A pipe string suitable for use in an oil casing annulus sealed gas well and a method of use

Abstract

This invention proposes a tubing string and its usage method suitable for annular sealing gas wells, including a production casing with a matching tubing inside, and a gas injection system connected to an external gas source and connected to the matching tubing. A continuous tubing is installed inside the matching tubing, and a downhole packer is installed between the lower part of the matching tubing and the production casing to achieve annular sealing of the matching tubing and the production casing, while simultaneously enabling gas lift (both forward and reverse). This invention has a wide range of applications and strong operability, significantly reducing downhole operation costs while meeting the production needs of gas wells.

Description

Technical Field

[0001] This application relates to the technical field of gas well drainage and gas production, and more specifically, to a tubing string and its usage method suitable for annular sealed gas wells. Background Technology

[0002] In oil and gas development, gas wells are typically used to extract oil and gas from underground producing formations. However, in the mid-to-late stages of gas well development, excessive fluid accumulation or severe water production may occur in the wellbore and surrounding formations. At this point, it is necessary to drain the gas well and restore normal production. For some gas wells, due to production needs, downhole packers must be installed in the wellbore to seal the oil and casing annulus. However, after sealing the oil and casing annulus, there is no annular flow channel within the wellbore. When fluid accumulates in the wellbore and affects normal production, gas lift, bubble drainage, and other drainage operations cannot be carried out to restore production. For gas wells with downhole packers installed, achieving oil and casing connection in later stages of production requires downhole operations to retrieve the matching tubing, drill holes in the tubing, and then run it back into the wellbore. While this method creates an annular flow channel within the wellbore, it increases the workload of downhole operations, raising labor and material costs, and also poses significant safety risks to the subsequent production of the gas well. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a tubing string and its usage method suitable for annular sealed gas wells, which addresses the above-mentioned problems. By running a continuous tubing string inside the tubing string, gas lift and reverse lift can be achieved in the gas well, thereby draining the accumulated fluid in the wellbore, reducing the bottom hole back pressure, increasing the gas well production, and further increasing the gas well recovery rate.

[0004] The embodiments of this application are implemented as follows:

[0005] This application provides a tubing string suitable for annular sealing gas wells, characterized in that it includes a production casing with a matching tubing inside, and a gas injection system connected to an external gas source and communicating with the matching tubing. Continuous tubing is installed inside the matching tubing, and a downhole packer is installed between the lower part of the matching tubing and the production casing.

[0006] In some alternative implementations, the gas injection system includes a gas injection string and a compressor. The bottom end of the gas injection string is connected to the side wall of the matching oil pipe, and the top end of the gas injection string is connected to the compressor through a well gas pipeline. The compressor is connected to the external gas source.

[0007] In some alternative implementations, a one-way valve is provided at the connection between the bottom end of the gas injection string and the side wall of the matching oil pipe.

[0008] In some optional implementations, a fixing connector, namely a pipe clamp, is provided between the gas injection string and the matching oil pipe.

[0009] In some alternative implementations, the gas injection string and the matching oil pipe are fastened together by welding.

[0010] In some alternative implementations, the external gas source is high-pressure natural gas.

[0011] In some alternative implementations, the bottom end of the gas injection string is located above the downhole packer, and the top end of the gas injection string is provided with an external connector that connects to the well gas pipeline. The external connector is equipped with a cock valve.

[0012] A method for using a tubing string suitable for annular sealing gas wells, characterized by comprising the following steps:

[0013] Step 1, sealing function: The multi-functional tubing string is lowered to the target depth through downhole operations. The downhole packer seals the annulus with the production casing and the matching tubing. During normal production of the gas well, the fluid flows to the wellhead through the matching tubing.

[0014] Step 2, Injection Function: The bottom end of the gas injection string is located above the downhole packer. An annular channel is formed between the gas injection string and the matching tubing. The well gas pipeline and the external connector of the gas injection string are connected. When high-pressure fluid is injected into the gas injection string from the wellhead, the check valve is opened and the fluid enters the matching tubing. When the gas well is in normal production, the cock valve of the external connector of the gas injection string is closed, the check valve is not opened, and the wellbore fluid is produced from the matching tubing.

[0015] Step 3, gas lift reverse lift operation in gas well: high pressure gas is injected into the gas injection string at the wellhead. The gas flow opens the one-way valve and enters the matching tubing. The accumulated liquid in the matching tubing is discharged through the outlet of the matching tubing, realizing the gas lift reverse lift operation of the annulus-sealed gas well.

[0016] Step 4: Perform gas lift operation in the well: High-pressure gas is injected into the coiled tubing at the wellhead, and the gas flow flows out from the tubing, carrying away the accumulated liquid in the wellbore, thus realizing the gas lift operation in the annulus-sealed gas well.

[0017] The beneficial effects of this application are as follows: This application provides a tubing string and method of use suitable for sealing gas wells in the annulus, which can realize a one-trip operation of running the tubing string for gas wells requiring annulus sealing, greatly reducing the operational risks and costs of multiple downhole operations; for gas wells with downhole packers running in the annulus, it effectively solves the problem of poor production and reduced output caused by the lack of annular channels in the wellbore, which prevents gas lift, bubble drainage and other drainage operations, thus realizing gas well recovery and further improving gas well recovery rate; compared with other gas lift tubing strings that can only achieve a single gas lift method of forward or reverse lift, this invention can achieve both forward and reverse lift simultaneously, effectively solving different types of liquid accumulation problems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the multifunctional tubular column according to an embodiment of this application;

[0020] Figure 2 This is an enlarged view of the connection between the gas injection string and the production oil pipe in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram of the gas well production process for running a multi-functional tubing string according to an embodiment of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0030] like Figures 1-3As shown, the present invention provides a tubing string suitable for sealing the annulus of a gas well, including a production casing 1, a matching tubing 2 installed in the production casing, and a gas injection system connected to an external gas source 3 and connected to the matching tubing. A continuous tubing 4 is installed inside the matching tubing, and a downhole packer 5 is installed between the lower part of the matching tubing and the production casing. The downhole packer is directly set inside the production casing while the matching tubing is installed, thereby achieving sealing of the gas well oil and annulus.

[0031] The gas injection system includes a gas injection string 6 and a compressor 7. The bottom end of the gas injection string is connected to the side wall of the matching tubing, and the top end of the gas injection string is connected to the compressor via a well gas pipeline 8. The compressor is connected to an external gas source. The top end of the gas injection string passes through the wellhead, leaving an external connector for connection to the well gas pipeline. The external connector is equipped with a cock valve to control the flow of high-pressure gas in the gas injection string.

[0032] A one-way valve 9 is installed at the connection between the bottom of the gas injection string and the side wall of the matching tubing. When high-pressure gas is injected, the one-way valve is opened and enters the matching tubing, and the accumulated liquid in the matching tubing is discharged through the outlet of the matching tubing. When the gas well is in normal production, the one-way valve is closed, and the wellbore fluid is produced from the matching tubing.

[0033] Furthermore, a fixing connector 10 is provided between the gas injection tubing and the matching tubing. The fixing connector can be a pipe clamp, which is used to fix the gas injection tubing and the matching tubing to prevent the gas injection tubing from detaching from the matching tubing and falling into the wellbore.

[0034] The gas injection tubing is welded to the matching oil tubing; the external gas source is high-pressure natural gas.

[0035] The principle of the multi-functional tubular column is as follows:

[0036] For gas wells requiring sealing of the oil and annulus spaces in the wellbore, a multi-functional tubing string is run. The downhole packer is connected to the matching tubing, and the gas injection string is installed on the outer wall of the matching tubing, communicating with it through the injection port. A fixing connector is used to secure the gas injection string and matching tubing, preventing them from detaching and falling into the wellbore. Simultaneously, coiled tubing is run inside the matching tubing. While running the matching tubing, the downhole packer is directly set inside the wellbore casing, reducing the number of downhole operations and achieving sealing of the gas well's oil and annulus spaces.

[0037] During normal production at the gas well, formation fluids flow to the wellhead through the associated tubing. When the gas well is undergoing gas lift operations or chemical injection, high-pressure gas or chemicals are injected into the injection tubing at the wellhead. The gas flow or chemicals push open the one-way valve at the injection port and enter the associated tubing. The gas flow then discharges the accumulated fluid in the associated tubing through the tubing outlet, thus achieving gas lift operations in a gas well with annular sealing, while chemicals can enter the wellbore.

[0038] The usage method of the above-mentioned multifunctional tubular column is as follows:

[0039] 1. Sealing function: The multi-functional tubing string is lowered to the target depth through downhole operations. The downhole packer seals the annulus between the production casing and the associated tubing. During normal production of the gas well, the fluid flows to the wellhead through the associated tubing.

[0040] 2. Injection function: The bottom end of the gas injection string is located above the downhole packer. An annular channel is formed between the gas injection string and the matching tubing. The well gas pipeline and the external connector of the gas injection string are connected. When high-pressure fluid is injected into the gas injection string from the wellhead, the check valve is opened and the fluid enters the matching tubing. When the gas well is in normal production, the cock valve of the external connector of the gas injection string is closed, the check valve is not opened, and the wellbore fluid is produced from the matching tubing.

[0041] 3. Drainage process implementation functions:

[0042] Gas lift reverse lift operation in gas wells: High-pressure gas is injected into the gas injection string at the wellhead. The gas flow opens the one-way valve and enters the matching tubing, discharging the accumulated liquid in the matching tubing through the outlet of the matching tubing, thus realizing the gas lift reverse lift operation of the gas well with annulus seal.

[0043] Gas lift operation is carried out in the well: high-pressure gas is injected into the coiled tubing at the wellhead, and the gas flow flows out from the tubing, carrying away the liquid accumulated in the wellbore, thus realizing the gas lift operation of the well with annulus seal.

[0044] By connecting the downhole packer to the matching tubing, an annular seal between the oil and casing can be achieved simultaneously with the tubing installation. A gas injection string is installed on the outer wall of the matching tubing, connected to the tubing, and installed together into the wellbore. This forms an annular channel above the downhole packer, allowing high-pressure gas to be injected into a designated well depth. Simultaneously, a coiled tubing is installed inside the string, enabling gas lift (both forward and reverse), thereby draining accumulated fluid from the wellbore, reducing bottomhole back pressure, increasing gas production, and further enhancing the gas recovery rate. This avoids the technical challenge of gas wells lacking a connecting channel between the casing and oil well, which prevents the implementation of gas lift and other drainage processes. This invention has a wide range of applications, suitable for conventional gas wells, unconventional gas wells, and sulfur-containing gas wells. The running depth of the coiled tubing can be adjusted according to the actual production conditions of the gas well, making it more adaptable to wells with accumulated fluid.

[0045] Example 1

[0046] For production needs, a multi-functional tubing string was installed when running tubing in a sulfur-containing gas well A. This effectively sealed the annulus passage between the tubing and casing. At the same time, when the tubing in the well accumulated fluid and could not be opened for production normally, a vehicle-mounted gas lift process was connected to the wellhead to inject high-pressure natural gas at 25MPa into the high-pressure injection tubing string. After 8 cubic meters of accumulated fluid were discharged from the tubing, the gas well resumed normal production, effectively extending the production time of the gas well and improving the gas recovery rate.

Claims

1. A tubing string suitable for annular sealing gas wells, characterized in that, The system includes a production casing with a matching tubing inside, and a gas injection system connected to an external gas source and in communication with the matching tubing. A continuous tubing is installed inside the matching tubing, and a downhole packer is installed between the lower part of the matching tubing and the production casing.

2. The tubing string suitable for annular sealing gas wells according to claim 1, characterized in that, The gas injection system includes a gas injection string and a compressor. The bottom end of the gas injection string is connected to the side wall of the matching oil pipe, and the top end of the gas injection string is connected to the compressor through a well gas pipeline. The compressor is connected to the external gas source.

3. The tubing string suitable for annular sealing gas wells according to claim 2, characterized in that, A one-way valve is provided at the connection between the bottom end of the gas injection string and the side wall of the matching oil pipe.

4. The tubing string suitable for annular sealing gas wells according to claim 3, characterized in that, The gas injection string and the matching oil pipe are provided with a fixed connection, which is a pipe clamp.

5. A tubing string suitable for annular sealing gas wells according to claim 3 or 4, characterized in that, The gas injection tubing and the matching oil tubing are connected and secured by welding.

6. A tubing string suitable for annular sealing gas wells according to claim 2 or 5, characterized in that, The external gas source is high-pressure natural gas.

7. A tubing string suitable for annular sealing gas wells according to claim 5, characterized in that, The bottom end of the gas injection string is located above the downhole packer, and the top end of the gas injection string is provided with an external connector that connects to the well gas pipeline. The external connector is equipped with a cock valve.

8. A method for using a tubing string suitable for annular sealing gas wells as described in claim 7, characterized in that, Includes the following steps: Step 1, sealing function: The multi-functional tubing string is lowered to the target depth through downhole operations. The downhole packer seals the annulus with the production casing and the matching tubing. During normal production of the gas well, the fluid flows to the wellhead through the matching tubing. Step 2, Injection Function: The bottom end of the gas injection string is located above the downhole packer. An annular channel is formed between the gas injection string and the matching tubing. The well gas pipeline and the external connector of the gas injection string are connected. When high-pressure fluid is injected into the gas injection string from the wellhead, the check valve is opened and the fluid enters the matching tubing. When the gas well is in normal production, the cock valve of the external connector of the gas injection string is closed, the check valve is not opened, and the wellbore fluid is produced from the matching tubing. Step 3, gas lift reverse lift operation in gas well: high pressure gas is injected into the gas injection string at the wellhead. The gas flow opens the one-way valve and enters the matching tubing. The accumulated liquid in the matching tubing is discharged through the outlet of the matching tubing, realizing the gas lift reverse lift operation of the annulus-sealed gas well. Step 4: Perform gas lift operation in the well: High-pressure gas is injected into the coiled tubing at the wellhead, and the gas flow flows out from the tubing, carrying away the accumulated liquid in the wellbore, thus realizing the gas lift operation in the annulus-sealed gas well.

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