A pipe string structure and control method for high-pressure layer self-flow gas injection into a low-pressure layer

Abstract

The application discloses a pipe string structure and a control method for self-flow gas injection from a high-pressure layer to a low-pressure layer, and improves technical problems such as high well completion operation cost and great process difficulty. The pipe string structure comprises a wellbore casing, an isolation assembly, a filter assembly and a gas injection assembly. The gas injection assembly comprises: a gas injection production pipe string arranged in the wellbore casing; a production packer arranged on the gas injection production pipe string and fixedly seated with the wellbore casing, and the production packer is located above a low-pressure layer of a formation; a distribution and injection valve arranged on the gas injection production pipe string and located below the production packer, and the distribution and injection valve is located at the low-pressure layer of the formation; and a sealing part connected to the bottom of the gas injection production pipe string and sealingly connected with the isolation assembly. The application can realize self-flow of natural energy of a high-pressure layer gas group to a low-pressure layer gas group in the same well, improve the recovery rate of the low-pressure layer gas group, save cost and reduce the well completion process difficulty, and the oil well can be subjected to separate layer exploitation in the later period.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well engineering technology, specifically relating to a tubing structure and control method for gravity-flow gas injection from a high-pressure layer to a low-pressure layer. Background Technology

[0002] With the continuous development of offshore oil and gas resources, the energy of the developed formations gradually depletes, leading to reduced recovery rates and poorer development results. Injecting gas into depleted formations to replenish energy and maintain reservoir pressure is currently an effective measure to improve recovery rates and gas production rates.

[0003] Currently, gas injection wells collect and process gas through surface gas injection pipelines before injecting it into the formation. This method has certain limitations: firstly, it requires a surface gas source; secondly, it necessitates a well-developed surface gas injection well network and supporting injection equipment. This method is unsuitable for oil and gas fields with limited resources, thus hindering their development. Furthermore, the significant interlayer differences between the high- and low-pressure reservoirs place high demands on well completion techniques, requiring further improvement. Summary of the Invention

[0004] In order to solve all or part of the above problems, the purpose of this invention is to provide a tubing structure and control method for gravity-flow gas injection from a high-pressure layer to a low-pressure layer, which can realize the gravity flow of natural energy from the high-pressure gas group to the low-pressure gas group in the same well, improve the recovery rate of the low-pressure gas group, save costs, reduce the difficulty of well completion process, and allow for stratified exploitation in the later stage of oil well development.

[0005] In a first aspect, the present invention provides a tubular structure for gravity-fed gas injection from a high-pressure layer to a low-pressure layer, comprising:

[0006] Well casing is used to be run into low-pressure areas of the formation.

[0007] An isolation assembly is installed inside the well casing and is used to separate the high-pressure layer and the low-pressure layer of the formation.

[0008] The filter assembly is connected to the bottom of the well casing and extends to the high-pressure layer of the formation to support the well wall and prevent sand from entering.

[0009] The gas injection assembly is installed inside the well casing and is inserted into and sealed to the isolation assembly;

[0010] The gas injection assembly includes:

[0011] The gas injection production string is installed inside the well casing;

[0012] A production packer is installed on the gas injection production tubing and fixed to the well casing, and the production packer is located above the low-pressure layer of the formation.

[0013] An injection valve is installed on the gas injection production line and located below the production packer, and the injection valve is located in the low-pressure layer of the formation.

[0014] The sealing part is connected to the bottom of the gas injection production column and is sealed to the isolation assembly.

[0015] Optionally, the gas injection assembly further includes:

[0016] A flow and pressure tester is connected to the gas injection production line and located between the injection valve and the sealing part. The flow and pressure tester is used to test the flow rate and pressure of the gas in the gas injection production line.

[0017] Optionally, the gas injection assembly further includes:

[0018] A safety valve is connected to the upper end of the gas injection production line and is used to control the emergency opening and closing of the gas injection production line.

[0019] Optionally, the sealing portion includes:

[0020] A placement connector is attached to the bottom of the gas injection production tubing;

[0021] An isolation sealing unit is connected to the bottom of the placement joint and is sealed to the isolation assembly.

[0022] Optionally, the isolation assembly includes a formation isolation valve and a suspended packer. The formation isolation valve is connected to the bottom of the suspended packer and together with the suspended packer, separates the low-pressure layer and the high-pressure layer of the formation. The sealing part is inserted into the sealing cylinder of the suspended packer for a sealing connection.

[0023] Optionally, the filter assembly includes:

[0024] The filter screen has its top located inside the well casing and its bottom extending to the high-pressure layer of the formation.

[0025] The tailpipe hanger is fixed to the top of the filter screen and is seated and fixed to the well casing.

[0026] Secondly, the present invention provides a method for controlling a tubular structure, comprising the following steps:

[0027] S1, after drilling through the low-pressure layer of the formation using drilling equipment, the well casing is run in for casing completion operation;

[0028] S2, after drilling through the high-pressure layer of the formation with drilling equipment, open hole completion is performed by selecting a completion fluid that is compatible with the high-pressure layer of the formation.

[0029] S3, lower the filter assembly to achieve open-hole wellbore support and sand control;

[0030] S4, lower the isolation assembly to separate the low-pressure layer and the high-pressure layer of the formation, and replace the completion fluid in the well casing with a completion fluid that is compatible with the low-pressure layer of the formation. Perforate the well casing at the low position of the low-pressure layer of the formation to make the low-pressure layer of the formation connected with the well casing.

[0031] S5, lower the gas injection assembly and make the gas injection assembly and the isolation assembly insert-sealed connection to construct the self-flowing gas injection channel of the high-pressure layer and the low-pressure layer of the formation;

[0032] S6, close the injection valve and control the isolation assembly to open and clean the high-pressure layer of the well;

[0033] S7, open the injection valve to clean and flush the low-pressure zone of the well.

[0034] Optionally, in S4, when the isolation assembly is lowered, ensure that the formation isolation valve is closed to achieve the separation of the high-pressure layer and the low-pressure layer of the formation.

[0035] Optionally, the gas inside the well casing can be tested using a flow and pressure tester, or a monitoring tool can be lowered to the joint location using a wireline to monitor formation parameters.

[0036] Optionally, the low-pressure zone of the formation can be put into production by controlling the opening and closing of the injection valve, and the high-pressure zone can be put into production by injecting a plug into the landing joint, so that the oil well has the ability to extract in layers.

[0037] As can be seen from the above technical solution, the tubing structure and control method for gravity-flow gas injection from a high-pressure layer to a low-pressure layer provided by the present invention have the following advantages:

[0038] This tubing structure and control method can enable the natural energy of the high-pressure gas formation in the same well to flow by gravity to the low-pressure gas formation, thereby improving the recovery rate of the low-pressure gas formation. At the same time, it can also save costs, reduce the difficulty of well completion, and allow for stratified production in the later stages of the well.

[0039] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0040] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0041] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the structure of the well casing, isolation assembly, and filter assembly in an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the gas injection assembly in an embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1. Well casing; 2. Isolation assembly; 21. Formation isolation valve; 22. Suspended packer; 3. Filter assembly; 31. Filter screen; 32. Tailpipe hanger; 4. Gas injection assembly; 41. Gas injection production tubing; 42. Safety valve; 43. Production packer; 44. Injection valve; 45. Flow and pressure gauge; 46. Sealing part; 461. Settlement joint; 462. Isolation sealing unit. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0047] like Figure 1 , Figure 2 , Figure 3 The illustration shows an embodiment of the present invention, which discloses a tubing structure for gravity-flow gas injection from a high-pressure layer to a low-pressure layer. The structure includes a well casing 1, an isolation assembly 2, a filter assembly 3, and a gas injection assembly 4. The well casing 1 is lowered into the low-pressure layer. The isolation assembly 2 is disposed within the well casing 1 and separates the high-pressure and low-pressure layers. The filter assembly 3 is connected to the bottom of the well casing 1 and extends to the high-pressure layer to support the wellbore and prevent sand buildup. The gas injection assembly 4 is disposed within the well casing 1 and connected to the isolation assembly 2 to construct a gravity-flow gas injection channel between the high-pressure and low-pressure layers.

[0048] In one embodiment, such as Figure 1 , Figure 2 As shown, the isolation assembly 2 includes a formation isolation valve 21 and a suspended packer 22. The formation isolation valve 21 is installed inside the well casing 1 and located between the low-pressure and high-pressure formation layers. The suspended packer 22 is fixedly seated to the well casing 1, and the formation isolation valve 21 is connected to the bottom of the suspended packer 22. The suspended packer 22 and the formation isolation valve 21 together separate the high-pressure and low-pressure formation layers. The formation isolation valve 21 can prevent interference between the high-pressure and low-pressure layers when the reservoir is opened.

[0049] In one embodiment, such as Figure 1 , Figure 2As shown, the filter assembly 3 includes a filter screen pipe 31 and a tailpipe hanger 32. The top of the filter screen pipe 31 is located inside the well casing 1, and the bottom extends to the high-pressure layer of the formation to achieve filtration of oil and gas. The tailpipe hanger 32 is fixed to the top of the filter screen pipe 31 and is seated and fixed with the well casing 1 to achieve a sealed connection between the filter assembly 3 and the isolation assembly 2.

[0050] In one embodiment, such as Figure 1 , Figure 3 As shown, the gas injection assembly 4 includes a gas injection production string 41 and, from top to bottom, a safety valve 42, a production packer 43, an injection valve 44, a flow and pressure gauge 45, and a sealing part 46 connected to the gas injection production string 41. The gas injection production string 41 is coaxially arranged inside the well casing 1 and is used as a gas injection and production channel. The safety valve 42 is used to control the emergency opening and closing of the gas injection production string 41 to meet safety production requirements.

[0051] In one embodiment, such as Figure 1 , Figure 3 As shown, the production packer 43 is fixedly seated with the well casing 1, and the production packer 43 is located above the low-pressure layer of the formation to meet production requirements. The injection valve 44 is located at the low-pressure layer of the formation and serves as an adjustable downhole production control device to control the appropriate gas injection volume. The flow and pressure tester 45 is used to test the flow rate and pressure of the gas in the gas injection production string 41. As a downhole flow monitoring device, it can monitor the production and injection volume at each stage. The sealing part 46 is inserted and sealed to the suspended packer 2 to meet the needs of gas injection and subsequent stratified exploitation.

[0052] In one embodiment, such as Figure 1 , Figure 3 As shown, the sealing part 46 includes a landing joint 461 and an isolation sealing unit 462. The landing joint 461 is connected to the bottom of the gas injection production column 41, and the isolation sealing unit 462 is connected to the bottom of the landing joint 461. The isolation sealing unit 462 is tightly inserted into the sealing cylinder of the suspension packer 22 to achieve a plug-in sealing connection between the two, thereby ensuring the connection stability and sealing effect of the two.

[0053] This embodiment also discloses a control method using the above-described tubular structure, comprising the following steps:

[0054] S1, after drilling through the low-pressure layer of the formation using drilling equipment, the casing 1 is run into the well for casing completion operation.

[0055] S2, after drilling through the high-pressure layer of the formation using drilling equipment, open-hole completion is performed using a completion fluid that is compatible with the high-pressure layer of the formation. At this time, the high-pressure layer of the formation is in the open state.

[0056] S3, connect the filter screen pipe 31 and the tailpipe hanger 32 to form a filter assembly 3, and then lower the filter assembly 3 to the predetermined position for simple sand control to achieve open hole well wall support and sand control.

[0057] S4, connect the suspended packer 22 and the formation isolation valve 21 to form the isolation assembly 2, and lower the isolation assembly 2 to the predetermined position between the high-pressure layer and the low-pressure layer of the formation, while ensuring that the formation isolation valve 21 is in the closed state, so that the formation isolation valve 21 and the suspended packer 22 together isolate the high-pressure layer and the low-pressure layer of the formation.

[0058] After the isolation assembly 2 is installed, the completion fluid in the well casing 1 is replaced with a completion fluid that is compatible with the low-pressure layer of the formation. The well casing 1 is then perforated at the position where the low-pressure layer of the formation is located, so that the low-pressure layer of the formation is connected to the well casing 1. At this time, due to the action of the formation isolation valve 21, there is no interference between the high-pressure and low-pressure layers of the formation.

[0059] S5, install components such as the injection valve 44 on the gas injection production string 41 to form the gas injection assembly 4, lower the gas injection assembly 4, and make the isolation sealing unit 462 and the suspension packer 22 form a plug-in sealing connection to construct the self-flowing gas injection channel between the high-pressure layer and the low-pressure layer of the formation.

[0060] S6, confirm that the formation isolation valve 21 is open, then open the formation isolation valve 21 to clean and flush the high-pressure layer of the well;

[0061] S7, confirm that the formation isolation valve 21 is open, then open the injection valve 44 to clean and flush the low-pressure layer of the well.

[0062] The gas inside the well casing 1 is tested using a flow and pressure tester 45, or formation parameters are monitored by lowering a monitoring tool string to the landing joint 461 using a wireline. Simultaneously, the low-pressure zone is controlled to be put into production by opening and closing the injection valve 44, and the high-pressure zone is controlled to be put into production by inserting a plug to the landing joint 461, thus enabling the oil well to have stratified production capabilities.

[0063] The tubing structure and control method for gravity-flow gas injection from the high-pressure layer to the low-pressure layer in this embodiment can control the gravity-flow gas injection from the high-pressure layer to the low-pressure layer. By using the gas from the high-pressure layer of an oil and gas well as the injection gas source, gravity-flow gas injection can be used to replenish the energy of the low-pressure layer of the same oil well, thereby improving the recovery rate and reducing the huge investment costs of perfecting the gas injection pipeline network equipment.

[0064] Overall, safe stratified well completion was achieved for reservoirs with significant pressure differences between the two layers, avoiding reservoir interference and ensuring reservoir protection. Simultaneously, a migration channel for gravity-flow gas injection was established to ensure flow control. Furthermore, the tubing structure, combined with monitoring devices, enables gas injection capacity testing and evaluation, and can also meet the needs of subsequent stratified exploitation of low-pressure and high-pressure layers.

[0065] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0066] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0067] 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 therein. 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, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A tubular structure for gravity-fed gas injection from a high-pressure layer to a low-pressure layer, characterized in that, include: Well casing (1) is used to be run into the low-pressure layer of the formation; An isolation assembly (2) is installed inside the well casing (1) and is used to separate the high-pressure layer and the low-pressure layer of the formation; The filter assembly (3) is connected to the bottom of the well casing (1) and extends to the high-pressure layer of the formation to support the well wall and prevent sand. The gas injection assembly (4) is installed inside the well casing (1) and is inserted into the isolation assembly (2) in a sealed connection. The gas injection assembly (4) includes: The gas injection production string (41) is installed inside the well casing (1); The production packer (43) is installed on the gas injection production string (41) and is fixed to the well casing (1), and the production packer (43) is located above the low-pressure layer of the formation. The injection valve (44) is installed on the gas injection production line (41) and located below the production packer (43), and the injection valve (44) is located in the low-pressure layer of the formation. A sealing part (46) is connected to the bottom of the gas injection production column (41) and is sealed to the isolation assembly (2); The gas injection assembly (4) also includes: A flow and pressure tester (45) is connected to the gas injection production line (41) and located between the injection valve (44) and the sealing part (46). The flow and pressure tester (45) is used to test the flow rate and pressure of the gas in the gas injection production line (41). The sealing part (46) includes: A placement connector (461) is connected to the bottom of the gas injection production line (41); An isolation sealing unit (462) is connected to the bottom of the placement joint (461) and is sealed to the isolation assembly (2); The isolation assembly (2) includes a formation isolation valve (21) and a suspended packer (22). The formation isolation valve (21) is connected to the bottom of the suspended packer (22) and together with the suspended packer (22) separates the low-pressure layer and the high-pressure layer of the formation. The sealing part (46) is inserted into the sealing cylinder of the suspended packer (22) for a sealed connection.

2. The tubular structure according to claim 1, characterized in that, The gas injection assembly (4) also includes: Safety valve (42) is connected to the upper end of the gas injection production line (41) and is used to control the emergency opening and closing of the gas injection production line (41).

3. The tubular structure according to claim 1, characterized in that, The filter assembly (3) includes: The top of the filter screen (31) is located inside the well casing (1), and the bottom extends to the high-pressure layer of the formation. Tailpipe hanger (32) is fixed to the top of the filter screen (31) and seated and fixed to the well casing (1).

4. A control method for a tubular structure according to any one of claims 1-3, characterized in that, Includes the following steps: S1, after drilling through the low-pressure layer of the formation using drilling equipment, the casing (1) is run into the well for casing completion operation; S2, after drilling through the high-pressure layer of the formation with drilling equipment, open hole completion is performed by selecting a completion fluid that is compatible with the high-pressure layer of the formation. S3, lower the filter assembly (3) to achieve open hole wellbore support and sand control; S4, lower the isolation assembly (2) to separate the low-pressure layer and the high-pressure layer of the formation, and replace the completion fluid in the well casing (1) with the completion fluid that is compatible with the low-pressure layer of the formation. Perforate the well casing (1) at the low position of the low-pressure layer of the formation so that the low-pressure layer of the formation can be connected with the well casing (1). S5, lower the gas injection assembly (4) and make the gas injection assembly (4) and the isolation assembly (2) insert into a sealed connection to construct the self-flowing gas injection channel of the high-pressure layer and the low-pressure layer of the formation; S6, close the injection valve (44), control the isolation assembly (2) to open, and clean the high-pressure layer of the well; S7, open the injection valve (44) to clean and spray the low-pressure layer of the well.

5. The control method according to claim 4, characterized in that, In S4, when the isolation assembly (2) is lowered, ensure that the formation isolation valve (21) is closed to achieve the separation of the high-pressure layer and the low-pressure layer of the formation.

6. The control method according to claim 4, characterized in that, The gas inside the well casing (1) is tested by a flow and pressure tester (45), or the formation parameters are monitored by lowering a monitoring tool string to the landing joint (461) via wireline operation.

7. The control method according to claim 4, characterized in that, The low-pressure zone of the formation is put into production by controlling the opening and closing of the injection valve (44), and the high-pressure zone is put into production by injecting the plug to the landing joint (461), so that the oil well has the ability to extract in layers.

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