A design method of a gas lock prevention and production string for a deep coal bed methane well

Abstract

This invention discloses a design method for a gas-lock-proof drainage string for deep coalbed methane wells, belonging to the field of coalbed methane extraction technology. It solves the technical problem of high equipment failure rate when existing rodless drainage equipment is applied to deep coalbed methane wells. The design method includes: providing the necessary components for the drainage string, which sequentially include tubing, a rod pump, an extension tube, a gas-liquid separator, and a sand settling pipe; obtaining the well type of the coalbed methane well; determining the target installation depth of the top of the gas-liquid separator based on the well type; determining the target length of the extension tube, the target installation depth of the rod pump, and the target length of the sand settling pipe based on the target installation depth of the top of the gas-liquid separator; assembling the drainage string; and providing multi-stage sucker rods, connecting the multi-stage sucker rods to the plunger of the rod pump. This invention provides good gas-lock prevention, high drainage efficiency, and reduces maintenance costs during production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coalbed methane exploitation, and particularly relates to a design method of a gas-lock-preventing drainage pipe column for a deep coalbed methane well. BACKGROUND

[0002] Domestic coalbed methane exploration and development work is mainly concentrated in the middle and shallow layers. With the deepening of exploration and development, the blocks available for scale and benefit development are moving towards the exploitation of deep coalbed methane. The exploitation of deep coalbed methane is difficult. When the existing rodless drainage equipment for shallow coalbed methane is applied in deep wells, the equipment failure rate is high, and the depth of deep wells greatly increases the maintenance time, and the continuity of coalbed methane drainage is poor. SUMMARY

[0003] The present application aims to at least solve the technical problem of the high equipment failure rate of the existing rodless drainage equipment when applied in deep coalbed methane, and therefore provides a design method of a gas-lock-preventing drainage pipe column for a deep coalbed methane well.

[0004] The technical scheme of the present application is as follows:

[0005] A design method of a gas-lock-preventing drainage pipe column for a deep coalbed methane well, comprising the following steps:

[0006] Providing components required for the drainage pipe column, the components of the drainage pipe column comprising, in sequence, a tubing, a rod pump, an extension pipe, a gas-liquid separation device and a sand settling pipe;

[0007] Obtaining the well type of the coalbed methane well;

[0008] Obtaining the target installation depth of the top end of the gas-liquid separation device through the obtained well type of the coalbed methane well;

[0009] Obtaining the target length of the extension pipe, the target installation depth of the rod pump and the sand settling pipe through the obtained target installation depth of the top end of the gas-liquid separation device, and obtaining the target length of the tubing through the obtained target installation depth of the rod pump;

[0010] Assembling the drainage pipe column;

[0011] Providing a multi-stage sucker rod, and connecting the multi-stage sucker rod with the plunger of the rod pump.

[0012] In some embodiments, the obtained type of the coalbed methane well is a first well type, and the first well type is a vertical well or a directional well;

[0013] The obtaining of the target installation depth of the top end of the gas-liquid separation device specifically comprises:

[0014] The bottom depth of the coal seam in the coalbed methane well is obtained. The top end of the extension pipe is aligned with the bottom end of the coal seam in the coalbed methane well. The distance between the bottom end of the coal seam and the bottom of the well is obtained. The target length of the extension pipe is obtained by using the distance between the bottom end of the coal seam and the bottom of the well. Thus, the target installation depth of the top end of the gas-liquid separation device can be obtained.

[0015] In some embodiments, the minimum target length of the extension tube is:

[0016]

[0017] The maximum target length of the extension tube is:

[0018]

[0019] in, D 1 represents the inner diameter of the extension tube. D 2 represents the inner diameter of the coalbed methane well near the extension pipe. S The plunger stroke of the rod pump is [the stroke of the plunger]. n The number of strokes of the rod pump. D p The plunger of the rod pump. d The diameter of the air bubbles in the well fluid within the coalbed methane well. gamma 0 represents the kinematic viscosity of the well fluid in the coalbed methane well. α 0 represents the volume utilization coefficient of the gas-liquid separation device.

[0020] In some implementations, take L max The target length of the extension tube;

[0021] Among them, if L max If the value is less than 30m, then 30m is taken as the target length of the extension tube.

[0022] In some embodiments, the multistage sucker rod includes a primary sucker rod and a secondary sucker rod;

[0023] The length of the first-stage sucker rod is:

[0024]

[0025] in:

[0026]

[0027]

[0028]

[0029] The length of the secondary sucker rod L 2 is:

[0030]

[0031] In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. D p The diameter of the rod pump is [missing information]. rho l For well fluid density, rho γ The density of the sucker rod steel. L l The depth of the moving liquid surface. S The stroke of the rod pump is... N The number of strokes of the rod pump. T The yield strength of the first-stage sucker rod. S F This refers to the utilization coefficient of the first-stage sucker rod. P L For stress ratio range, L This refers to the length of the oil pipe.

[0032] In some embodiments, the obtained coalbed methane well is of type II well type, which is a horizontal well.

[0033] The process of obtaining the target installation depth at the top of the gas-liquid separator specifically includes:

[0034] Obtain the well inclination data of the coalbed methane well along its depth direction;

[0035] Confirm the well inclination angle in degrees when the top of the gas-liquid separation device is installed inside the coalbed methane well;

[0036] The target depth of the top of the gas-liquid separator is obtained by confirming the well inclination angle of the gas-liquid separator.

[0037] In some embodiments, the inclination angle of the top of the gas-liquid separation device within the coalbed methane well is less than 70°.

[0038] In some embodiments, the axis of the extension tube is at an angle to the axis of the oil tube.

[0039] In some embodiments, a pressure gauge is provided on the extension tube.

[0040] In some embodiments, the multi-stage sucker rod includes a first-stage sucker rod, a second-stage sucker rod, and a third-stage sucker rod;

[0041] The length of the first-stage sucker rod L 1 is:

[0042]

[0043] The length of the secondary sucker rod L 2 is:

[0044]

[0045] in:

[0046]

[0047]

[0048]

[0049] The length of the third-stage sucker rod L 3 is:

[0050]

[0051] In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. f 2 represents the cross-sectional area of ​​the secondary sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. q 2 represents the mass per unit length of the second-stage sucker rod. D p The diameter of the rod pump is [missing information]. rho l For well fluid density, rho γ The density of the sucker rod steel. L l The depth of the moving liquid surface. S The stroke of the rod pump is... N For the stroke of the rod pump. T The yield strength of the first-stage sucker rod. S F This refers to the utilization coefficient of the first-stage and second-stage sucker rods. P L For stress ratio range, L This refers to the length of the oil pipe.

[0052] The embodiments of this application have at least the following beneficial effects:

[0053] As can be seen from the above technical solution, the design method of the drainage string for deep coalbed methane wells disclosed in this invention uses the target installation depth of the gas-liquid separation device as the reference point for the drainage string. Based on the well type of the coalbed methane well, the tubing, rod pump, extension pipe, gas-liquid separation device, and sand settling pipe of the drainage string are designed. A multi-stage sucker rod is used in conjunction with the rod pump to discharge water from the well, resulting in high drainage efficiency and targeted application, suitable for deep coalbed methane drainage. Simultaneously, the use of the gas-liquid separation device effectively avoids the reduction in pump efficiency due to gas lock during the drainage process in deep coalbed methane wells, extending the pump inspection cycle of deep coalbed methane wells, reducing secondary damage to the coal seam caused by repeated well workovers, and thus increasing gas production and reducing maintenance costs. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of the present invention, 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 the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 A flowchart illustrating the design method of the drainage pipe string in Embodiment 1 of this application is shown;

[0056] Figure 2 A schematic diagram of the drainage pipe string in Embodiment 1 of this application is shown;

[0057] Figure 3 A schematic diagram of the drainage pipe string in Embodiment 2 of this application is shown;

[0058] The markings in the diagram are: 1-oil tubing, 2-multi-stage sucker rod, 3-coal seam, 4-rod pump, 5-extension pipe, 61-spiral gas anchor, 62-multi-stage high-efficiency gas-liquid separator, 7-sand settling pipe, 8-plug. Detailed Implementation

[0059] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0060] Furthermore, reference numerals and / or reference letters may be repeated in different examples in this application. Such repetition is for simplification and clarity purposes and does not in itself indicate a relationship between the various embodiments and / or settings discussed. In addition, this application provides examples of various specific processes and materials; however, those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0061] Because deep coalbed methane wells are characterized by deep coal seams, early gas discovery, rapid production, and high gas-liquid ratios, their extraction is very difficult. Conventional pumping and drainage tubing used in shallow coalbed methane wells is not well-suited for deep coalbed methane wells, resulting in rapid decline in pump efficiency and severe gas lock-up. After three months of drainage, pump efficiency is generally below 20%, and well workover cycles are short.

[0062] Figure 1 A flowchart illustrating the design method of the drainage pipe string in Embodiment 1 of this application is shown; Figure 2 A schematic diagram of the drainage pipe string in Embodiment 1 of this application is shown; Figure 3 A schematic diagram of the drainage pipe string in Embodiment 2 of this application is shown.

[0063] This application is described below with reference to the accompanying drawings and specific embodiments:

[0064] Example 1

[0065] like Figure 1 and Figure 2 As shown in the figure, this embodiment provides a design method for a gas-lock-proof drainage string for deep coalbed methane wells, including the following steps:

[0066] Step 1: Provide the components required for the drainage tubing string. The components of the drainage tubing string include, in sequence, tubing 1, rod pump 4, extension tube 5, gas-liquid separator and sand settling tube 7.

[0067] Step 2: Obtain the well type of the coalbed methane well.

[0068] Step 3: Obtain the target installation depth of the top of the gas-liquid separator by using the well type of the coalbed methane well.

[0069] Step 4: Obtain the target length of extension pipe 5, the target installation depth of rod pump 4 and the target length of sand settling pipe 7 by obtaining the target installation depth of the top of the gas-liquid separator. Obtain the target length of oil pipe 1 by obtaining the target installation depth of rod pump 4.

[0070] Step 5: Assemble the drainage tubing string.

[0071] Step 6: Provide the multi-stage sucker rod 2 and connect it to the plunger of the rod pump 4.

[0072] After drilling a deep coalbed methane well, casing is run into the well for support of the wellbore after completion. Generally, the accurate well type and depth of the coal seam 3 within the well can be obtained immediately after drilling. Using the target installation depth of the gas-liquid separator as a reference point for the production tubing string, the tubing string (1, rod pump 4, extension pipe 5, gas-liquid separator, and sand removal pipe 7) is designed according to the well type. A multi-stage sucker rod 2 works in conjunction with the rod pump 4 to discharge well fluid, resulting in high and targeted production efficiency, suitable for deep coalbed methane production. Simultaneously, the gas-liquid separator effectively avoids reduced pump efficiency due to gas lock during production in deep coalbed methane wells, extending the pump inspection cycle and reducing secondary damage to the coal seam 3 caused by repeated well workovers, thereby increasing gas production and reducing maintenance costs. The design of the gas-liquid separator's installation depth makes the production tubing string highly adaptable to deep coalbed methane wells.

[0073] In the actual implementation on site, technicians can design the drainage and production tubing according to the actual conditions of the deep coalbed methane well. Specifically, based on the shape of the coalbed methane well obtained from the drilling, the type of coalbed methane well is determined. In the exploitation of deep coalbed methane, the types of coalbed methane wells include the first type and the second type. The first type is a vertical well or a directional well, and the second type is a horizontal well.

[0074] Reference Figure 2 When the coalbed methane well is of type I, step 3 specifically includes:

[0075] Step 301: Obtain the bottom depth of coal seam 3, align the top end of the extension pipe with the bottom end of the coal seam of the coalbed methane well, obtain the distance between the bottom end of the coal seam of the coalbed methane well and the bottom of the well, and obtain the target length of the extension pipe 5 by obtaining the distance between the bottom end of the coal seam 3 and the bottom of the well, thereby obtaining the target installation depth of the top end of the gas-liquid separation device.

[0076] When drilling vertical or directional wells, a relatively long gap is left between the bottom of the well and the coal seam 3. This allows for sufficient installation margin for the production tubing and provides space for well fluid to settle sand. The top of the extension pipe 5 is aligned with the bottom of the coal seam in the coalbed methane well. The top of the extension pipe 5 is connected to the rod pump 4, which is typically equipped with a pump base and is fixed inside the well via the base. The rod pump 4 can be selected as a segmented plunger rod pump depending on the well inclination. The bottom of the extension pipe 5 is connected to the gas-liquid separator. It is understood that the target installation depth of the top of the gas-liquid separator is equal to the sum of the depth of the bottom of the coal seam 3 and the length of the extension pipe 5.

[0077] The target installation depth of the gas-liquid separation device is deeper than the coal seam 3, so as to separate the well fluid with a high gas-liquid ratio in the well. The extension pipe 5 is used to ensure that the gas-liquid separation device can reach the target depth in the coalbed gas well. Considering the errors that may exist during construction, the target length of the extension pipe 5 can be selected within a certain length range.

[0078] In this embodiment, the minimum target length of the extension tube 5 is... L min for:

[0079]

[0080] The maximum target length of extension tube 5 is:

[0081]

[0082] in, D 1 represents the inner diameter of extension tube 5. D 2 represents the inner diameter of the well near extension pipe 5. Since the coalbed methane well is equipped with casing, at this time... D 2. The inner diameter of the sleeve can be selected. S This refers to the plunger stroke of rod pump 4. n For the stroke of rod pump 4 D p The diameter of the plunger in the rod pump. d This refers to the diameter of the air bubbles in the well fluid within the coalbed methane well. d Generally, a value of 0.001-0.002m is used; gamma 0 represents the kinematic viscosity of the well fluid in a coalbed methane well. α 0 represents the volume utilization coefficient of the gas-liquid separation device.

[0083] The target length of extension tube 5 can be obtained through calculation. L min and L max Choose from the options.

[0084] Furthermore, this embodiment takes L max To extend the target length of pipe 5, and considering the greater depth of vertical and directional wells, the inventors conducted numerous experiments and confirmed that the target length of extension pipe 5 is no less than 30m. L max If the value is less than 30m, we will still take 30m as the target length of the extension tube 5 to ensure the depth of the gas-liquid separation device.

[0085] When the coalbed methane well is of type I, the well channel is relatively straight. Therefore, the number of sucker rod stages in multi-stage sucker rod 2 is 2, that is, multi-stage sucker rod 2 includes a first-stage sucker rod and a second-stage sucker rod. By reducing the number of sucker rod stages, the failure rate of the sucker rod is reduced.

[0086] Specifically, the length of the first-stage sucker rod L 1 is:

[0087]

[0088] in:

[0089]

[0090]

[0091]

[0092] Length of the second-stage sucker rod L 2 is:

[0093]

[0094] In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. D p The diameter of rod pump 4 is... rho l For well fluid density, rho γ The density of the sucker rod steel. L l This refers to the depth of the dynamic fluid level within a coalbed methane well. S For the stroke of rod pump 4, N For the stroke of rod pump 4 T The yield strength of a first-class sucker rod. S F This is the utilization factor for the first-stage sucker rod. P L For stress ratio range, P L It takes a value between 0.8 and 1.0. L The length of tubing 1 is equal to the difference between the rod pump 4 and the wellhead.

[0095] The lengths of the first and second sucker rods in tubing 1 are calculated using the above formula, so that the stress on the second-stage sucker rod is lower during operation, thereby reducing the failure rate of the multi-stage sucker rod 2.

[0096] In practice, considering production costs, the gas-liquid separation device used in the first well type is a spiral gas anchor 61, and the bottom end of the sand settling pipe 7 is connected to a threaded plug 8.

[0097] Example 2

[0098] Reference Figure 1 and Figure 3The design method of the gas-lock prevention drainage pipe string for deep coalbed methane wells disclosed in this embodiment has the same steps 1-6 as in embodiment 1. The difference is that the coalbed methane well type in this embodiment is the second type, that is, the well in this embodiment is a horizontal well.

[0099] Step 3 includes the following specific steps:

[0100] Step 301': Obtain well inclination data of the coalbed methane well along its depth direction.

[0101] Step 302': Confirm the well inclination angle when the top of the gas-liquid separator is installed inside the coalbed methane well.

[0102] Step 303': Obtain the target depth of the top of the gas-liquid separator by confirming the well inclination angle of the gas-liquid separator.

[0103] Based on the nature of the horizontal well, the gas-liquid separation device cannot be located below coal seam 3. In order to ensure that the gas-liquid separation device can contact and pump a sufficient amount of well fluid, the gas-liquid separation device is located at a location with a large well inclination in the horizontal well. Specifically, in step 302', the well inclination angle of the top position of the gas-liquid separation device is set to be less than ≤70°.

[0104] In step 301', the well inclination data along its depth direction can be obtained after drilling. By searching the well inclination data at different depths, the depth range in which the top of the gas-liquid separator can be set in the coalbed methane well can be obtained, and the installation position of the gas-liquid separator in the horizontal well can be further obtained.

[0105] To further adapt to the shape of the horizontal well, the rod pump 4 is preferably a segmented plunger rod pump. The axis of the extension pipe 5, which is located between the rod pump 4 and the gas-liquid separator, is at an angle to the axis of the tubing 1. A pressure gauge is installed on the outer wall of the extension pipe 5 to monitor the bottom hole pressure at the location of the pressure gauge in real time. In this embodiment, the length of the extension pipe 5 is generally no more than 1m.

[0106] Considering the inclination limitations of horizontal wells, the multi-stage sucker rod 2 in this embodiment includes a first-stage sucker rod, a second-stage sucker rod, and a third-stage sucker rod. Specifically, the length of the first-stage sucker rod... L 1 is:

[0107]

[0108] Length of the second-stage sucker rod L 2 is:

[0109]

[0110] in:

[0111]

[0112]

[0113]

[0114] The length of the third-stage sucker rod L 3 is:

[0115]

[0116] In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. f 2 represents the cross-sectional area of ​​the second-stage sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. q 2 represents the mass per unit length of the second-stage sucker rod. D p The diameter of rod pump 4 is... rho l The density of the well fluid inside the coalbed methane well. rho γ The density of the sucker rod steel. L l The depth of the moving liquid surface. S For the stroke of rod pump 4, N For the stroke of rod pump 4 T The yield strength of the first-stage and second-stage sucker rods. S F This refers to the utilization coefficient of the first-stage and second-stage sucker rods. P L The stress ratio range is 0.8 to 1.0. L This is the difference between rod pump 4 and the wellhead.

[0117] In practical implementation, considering the separation effect in horizontal wells, the gas-liquid separation device used in the second well type is a multi-stage high-efficiency gas-liquid separator 62.

[0118] 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.

[0119] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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. Therefore, they should not be construed as limitations on this application.

[0120] It should be noted that all directional indications in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0121] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0122] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0123] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0124] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0125] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A design method for a gas-lock-proof drainage tubing string for deep coalbed methane wells, characterized in that, Includes the following steps: Provide the components required for the drainage and production tubing string, wherein the components of the drainage and production tubing string include, in sequence, tubing, rod pump, extension tube, gas-liquid separator and sand settling tube; Obtain the well type of the coalbed methane well; The target installation depth of the top of the gas-liquid separation device is obtained by acquiring the well type of the coalbed methane well. By obtaining the target installation depth at the top of the gas-liquid separator, the target length of the extension pipe, the target installation depth of the rod pump and the sand settling pipe are obtained, and the target length of the oil pipe is obtained by obtaining the target installation depth of the rod pump. Assemble the drainage pipe string; A multi-stage sucker rod is provided, and the multi-stage sucker rod is connected to the plunger of the rod pump; If the obtained coalbed methane well is of type 1, then the first well type is either a vertical well or a directional well; Obtaining the target installation depth at the top of the gas-liquid separator specifically includes: The bottom depth of the coal seam in the coalbed methane well is obtained. The top end of the extension pipe is aligned with the bottom end of the coal seam in the coalbed methane well. The distance between the bottom end of the coal seam and the bottom of the well is obtained. The target length of the extension pipe is obtained by using the distance between the bottom end of the coal seam and the bottom of the well. Thus, the target installation depth of the top end of the gas-liquid separation device can be obtained. Wherein, the minimum target length of the extension tube is: The maximum target length of the extension tube is: in, D 1 represents the inner diameter of the extension tube. D 2 represents the inner diameter of the coalbed methane well near the extension pipe. S The plunger stroke of the rod pump is [the stroke of the plunger]. n The number of strokes of the rod pump. D p The plunger of the rod pump. d The diameter of the air bubbles in the well fluid within the coalbed methane well. γ 0 represents the kinematic viscosity of the well fluid in the coalbed methane well. α 0 represents the volume utilization coefficient of the gas-liquid separation device.

2. The design method for the gas-blocking drainage tubing string of a deep coalbed gas well according to claim 1, characterized in that, Pick L max The target length of the extension tube; Among them, if L max If the value is less than 30m, then 30m is taken as the target length of the extension tube.

3. The design method for the gas-blocking drainage tubing string of deep coalbed gas wells according to claim 1, characterized in that, The multi-stage sucker rod includes a primary sucker rod and a secondary sucker rod; The length of the first-stage sucker rod is: in: The length of the secondary sucker rod L 2 is: In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. D p The diameter of the rod pump is [missing information]. ρ l For well fluid density, ρ γ The density of the sucker rod steel. L l The depth of the moving liquid surface. S The stroke of the rod pump is... N The number of strokes of the rod pump. T The yield strength of the first-stage sucker rod. S F This refers to the utilization coefficient of the first-stage sucker rod. P L For stress ratio range, L This is the difference between the rod pump and the wellhead.

4. The design method for the gas-lock prevention and drainage tubing string of deep coalbed gas wells according to claim 1, characterized in that, The obtained coalbed methane well is of type II, which is a horizontal well. The process of obtaining the target installation depth at the top of the gas-liquid separator specifically includes: Obtain the well inclination data of the coalbed methane well along its depth direction; Confirm the well inclination angle in degrees when the top of the gas-liquid separation device is installed inside the coalbed methane well; The target depth of the top of the gas-liquid separator is obtained by confirming the well inclination angle of the gas-liquid separator.

5. The design method for the gas-blocking drainage tubing string of a deep coalbed gas well according to claim 4, characterized in that, The inclination angle of the top of the gas-liquid separation device within the coalbed methane well is less than ≤70°.

6. The design method for the gas-proof production tubing string of a deep coalbed methane well according to claim 5, characterized in that, The axis of the extension tube is at an angle to the axis of the oil tube.

7. The design method for the gas-proof drainage tubing string of a deep coalbed gas well according to claim 6, characterized in that, A pressure gauge is installed on the extension tube.

8. The design method for the gas-blocking drainage tubing string of a deep coalbed gas well according to claim 5, characterized in that, The multi-stage sucker rod includes a first-stage sucker rod, a second-stage sucker rod, and a third-stage sucker rod; The length of the first-stage sucker rod L 1 is: The length of the secondary sucker rod L 2 is: in: The length of the third-stage sucker rod L 3 is: In the formula: f 1 represents the cross-sectional area of ​​the first-stage sucker rod. f 2 represents the cross-sectional area of ​​the secondary sucker rod. q 1 represents the mass per unit length of the first-stage sucker rod. q 2 represents the mass per unit length of the second-stage sucker rod. D p The diameter of the rod pump is [missing information]. ρ l For well fluid density, ρ γ The density of the sucker rod steel. L l The depth of the moving liquid surface. S The stroke of the rod pump is... N For the stroke of the rod pump. T The yield strength of the first-stage sucker rod. S F This refers to the utilization coefficient of the first-stage and second-stage sucker rods. P L For stress ratio range, L This is the difference between the rod pump and the wellhead.

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