invention adopts an integrated overall process of a water-polymer injection string and a layered control string to achieve dual pipes in the same well, simultaneous injection of water and polymer in multiple layers, online stepless regulation of injection, and implementation of targeted acidification according to production requirements, thus solving many problems brought about by previous water-polymer surface injection strings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 This is a schematic diagram of the cable positioning and sealing structure;

[0019] Figure 3 Schematic diagram of the sealing structure for cable insertion;

[0020] Figure 4This is a structural diagram of a dual-medium dispensing working cylinder;

[0021] Figure 5 This is a schematic diagram of the fluid flow direction of the dual-medium dispensing working cylinder;

[0022] In the figure, 1-ground controller; 2-host computer; 3-hydraulic control pipeline; 4-downhole safety valve; 5-casing; 6-concentric oil pipe outer tube; 7-concentric oil pipe inner tube; 8-steel armored cable; 9-cable positioning seal; 10-top packer; 11-dual medium injection working cylinder; 12-isolation packer; 13-cable insertion seal; 14-bottom packer; 15-round plug; 16-positioning seal body; 17-positioning seal pressure cap; 18-positioning seal module; 19-positioning cable passing channel; 20-positioning cable sealing interface; 21-cable protection cover; 22-insertion seal body; 2 3-Insert the sealing cap; 24-Insert the sealing module; 25-Insert the cable passage; 26-Insert the cable sealing interface; 27-Cable protective cover; 28-Upper connector; 29-Cable upper connector; 30-Control circuit board; 31-Control unit cabin; 32-Inner tube; 33-Outer tube; 34-Polymer injection string pressure sensor; 35-Motor and reducer; 36-Adjusting mechanism; 37-Motor sealing cabin; 38-Water injection string pressure sensor; 39-Formation pressure monitoring sensor; 40-Three-way valve; 41-Flowmeter; 42-Lower connector; 43-Cable lower connector; 44-Liquid outlet. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Combine Figure 1-5 To illustrate this embodiment, a smart layered injection string for a water-polymer injection well includes a casing 5, a layered completion string and a layered injection string arranged in sequence from the outside to the inside. The layered completion string includes a top packer 10, at least one isolation packer 12 and a bottom packer 14 arranged in the casing 5, and an injection layer is formed between two adjacent top packers 10 and the isolation packers 12; the layered injection string includes a hydraulic control pipeline 3, a downhole safety valve 4, a cable positioning seal 9, a plurality of dual-medium injection working cylinders 11, a plurality of cable insertion seals 13 and a round plug 15, which are connected to the concentric oil pipe outer tube 6 and the concentric oil pipe inner tube 7 in sequence from top to bottom; each dual-medium injection working cylinder 11 is connected to a ground controller 1 connected to a host computer 2 through a steel armored cable 8.

[0025] The optimized dual-medium dispensing working cylinder 11 includes an upper joint 28, an outer tube 33, an inner tube 32, a three-way valve 40, a flow meter 41 and a lower joint 42 connected in sequence from top to bottom. The upper joint 28 and the lower joint 42 are respectively provided with a cable upper joint 29 and a cable lower joint 43 for connecting to the armored cable 8. A double channel is axially provided in the upper joint 28 and the lower joint 42. The double channel is respectively connected to the annulus formed between the concentric oil pipe outer tube 6 and the concentric oil pipe inner tube 7 and the center pipe. The annulus between the outer tube 33 and the inner tube 32 is connected to the channel of the concentric oil pipe outer tube 6 through the channel of the upper joint 28 and the lower joint 42. The inner tube 32. The channel formed between the control unit cabin 31 and the motor sealed cabin 37 is connected to the central tube of the concentric oil pipe inner tube 7 through the channel of the upper joint 28 and the lower joint 42. The lower joint 42 is provided with a liquid outlet 44 and is connected to its corresponding injection layer. The control unit cabin 31 and the motor sealed cabin 37 are provided with a control circuit board 30, a motor and a reducer 35 and an adjustment mechanism 36. The lower end of the adjustment mechanism 36 is connected to the valve core of the three-way valve 40. The valve core is controlled by the adjustment mechanism 36 to realize the communication between the three-way valve 40, the outer tube 33 and the inner tube 32, and the channels between the inner tube 32, the control unit cabin 31 and the motor sealed cabin 37.

[0026] Optimally, the double-layer oil pipe of the concentric oil pipe outer pipe 6 and the concentric oil pipe inner pipe 7 can realize the simultaneous injection of dual media into the channel.

[0027] The optimized dual-medium injection working cylinder 11 internal channel is respectively provided with a polymer injection string pressure sensor 34, a water injection string pressure sensor 38 and a formation pressure monitoring sensor 39 connected to the control circuit board 30, and presents an electromechanical integrated structure. The motor and reducer 35 is connected to the head end of the regulating mechanism 36, and the tail end of the regulating mechanism 36 is connected to the head end of the three-way valve 40. The three-way valve 40 is arranged in the flow regulating inner tube, and the motor and reducer 35 and the regulating mechanism 36 are both arranged in the motor sealing cabin 37. The control device does not require the lowering of instruments for testing and adjustment, is not restricted by well inclination, and can adjust the injection volume in real time.

[0028] The optimized cable positioning seal 9 includes a positioning seal body 16, a positioning seal pressure cap 17 and a positioning seal module 18. A positioning cable passing channel 19 is opened on the side wall of the positioning seal body 16. Positioning cable sealing interfaces 20 are provided at the upper and lower ends of the positioning cable passing channel 19. The positioning seal module 18 and the top packer 10 are sealed by plug-in connection. The positioning seal pressure cap 17 and the positioning seal body 16 are threadedly connected. The maximum outer diameter of the positioning seal pressure cap is significantly larger than the maximum outer diameter of the positioning seal module 18. The lower end of the positioning seal pressure cap 17 is provided with a positioning step that matches the top packer 10.

[0029] The optimized cable insertion seal 13 includes an insertion seal body 22, an insertion seal pressure cap 23 and an insertion seal module 24. An insertion cable passage 25 is opened on the side wall of the insertion seal body 22, and an insertion cable sealing interface 26 is provided at the upper and lower ends of the insertion cable passage 25; the insertion seal module 24 is plugged into the isolation seal 12 to achieve sealing, and the maximum outer diameter of the insertion seal pressure cap 23 is smaller than the outer diameter of the insertion seal module 24.

[0030] Optimized, the dual-medium injection working cylinder 11 corresponds to each injection layer respectively, and the sealing between different layers is achieved through the top seal 10, the isolation seal 12, the cable positioning seal 9 and the cable insertion seal 13. The round plug 15 is placed at the bottom of the tubing string, and the cable positioning seal 9, the dual-medium injection working cylinder 11 and the cable insertion seal 13 are connected to each other through the outer layer pipe of the concentric oil tubing inner pipe 7.

[0031] The method for intelligently distributing injection strings in water-polymer injection wells of the present invention comprises the following steps:

[0032] Step 1: In order to ensure that the dual-medium injection working cylinder 11 can be lowered to the predetermined position in one time, the impact of the steps and obstruction points in the downhole sand control section is judged, and the well clearing string is first lowered. The outer dimensions of the well clearing tool are the same as those of the dual-medium injection working cylinder 11. Ensure that the well clearing tool is lowered to the bottom of the well multiple times, and the well clearing string is pulled out after the well clearing is completed; the outer dimensions of the well clearing tool are the same as those of the dual-medium injection working cylinder 11.

[0033] Step 2: Number the dual-medium dispensing mandrels 11 according to the different layers they are placed in. All the mandrels on the ground are tested and tested normally. Set the outlet 44 of the lowest dual-medium dispensing mandrel 11 to be fully open and the outlets 44 of the other dual-medium dispensing mandrels 11 to be fully closed. Figure 1 As shown, a pipe string for intelligent stratified injection of water-polymerized wells is lowered, and a steel-armored cable 8 is lowered along with the pipe string. During the lowering process, every 200 meters of the pipe string is lowered, the steel-armored cable 8 connects to the ground controller 1 and the host computer 2 to determine whether the communication is normal. If the communication is normal, the pipe string is continued to be lowered. Otherwise, the lowering is stopped and the cause of the fault and the solution are analyzed.

[0034] Step 3: After the intelligent layered injection string of the water-polymer injection well is in place, it is inspected and sealed; the specific method of the string inspection and sealing is as follows: keep the liquid outlet 44 of the uppermost dual-medium injection working cylinder 11 fully open, and the liquid outlets 44 of other dual-medium injection working cylinders 11 fully closed, inject clean water from the annulus, and observe the changes in the external pressure of the uppermost dual-medium injection working cylinder 11. If the external pressure of the dual-medium injection working cylinder 11 does not change, it means that the sealing of the cable positioning seal 9 is good, otherwise, the string should be pulled out and replaced with a new tool and then re-inserted. Then keep the liquid outlet 44 of any middle layer of the dual-medium injection working cylinder 11 fully open, and the liquid outlets 44 of the two adjacent dual-medium injection working cylinders 11 fully closed, inject clean water from the oil pipe, and observe the changes in the external pressure of the adjacent dual-medium injection working cylinders 11. If the pressure of both does not change, it means that the adjacent cable insertion seal 13 is sealed well, otherwise, the string should be pulled out and replaced and re-inserted.

[0035] Step 4: After the sealing is completed, the liquid outlet 44 of the dual-medium dispensing working cylinder 11 corresponding to each injection layer is controlled to be fully opened, and the pump is started for layered injection; the switch position of the three-way valve 40 of the dual-medium dispensing working cylinder 11 is adjusted according to the different requirements of the reservoir for the injection layer medium; the upper computer 2 sends an instruction, which is transmitted to the control unit 30 of the dual-medium dispensing working cylinder 11 of this layer through the ground controller 1 and the armored cable 8. The motor 35 rotates forward or reverse according to the instruction of the control unit 30, thereby driving the spool of the three-way valve 40 to move axially. The sensor detects the position of the spool and judges the status of the three-way valve 40 in turn, injecting water, injecting polymer and closing.

[0036] Step 5: When acidizing operation is required for a certain layer, the liquid outlet 44 of the dual-medium dispensing working cylinder 11 of this layer is controlled to be fully open, and the liquid outlets 44 of the dual-medium dispensing working cylinders 11 of other layers are fully closed, and acid is injected into the ground to achieve targeted acidification of this layer.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An intelligent layered injection string for water-polymer injection wells, characterized by: The invention comprises a casing (5), a layered completion string and a layered injection string arranged in sequence from the outside to the inside, wherein the layered completion string comprises a top packer (10), at least one isolation packer (12) and a bottom packer (14) arranged in the casing (5), and an injection layer is formed between two adjacent top packers (10) and the isolation packers (12); the layered injection string comprises a hydraulic control line (3), a downhole safety valve (4), a cable positioning seal (9), a plurality of dual-medium injection working cylinders (11), which are connected in sequence with a concentric oil pipe outer tube (6) and a concentric oil pipe inner tube (7) from top to bottom, respectively. A plurality of cable-inserted seals (13) and round plugs (15); each of the dual-medium dispensing working cylinders (11) is connected to a ground controller (1) connected to a host computer (2) via a steel armor cable (8); the dual-medium dispensing working cylinder (11) comprises an upper joint (28), an outer tube (33), an inner tube (32), a three-way valve (40), a flow meter (41) and a lower joint (42) connected in sequence from top to bottom, the upper joint (28) and the lower joint (42) are respectively provided with a cable upper joint (29) and a cable lower joint (43) for connecting to the steel armor cable (8), the upper joint (28) and the lower joint (42) are provided with a double channel in the axial direction, and the double channel is respectively connected to the annulus formed between the concentric oil pipe outer tube (6) and the concentric oil pipe inner tube (7) and the center tube, the annulus between the outer tube (33) and the inner tube (32) is connected to the channel of the concentric oil pipe outer tube (6) through the channel of the upper joint (28) and the lower joint (42), and the channel formed between the inner tube (32), the control unit cabin (31) and the motor sealing cabin (37) is connected to the center of the concentric oil pipe inner tube (7) through the channel of the upper joint (28) and the lower joint (42). The outer tube (33) and the inner tube (32) are connected to each other, the lower joint (42) is provided with a liquid outlet (44) and is connected to the corresponding injection layer, the control unit cabin (31) and the motor sealed cabin (37) are provided with a control circuit board (30), a motor and a reducer (35) and an adjusting mechanism (36), the lower end of the adjusting mechanism (36) is connected to the valve core of the three-way valve (40), and the regulating mechanism (36) controls the valve core to realize the communication between the three-way valve (40), the outer tube (33) and the inner tube (32), and the inner tube (32), the control unit cabin (31) and the motor sealed cabin (37).

2. The intelligent layered injection string for water-polymer injection wells according to claim 1, characterized in that: The internal channel of the dual-medium injection working cylinder (11) is respectively provided with a polymer injection string pressure sensor (34), a water injection string pressure sensor (38) and a formation pressure monitoring sensor (39) connected to the control circuit board (30); the motor and reducer (35) are connected to the head end of the regulating mechanism (36); the tail end of the regulating mechanism (36) is connected to the head end of the three-way valve (40); the three-way valve (40) is arranged in the flow regulating inner tube; the motor and reducer (35) and the regulating mechanism (36) are both arranged in the motor sealing cabin (37).

3. The intelligent layered injection string for water-polymer injection wells according to claim 2, characterized in that: The cable positioning seal (9) includes a positioning seal body (16), a positioning seal pressure cap (17) and a positioning seal module (18). A positioning cable passing channel (19) is provided on the side wall of the positioning seal body (16). Positioning cable sealing interfaces (20) are provided at the upper and lower ends of the positioning cable passing channel (19). The positioning seal module (18) and the top packer (10) are sealed by plug-in connection. The positioning seal pressure cap (17) and the positioning seal body (16) are connected by threads. The lower end of the positioning seal pressure cap (17) is provided with a positioning step that matches the top packer (10).

4. The intelligent layered injection string for water-polymer injection wells according to claim 3, characterized in that: The cable insertion seal (13) comprises an insertion seal body (22), an insertion seal pressure cap (23) and an insertion seal module (24); a cable insertion passage (25) is provided on the side wall of the insertion seal body (22); and cable insertion sealing interfaces (26) are provided at the upper and lower ends of the insertion cable insertion passage (25); the insertion seal module (24) is plugged into and sealed with the isolation packer (12).

5. The intelligent layered injection string for water-polymer injection wells according to claim 4, characterized in that: The dual-medium injection working cylinder (11) corresponds to each injection layer respectively, and the sealing between different layers is achieved by the top seal (10), the isolation seal (12), the cable positioning seal (9) and the cable insertion seal (13). The round plug (15) is placed at the bottom end of the pipe string, and the cable positioning seal (9), the dual-medium injection working cylinder (11) and the cable insertion seal (13) are connected to each other through the outer layer pipe of the concentric oil pipe inner pipe (7).

6. The method for intelligently distributing injection strings in water-polymer injection wells according to claim 1, characterized in that: The following steps are involved: Step 1: First, run the dredging string and ensure that the dredging tools are lowered to the bottom of the well several times. After the dredging is completed, pull out the dredging string. Step 2: Test the dual-medium injection working cylinder (11) to ensure that it is normal, set the liquid outlet (44) of the lowest dual-medium injection working cylinder (11) to be fully open, and the liquid outlets (44) of other dual-medium injection working cylinders (11) to be fully closed, and lower the intelligent layered injection string of the water-polymer injection well into the water-polymer injection well, and lower the steel armored cable (8) together with the string; Step 3: After the intelligent layered injection string of the water-polymer injection well is in place, the sealing is checked; Step 4: After the seal is verified, the liquid outlets (44) of the dual-medium dispensing working cylinders (11) corresponding to each injection layer are fully opened, and the pump is started to inject the liquid in layers; Step 5: When acidizing operation is required for a certain layer, the liquid outlet (44) of the dual-medium dispensing working cylinder (11) of this layer is controlled to be fully open, and the liquid outlets (44) of the dual-medium dispensing working cylinders (11) of other layers are fully closed, and acid is injected into the ground to achieve the targeted acidizing of this layer.

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