Treatment method for managing and controlling leakage of production string in shaft

Abstract

The invention provides a processing method for managing and controlling leakage of a production pipe column in a shaft. The method comprises the steps that all operation parameters of the shaft are obtained; acquiring the installation depth of the underground throttler; calculating the annulus allowable pressure of the casing annulus according to each operation parameter; the production pipe column is subjected to segmented numbering treatment, so that multiple segments of sub production pipe columns with numbers are obtained; constructing a pressure iteration model according to the obtained segment pressure and segment temperature of each segment of sub-production tubular column; according to the installation depth, the target number of the sub-production pipe column where the underground throttler is located is determined; determining the allowable annulus pressure as the initial pressure of the first section of sub-production pipe column; determining the pressure at the target number according to the initial pressure and a pressure iteration model; according to the obtained bottom maximum pressure before wellbore throttling, the temperature in the production pipe column and the pressure at the target number, the throttling hole area of the downhole throttler is determined; and the throttling hole diameter of the underground throttler is determined according to the area of the throttling hole, so that the problem of leakage of a production pipe column is solved.

Description

Technical Field

[0001] The present application relates to the technical field of natural gas drilling and completion, and particularly relates to a method for dealing with leakage of production strings in a wellbore. Background Art

[0002] Natural gas has become an alternative product to high-carbon fossil fuels such as coal. In natural gas exploitation, it is usually necessary to use a wellbore to establish a passage from underground to the ground. Among them, the production string in the wellbore is the direct passage for natural gas production. The production string is connected by steel tubing and related components. However, under the combined pressure of stress, load and fluid, it is prone to seal failure and perforation cracking.

[0003] In the related art, when seal failure and perforation cracking occur in the production string, it is first necessary to determine the failure or cracking position of the production string, and then seal and treat this position through chemical plugging agents or mechanical patches to complete the repair of the production string.

[0004] However, in the related art, there are usually dirt or solid-phase deposits on the inner wall of the production string. Plugging the failure or cracking position with chemical plugging agents or mechanical patches cannot form an effective seal with the inner wall of the production string, making it impossible to solve the problem of production string leakage. Summary of the Invention

[0005] The present application provides a method for dealing with leakage of production strings in a wellbore to solve the problem that there are usually dirt or solid-phase deposits on the inner wall of the production string, and plugging the failure or cracking position with chemical plugging agents or mechanical patches cannot form an effective seal with the inner wall of the production string, making it impossible to solve the problem of production string leakage.

[0006] In a first aspect, the present application provides a method for dealing with leakage of production strings in a wellbore, including:

[0007] Obtaining the operating parameters of the wellbore, where the wellbore at least includes a casing annulus, a production string, a packer and a downhole choker. The casing annulus is a circular space around the production string, and the packer is installed on the production string; the operating parameters at least include the internal pressure resistance of the production casing at the packer, the external extrusion resistance of the production string at the packer, the wellhead pressure after well production, the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing outside the casing annulus, the minimum external extrusion resistance of the production string, and the casing head strength of the production casing;

[0008] Obtaining the pre-determined installation depth of the downhole choker and installing the downhole choker on the production string according to the installation depth;

[0009] Calculate the annulus allowable pressure of the casing annulus based on the internal pressure resistance of the production casing, the external extrusion resistance of the production string, the wellhead pressure, the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, and the strength of the casing head;

[0010] Segment and number the production string according to a preset length to obtain multiple segmented sub-production strings with numbers;

[0011] Obtain the segmented pressure and segmented temperature of each sub-production string;

[0012] Construct a pressure iteration model corresponding to each sub-production string according to the segmented pressure and the segmented temperature;

[0013] Determine the target number of the sub-production string where the downhole throttle is located according to the installation depth;

[0014] Determine the initial pressure of the first sub-production string as the annulus allowable pressure;

[0015] Determine the pressure at the target number according to the initial pressure and the pressure iteration model;

[0016] Obtain the maximum bottom pressure before throttling in the wellbore and the temperature inside the production string;

[0017] Determine the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state according to the maximum bottom pressure, the temperature inside the production string, and the pressure at the target number;

[0018] Determine the throttle orifice diameter of the downhole throttle according to the throttle orifice area to ensure that the production string is in a critical leakage state or a non-critical leakage state and prevent the production string from leaking.

[0019] In a possible design, the downhole throttle needs to be installed below the packer, and the production string is spliced by multiple tubing strings; the operating parameters further include the weight of the production string, the weight per unit length of the production string, the designed depth of the packer, the surface temperature, the initial length of a single tubing string, the geothermal gradient, and the initial temperature of the single tubing string; accordingly, the process for determining the installation depth of the downhole throttle includes: calculating the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string; determining the second initial length of the production string under compressive action according to the designed depth of the packer and the initial length of the production string under tensile action; calculating the tensile length of the production string according to the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string; calculating the compressive length of the production string according to the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string; calculating the thermal expansion elongation of any tubing string according to the surface temperature, the initial length of the single tubing string, the geothermal gradient, and the initial temperature of the single tubing string; determining the total thermal expansion elongation of the production string according to the thermal expansion elongations corresponding to each tubing string; determining the actual depth of the packer according to the designed depth of the packer, the tensile length, the compressive length, and the total thermal expansion elongation; and determining the installation depth of the downhole throttle according to the actual depth of the packer.

[0020] In a possible design, the calculation formula for calculating the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string includes:

[0021]

[0022] In the formula, H L is the first initial length of the production string under tensile action, m; F X is the weight of the production string, N; M T is the mass per unit length of the production string, kg / m; g is the acceleration due to gravity, m / s 2 ;

[0023] Accordingly, the calculation formula for determining the second initial length of the production string under compressive action according to the designed depth of the packer and the initial length of the production string under tensile action includes:

[0024]

[0025] In the formula, H Y is the second initial length of the production string under compressive action, m; H FS is the designed depth of the packer, m; HL is the first initial length of the production string under tensile action, m;

[0026] Correspondingly, the calculation formula for calculating the tensile length of the production string based on the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string includes:

[0027]

[0028] In the formula, △H L is the tensile length of the production string, m; E is the elastic modulus of the production string, Pa; A is the cross-sectional area of the production string; H L is the first initial length of the production string under tensile action, m;

[0029] Correspondingly, the calculation formula for calculating the compression length of the production string based on the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string includes:

[0030]

[0031] In the formula, △H Y is the compression length of the production string, m; E is the elastic modulus of the production string, Pa; A is the cross-sectional area of the production string; H Y is the second initial length of the production string under compression action, m;

[0032] Correspondingly, the calculation formula for calculating the thermal expansion elongation of any oil pipe based on the surface temperature, the initial length of a single oil pipe, the geothermal gradient, and the initial temperature of a single oil pipe includes:

[0033]

[0034] In the formula, △H T i is the thermal expansion elongation of the i-th oil pipe, m; T0 is the surface temperature, °C; g e is the geothermal gradient, °C / m; i is the number of the oil pipe in the wellbore, numbered 1, 2,..., N from the wellhead to the bottom of the well; H T is the initial length of a single oil pipe, m; T T is the initial temperature of a single oil pipe, °C; α is the thermal expansion rate of the oil pipe, °C -1 ;

[0035] Correspondingly, the calculation formula for determining the total thermal expansion elongation of the production string based on the thermal expansion elongation of each oil pipe includes:

[0036]

[0037] In the formula, △H TZ is the total thermal expansion elongation of the production string above the packer, m; △H T i is the thermal expansion elongation of the i-th tubing;

[0038] Correspondingly, the calculation formula for determining the actual depth of the packer according to the design depth, the tensile length, the compression length and the total thermal expansion elongation of the packer includes:

[0039]

[0040] In the formula, H F is the actual depth of the packer, m; H FS is the design depth of the packer, m; △H L is the tensile length of the production string, m; △H Y is the compression length of the production string, m; △H TZ is the total thermal expansion elongation of the production string above the packer, m;

[0041] Correspondingly, the calculation formula for determining the installation depth of the downhole throttle according to the actual depth of the packer includes:

[0042]

[0043] In the formula, H J is the installation depth of the downhole throttle, m; H F is the actual depth of the packer, m; H W is the depth installation allowance, H W > 0, m.

[0044] In a possible design, calculating the allowable annulus pressure of the casing annulus based on the internal pressure resistance of the production casing, the external extrusion resistance of the production string, the wellhead pressure, the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, and the casing head strength includes: calculating the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer based on the internal pressure resistance of the production casing; calculating the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer based on the external extrusion resistance of the production string and the wellhead pressure; calculating the allowable annulus pressure of the casing annulus based on the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, the casing head strength, the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer.

[0045] In a possible design, the calculation formula for calculating the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer based on the internal pressure resistance of the production casing includes:

[0046]

[0047] In the formula, p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer; p7 is the internal pressure resistance of the production casing, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; h p is the depth where the packer is located, m;

[0048] Correspondingly, the calculation formula for calculating the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer based on the external extrusion resistance of the production string and the wellhead pressure includes:

[0049]

[0050] In the formula, p6 is the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer; p8 is the external extrusion resistance of the production string, MPa; p9 is the wellhead pressure, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; hp is the depth where the packer is located, m;

[0051] Correspondingly, the calculation formula for the allowable annulus pressure of the casing annulus determined by the maximum allowable annulus pressure determined by the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, the casing head strength, the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer includes:

[0052]

[0053] In the formula, △p aA is the allowable annulus pressure of the casing annulus, MPa; p1 is the minimum internal pressure resistance of the production casing, MPa; p2 is the minimum internal pressure resistance of the technical casing, MPa; p3 is the minimum external extrusion resistance of the production string, MPa; p4 is the casing head strength, MPa; p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, MPa; p6 is the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer, MPa.

[0054] In a possible design, the pressure iteration model corresponding to each sub-production string constructed according to the sectional pressure and the sectional temperature includes: calculating the gas density of each sub-production string according to the sectional pressure and the sectional temperature; calculating the gravitational pressure drop of each sub-production string according to the gas density; calculating the gas flow rate of each sub-production string according to the gas density; calculating the friction coefficient of each sub-production string according to the gas density and the gas flow rate; calculating the frictional pressure drop of each sub-production string according to the gas density, the gas flow rate and the friction coefficient; constructing the pressure iteration model corresponding to each sub-production string according to the sectional pressure, the gravitational pressure drop and the frictional pressure drop.

[0055] In a possible design, the calculation formula for calculating the gas density of each sub-production string according to the sectional pressure and the sectional temperature includes:

[0056]

[0057] In the formula, is the gas density of the kth sub-production string, kg / m 3 ; p k is the sectional pressure of the kth section, Pa; T s is the standard condition temperature, °C; p s is the standard condition pressure, Pa; T kis the sectional temperature of the k-th section, °C; ρ s is the standard condition density of the gas, kg / m 3 ;

[0058] Correspondingly, the calculation formula for calculating the gravitational pressure drop of each section of the sub-production string according to the gas density includes:

[0059]

[0060] In the formula, is the gravitational pressure drop of the sub-production string of the k-th section, MPa; H FD is the preset length, m; is the gas density of the k-th sub-production string, kg / m 3 ; g is the acceleration of gravity, m 2 / s; H FD is the preset length, m;

[0061] Correspondingly, the calculation formula for calculating the gas flow rate of each section of the sub-production string according to the gas density includes:

[0062]

[0063] In the formula, is the gas flow rate of the k-th sub-production string, m / s; Q min is the minimum production rate, m 3 / d; d tn is the inner diameter of the production string, m; is the gas density of the k-th sub-production string, kg / m 3 ; ρ s is the standard condition density of the gas, kg / m 3 ;

[0064] Correspondingly, the calculation formula for calculating the friction coefficient of each section of the sub-production string according to the gas density and the gas flow rate includes:

[0065]

[0066] In the formula, is the friction coefficient of the k-th sub-production string, dimensionless; Ra is the roughness of the corresponding sub-production string, m; d tn is the inner diameter of the production string, m; is the gas viscosity, Pa•s;

[0067] Correspondingly, the calculation formula for calculating the frictional pressure drop of each section of the sub-production string according to the gas density, the gas flow rate and the friction coefficient includes:

[0068]

[0069] In the formula, is the frictional pressure drop of the k-th sub-production string, MPa; is the friction coefficient of the k-th sub-production string, dimensionless; is the gas density of the k-th sub-production string, kg / m 3 ; is the gas flow velocity of the k-th sub-production string, m / s; d tn is the inner diameter of the production string, m; H FD is the preset length, m;

[0070] Correspondingly, the calculation formula for constructing the pressure iteration model corresponding to each sub-production string according to the sectional pressure, gravitational pressure drop, and the frictional pressure drop includes:

[0071]

[0072] In the formula, is the pressure corresponding to the (k + 1)-th sub-production string, MPa; p k is the sectional pressure of the k-th section, Pa; is the frictional pressure drop of the k-th sub-production string, MPa; is the gravitational pressure drop of the k-th sub-production string, MPa.

[0073] In a possible design, the method for determining the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state according to the maximum bottom pressure, the temperature inside the production string, and the pressure at the target number includes: determining the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string; determining whether the throttle process type is a critical leakage state or a non-critical leakage state according to the pressure at the target number and the maximum bottom pressure; if it is determined that the throttle process type is a critical leakage state, then determining the throttle orifice area of the downhole throttle according to the gas compressibility factor, the maximum bottom pressure before throttling in the wellbore, and the temperature inside the production string; if it is determined that the throttle process type is a non-critical leakage state, then determining the throttle orifice area of the downhole throttle according to the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before throttling in the wellbore, and the temperature inside the production string.

[0074] In a possible design, the calculation formula for determining the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string includes:

[0075]

[0076] Wherein, Zg is the gas compressibility factor, dimensionless; A1, A2, A3, A4, A5, A6, A7, A8, A9, A 10 — constants, dimensionless, being 1.1153, -0.079, 0.01588, 0.00886, -2.1619, 1.1575, -0.05368, 0.014655, -1.80997, 0.9548 respectively; p max is the maximum bottom pressure, MPa; γ g is the relative density of the gas, dimensionless; p r is the pseudo-reduced pressure, dimensionless, serving as an intermediate quantity for solving the gas compressibility factor; T r is the pseudo-reduced temperature, dimensionless, serving as an intermediate quantity for solving the gas compressibility factor; T fL is the temperature inside the production string, °C;

[0077] Correspondingly, the calculation formula for determining the throttling process type as the critical leakage state or the non-critical leakage state based on the pressure at the target number and the maximum bottom pressure includes:

[0078]

[0079] Wherein, k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; p max is the maximum bottom pressure; p J is the pressure at the target number;

[0080] Correspondingly, if it is determined that the throttling process type is the critical leakage state, then the calculation formula for the throttling orifice area of the downhole throttler based on the gas compressibility factor, the maximum bottom pressure before wellbore throttling, and the temperature inside the production string includes:

[0081]

[0082] Wherein, A L is the throttling orifice area, m 2 ; Q min is the minimum production rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient, the throttling orifice is a round hole, taking a value of 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fLis the temperature inside the production string, °C;

[0083] Correspondingly, if it is determined that the throttling process type is a non-critical leakage state, then according to the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before wellbore throttling, and the temperature inside the production string, the calculation formula for the throttling orifice area of the downhole throttler includes:

[0084]

[0085] In the formula, A L is the throttling orifice area, m 2 ; Q min is the minimum production rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient. The throttling orifice is a round hole, with a value of 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fL is the temperature inside the production string, °C; p J is the pressure at the target number.

[0086] In a possible design, the calculation formula for determining the target number of the sub-production string where the downhole throttler is located according to the installation depth includes:

[0087]

[0088] In the formula, M is the target number of the sub-production string where the downhole throttler is located, dimensionless integer; H J is the installation depth; H FD is the preset length.

[0089] The method for dealing with the leakage of the production string in the controlled wellbore provided by this application includes obtaining the operating parameters of the wellbore; obtaining the pre-determined installation depth of the downhole throttle; calculating the allowable annulus pressure of the casing annulus according to the internal pressure resistance strength of the production casing, the external extrusion resistance strength of the production string, the wellhead pressure, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing, the minimum external extrusion resistance strength of the production string, and the strength of the casing head; segmenting and numbering the production string according to a preset length to obtain multiple sub-production strings with numbers; constructing a pressure iteration model corresponding to each sub-production string according to the segmented pressure and segmented temperature of each obtained sub-production string; determining the target number of the sub-production string where the downhole throttle is located according to the installation depth; determining the initial pressure of the first sub-production string as the allowable annulus pressure; determining the pressure at the target number according to the initial pressure and the pressure iteration model; determining the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state according to the maximum bottom pressure before throttling in the wellbore, the temperature inside the production string, and the pressure at the target number; determining the throttle aperture of the downhole throttle according to the throttle orifice area to ensure that the production string is in a critical leakage state or a non-critical leakage state, prevent the production string from leaking, and solve the problem of production string leakage from the root by reducing the annulus pressure to within the safety threshold. Description of the Drawings

[0090] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0091] Figure 1 It is a schematic structural diagram of the wellbore provided by the embodiment of this application;

[0092] Figure 2 It is a schematic flow chart of the method for dealing with the leakage of the production string in the controlled wellbore provided by the embodiment of this application Figure 1 ;

[0093] Figure 3 It is a schematic flow chart of the method for dealing with the leakage of the production string in the controlled wellbore provided by the embodiment of this application Figure 2 。 Detailed Embodiments

[0094] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0095] Natural gas has become an alternative product to high-carbon fossil fuels such as coal. At the same time, the scale of underground hydrogen storage, underground compressed air energy storage, and underground carbon dioxide storage has also increased rapidly. In the above scenarios, it is usually necessary to use a wellbore to establish a channel from underground to the ground, and the production string in the wellbore is the direct channel for gas injection and production. The production string is connected by steel tubing and related components, but under the combined pressure of stress, load, and fluid, it is prone to seal failure and perforation cracking. In related technologies, when the production string has seal failure and perforation cracking, it is first necessary to determine the failure or cracking position of the production string, and then seal and treat this position through chemical plugging agents or mechanical patches to complete the repair of the production string. However, in related technologies, there are often dirt or solid-phase deposits on the inner wall of the production string. Sealing the failure or cracking position through chemical plugging agents or mechanical patches cannot form an effective seal with the inner wall of the production string, making it impossible to solve the problem of production string leakage.

[0096] To solve the above technical problems, the embodiments of this application propose the following technical concept: The inventor considered the operating parameters of the wellbore, the installation depth of the downhole throttler, and each section of the production string, determined the allowable annulus pressure based on the operating parameters, and used the allowable annulus pressure as the initial pressure of the first section of the production string. The target number of the sub-production string was determined based on the installation depth of the downhole throttler, the pressure at the target number was determined based on the initial pressure, and the throttling orifice area of the downhole throttler when the production string was in a critical leakage state or a non-critical leakage state was determined using the measured maximum bottom pressure, the temperature inside the production string, and the pressure at the target number. The throttling aperture of the downhole throttler was determined, thus fundamentally solving the problem of production string leakage.

[0097] Figure 1 It is a schematic structural diagram of the wellbore provided by the embodiments of this application.

[0098] As Figure 1 shown, the structure of this wellbore specifically includes: wellhead 101, tubing-casing annulus 102, annulus liquid 103, casing annulus 104, production casing 105, production string 106, technical casing 107, packer 108, and downhole throttler 109;

[0099] Among them, the annulus between the tubing and the casing 102 is an annular space formed by the wellhead 101, the production casing 105, the production string 106, and the packer 108.

[0100] The annulus fluid 103 is stored in the annulus between the tubing and the casing 102 and is used to protect the production casing 105 and the production string 106.

[0101] The casing annulus 104 is an annular space formed by the wellhead 101, the production casing 105, and the technical casing 107.

[0102] The production string 106 is composed of multiple tubing joints spliced together and is used to transmit gas.

[0103] The packer 108 is used to fix the production string 106.

[0104] The downhole choke 109 adjusts the gas flow through the principles of pressure balance and fluid mechanics.

[0105] Figure 2 Schematic flow of the method for controlling and handling leaks in the production string in the wellbore provided in the embodiment of the present application Figure 1 In this embodiment, the execution subject can be a computer device, and no special limitation is made here in this embodiment. As Figure 2 shown, the method includes:

[0106] S201: Obtain the operating parameters of the wellbore, where the wellbore at least includes the casing annulus, the production string, the packer, and the downhole choke. The casing annulus is a circular space around the production string, and the packer is installed on the production string; the operating parameters at least include the internal pressure resistance strength of the production casing at the packer, the external extrusion resistance strength of the production string at the packer, the wellhead pressure after well production, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing outside the casing annulus, the minimum external extrusion resistance strength of the production string, and the casing head strength of the production casing.

[0107] S202: Obtain the pre-determined installation depth of the downhole choke and install the downhole choke on the production string according to the installation depth.

[0108] Specifically, step S202 is specifically: Lower the downhole choke into the interior of the production string for installation according to the installation depth by using coiled tubing or a cable.

[0109] S203: Calculate the allowable annulus pressure of the casing annulus according to the internal pressure resistance strength of the production casing, the external extrusion resistance strength of the production string, the wellhead pressure, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing, the minimum external extrusion resistance strength of the production string, and the casing head strength.

[0110] Specifically, step S203 specifically includes:

[0111] S2031: Determine the maximum allowable annulus pressure based on the internal pressure resistance of the production casing at the packer, which is calculated according to the internal pressure resistance of the production casing.

[0112] In this embodiment, the calculation formula for determining the maximum allowable annulus pressure based on the internal pressure resistance of the production casing at the packer, which is calculated according to the internal pressure resistance of the production casing, includes:

[0113]

[0114] In the formula, p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer; p7 is the internal pressure resistance of the production casing, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; h p is the depth where the packer is located, m.

[0115] S2032: Determine the maximum allowable annulus pressure based on the external extrusion resistance of the production string and the wellhead pressure, which is calculated according to the external extrusion resistance of the production casing at the packer.

[0116] In this embodiment, the calculation formula for determining the maximum allowable annulus pressure based on the external extrusion resistance of the production string and the wellhead pressure, which is calculated according to the external extrusion resistance of the production casing at the packer, includes:

[0117]

[0118] In the formula, p6 is the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer; p8 is the external extrusion resistance of the production string, MPa; p9 is the wellhead pressure, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; h p is the depth where the packer is located, m.

[0119] S2033: Calculate the allowable annulus pressure of the casing annulus based on the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, the casing head strength, the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer.

[0120] In this embodiment, the calculation formula for the allowable annulus pressure of the casing annulus is determined according to the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, the casing head strength, the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer, and includes:

[0121]

[0122] Wherein, △p aA is the allowable annulus pressure of the casing annulus, MPa; p1 is the minimum internal pressure resistance of the production casing, MPa; p2 is the minimum internal pressure resistance of the technical casing, MPa; p3 is the minimum external extrusion resistance of the production string, MPa; p4 is the casing head strength, MPa; p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, MPa; p6 is the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer, MPa.

[0123] S204: Segment and number the production string according to a preset length to obtain multiple segmented sub-production strings with numbers.

[0124] In this embodiment, the preset length ≤ 1 / 1000 of the total length of the production string.

[0125] In this embodiment, the multiple segmented sub-production strings are equal-length sub-production strings.

[0126] S205: Obtain the segmented pressure and segmented temperature of each sub-production string.

[0127] S206: Construct a pressure iteration model corresponding to each sub-production string according to the segmented pressure and segmented temperature.

[0128] Specifically, step S206 specifically includes:

[0129] S2061: Calculate the gas density of each sub-production string according to the segmented pressure and segmented temperature.

[0130] In this embodiment, the calculation formula for calculating the gas density of each sub-production string according to the segmented pressure and segmented temperature includes:

[0131]

[0132] Wherein, is the gas density of the kth sub-production string, kg / m 3 ; p k is the segmented pressure of the kth segment, Pa; T s is the standard temperature, °C; p s is the standard pressure, Pa; Tk is the sectional temperature of the k-th section, °C; ρ s is the standard condition density of the gas, kg / m 3 .

[0133] S2062: Calculate the gravitational pressure drop of each section of the sub-production string according to the gas density.

[0134] In this embodiment, the calculation formula for calculating the gravitational pressure drop of each section of the sub-production string according to the gas density includes:

[0135]

[0136] In the formula, is the gravitational pressure drop of the k-th section of the sub-production string, MPa; H FD is the preset length, m; is the gas density of the k-th section of the sub-production string, kg / m 3 ; g is the acceleration due to gravity, m 2 / s; H FD is the preset length, m.

[0137] S2063: Calculate the gas flow velocity of each section of the sub-production string according to the gas density.

[0138] In this embodiment, the calculation formula for calculating the gas flow velocity of each section of the sub-production string according to the gas density includes:

[0139]

[0140] In the formula, is the gas flow velocity of the k-th section of the sub-production string, m / s; Q min is the minimum production rate, m 3 / d; d tn is the inner diameter of the production string, m; is the gas density of the k-th sub-production string, kg / m 3 ; ρ s is the standard condition density of the gas, kg / m 3 .

[0141] S2064: Calculate the friction coefficient of each section of the sub-production string according to the gas density and gas flow velocity.

[0142] In this embodiment, the calculation formula for calculating the friction coefficient of each section of the sub-production string according to the gas density and gas flow velocity includes:

[0143]

[0144] In the formula, is the friction coefficient of the k-th sub-production string, dimensionless; Ra is the roughness corresponding to the sub-production string, m; d tn is the inner diameter of the production string, m; is the gas viscosity, Pa•s.

[0145] S2065: Calculate the frictional pressure drop of each sub-production string according to the gas density, gas flow rate and friction coefficient.

[0146] In this embodiment, the calculation formula for calculating the frictional pressure drop of each sub-production string according to the gas density, gas flow rate and friction coefficient includes:

[0147]

[0148] In the formula, is the frictional pressure drop of the k-th sub-production string, MPa; is the friction coefficient of the k-th sub-production string, dimensionless; is the gas density of the k-th sub-production string, kg / m 3 ; is the gas flow rate of the k-th sub-production string, m / s; d tn is the inner diameter of the production string, m; H FD is the preset length, m.

[0149] S2066: Construct a pressure iteration model corresponding to each sub-production string according to the sectional pressure, gravitational pressure drop and frictional pressure drop.

[0150] In this embodiment, the calculation formula for constructing a pressure iteration model corresponding to each sub-production string according to the sectional pressure, gravitational pressure drop and frictional pressure drop includes:

[0151]

[0152] In the formula, is the pressure corresponding to the (k + 1)-th sub-production string, MPa; p k is the sectional pressure of the k-th section, Pa; is the frictional pressure drop of the k-th sub-production string, MPa; is the gravitational pressure drop of the k-th sub-production string, MPa.

[0153] S207: Determine the target number of the sub-production string where the downhole throttle is located according to the installation depth.

[0154] In this embodiment, the calculation formula for determining the target number of the sub-production string where the downhole throttle is located according to the installation depth includes:

[0155]

[0156] In the formula, M is the target number of the sub-production string where the downhole throttler is located, a dimensionless integer; H J is the installation depth; H FD is the preset length.

[0157] S208: Determine the annulus allowable pressure as the initial pressure of the first sub-production string.

[0158] S209: Determine the pressure at the target number according to the initial pressure and the pressure iteration model.

[0159] S210: Obtain the maximum bottom pressure before wellbore throttling and the temperature inside the production string.

[0160] Specifically, step S210 is specifically: Obtain the maximum bottom pressure of the production string and the temperature inside the production string under the condition of the minimum production rate before wellbore throttling according to the thermometer and pressure gauge or distributed optical fiber.

[0161] S211: Determine the throttling orifice area of the downhole throttler when the production string is in a critical leakage state or a non-critical leakage state according to the maximum bottom pressure, the temperature inside the production string, and the pressure at the target number.

[0162] Specifically, step S211 specifically includes:

[0163] S2111: Determine the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string.

[0164] In this embodiment, the calculation formula for determining the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string includes:

[0165]

[0166] In the formula, Zg is the gas compressibility factor, dimensionless; A1, A2, A3, A4, A5, A6, A7, A8, A9, A 10 —constants, dimensionless, 1.1153, -0.079, 0.01588, 0.00886, -2.1619, 1.1575, -0.05368, 0.014655, -1.80997, 0.9548 respectively; p max is the maximum bottom pressure, MPa; γ g is the gas relative density, dimensionless; p r is the pseudo-reduced pressure, dimensionless, as an intermediate quantity for solving the gas compressibility factor; T r is the pseudo-reduced temperature, dimensionless, as an intermediate quantity for solving the gas compressibility factor; T fL is the temperature inside the production string, °C.

[0167] S2112: Determine whether the throttling process type is in a critical leakage state or a non-critical leakage state based on the pressure at the target number and the maximum bottom pressure.

[0168] In this embodiment, the calculation formula for determining whether the throttling process type is in a critical leakage state or a non-critical leakage state based on the pressure at the target number and the maximum bottom pressure includes:

[0169]

[0170] In the formula, k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; p max is the maximum bottom pressure; p J is the pressure at the target number.

[0171] S2113: If it is determined that the throttling process type is in a critical leakage state, then determine the throttling orifice area of the downhole throttler based on the gas compressibility factor, the maximum bottom pressure before wellbore throttling, and the temperature in the production string.

[0172] In this embodiment, the calculation formula for determining the throttling orifice area of the downhole throttler based on the gas compressibility factor, the maximum bottom pressure before wellbore throttling, and the temperature in the production string when it is determined that the throttling process type is in a critical leakage state includes:

[0173]

[0174] In the formula, A L is the throttling orifice area, m 2 ; Q min is the minimum production rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient. The throttling orifice is a round hole, taking a value of 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fL is the temperature in the production string, °C.

[0175] S2114: If it is determined that the throttling process type is in a non-critical leakage state, then determine the throttling orifice area of the downhole throttler based on the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before wellbore throttling, and the temperature in the production string.

[0176] In this embodiment, if it is determined that the throttling process type is in a non-critical leakage state, then according to the calculation formula of the throttling orifice area of the downhole throttler based on the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before wellbore throttling, and the temperature in the production string, it includes:

[0177]

[0178] In the formula, A L is the throttling orifice area, m 2 ; Q min is the minimum production rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient. The throttling orifice is a round hole, and the value is 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fL is the temperature in the production string, °C; p J is the pressure at the target number.

[0179] S212: Determine the throttling orifice diameter of the downhole throttler according to the throttling orifice area to ensure that the production string is in a critical leakage state or a non-critical leakage state and prevent the production string from leaking.

[0180] In addition, instructions can also be sent through optical fibers, cables, or wireless transmission to dynamically adjust the throttling orifice diameter of the downhole throttler.

[0181] In this embodiment, the calculation formula for determining the throttling orifice diameter of the downhole throttler according to the throttling orifice area is:

[0182]

[0183] In the formula, D J is the throttling orifice diameter of the throttler, m; A L is the throttling orifice area, m 2 .

[0184] In summary, the method for handling the leakage of the production string in the control wellbore provided in this embodiment includes: obtaining the operating parameters of the wellbore; obtaining the pre-determined installation depth of the downhole throttle; calculating the allowable annulus pressure of the casing annulus according to the internal pressure resistance strength of the production casing, the external extrusion resistance strength of the production string, the wellhead pressure, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing, the minimum external extrusion resistance strength of the production string, and the casing head strength; segmenting and numbering the production string according to a preset length to obtain multiple sub-production strings with numbers; constructing a pressure iteration model for each sub-production string according to the segmented pressure and segmented temperature of each obtained sub-production string; determining the target number of the sub-production string where the downhole throttle is located according to the installation depth; determining the initial pressure of the first sub-production string as the allowable annulus pressure; determining the pressure at the target number according to the initial pressure and the pressure iteration model; determining the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state according to the obtained maximum bottom pressure before throttling in the wellbore, the temperature inside the production string, and the pressure at the target number; determining the throttle orifice diameter of the downhole throttle according to the throttle orifice area to ensure that the production string is in a critical leakage state or a non-critical leakage state, preventing the production string from leaking. By reducing the annulus pressure to within the safety threshold, the problem of production string leakage is solved at the root. Further, it is applicable to various complex leakage conditions.

[0185] Figure 3 Schematic flow of the method for handling the leakage of the production string in the control wellbore provided in the embodiments of the present application Figure 2 . In the embodiments of the present application, based on the embodiments provided Figure 2 , a detailed description is given of the specific implementation method for determining the installation depth of the downhole throttle in step S202. As Figure 3 shown, the method includes:

[0186] S301: Calculate the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string.

[0187] In this embodiment, the calculation formula for calculating the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string includes:

[0188]

[0189] In the formula, H L is the first initial length of the production string under tensile action, m; F X is the weight of the production string, N; M T is the mass per unit length of the production string, kg / m; g is the acceleration due to gravity, m / s 2 .

[0190] S302: Determine the second initial length of the production string under compression according to the designed depth of the packer and the initial length of the production string under tension.

[0191] In this embodiment, the calculation formula for determining the second initial length of the production string under compression according to the designed depth of the packer and the initial length of the production string under tension includes:

[0192]

[0193] In the formula, H Y is the second initial length of the production string under compression, m; H FS is the designed depth of the packer, m; H L is the first initial length of the production string under tension, m.

[0194] S303: Calculate the tensile length of the production string according to the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string.

[0195] In this embodiment, the calculation formula for calculating the tensile length of the production string according to the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string includes:

[0196]

[0197] In the formula, △H L is the tensile length of the production string, m; E is the elastic modulus of the production string, Pa; A is the cross-sectional area of the production string; H L is the first initial length of the production string under tension, m.

[0198] S304: Calculate the compression length of the production string according to the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string.

[0199] In this embodiment, the calculation formula for calculating the compression length of the production string according to the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string includes:

[0200]

[0201] In the formula, △H Y is the compression length of the production string, m; E is the elastic modulus of the production string, Pa; A is the cross-sectional area of the production string; H Y is the second initial length of the production string under compression, m.

[0202] S305: Calculate the thermal expansion elongation of any oil pipe according to the surface temperature, the initial length of a single oil pipe, the geothermal gradient, and the initial temperature of the single oil pipe.

[0203] In this embodiment, the calculation formula for calculating the thermal expansion elongation of any oil pipe according to the surface temperature, the initial length of a single oil pipe, the geothermal gradient, and the initial temperature of the single oil pipe includes:

[0204]

[0205] In the formula, △H T i is the thermal expansion elongation of the i-th oil pipe, m; T0 is the surface temperature, °C; g e is the geothermal gradient, °C / m; i is the number of the oil pipe in the wellbore, numbered 1, 2,..., N from the wellhead to the bottom of the well; H T is the initial length of a single oil pipe, m; T T is the initial temperature of the single oil pipe, °C; α is the thermal expansion rate of the oil pipe, °C -1 .

[0206] S306: Determine the total thermal expansion elongation of the production string according to the thermal expansion elongation corresponding to each oil pipe.

[0207] In this embodiment, the calculation formula for determining the total thermal expansion elongation of the production string according to the thermal expansion elongation corresponding to each oil pipe includes:

[0208]

[0209] In the formula, △H TZ is the total thermal expansion elongation of the production string above the packer, m; △H T i is the thermal expansion elongation of the i-th oil pipe.

[0210] S307: Determine the actual depth of the packer according to the designed depth, the tensile length, the compression length, and the total thermal expansion elongation of the packer.

[0211] In this embodiment, the calculation formula for determining the actual depth of the packer according to the designed depth, the tensile length, the compression length, and the total thermal expansion elongation of the packer includes:

[0212]

[0213] In the formula, H F is the actual depth of the packer, m; H FS is the designed depth of the packer, m; △H L is the tensile length of the production string, m; △H Y is the compression length of the production string, m; △H TZis the total thermal expansion elongation of the production string above the packer, in m.

[0214] S308: Determine the installation depth of the downhole throttle according to the actual depth of the packer.

[0215] In this embodiment, the calculation formula for determining the installation depth of the downhole throttle according to the actual depth of the packer includes:

[0216]

[0217] In the formula, H J is the installation depth of the downhole throttle, in m; H F is the actual depth of the packer, in m; H W is the depth installation allowance, H W > 0, in m.

[0218] In summary, the method for dealing with the leakage of the production string in the controlled wellbore provided in this embodiment calculates the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string; determines the second initial length of the production string under compressive action according to the designed depth of the packer and the initial length of the production string under tensile action; calculates the tensile length of the production string according to the weight per unit length of the production string, the first initial length and the cross-sectional area of the production string; calculates the compressive length of the production string according to the weight per unit length of the production string, the second initial length and the cross-sectional area of the production string; calculates the thermal expansion elongation of any tubing according to the surface temperature, the initial length of a single tubing, the geothermal gradient and the initial temperature of a single tubing; determines the total thermal expansion elongation of the production string according to the thermal expansion elongation corresponding to each tubing; determines the actual depth of the packer according to the designed depth, the tensile length, the compressive length and the total thermal expansion elongation of the production string; determines the installation depth of the downhole throttle according to the actual depth of the packer, laying a foundation for determining the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state, and fundamentally solving the problem of production string leakage.

[0219] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for dealing with the leakage of production tubing in a control wellbore, characterized in that, Comprising: Obtaining the operating parameters of the wellbore, where the wellbore at least includes a casing annulus, a production string, a packer, and a downhole choker. The casing annulus is a circular space around the production string, and the packer is installed on the production string; the operating parameters at least include the internal pressure resistance strength of the production casing at the packer, the external extrusion resistance strength of the production string at the packer, the wellhead pressure after well production, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing outside the casing annulus, the minimum external extrusion resistance strength of the production string, and the casing head strength of the production casing; Obtaining the pre-determined installation depth of the downhole choker, and installing the downhole choker on the production string according to the installation depth; Calculating the allowable annulus pressure of the casing annulus according to the internal pressure resistance strength of the production casing, the external extrusion resistance strength of the production string, the wellhead pressure, the minimum internal pressure resistance strength of the production casing, the minimum internal pressure resistance strength of the technical casing, the minimum external extrusion resistance strength of the production string, and the casing head strength; Performing segmented numbering processing on the production string according to a preset length to obtain multiple sub-production strings with numbers; Obtaining the segmented pressure and segmented temperature of each sub-production string; Constructing a pressure iteration model corresponding to each sub-production string according to the segmented pressure and the segmented temperature; Determining the target number of the sub-production string where the downhole choker is located according to the installation depth; Determining the allowable annulus pressure as the initial pressure of the first sub-production string; Determining the pressure at the target number according to the initial pressure and the pressure iteration model; Obtaining the maximum bottom pressure and the temperature inside the production string before well throttling; Determining the throttle orifice area of the downhole choker when the production string is in a critical leakage state or a non-critical leakage state according to the maximum bottom pressure, the temperature inside the production string, and the pressure at the target number; Determining the throttle aperture of the downhole choker according to the throttle orifice area to ensure that the production string is in a critical leakage state or a non-critical leakage state and prevent the production string from leaking.

2. The method according to claim 1, wherein Wherein the downhole choker needs to be installed below the packer, and the production string is spliced by multiple tubing strings; the operating parameters further include the weight of the production string, the weight per unit length of the production string, the designed depth of the packer, the surface temperature, the initial length of a single tubing string, the geothermal gradient, and the initial temperature of the single tubing string; Correspondingly, the process of determining the installation depth of the downhole choker includes: Calculating the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string; Determining the second initial length of the production string under compressive action according to the designed depth of the packer and the initial length of the production string under tensile action; Calculating the tensile length of the production string according to the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string; Calculating the compressive length of the production string according to the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string; Calculate the thermal expansion elongation of any oil pipe according to the surface temperature, the initial length of a single oil pipe, the geothermal gradient, and the initial temperature of the single oil pipe; Determine the total thermal expansion elongation of the production string according to the thermal expansion elongation corresponding to each oil pipe; Determine the actual depth of the packer according to the designed depth of the packer, the tensile length, the compression length, and the total thermal expansion elongation; Determine the installation depth of the downhole throttle according to the actual depth of the packer.

3. The method according to claim 2, characterized in that, The calculation formula for calculating the first initial length of the production string under tensile action according to the weight of the production string and the weight per unit length of the production string includes: Where, H L is the first initial length of the production string under tensile action, m; F X is the weight of the production string, N; M T is the mass per unit length of the production string, kg / m; g is the acceleration of gravity, m / s 2 ; Correspondingly, the calculation formula for calculating the second initial length of the production string under compression action according to the designed depth of the packer and the initial length of the production string under tensile action includes: Wherein, H Y is the second initial length of the production string under compression, in m; H FS is the designed depth of the packer, in m; H L is the first initial length of the production string under tension, in m; Correspondingly, the calculation formula for calculating the tensile length of the production string according to the weight per unit length of the production string, the first initial length, and the cross-sectional area of the production string includes: wherein, △H L is the tensile length of the production string, in m; E is the elastic modulus of the production string, in Pa; A is the cross-sectional area of the production string; H L is the first initial length of the production string under tensile action, in m; Correspondingly, the calculation formula for calculating the compression length of the production string according to the weight per unit length of the production string, the second initial length, and the cross-sectional area of the production string includes: Where, △H Y is the compression length of the production string, m; E is the elastic modulus of the production string, Pa; A is the cross-sectional area of the production string; H Y is the second initial length of the production string under compression, m; Correspondingly, the calculation formula for calculating the thermal expansion elongation of any oil pipe according to the surface temperature, the initial length of a single oil pipe, the geothermal gradient, and the initial temperature of the single oil pipe includes: where, △H T i is the thermal expansion elongation of the i-th tubing string, m; T0 is the surface temperature, °C; g e is the geothermal gradient, °C / m; i is the number of the tubing string in the wellbore, numbered 1, 2, ..., N successively from the wellhead to the bottom of the well; H T is the initial length of the single tubing string, m; T T is the initial temperature of the single tubing string, °C; α is the thermal expansion rate of the tubing string, °C -1 ; Correspondingly, the calculation formula for determining the total thermal expansion elongation of the production string according to the thermal expansion elongations corresponding to each oil pipe includes: Where, △H TZ is the total thermal expansion elongation of the production string above the packer, m; △H T i is the thermal expansion elongation of the i-th tubing; Correspondingly, the calculation formula for determining the actual depth of the packer according to the designed depth of the packer, the tensile length, the compression length, and the total thermal expansion elongation includes: where, H F is the actual depth of the packer, m; H FS is the designed depth of the packer, m; △H L is the tensile length of the production string, m; △H Y is the compression length of the production string, m; △H TZ is the total thermal expansion elongation of the production string above the packer, m; Correspondingly, the calculation formula for determining the installation depth of the downhole throttle according to the actual depth of the packer includes: Wherein, H J is the installation depth of the downhole throttle, m; H F is the actual depth of the packer, m; H W is the depth installation allowance, H W > 0, m.

4. The method according to claim 1, wherein Calculate the allowable annulus pressure of the casing annulus according to the internal pressure resistance of the production casing, the external extrusion resistance of the production string, the wellhead pressure, the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, and the casing head strength, including: Calculate the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer according to the internal pressure resistance of the production casing; Calculate the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer according to the external extrusion resistance of the production string and the wellhead pressure; Calculate the allowable annulus pressure of the casing annulus according to the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external extrusion resistance of the production string, the casing head strength, the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external extrusion resistance of the production casing at the packer.

5. The method according to claim 4, wherein The calculation formula for calculating the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer according to the internal pressure resistance of the production casing includes: Wherein, p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer; p7 is the internal pressure resistance of the production casing, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; h p is the depth where the packer is located, m; Accordingly, the calculation formula for the maximum allowable annulus pressure determined by calculating the external collapse strength of the production casing at the packer based on the external collapse strength of the production string and the wellhead pressure includes: Wherein, p6 is the maximum allowable annulus pressure determined by the external extrusion strength of the production casing at the packer; p8 is the external extrusion strength of the production string, MPa; p9 is the wellhead pressure, MPa; ρ cs is the density of the cement slurry for well cementing, g / cm 3 ; ρ co is the density of the annulus fluid, g / cm 3 ; g is the acceleration due to gravity, m 2 / s; h p is the depth where the packer is located, m; Accordingly, the calculation formula for calculating the allowable annulus pressure of the casing annulus based on the minimum internal pressure resistance of the production casing, the minimum internal pressure resistance of the technical casing, the minimum external collapse strength of the production string, the casing head strength, the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, and the maximum allowable annulus pressure determined by the external collapse strength of the production casing at the packer includes: where Δp aA is the allowable annulus pressure of the casing annulus, MPa; p1 is the minimum internal pressure resistance of the production casing, MPa; p2 is the minimum internal pressure resistance of the technical casing, MPa; p3 is the minimum external extrusion resistance of the production string, MPa; p4 is the casing head strength, MPa; p5 is the maximum allowable annulus pressure determined by the internal pressure resistance of the production casing at the packer, MPa; p6 is the maximum annulus allowable pressure determined by the external extrusion resistance of the production casing at the packer, MPa.

6. The method according to claim 1, wherein The construction of the pressure iteration model corresponding to each sub-production string based on the sectional pressure and the sectional temperature includes: Calculating the gas density of each sub-production string according to the sectional pressure and the sectional temperature; Calculating the gravitational pressure drop of each sub-production string according to the gas density; Calculating the gas flow velocity of each sub-production string according to the gas density; Calculating the friction coefficient of each sub-production string according to the gas density and the gas flow velocity; Calculating the frictional pressure drop of each sub-production string according to the gas density, the gas flow velocity and the friction coefficient; Constructing the pressure iteration model corresponding to each sub-production string according to the sectional pressure, the gravitational pressure drop and the frictional pressure drop.

7. The method according to claim 6, characterized in that, The calculation formula for calculating the gas density of each sub-production string according to the sectional pressure and the sectional temperature includes: In the formula, is the gas density of the k-th sub-production string, kg / m 3 ; p k is the sectional pressure of the k-th section, Pa; T s is the standard condition temperature, °C; p s is the standard condition pressure, Pa; T k is the sectional temperature of the k-th section, °C; ρ s is the gas standard condition density, kg / m 3 ; Accordingly, the calculation formula for calculating the gravitational pressure drop of each sub-production string according to the gas density includes: In the formula, is the gravitational pressure drop of the sub-production string in the k-th section, MPa; H FD is the preset length, m; is the gas density of the sub-production string in the k-th section, kg / m 3 ; g is the acceleration of gravity, m 2 / s; H FD is the preset length, m; Accordingly, the calculation formula for calculating the gas flow velocity of each sub-production string according to the gas density includes: In the formula, is the gas flow velocity of the k-th sub-production string, m / s; Q min is the minimum production rate, m 3 / d; d tn is the inner diameter of the production string, m; is the gas density of the k-th sub-production string, kg / m 3 ; ρ s is the standard gas density, kg / m 3 ; Accordingly, the calculation formula for calculating the friction coefficient of each sub-production string according to the gas density and the gas flow velocity includes: In the formula, is the friction coefficient of the k-th sub-production string, dimensionless; Ra is the roughness corresponding to the sub-production string, m; d tn is the inner diameter of the production string, m; is the gas viscosity, Pa•s; Accordingly, the calculation formula for calculating the frictional pressure drop of each sub-production string according to the gas density, the gas flow velocity and the friction coefficient includes: wherein, is the frictional pressure drop of the k-th sub-production string, MPa; is the friction coefficient of the k-th sub-production string, dimensionless; is the gas density of the k-th sub-production string, kg / m 3 ; is the gas flow velocity of the k-th sub-production string, m / s; d tn is the inner diameter of the production string, m; H FD is the preset length, m; Accordingly, the calculation formula for constructing the pressure iteration model corresponding to each sub-production string according to the sectional pressure, the gravitational pressure drop and the frictional pressure drop includes: In the formula, is the pressure corresponding to the (k + 1)-th sub-production string, MPa; p k is the sectional pressure of the k-th section, Pa; is the frictional pressure drop of the k-th sub-production string, MPa; is the gravitational pressure drop of the k-th sub-production string, MPa.

8. The method according to claim 1, characterized in that, Determining the throttle orifice area of the downhole throttle when the production string is in a critical leakage state or a non-critical leakage state based on the maximum bottom pressure, the temperature inside the production string, and the pressure at the target number includes: Determining the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string; Determining whether the throttling process type is a critical leakage state or a non-critical leakage state according to the pressure at the target number and the maximum bottom pressure; If it is determined that the throttling process type is a critical leakage state, then determine the throttle orifice area of the downhole throttle according to the gas compressibility factor, the maximum bottom pressure before throttling in the wellbore, and the temperature inside the production string; If it is determined that the throttling process type is a non-critical leakage state, the throttling orifice area of the downhole throttler is determined according to the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before wellbore throttling, and the temperature inside the production string.

9. The method according to claim 8, wherein The calculation formula for determining the gas compressibility factor according to the maximum bottom pressure and the temperature inside the production string includes: where Zg is the gas compressibility factor, dimensionless; A1, A2, A3, A4, A5, A6, A7, A8, A9, A 10 — constants, dimensionless, being 1.1153, -0.079, 0.01588, 0.00886, -2.1619, 1.1575, -0.05368, 0.014655, -1.80997, 0.9548; p max is the maximum bottom pressure, MPa; γ g is the relative gas density, dimensionless; p r is the pseudo-reduced pressure, dimensionless, serving as an intermediate quantity for solving the gas compressibility factor; T r is the pseudo-reduced temperature, dimensionless, serving as an intermediate quantity for solving the gas compressibility factor; T fL is the temperature inside the production string, °C; Correspondingly, the calculation formula for determining whether the throttling process type is a critical leakage state or a non-critical leakage state according to the pressure at the target number and the maximum bottom pressure includes: where k g is the adiabatic index of the leakage gas, taken as 1.66, dimensionless; p max is the maximum pressure at the bottom; p J is the pressure at the target number Correspondingly, if it is determined that the throttling process type is a critical leakage state, the calculation formula for the throttling orifice area of the downhole throttler according to the gas compressibility factor, the maximum bottom pressure before wellbore throttling, and the temperature inside the production string includes: Wherein, A L is the throttle orifice area, m 2 ; Q min is the minimum output rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient. The throttle orifice is a round hole, with a value of 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fL is the temperature inside the production string, °C; Correspondingly, if it is determined that the throttling process type is a non-critical leakage state, the calculation formula for the throttling orifice area of the downhole throttler according to the gas compressibility factor, the pressure at the target number, the maximum bottom pressure before wellbore throttling, and the temperature inside the production string includes: Where, A L is the throttle orifice area, m 2 ; Q min is the minimum output rate, m 3 / d; ρ s is the standard condition density of the gas, kg / m 3 ; C o is the flow coefficient. The throttle orifice is a round hole, and the value is 1.0, dimensionless; p max is the maximum bottom pressure, MPa; M g is the molar mass of the gas, kg / mol; k g is the adiabatic index of the leaked gas, taking 1.66, dimensionless; Zg is the gas compressibility factor, dimensionless; R is the gas constant, taking 8.3414; T fL is the temperature inside the production string, °C; p J is the pressure at the target number.

10. The method according to any one of claims 1 to 9, characterized in that The calculation formula for determining the target number of the sub-production string where the downhole throttler is located according to the installation depth includes: Where M is the target number of the sub-production string where the downhole throttler is located, a dimensionless integer; H J is the installation depth; H FD is the preset length.

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