A method and apparatus for designing a horizontal well retarded wellbore string

Abstract

The application discloses a design method of a horizontal well slow-speed type wellbore pipe column, S1, determining the size of the wellbore pipe column of the horizontal well; S2, dividing the flow speed stage of the wellbore pipe column; S3, calculating the flow speed value of each flow speed stage according to the flow speed stage divided in the step S2; S4, designing the matching principle of the flow speed stage, and ensuring that the flow speed located in the middle stage is the lowest; S5, determining the length of the speed reducer; S6, determining the complete structure of the wellbore pipe column of the horizontal well. The application further discloses a horizontal well slow-speed type wellbore pipe column device. In the design method of the horizontal well slow-speed type wellbore pipe column, the conventional drainage structure is optimized, the flow speed of a section located in the middle stage is kept the lowest, the settlement of the wellbore solid particles is realized while meeting the drainage requirement, the impurities entering the downhole screw pump are greatly reduced, the operation state of the screw pump is better improved, the torque rise, pump jam and other faults are reduced, the pump inspection period is prolonged, and the stable operation of the coalbed methane well is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal bed gas exploration, in particular to a design method and device of horizontal well slow-speed wellbore pipe column. BACKGROUND

[0002] L-type horizontal well is a main well type in the present stage of coal bed gas exploration and development, and the used drainage equipment includes top drive screw pump, electric submersible screw pump and other processes. The top drive screw pump is a rod drainage process applied in the L-type horizontal well of coal bed gas, and the commonly used downhole drainage pump types include GLB180-23, GLB250-23, GLB300-25 and GLB600-25 according to different daily water production. The commonly used wellbore pipe column structure is from bottom to top: plug + tail pipe + inserted gravity gas anchor + screw pump + oil pipe + oil pipe hanger, the structure of the inserted gravity gas anchor is divided into upper and lower parts, the upper part can use a circular hole screen pipe with a hole diameter of 6mm or 8mm; the lower part can use a center pipe with a length of 15-25m and an outer diameter of D48.3mm installed in a D73mm oil pipe, and the bottom of the center pipe is in an open state. The top drive screw pump drainage process can use H22mm or H25mm sucker rod to connect the ground drive head and the downhole screw pump rotor; the pump hanger position is generally placed at a position with a well inclination of 70° and a full angle change rate less than 4° / 30m.

[0003] When the top drive screw pump drainage process is normally operated, the wellbore fluid first enters the bottom of the D48.3mm center pipe with an open bottom through the circular hole screen pipe, enters the screw pump through the center pipe, and finally flows out of the oil pipe to the ground under the lifting action of the screw pump, so as to realize the pressure reduction and drainage of the L-type horizontal well.

[0004] However, using the above wellbore pipe column structure, the speed of the wellbore fluid above and below the pump is medium and high respectively with the screw pump as the dividing point. In the process of drainage of the L-type horizontal well of coal bed gas, due to the fast speed of the fluid in the pipe column structure, gas, coal ash, coal particles and fracturing sand are carried into the pump cylinder of the screw pump, which easily causes phenomena such as gas stringing of water pipe line, increase of screw pump operation torque value, sucker rod breakage and pump sticking, and the relatively high failure rate leads to interruption of drainage, which requires pump inspection operation to restore normal drainage, shortens the pump inspection period of the coal bed gas well, and increases the development cost of the coal bed gas.

[0005] The utility model patent with the publication number CN205638294U discloses a kind of pipe column device for realizing continuous circulation horizontal well wellbore processing process by using ordinary oil pipe. The application can automatically change circulation channel when connecting single pipe by using ordinary oil pipe, through the ingenious cooperation of reversing wellhead and reversing valve, creating the construction condition of continuous circulation without stopping pump. But for specific tubular structure, the above-mentioned problems still cannot be solved. SUMMARY

[0006] The technical problem solved by the present application is to solve the problem that the higher failure rate leads to the interruption of drainage in the existing coalbed methane L-type horizontal well drainage process.

[0007] To solve the above technical problem, the present application provides the following technical scheme:

[0008] A design method of a horizontal well slow-speed type wellbore string, comprising the following steps:

[0009] S1, determining the size of the wellbore string of the horizontal well;

[0010] S2, dividing the flow rate stage of the wellbore string;

[0011] S3, calculating the flow rate value of each flow rate stage according to the flow rate stage divided in step S2;

[0012] S4, designing a matching principle to ensure that the flow rate in the middle stage is the lowest;

[0013] S5, determining the length of the speed reducer;

[0014] S6, determining the complete structure of the wellbore string of the horizontal well.

[0015] Advantages: The design method of the horizontal well slow-speed type wellbore string optimizes the conventional drainage structure, keeps the flow rate in the middle stage the lowest, forms a slow-speed area in the string, meets the drainage demand while realizing the sedimentation of wellbore solid particles, greatly reduces the impurities entering the downhole screw pump, better improves the operation state of the screw pump, reduces the torque rise, pump sticking and other failures, prolongs the pump inspection period, and realizes the stable operation of the coalbed methane well.

[0016] Preferably, in step S1, the tubing with an outer diameter of 73mm and an inner diameter of 62mm is used, the sucker rod with an outer diameter of 25mm is used, and the central tube with an outer diameter of 48.3mm and an inner diameter of 40.94mm is used.

[0017] Preferably, the division step in step S2 is:

[0018] S21, dividing the fluid flow rate in the overall string structure into two parts of an upper part and a lower part with the screw pump as a boundary point; the upper part is from the screw pump to the tubing hanger at the wellhead, and the lower part is from the screw pump to the pipe thread at the bottom of the string structure; the lower part is further divided into a speed reducer flow rate part and a gas anchor flow rate part composed of the tubing with an inner diameter of 62mm;

[0019] S22, the first flow rate stage: the flow rate space of the upper part is composed of the tubing with an inner diameter of 62mm and the sucker rod with an outer diameter of 25mm, and the fluid flow rate is represented by v1;

[0020] S23, Second velocity stage: The retarder velocity space consists of an oil pipe with an inner diameter of 62mm, and the fluid velocity is represented by v2;

[0021] S24, Third velocity stage: The air anchor velocity space consists of a central tube with an outer diameter of 48.3 mm and an inner diameter of 40.94 mm, and the fluid velocity is represented by v3.

[0022] Preferably, the formulas for calculating the flow velocity values ​​at each flow velocity stage in step S3 are as follows:

[0023] The formula for calculating the flow velocity v1 in the first velocity stage is:

[0024]

[0025] The formula for calculating the velocity v2 in the second velocity stage is:

[0026]

[0027] The formula for calculating the velocity v3 in the third velocity stage is:

[0028]

[0029] In the formula, Q is the fluid flow rate per unit time in the wellbore, with units of m³ / s. 3 / s; r1 is the radius of the inner diameter of the tubing in the upper velocity space, in meters; r2 is the radius of the outer diameter of the sucker rod in the upper velocity space, in meters; r3 is the radius of the inner diameter of the tubing in the retarder velocity space, in meters; r4 is the radius of the inner diameter of the central tube in the air anchor velocity space, in meters.

[0030] Preferably, the matching principle in step S4 is as follows:

[0031] In the structure of the integral wellbore string, the flow velocity is matched by v2 < v1 < v3 to ensure that the flow velocity in the retarder space of the second flow velocity stage is the lowest.

[0032] Preferably, the determination of the retarder length in step S5 is as follows:

[0033] S51. The length of the retarder is greater than the range affected by the self-priming pressure of the screw pump, and the minimum value is not less than 9.5 meters;

[0034] S52. The formula for calculating the length of the retarder for different types of screw pumps is as follows:

[0035]

[0036] In the formula: l is the length of the retarder in meters; k is a coefficient in meters per ml; q is the theoretical displacement of the screw pump per revolution in ml; n is a constant; and 10 ml is the specific volume.

[0037] The value of the coefficient k in the embodiment is as follows:

[0038] When the single rotation theoretical displacement of the screw pump is 80ml, the value of the coefficient k is 0.13m / ml; when the single rotation theoretical displacement of the screw pump is 180ml, the value of the coefficient k is 0.08m / ml; when the single rotation theoretical displacement of the screw pump is 200ml, the value of the coefficient k is 0.09m / ml; when the single rotation theoretical displacement of the screw pump is 250ml, the value of the coefficient k is 0.08m / ml; when the single rotation theoretical displacement of the screw pump is 300ml, the value of the coefficient k is 0.07m / ml; when the single rotation theoretical displacement of the screw pump is 400ml, the value of the coefficient k is 0.06m / ml; and when the single rotation theoretical displacement of the screw pump is 600ml, the value of the coefficient k is 0.05m / ml.

[0039] Preferably, the value of n is 9.5.

[0040] Preferably, the complete structure of the wellbore string in step S6 is in sequence a nipple, a sand settling pipe, an inserted gravity gas anchor, a retarder, a screw pump, a tubing, and a tubing hanger.

[0041] The application further discloses a wellbore string device made by the design method of the horizontal well retarder type wellbore string, which comprises a gas anchor, a nipple, a central pipe, a retarder, a screw pump, a tubing, and a tubing hanger.

[0042] One end of the gas anchor is fixedly provided with the nipple, and the other end is provided with one end of the retarder, and the other end of the retarder is provided with the screw pump; the tubing is arranged at one end of the screw pump away from the retarder, and the tubing hanger is arranged in the tubing and connected with the screw pump; the central pipe is in sequence communicated with the retarder and the screw pump; and the flow rate of the retarder is less than that of the tubing and the gas anchor.

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] (1) In the design method of the horizontal well retarder type wellbore string, the conventional drainage structure is optimized, a retarder is formed in the string structure, the flow rate of a section located in the middle stage is kept to be the lowest, a retardation area is formed in the string, the mode that the inserted gravity gas anchor and the downhole screw pump are directly connected is changed, the settlement of the solid particles in the wellbore is realized while meeting the drainage requirement, the impurities entering the downhole screw pump are greatly reduced, the operation state of the screw pump is better improved, the torque rise and pump sticking faults are reduced, the pump inspection period is prolonged, and the stable operation of the coalbed methane well is realized.

[0045] (2) The application effectively solves the condition that the torque value greatly fluctuates due to the large amount of coal powder in the produced liquid, the produced liquid is clearer, and the screw pump drainage equipment runs more stably.

[0046] (3) The technology of the present invention has significant economic benefits in reducing the number of well pump inspection operations and increasing the gas production of a single well. In the Huainan mining area alone, it is expected to reduce the number of well pump inspection operations by more than 10 wells per year, save about RMB1.5 million in pump inspection operation costs, and increase the gas production by RMB1.5 million per year, resulting in direct economic benefits of about RMB3 million. Attached Figure Description

[0047] Figure 1 This is a flowchart of Embodiment 1 of the present invention;

[0048] Figure 2 This is a schematic diagram of the wellbore string structure according to an embodiment of the present invention;

[0049] In the diagram: 1. Air anchor; 2. Plug; 3. Center tube; 4. Retarder; 5. Screw pump; 6. Oil pipe; 7. Oil pipe hanger. Detailed Implementation

[0050] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0051] The terms "first" and "second" 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0052] See Figure 1 and Figure 2 This embodiment discloses a design method for a horizontal well slow-moving wellbore string, including the following steps:

[0053] S1. Determine the dimensions of the wellbore string for the horizontal well.

[0054] Specifically, in this embodiment, an oil pipe 6 with an outer diameter of 73mm and an inner diameter of 62mm, an oil pipe hanger 7 with an outer diameter of 25mm, and a center pipe 3 with an outer diameter of 48.3mm and an inner diameter of 40.94mm are used.

[0055] S2. Determine the velocity stages of the wellbore string. The detailed steps are as follows:

[0056] S21. Using screw pump 5 as the dividing point, the fluid velocity in the overall tubing structure is divided into two parts: the upper part and the lower part. The upper part is from screw pump 5 to the wellhead tubing hanger 7, and the lower part is from screw pump 5 to the bottom plug 2 of the tubing structure. The lower part is further divided into the velocity part of the retarder 4 composed of tubing 6 with an inner diameter of 62mm and the velocity part of the gas anchor 1.

[0057] S22, the first flow rate stage: the upper flow rate space is composed of the tubing 6 with an inner diameter of 62 mm and the tubing hanger 7 with an outer diameter of 25 mm, and the fluid flow rate is represented by v1;

[0058] S23, the second flow rate stage: the flow rate space of the retarder 4 is composed of the tubing 6 with an inner diameter of 62 mm, and the fluid flow rate is represented by v2;

[0059] S24, the third flow rate stage: the flow rate space of the gas anchor 1 is composed of the central pipe 3 with an outer diameter of 48.3 mm and an inner diameter of 40.94 mm, and the fluid flow rate is represented by v3.

[0060] The embodiment changes the speed of the wellbore fluid of the L-shaped horizontal well discharged by the top drive screw pump 5 from two to three, and changes the direct connection mode of the plug-in gravity gas anchor 1 and the downhole screw pump 5 in the previous discharge string. Through the change of the flow rate, the settlement of larger solid particles is realized.

[0061] S3, according to the flow rate stage divided in step S2, the flow rate value of each flow rate stage is calculated.

[0062] The calculation formula of each flow rate stage of the step S3 is as follows:

[0063] The flow rate v1 of the first flow rate stage is calculated by the formula:

[0064]

[0065] The flow rate v2 of the second flow rate stage is calculated by the formula:

[0066]

[0067] The flow rate v3 of the third flow rate stage is calculated by the formula:

[0068]

[0069] In the formula, Q is the fluid flow rate in the wellbore per unit time, with the unit of m3 / s; r1 is the radius of the inner diameter of the tubing 6 in the upper flow rate space, with the unit of m; r2 is the radius of the outer diameter of the tubing hanger 7 in the upper flow rate space, with the unit of m; r3 is the radius of the inner diameter of the tubing 6 in the flow rate space of the retarder 4, with the unit of m; and r4 is the radius of the inner diameter of the central pipe 3 in the flow rate space of the gas anchor 1, with the unit of m. Through specific formula calculation, the flow rate value of the fluid in the specific stage is determined, which provides a basis for subsequent flow rate matching.

[0070] S4, the matching principle is designed to ensure that the flow rate in the middle stage is the lowest.

[0071] The matching mode of v2 < v1 < v3 is adopted in the structure of the whole wellbore string to ensure that the flow rate in the space of the retarder 4 in the second flow rate stage is the lowest. In order to reduce the solid particles such as gas, coal ash, coal particles and fracturing sand in the L-shaped horizontal wellbore of the coalbed gas into the screw pump 5, ensure that the flow rate in the space of the retarder 4 in the second flow rate stage is the lowest, and realize the function of settling and separating solid particles according to the flow rate change.

[0072] S5, determining the length of the retarder 4.

[0073] The confirmation step of the length of the retarder is as follows:

[0074] S41, the length of the retarder 4 is greater than the self-suction pressure influence range of the screw pump 5, and the minimum value is not less than 9.5 meters;

[0075] S42, the calculation formula of the length of the retarder 4 of different models of screw pumps 5 is:

[0076]

[0077] In the formula, l is the length of the retarder 4, the unit is m; k is the coefficient, the unit is m / ml, q is the single rotation theoretical displacement of the screw pump 5, ml; n is a constant; and 10ml is the specific volume.

[0078] The self-suction capacity of different screw pumps 5 in the operation process of the wellbore liquid is not the same, the larger the model of the pump, the stronger the self-suction capacity, and by setting the coefficient k, it is more conducive to targeted and detailed calculation of the length of the retarder of different models of screw pumps 5, therefore, different screw pumps 5 cannot adopt a unified coefficient, and the values of the coefficient k of different models of screw pumps 5 are shown in Table 1 according to the design:

[0079] Table 1

[0080] Screw pump single revolution theoretical displacement (ml) Coefficient k (m / ml) 80 0.13 180 0.08 200 0.09 250 0.08 300 0.07 400 0.06 600 0.05

[0081] When the single rotation theoretical displacement of the screw pump 5 is 80ml, the value of the coefficient k is 0.13m / ml; when the single rotation theoretical displacement of the screw pump 5 is 180ml, the value of the coefficient k is 0.08m / ml; when the single rotation theoretical displacement of the screw pump 5 is 200ml, the value of the coefficient k is 0.09m / ml; when the single rotation theoretical displacement of the screw pump 5 is 250ml, the value of the coefficient k is 0.08m / ml; when the single rotation theoretical displacement of the screw pump 5 is 300ml, the value of the coefficient k is 0.07m / ml; when the single rotation theoretical displacement of the screw pump 5 is 400ml, the value of the coefficient k is 0.06m / ml; and when the single rotation theoretical displacement of the screw pump 5 is 600ml, the value of the coefficient k is 0.05m / ml. Through this step, the length of the retarder 4 can be adapted to different models of screw pumps 5.

[0082] S6, determine the complete structure of the wellbore string of the horizontal well. In turn, it is the nipple 2, the sand pipe, the plug-in gravity gas anchor 1, the retarder 4, the screw pump 5, the tubing 6 and the tubing hanger 7.

[0083] The embodiment optimizes the adjustment of the top drive screw pump displacement string structure, forms a retarder 4 in the string structure, takes the screw pump 5 and the plug-in gravity gas anchor 1 as two demarcation points, changes the wellbore fluid velocity of the L-shaped horizontal well from two states of medium speed and high speed to three states of low speed, medium speed and high speed. Through the optimization of the string structure, the high-speed fluid passing through the plug-in gravity gas anchor 1 is reduced to a low-speed state, and then enters the screw pump 5. Through the change of the flow rate, the settlement of larger solid particles is realized.

[0084] The velocity change of the wellbore fluid from high speed to low speed to medium speed is realized, the velocity change can effectively realize the settlement of the solid particles in the wellbore, greatly reduces the impurities entering the downhole screw pump 5, can better improve the running state of the screw pump 5, reduces the torque rise, pump sticking and other failures, prolongs the pump inspection period, and realizes the stable operation of the coalbed methane well.

[0085] The application has been successfully popularized and applied in the top drive screw pump displacement L-shaped horizontal wells of PX2-2 well, PX1-1 well, XX1-2 well, GQ2-2 well and PE1-2 well in Huainan Mining Area, effectively solves the condition that the torque value fluctuates greatly due to the coal powder in the XX1-2 well and the GQ2-2 well, the produced liquid is clearer, and the screw pump displacement equipment runs more stably; and the GQ2-2 well and the PE1-2 well are successfully desorbed and gas is found, wherein the highest daily gas production of the PE1-2 well reaches 4500 square meters, the bottom hole flow pressure and the casing pressure data are stable, and the space for continuously improving the gas production is provided.

[0086] The technology has obvious economic benefits in reducing the pump inspection operation of the coalbed methane well and improving the single well gas production, and only in Huainan Mining Area, more than 10 well times of pump inspection operation are expected to be reduced annually, about 1.5 million yuan of pump inspection operation cost is saved, 1.5 million square meters of gas is accumulated annually, and about 3 million yuan of direct economic benefits is obtained.

[0087] Embodiment two

[0088] Reference Figure 2 The embodiment further discloses a wellbore string device made by a design method of the horizontal well retarder type wellbore string, which comprises a gas anchor 1, a nipple 2, a central pipe 3, a retarder 4, a screw pump 5, a tubing 6 and a tubing hanger 7; the gas anchor 1 is fixedly provided with the nipple 2 at one end and is provided with one end of the retarder 4 at the other end, and the other end of the retarder 4 is provided with the screw pump 5; the tubing 6 is arranged at the end of the screw pump 5 away from the retarder 4, and the tubing hanger 7 is arranged in the tubing 6 and connected with the screw pump 5; the central pipe 3 is in communication with the retarder 4 and the screw pump 5 in turn; and the flow rate of the retarder 4 is less than that of the tubing 6 and the gas anchor 1.

[0089] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are considered in all respects to be illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes coming within the meaning and equivalency range of the claims are intended to be embraced therein and no appended claim is to be considered as limiting as to the subject matter recited in that claim.

[0090] The above-described embodiments are merely exemplary implementations of the application, and the protection scope of the application is not limited to the above-described embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the application, and these are within the protection scope of the application.

Claims

1. A design method for a horizontal well slow-speed wellbore tubing device, characterized in that: It comprises the following steps: S1, determining the size of the wellbore string of the horizontal well; S2, dividing the flow rate stage of the wellbore string; The dividing step in step S2 is: S21, dividing the fluid flow rate in the overall string structure into two parts of upper and lower parts with the screw pump (5) as the dividing point; the upper part is from the screw pump (5) to the wellhead tubing (6) hanger, and the lower part is from the screw pump (5) to the bottom plug (2) of the string structure; the lower part is further divided into a flow rate part of the retarder (4) composed of the tubing (6) with an inner diameter of 62 mm and a flow rate part of the gas anchor (1); S22, the first flow rate stage: the flow rate space of the upper part is composed of the tubing (6) with an inner diameter of 62 mm and the tubing hanger (7) with an outer diameter of 25 mm, and the fluid flow rate is represented by v1; S23, the second flow rate stage: the flow rate space of the retarder (4) is composed of the tubing (6) with an inner diameter of 62 mm, and the fluid flow rate is represented by v2; S24, the third flow rate stage: the flow rate space of the gas anchor (1) is composed of the central tube (3) with an outer diameter of 48.3 mm and an inner diameter of 40.94 mm, and the fluid flow rate is represented by v3; S3, according to the flow rate stages divided in step S2, calculating the flow rate values of each flow rate stage; S4, designing the matching principle of the flow rate stage to ensure that the flow rate in the middle stage is the lowest; S5, determining the length of the retarder (4); The confirmation step of the length of the retarder (4) in step S5 is as follows: S51, the length of the retarder (4) is greater than the self-suction pressure influence range of the screw pump (5), and the minimum value is not less than 9.5 meters; S52, the calculation formula of the length of the retarder (4) for different types of screw pumps (5) is: In the formula: l is the length of the retarder (4), the unit is m; k is the coefficient, the unit is m / ml, q is the single rotation theoretical displacement of the screw pump (5), ml; n is a constant; 10 ml is the specific volume; The value of the coefficient k is as follows: When the single rotation theoretical displacement of the screw pump (5) is 80 ml, the value of the coefficient k is 0.13 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 180 ml, the value of the coefficient k is 0.08 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 200 ml, the value of the coefficient k is 0.09 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 250 ml, the value of the coefficient k is 0.08 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 300 ml, the value of the coefficient k is 0.07 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 400 ml, the value of the coefficient k is 0.06 m / ml; when the single rotation theoretical displacement of the screw pump (5) is 600 ml, the value of the coefficient k is 0.05 m / ml; S6, determining the complete structure of the wellbore string of the horizontal well.

2. The method of designing a horizontal well rate-controlled wellbore string apparatus of claim 1, wherein: In the step S1, the tubing (6) with an outer diameter of 73 mm and an inner diameter of 62 mm, the tubing hanger (7) with an outer diameter of 25 mm, and the central tube (3) with an outer diameter of 48.3 mm and an inner diameter of 40.94 mm are used.

3. The method of designing a horizontal well rate-controlled wellbore string apparatus of claim 1, wherein: The calculation formula of the flow rate value of each flow rate stage in step S3 is as follows: The calculation formula of the flow rate v1 of the first flow rate stage is: The calculation formula of the flow rate v2 of the second flow rate stage is: The flow rate v3 of the third flow rate stage is calculated by the following formula: where Q is the fluid flow rate in the wellbore per unit time, in m 3 / s; r1 is the radius of the inner diameter of the flow conduit (6), in m; r2 is the radius of the outer diameter of the flow conduit hanger (7), in m; r3 is the radius of the inner diameter of the flow conduit (6) of the flow moderator (4), in m; and r4 is the radius of the inner diameter of the flow conduit (3) of the gas anchor (1), in m.

4. The method of designing a horizontal well rate-controlled wellbore string apparatus of claim 1, wherein: The matching principle of step S4 is: The matching mode of the flow rate in the structure of the whole wellbore string is v2 5. The method of designing a horizontal well rate-controlled wellbore string apparatus of claim 1, wherein: The value of n is 9.

5.

6. The method of designing a horizontal well rate-controlled wellbore string apparatus of claim 1, wherein: The complete structure of the wellbore string in step S6 is in sequence a nipple (2), a sand trap, an air anchor (1), a flow reducer (4), a screw pump (5), a tubing (6) and a tubing hanger (7).

7. A wellbore string apparatus made using the method of designing a horizontal well retarded wellbore string of any one of claims 1-6, characterized by: The air anchor (1), the nipple (2), the central pipe (3), the flow reducer (4), the screw pump (5), the tubing (6) and the tubing hanger (7) are included. One end of the air anchor (1) is fixedly provided with the nipple (2), and the other end is provided with one end of the flow reducer (4). The other end of the flow reducer (4) is provided with the screw pump (5). The tubing (6) is installed at one end of the screw pump (5) away from the flow reducer (4). The tubing hanger (7) is installed inside the tubing (6) and connected with the screw pump (5). The central pipe (3) is in sequence communicated with the flow reducer (4) and the screw pump (5). The flow rate of the flow reducer (4) is less than the flow rates of the tubing (6) and the air anchor (1).

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