Downhole separate injection tubular column and separate layer water injection method
By designing the downhole injection string, including the combination of sliding sleeves and screen pipes for water injection, the problem of insufficient water injection in the high-pressure zone was solved, achieving sufficient water injection in the high-pressure zone and long service life of the packer, thus ensuring stable oil production and the effectiveness of stratified water injection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2026-04-10
AI Technical Summary
Existing injection tubing is prone to insufficient injection when injecting water into high-pressure layers, and packers are prone to failure under large pressure differentials, resulting in short service life and difficulty in meeting the injection needs of reservoirs with long well sections and complex depths.
The downhole injection string consists of a first packer, a water distributor, a second packer, a sliding sleeve, a screen pipe, and a plug, arranged in sequence. Water is injected into the high-pressure layer by opening the injection hole and the screen pipe through the sliding sleeve. Combined with the bidirectional anchor of the water well and the connection with the well wall, fixation and stability are ensured. Water injection with a fixed flow section is achieved by using a washable packer that can be unsealed step by step and an expansion auxiliary packer.
It effectively solved the problem of insufficient water injection in the high-pressure layer, ensured sufficient and accurate injection volume in the high-pressure layer, extended the service life of the packer, avoided the risk of major overhaul, and realized effective water injection and fine stratified water injection in the oilfield.
Smart Images
Figure CN121827761A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield water injection well technology, and in particular to a downhole injection string and a layered water injection method. Background Technology
[0002] Due to the long well section, as well as the characteristics of well depth and large pressure difference, the requirements for injection isolation and supporting tools and tubing anchoring are high. Due to the complex situation of different lithological reservoirs and large inter-layer differences, the water distributor is difficult to adjust, and the high-pressure layer injection is prone to be insufficient. Summary of the Invention
[0003] The purpose of this invention is to provide a downhole injection string and a layered water injection method to solve the problem of insufficient high-pressure layer injection in existing injection strings.
[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0005] A downhole injection string includes a first packer, a water distributor, a second packer, a sliding sleeve, a screen pipe, and a plug arranged in sequence.
[0006] The tubing is provided with a water injection hole, and the sliding sleeve is used to open and close the water injection hole;
[0007] The first water injection layer is located between the first packer and the second packer, and the second water injection layer is located at the end of the second packer away from the first packer.
[0008] The water distributor is used to inject water into the first water injection layer, and the water injection hole and the screen pipe are used to inject water into the second water injection layer. The oil layer pressure of the second water injection layer is higher than that of the first water injection layer.
[0009] The plug is used to seal the end of the tubing.
[0010] Furthermore, the sliding sleeve can move along its own axis to open the water injection hole and the screen tube.
[0011] Furthermore, the first packer and the second packer are configured as washable packers that can be unlocked step by step.
[0012] Furthermore, the downhole injection string also includes a bidirectional water well anchor, which is located at the end of the first packer away from the water distributor and is used to connect to the well wall.
[0013] Optionally, the downhole injection string also includes an auxiliary packer and a bidirectional anchor for the water well, wherein the auxiliary packer and the bidirectional anchor for the water well are disposed between the water distributor and the second packer, and the bidirectional anchor for the water well is disposed between the auxiliary packer and the second packer;
[0014] The first water injection layer is located between the first packer and the auxiliary packer, and the second water injection layer is located at the end of the second packer away from the bidirectional anchor of the well.
[0015] Furthermore, the auxiliary packer is configured as an expansion packer.
[0016] Furthermore, the water nozzle of the water distributor is made of Stellite alloy.
[0017] In another aspect, the present invention proposes a layered water injection method, employing the aforementioned downhole injection string, comprising the following steps:
[0018] Set the packer string: After configuring the completion string, lower it to the designed position, then raise the completion string and drop the packer ball, then pressurize to set the packer; finally, press the raised part of the completion string back to set the bidirectional anchor of the water well.
[0019] Instrument calibration: Install and calibrate the calibration instrument; lower the calibration instrument into the wellbore; start the calibration vehicle and lower it into the wellbore; the ground controller monitors and displays the lowering position of the calibration instrument in the wellbore in real time; adjust the water distributor according to the designed injection volume; after completion, raise it below the water distributor and read the flow rate; raise it above the water distributor and read the flow rate again; after the injection is satisfied, remove the water distributor, dismantle the calibration instrument and close the gate;
[0020] Inspection and unsealing: Unseal all packers and the bidirectional anchor of the well.
[0021] Furthermore, the first packer and the second packer can be unsealed by lifting the completion tubing.
[0022] Furthermore, during pressurization, the pressure is stabilized for a preset time every 5 MPa increase until the pressure reaches 20 MPa. After setting, the pressure must be stabilized for a preset time to prevent it from dropping.
[0023] In summary, the technical effects achieved by this invention are as follows:
[0024] The downhole injection string provided by this invention includes a first packer, a water distributor, a second packer, a sliding sleeve, a screen pipe, and a plug arranged sequentially. The string has injection holes, and the sliding sleeve is used to open and close these holes. A first injection layer is formed between the first and second packers, and a second injection layer is formed at the end of the second packer furthest from the first packer. The water distributor is used to inject water into the first injection layer, and the injection holes and screen pipe are used to inject water into the second injection layer. The oil layer pressure in the second injection layer is higher than that in the first injection layer. The plug is used to seal the end of the string.
[0025] The downhole injection string provided by this invention uses a water distributor to inject water into the low-pressure zone, and a sliding sleeve to open the injection port, through which water is injected into the high-pressure zone via the injection port and screen pipe, thus avoiding the problem of insufficient injection into the high-pressure zone. In other words, a fixed flow cross-section injection method replaces the water distributor for injecting water into the high-pressure zone, avoiding the problem of insufficient flow when using a water distributor. During construction, the injection volume into the high-pressure zone is adjusted by comprehensively regulating the total injection volume and the injection volume of the water distributor into the low-pressure zone, ensuring sufficient and accurate injection volume into the high-pressure zone. Attached Figure Description
[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 This is a schematic diagram of the downhole injection string under 8-15 MPa operating conditions provided in an embodiment of the present invention;
[0028] Figure 2 This is a schematic diagram of the downhole injection string under 15-20 MPa conditions provided in an embodiment of the present invention.
[0029] Icons: 100-First packer; 200-Water distributor; 300-Second packer; 400-Sliding sleeve; 500-Screw pipe; 600-Plug; 700-Well bidirectional anchor; 800-Auxiliary packer; 10-First water injection layer; 20-Second water injection layer. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0032] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0033] Due to the long well section, as well as the characteristics of well depth and large pressure difference, the requirements for injection isolation and supporting tools and tubing anchoring are high. Due to the complex situation of different lithological reservoirs and large inter-layer differences, the water distributor is difficult to adjust, and the high-pressure layer injection is prone to be insufficient.
[0034] In view of this, the present invention provides a downhole injection string, comprising a first packer 100, a water distributor 200, a second packer 300, a sliding sleeve 400, a screen pipe 500, and a plug 600 arranged sequentially; the string is provided with an injection port, and the sliding sleeve 400 is used to open and close the injection port; the first injection layer 10 is located between the first packer 100 and the second packer 300, and the end of the second packer 300 away from the first packer 100 is the second injection layer 20; the water distributor 200 is used to inject water into the first injection layer 10, and the injection port and screen pipe 500 are used to inject water into the second injection layer 20, wherein the reservoir pressure of the second injection layer 20 is higher than that of the first injection layer 10; the plug 600 is used to seal the end of the string.
[0035] The downhole injection string provided by this invention uses a water distributor 200 to inject water into the low-pressure zone, and a sliding sleeve 400 to open the injection port, through which water is injected into the high-pressure zone via the injection port and screen pipe 500, thus avoiding the problem of insufficient injection into the high-pressure zone. Specifically, it replaces the water distributor 200 with a fixed flow cross-section injection method for injecting water into the high-pressure zone, avoiding the problem of insufficient flow when using the water distributor 200. During construction, the injection volume into the high-pressure zone is adjusted by comprehensively regulating the total injection volume and the injection volume of the water distributor 200 into the low-pressure zone, ensuring sufficient and accurate injection volume into the high-pressure zone.
[0036] The following combination Figure 1 , Figure 2 The structure and shape of the downhole injection string provided in this embodiment are described in detail:
[0037] In this embodiment, the sliding sleeve 400 can move along its own axis to open the water injection hole and the screen pipe 500; the water nozzle of the water distributor 200 is made of Stellite alloy to improve corrosion resistance and large pressure difference capability, thereby extending the service life and dispensing validity period of the water distributor 200.
[0038] In this embodiment, the downhole injection string also includes a bidirectional water well anchor 700, which is used to connect with the well wall to fix the injection string.
[0039] Specifically, when applied to operating conditions with a differential pressure range of 8-15 MPa, the downhole injection string includes, sequentially arranged from the wellhead to the bottom, a bidirectional water well anchor 700, a first packer 100, a water distributor 200, a second packer 300, a sliding sleeve 400, a screen pipe 500, and a plug 600, such as... Figure 1As shown. The bidirectional well anchor 700 and the first packer 100 are located above the first water injection layer 10, and the second packer 300 is located below the first water injection layer 10 and above the second water injection layer 20. Obviously, the first water injection layer 10 is a low-pressure layer, and the second water injection layer 20 is a high-pressure layer. The water distributor 200 is used to inject water into the low-pressure layer. The first packer 100 and the second packer 300 separate the low-pressure layer, while the second packer 300 separates the high-pressure layer from the low-pressure layer.
[0040] When applied to operating conditions with a differential pressure range of 15-20 MPa, the downhole injection string includes, sequentially arranged from the wellhead to the bottom, a first packer 100, a water distributor 200, an auxiliary packer 800, a bidirectional water well anchor 700, a second packer 300, a sliding sleeve 400, a screen pipe 500, and a plug 600, such as... Figure 2 As shown. Similarly, the first water injection layer 10 is the low-pressure layer, and the second water injection layer 20 is the high-pressure layer. The water distributor 200 is used to inject water into the low-pressure layer. The first packer 100 and the auxiliary packer 800 separate the low-pressure layer, while the second packer 300 separates the high-pressure layer. That is, the area between the first packer 100 and the auxiliary packer 800 is the first water injection layer 10, and the end of the second packer 300 away from the bidirectional anchor 700 is the second water injection layer 20. At this time, the bidirectional anchor 700 is set between the auxiliary packer 800 and the second packer 300 to avoid contact between the bidirectional anchor 700 and the first water injection layer 10 and the second water injection layer 20, thereby ensuring that the bidirectional anchor 700 is reliably anchored to the well wall and preventing loosening.
[0041] When using steel strip SPARs or long rubber sleeve packers, successful measurement and adjustment are possible when the injection pressure differential is less than 8 MPa. However, when the injection pressure differential is large, exceeding 8 MPa, successful measurement and adjustment are difficult, and the average effective period of the packer is 231 days, with the longest effective period being 341 days. Furthermore, there is a high risk of failure to release the packer due to heavy load, leading to major overhauls, with a probability as high as 75%. In this embodiment, for high pressure differential conditions, a bidirectional anchor 700 is placed between the first injection layer 10 and the second injection layer 20. This effectively shortens the distance between the bidirectional anchor 700 and the packer, strengthens the auxiliary support of the bidirectional anchor 700 for the packer, reduces the stress on the packer, and prevents packer failure under high pressure differential conditions. Compared to simply increasing the packer's strength, this method more effectively solves the problem of packer failure caused by pressure differential and tubing creep when using long rubber sleeves and steel strip packers, extending the packer's service life, avoiding major tubing overhauls, and facilitating the smooth implementation of high-pressure deep deviated well high-pressure differential injection.
[0042] In an optional embodiment, the first packer 100 and the second packer 300 are configured as washable packers that can be released step by step; the auxiliary packer 800 is configured as an expansion packer.
[0043] Based on the downhole injection string provided in this embodiment, a layered water injection method is proposed, which uses the above-mentioned downhole injection string and includes the following steps:
[0044] Set the packer string: After configuring the completion string, lower it to the designed position, then raise the completion string and drop the ball, then pressurize to set the packer; finally, press the raised part of the completion string back to set the water well bidirectional anchor 700.
[0045] Instrument calibration: Install and calibrate the calibration instrument; lower the calibration instrument into the wellbore; start the calibration vehicle and lower it into the wellbore; the ground controller monitors and displays the lowering position of the calibration instrument in the wellbore in real time; adjust the water distributor 200 according to the designed injection volume; after completion, raise it below the water distributor 200 and read the flow rate; raise it again above the water distributor 200 and read the flow rate; after the injection is satisfied, remove the water distributor 200, dismantle the calibration instrument and close the gate;
[0046] Inspection and unsealing operations: Unseal all packers and the bidirectional anchor of the well 700.
[0047] The first packer 100 and the second packer 300 can be unsealed by lifting the completion tubing. During pressurization, the pressure is stabilized for a preset time every 5 MPa increase until the pressure reaches 20 MPa. After setting, the pressure must be stabilized for a preset time to prevent it from dropping.
[0048] When applied to working conditions of 8-15 MPa, the specific steps are as follows:
[0049] Setting of tubing: according to Figure 1 After configuring the completion string, run it to the designed position. All tools are threaded connections. Before setting, inspect the wellhead of the production tree and replace the tubing with a qualified rubber ring. After raising the completion string 50cm, drop the ball. Once the ball is seated, slowly pressurize the tubing to 5MPa, 10MPa, 15MPa, and 20MPa. Stabilize the pressure for 5 minutes after each 5MPa increase, until the pressure reaches 20MPa. Then, lower the completion string back to allow the bidirectional anchor 700 to set. Continue pressurizing until the sliding sleeve 400 opens, simultaneously setting the first packer 100 and the second packer 300.
[0050] Instrument calibration: Install and calibrate the calibration instrument; lower the calibration instrument into the wellbore; start the calibration vehicle and lower it into the wellbore; the ground controller monitors and displays the lowering position of the calibration instrument in the wellbore in real time; adjust the water distributor 200 according to the designed injection volume; after completion, raise it below the water distributor 200 and read the flow rate; raise it above the water distributor 200 and read the flow rate; after the injection is satisfied, remove the water distributor 200, dismantle the calibration instrument and close the gate.
[0051] Unsealing during inspection: In this completion string, the bidirectional anchor 7001, the first packer 100, and the second packer 300 of the water well are unsealed by lifting the tubing string. During the operation, simply lift the tubing string to unseal the bidirectional anchor 700, the first packer 100, and the second packer 300 of the water well.
[0052] When applied to working conditions of 15-20 MPa, the specific steps are as follows:
[0053] Setting of tubing: according to Figure 2 After configuring the completion string, run it to the designed position. All tools use threaded connections. Before setting, inspect the wellhead of the production tree and replace the tubing with a qualified rubber ring. After raising the string 50cm, slowly pressurize it to 5MPa using a pump truck. Continue pressurizing, stabilizing the pressure for 5 minutes after each 5MPa increase, until reaching 20MPa, thus completing the setting of the completion string. After setting, the pressure should not drop after stabilizing for 5 minutes to be considered acceptable. Then, push the raised portion of the completion string back to set the bidirectional anchor 700 in the water well, simultaneously setting the first packer 100, the second packer 300, and the auxiliary packer 800.
[0054] Instrument calibration: Install and calibrate the calibration instrument; lower the calibration instrument into the wellbore; start the calibration vehicle and lower it into the wellbore; the ground controller monitors and displays the lowering position of the calibration instrument in the wellbore in real time; adjust the water distributor 200 according to the designed injection volume; after completion, raise it below the water distributor 200 and read the flow rate; raise it above the water distributor 200 and read the flow rate; after the injection is satisfied, remove the water distributor 200, dismantle the calibration instrument and close the gate.
[0055] Unsealing during inspection: First, unseal the auxiliary packer 800, then lift the pipe string to release the anchor, first packer 100, and second packer 300.
[0056] The downhole injection string provided in this embodiment effectively solves the technical problems of insufficient injection in high-pressure layers, inability to control low-pressure layers, and easy failure and short effective period of packers. It realizes effective and precise water injection in oil fields, provides technical support for stable production and production increase in old oil fields, eliminates the safety hazard of major repairs caused by failure to unblock due to high load, and ensures the large-scale application of the large pressure differential injection technology in long well sections, deep deviated wells, and oil reservoirs of different lithologies.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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. A downhole injection string, characterized in that, It includes a first packer (100), a water distributor (200), a second packer (300), a sliding sleeve (400), a screen tube (500), and a plug (600) arranged in sequence; The tubing is provided with a water injection hole, and the sliding sleeve (400) is used to open and close the water injection hole; The first water injection layer (10) is located between the first packer (100) and the second packer (300), and the end of the second packer (300) away from the first packer (100) is the second water injection layer (20). The water distributor (200) is used to inject water into the first water injection layer (10), and the water injection hole and the screen pipe (500) are used to inject water into the second water injection layer (20). The oil layer pressure of the second water injection layer (20) is higher than that of the first water injection layer (10). The plug (600) is used to seal the end of the tubing.
2. The downhole injection string according to claim 1, characterized in that, The sliding sleeve (400) can move along its own axis to open the water injection hole and the screen tube (500).
3. The downhole injection string according to claim 1, characterized in that, The first packer (100) and the second packer (300) are configured as washable packers that can be unsealed step by step.
4. The downhole injection string according to claim 1, characterized in that, It also includes a well bidirectional anchor (700), which is located at the end of the first packer (100) away from the water distributor (200) and is used to connect to the well wall.
5. The downhole injection string according to claim 1, characterized in that, It also includes an auxiliary packer (800) and a well bidirectional anchor (700), wherein the auxiliary packer (800) and the well bidirectional anchor (700) are disposed between the water distributor (200) and the second packer (300), and the well bidirectional anchor (700) is disposed between the auxiliary packer (800) and the second packer (300); The first packer (100) and the auxiliary packer (800) form a first water injection layer (10), and the end of the second packer (300) away from the bidirectional anchor (700) of the well forms a second water injection layer (20).
6. The downhole injection string according to claim 5, characterized in that, The auxiliary packer (800) is configured as an expansion packer.
7. The downhole injection string according to claim 1, characterized in that, The water nozzle of the water distributor (200) is made of Stellite alloy.
8. A stratified water injection method, employing the downhole sub-injection string as described in any one of claims 4-6, characterized in that, Includes the following steps: Set the well completion string: After configuring the well completion string, lower the well completion string to the designed position, then lift the well completion string and drop the ball, then pressurize to set the packer; finally, press the lifted part of the well completion string back to set the bidirectional anchor (700) of the water well. Instrument calibration: Install and calibrate the instrument; lower the instrument into the system. Start the test and adjustment vehicle and lower it into the well shaft; The ground controller monitors and displays the position of the measuring instrument in the wellbore in real time, adjusts the water distributor (200) according to the designed injection volume, and then raises it below the water distributor (200) and reads the flow rate. Raise it up above the water distributor (200) and read the flow rate. After the water distribution is satisfied, remove the water distributor (200), remove the measuring instrument and close the gate. Inspection and unsealing: Unseal all packers and the bidirectional anchor (700) of the well.
9. The layered water injection method according to claim 8, characterized in that, The first packer (100) and the second packer (300) can be unsealed by lifting the completion tubing.
10. The layered water injection method according to claim 9, characterized in that, During pressurization, the pressure is stabilized for a preset time every 5MPa increase until the pressure reaches 20MPa. After setting, the pressure must be stabilized for a preset time and then not drop.