Method and system for calculating limit yield threshold value of test pipeline

Abstract

The invention provides a method and a system for calculating a limit yield threshold value of a test pipeline. The method comprises the following steps: S1, establishing an outlet pressure calculation equation at the tail end of the test pipeline; s2, establishing an internal pressure calculation equation of the initial end of the test pipeline; s3, testing a pipeline on-way hydraulic friction calculation equation; s4, deducing by combining the equations established in S2 and S3 to obtain a test pipeline tail end pressure calculation equation; s5, inversely calculating the initial end pressure of the current test pipeline in combination with the equations established in the steps S3 to S4 and the characteristic change of the hydrate in the test pipeline; and S6, comparing the initial end pressure of the test pipeline in the step S5 with the highest permissible working pressure of the test separator, and determining the limit yield threshold values of the test pipelines with different lengths and sizes. The system is configured to establish a calculation equation of the above S1 to S2 and calculate a limit yield threshold value. The system provided by the invention has high applicability, and the calculation result of the calculation method provided by the invention is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas resource test production. Specifically, it relates to a method and system for calculating the limit production threshold of a test pipeline. Background Art

[0002] Oil and gas well testing is an important part of oil and gas field exploration and development, and is the most direct and effective means to understand oil and gas reservoirs and verify the accuracy of data such as seismic, logging, and mud logging. As an important part of oil and gas well testing, surface testing obtains wellhead pressure and temperature, measures oil, gas, and water production through surface testing equipment, and at the same time obtains stable production at several different flowing pressures by changing the choke size, providing reliable support for the later development of oil and gas fields.

[0003] Currently, during the test operation process, there is little research on calculating the limit production threshold of the test pipeline considering the coupling effect of complex working conditions. The description method of the internal pressure distribution of the test pipeline is only limited to the basic hydraulic calculation method of the pipeline, which does not consider the influence of factors such as the change of the internal environmental temperature of the pipeline, the formation of hydrates, and pipeline vibration, and has great limitations. Therefore, it is particularly important to optimize the pressure calculation results in the test pipeline and form a method for calculating the limit production threshold of the test pipeline considering the coupling effect of complex working conditions.

[0004] The patent with the publication number "CN107563899A" and the name "Method and Device for Predicting Oil and Gas Well Productivity" provides a method for predicting oil and gas well productivity. The method includes obtaining test information of an oil and gas well; determining an inflow performance model of the oil and gas well in the current productivity prediction period according to the test information; determining the future average formation pressure of the oil and gas well in the next productivity prediction period according to the inflow performance model of the oil and gas well in the current productivity prediction period; determining the inflow performance model of the oil and gas well in the next productivity prediction period according to the inflow performance model of the oil and gas well in the current productivity prediction period and the future average formation pressure of the oil and gas well in the next productivity prediction period; and predicting the productivity of the oil and gas well in the next productivity prediction period according to the inflow performance model of the oil and gas well in the next productivity prediction period. Compared with this patent, the present invention combines more complex working conditions in the pipeline, optimizes the pressure calculation results in the test pipeline, and provides a calculation method for calculating the limit production threshold, which can more accurately calculate the internal pressure of the test pipeline and obtain the limit production threshold. Summary of the Invention

[0005] The object of the invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, one object of the present invention is to provide a method for calculating the limit production threshold of a test pipeline that is convenient, efficient, and has a high accuracy rate. Another object of the present invention is, for another example, a system for calculating the limit production threshold of a test pipeline considering the coupling effect of complex working conditions based on the ground process. Still another object of the present invention is to provide a device for calculating the limit production threshold of a test pipeline.

[0006] To achieve the above object, on the one hand, the present invention provides a method for calculating the limit production threshold of a test pipeline, and the method may include the following steps: S1: Establish a vibration model of the ground test pipeline. Based on the vibration model of the ground test pipeline, establish a multiphase flow model considering the influence of different water contents and solid-phase erosion wear in the pipeline on the vibration of the test pipeline. Establish a three-phase continuity equation through the multiphase flow model, calculate the fluid velocity distribution in the test pipe, analyze the internal fluid flow characteristics of the test pipeline, and combine the pipeline length and size data and the multiphase flow model to derive and establish a calculation equation for the outlet pressure at the end of the test pipeline; S2: Establish a friction resistance analysis method for different flow patterns and sand contents in the test pipeline, and establish a calculation equation for the internal pressure at the initial end of the test pipeline in combination with the internal fluid flow resistance conditions of the test pipeline; S3: Establish a calculation equation for the hydraulic friction resistance along the test pipeline according to the pressure loss of natural gas during the flow process in test pipelines of different sizes and lengths under different flow rates; S4: Combine the equations established in S2 and S3 to derive the pressure at the end of the test pipeline; S5: Combine the equations established in S3 - S4 and the change of hydrate characteristics in the test pipeline to back-calculate the initial pressure of the current test pipeline; S6: Compare the initial pressure of the test pipeline in S5 with the maximum allowable working pressure of the test separator to determine the limit production threshold of test pipelines of different lengths and sizes.

[0007] According to one or more exemplary embodiments of one aspect of the present invention, the vibration model of the ground test pipeline may include a pipeline axial vibration equation and a pipeline lateral vibration equation. The pipeline axial vibration equation is as follows:

[0008]

[0009] The pipeline lateral vibration equation is as follows:

[0010]

[0011] Wherein, m p is the mass of the test pipeline, kg; m f is the mass of the fluid, kg; is the axial velocity of the test pipeline, m / s; is the axial acceleration of the test pipeline, m / s 2; u' is the first derivative of the axial displacement of the test pipeline with respect to the coordinate; u'' is the second derivative of the axial displacement of the test pipeline with respect to the coordinate; v f is the fluid velocity, m / s; is the fluid acceleration, m / s 2 ; v' f is the first derivative of the fluid velocity with respect to the coordinate; w' is the first derivative of the lateral displacement of the test pipeline with respect to the coordinate; w'' is the second derivative of the lateral displacement of the test pipeline with respect to the coordinate; w''' is the third derivative of the lateral displacement of the test pipeline with respect to the coordinate; E is the elastic modulus of the test pipeline, Pa; A p is the cross-sectional area of the pipeline, m 2 ; A f is the flow-through area of the pipeline, m 2 ; I p is the moment of inertia of the pipeline cross-section, mm 4 ; μ* is μ is the Poisson's ratio; E* is c a , c t are the axial and lateral structural damping coefficients.

[0012] According to one or more exemplary embodiments of one aspect of the present invention, the three-phase continuity equation can be as follows:

[0013] Gas-phase continuity equation:

[0014]

[0015] Liquid-phase continuity equation:

[0016]

[0017] Solid-phase continuity equation:

[0018]

[0019] Wherein, ρ g , ρ l , ρ s are the densities of the gas, liquid, and solid in the pipeline, kg / m 3 ; v g , v l , v s are the velocities of the gas, liquid, and solid in the pipeline, m / s; A is the cross-sectional area of the pipeline, m / s 2 ; E g , E l , E s are the gas volume fraction, liquid volume fraction, and solid fraction of the pipeline cross-sectional area; r H is the hydrate decomposition rate, m3 / s.

[0020] According to one or more exemplary embodiments of one aspect of the present invention, based on the three-phase hybrid continuity equation in combination with the law of conservation of momentum, a gas-liquid-solid three-phase hybrid momentum equation can be established, and the gas-liquid-solid three-phase hybrid momentum equation is as follows:

[0021]

[0022] Among them, ρ g , ρ l , ρ s are respectively the densities of the gas, liquid, and solid in the pipe, kg / m 3 ; v g , v l , v s are respectively the velocities of the gas, liquid, and solid in the pipe, m / s; A is the cross-sectional area of the pipeline, m / s 2 ; E g , E l , E s are the gas holdup, liquid holdup, and solid proportion in the cross-sectional area of the pipeline; P is the pressure in the pipe, Pa.

[0023] According to one or more exemplary embodiments of one aspect of the present invention, if the volumetric gas holdup, cross-sectional gas holdup, and slip velocity ratio of different degrees of slip between the two-phase flow and the multiphase flow in the test pipeline satisfy the following formula:

[0024]

[0025] Among them, ε g is the volumetric gas holdup; α g is the cross-sectional gas holdup, K is the slip velocity ratio, then the equation of the outlet pressure at the end of the test pipeline can be as follows:

[0026] P z = ρ e RT e ;

[0027] Among them, P Z is the outlet pressure at the end of the test pipeline, MPa; ρ e is the density of natural gas at the blowout outlet, kg / m 3 ; R is the gas constant of air, J / (Kg k); T e is the temperature at the end of the test pipeline, °C.

[0028] According to one or more exemplary embodiments of one aspect of the present invention, the method for analyzing the friction resistance under different flow patterns and sand contents in the test pipeline may include the following steps:

[0029] Establish the two-phase flow hydraulic friction coefficient:

[0030]

[0031] where λ m is the two-phase flow hydraulic friction coefficient; C is a dimensionless coefficient; Re is the fluid Reynolds number at this time;

[0032] Using the natural gas mass flow formula, the internal pressure at the initial end of the test pipeline is iteratively calculated. The natural gas mass flow formula is as follows:

[0033]

[0034] where M is the mass flow rate of natural gas, kg / s; P Q is the internal pressure at the initial end of the pipeline, MPa; A is the cross-sectional area of the pipeline, m 2 ; Z is the compressibility factor of natural gas; T is the stagnation temperature, K; λ m is the hydraulic friction coefficient of the mixed fluid; L is the length of the blowout prevention pipeline, m; D is the inner diameter of the pipeline, m.

[0035] According to one or more exemplary embodiments of one aspect of the present invention, the calculation equation for the hydraulic friction along the test pipeline is as follows:

[0036]

[0037] where ΔP is the hydraulic friction along the pipeline, MPa; ρ is the density of the fluid in the pipeline, kg / m 3 ; L is the equivalent length of the blowout prevention pipeline, m; D is the inner diameter of the pipeline, m.

[0038] According to one or more exemplary embodiments of one aspect of the present invention, the process of calculating the pressure at the end of the test pipeline may include: The density of air under standard conditions can be calculated from the state equation:

[0039]

[0040] where R is the gas constant of air, and T is the temperature under standard conditions, °C;

[0041] The density of natural gas under standard conditions is ρ = ρ a Δ. Therefore, the density of natural gas at the blowout outlet can be calculated according to the following formula:

[0042]

[0043] The temperature at the blowout outlet is the critical temperature T e , which is obtained from the formula:

[0044]

[0045] Therefore, the state equation can be listed to obtain the end pressure at the blowout pipeline outlet:

[0046] P z = ρ e RT e 。

[0047] Among them, ρ a is the air density under standard conditions, kg / m 3 ; ρ e is the natural gas density at the blowout outlet, kg / m 3 ; ρ is ρ a Δ, kg / m 3 , Δ is the relative density of natural gas, dimensionless; T0 is the stagnation temperature, K; T e is the critical temperature at the blowout outlet, K; k is the adiabatic index of natural gas, dimensionless.

[0048] According to one or more exemplary embodiments of one aspect of the present invention, the back-calculation step of the initial end pressure of the test pipeline may include: First, calculate the two-phase flow hydraulic friction coefficient, and the calculation equation is as follows:

[0049]

[0050] Among them, λ m is the two-phase flow hydraulic friction coefficient; C is a coefficient, dimensionless; Re is the fluid Reynolds number at this time,

[0051] Calculate the compression coefficient Z, and the calculation equation is as follows:

[0052]

[0053] Calculate the average pressure P, and the calculation equation is as follows:

[0054]

[0055] Use the natural gas mass flow formula to iteratively calculate the internal pressure at the initial end of the test pipeline. The natural gas mass flow formula is as follows:

[0056]

[0057] On the other hand, the present invention provides a system for extremely testing the limit production threshold of a pipeline. The system for calculating the limit production threshold of the test pipeline may include a first calculation unit, a second calculation unit, a third calculation unit and a limit production threshold calculation unit. The first calculation unit, the second calculation unit, the third calculation unit and the fourth calculation unit are connected to the limit production threshold calculation unit. Among them, the first calculation unit is configured to establish a vibration model of the ground test pipeline. On the basis of the vibration model of the ground test pipeline, a multiphase flow model considering the influence of different water contents in the pipeline and solid-phase erosion wear on the vibration of the test pipeline is established. A three-phase continuity equation is established through the multiphase flow model, the fluid velocity distribution in the test pipeline is calculated, the internal fluid flow characteristics of the test pipeline are analyzed, and a calculation equation for the outlet pressure at the end of the test pipeline is derived in combination with the pipeline length and size data and the multiphase flow model; the second calculation unit is configured to establish a friction resistance analysis method under different flow patterns and sand contents in the test pipeline, and establish a calculation equation for the internal pressure at the initial end of the test pipeline in combination with the internal fluid flow resistance conditions of the test pipeline; the third calculation unit is configured to establish a calculation equation for the hydraulic friction resistance along the test pipeline according to the pressure loss of natural gas during the flow process in test pipelines of different sizes and lengths under different flow rates; the fourth calculation unit is configured to derive a calculation equation for the pressure at the end of the test pipeline in combination with the calculation equations established by the second calculation unit and the third calculation unit; the limit production threshold calculation unit is configured to inversely calculate the initial pressure of the current test pipeline in combination with the equations established by the third calculation unit and the fourth calculation unit and the change of hydrate characteristics in the test pipeline, and compare the initial pressure with the maximum allowable working pressure of the test separator to determine the limit production threshold of test pipelines of different lengths and sizes.

[0058] On yet another aspect, the present invention provides a computer device, which includes a processor and a memory. When the computer program is executed by the processor, the method for calculating the limit production threshold of the test pipeline as described in the above exemplary embodiment can be implemented.

[0059] On yet another aspect, the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by the processor, the method for calculating the limit production threshold of the test pipeline as described in the above exemplary embodiment can be implemented.

[0060] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0061] (1) The calculation model provided by the present invention can effectively calculate the initial pressure of the pipeline during the test operation, and obtain the hydraulic friction resistance along the pipeline during the flow process of natural gas in test pipelines of different sizes and lengths under different flow rates;

[0062] (2) The calculation method provided by the present invention can successfully obtain the ultimate production threshold of surface pipelines with different lengths and sizes during the testing operation by comparing the pressure at the initial end of the test pipeline with the maximum allowable working pressure of the test separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Through the following description in conjunction with the drawings, the above and other objects and / or features of the present invention will become clearer, wherein:

[0064] Figure 1 Shows a schematic diagram of the force condition of a pipeline micro-element section according to an exemplary embodiment of the present invention;

[0065] Figure 2 Shows a schematic diagram of the force condition of a fluid micro-element section according to an exemplary embodiment of the present invention;

[0066] Figure 3 Shows a schematic diagram of a multiphase flow model of a test pipeline according to an exemplary embodiment of the present invention;

[0067] Figure 4 Shows a schematic diagram of the equivalent length of an elbow according to an exemplary embodiment of the present invention;

[0068] Figure 5 Shows a schematic diagram of the process of a surface test system of a certain well according to an exemplary embodiment of the present invention;

[0069] Figure 6 Shows a comparative analysis diagram of the pressure at the initial end of the test pipeline and the separator pressure of a certain well according to an exemplary embodiment of the present invention;

[0070] Figure 7 Shows a schematic diagram of the working pressure of the separator of a certain well according to an exemplary embodiment of the present invention.

[0071] DESCRIPTION OF THE REFERENCE NUMERALS:

[0072] 1 - Gas production tree, 2 - Diverting manifold, 3 - Choke manifold, 4 - Drainage pit, 5 - Combustion pit, 6 - Heat exchanger, 7 - Separator, 71 - Flowmeter, 81 - High-voltage line #1, 82 - High-voltage line #2, 83 - Emergency shutdown valve, 84 - Chip trap, 85 - Throttle valve, 86 - Wellhead high-pressure pipeline, 9 - Direct discharge pipeline, 10 - Drainage pipeline, 11 - Safety valve relief pipeline, 12 - Test pipeline, 13 - Power source, 14 - Control end. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] In the following, a method and system for calculating the ultimate production threshold of a test pipeline of the present invention will be described in detail in conjunction with the drawings and exemplary embodiments.

[0074] It should be noted that "first", "second", "third", "fourth", "fifth", etc. are only for convenience of description and differentiation, and cannot be construed as indicating or implying relative importance. "Upper", "lower", "inner", "outer", etc. are only for convenience of description and to form relative orientation or positional relationships, and do not indicate or imply that the components referred to must have such specific orientations or positions.

[0075] First exemplary embodiment

[0076] This exemplary embodiment provides a method for calculating the limit production threshold of a test pipeline.

[0077] In this exemplary embodiment, the method for calculating the limit production threshold of a test pipeline mainly includes the following steps:

[0078] S1: Establish a mathematical model of the temperature and pressure of the surface flow test pipeline according to the ambient temperature, water content, erosion and wear conditions, and the vibration conditions of the pipeline during the test.

[0079] S2: Based on the mathematical model of the temperature and pressure of the surface flow test pipeline in S1, establish a calculation model of the frictional resistance along the surface flow according to the length, size, friction coefficient along the way, and natural gas flow state of the test pipeline, and obtain the frictional resistance along the way of natural gas flowing through test pipelines of different sizes and lengths at different flow rates.

[0080] S3: Combine the mathematical model of the temperature and pressure of the surface flow test pipeline and the frictional resistance along the way to calculate the pressure at the end of the test pipeline (end point pressure) respectively. Combine the pressure at the end of the test pipeline with the frictional resistance along the way and the change in the characteristics of hydrates inside the test pipeline to back-calculate the initial pressure of the test pipeline, and compare the initial pressure of the test pipeline with the maximum allowable working pressure of the test separator to determine the limit production threshold under test pipelines of different lengths and sizes.

[0081] In this exemplary embodiment, establishing the mathematical model of the temperature and pressure of the surface flow test pipeline may include the following steps:

[0082] S11: Establish a vibration model of the surface test pipeline according to the ambient temperature, water content, erosion and wear conditions of the main equipment, and the vibration conditions of the pipeline during the test, and simulate the vibration conditions of the surface test pipeline. As Figure 1 shown, according to the schematic diagrams of the axial and transverse forces of the micro-element section of the test pipeline, combined with Newton's second law, the axial motion equation (Equation 1) and the transverse motion equation (Equation 2) of the pipeline micro-element section can be derived

[0083]

[0084]

[0085] And, asFigure 2 As shown, according to the schematic diagram of the forces acting on the fluid micro-element in the axial and transverse directions, and combining Newton's second law, the axial motion equation (Equation 3) and the transverse motion equation (Equation 4) of the fluid micro-element can be derived as follows:

[0086]

[0087]

[0088] Where T is the axial internal force of the pipeline micro-element, N; Q is the shear force of the cross-section, N; F t is the tangential frictional force between the pipe wall and the liquid, N; N is the normal force between the pipeline and the liquid, N; C a is the structural resistance coefficient in the axial direction; C t is the structural damping coefficient in the transverse direction; g is the acceleration due to gravity, m / s 2 ; m p is the mass of the pipe segment per unit length, kg / m; ρ f is the mass density of the fluid, kg / m 3 ; v r is the relative flow velocity between the fluid and the pipeline, m / s; m f is the mass of the fluid per unit length, kg / m; A is the cross-sectional area of the pipeline, m 2 .

[0089] Furthermore, the tangential frictional force between the pipe wall and the liquid can be expressed as follows:

[0090]

[0091] Where D is the inner diameter of the test pipeline, m; ρ f is the density of the fluid inside the pipe, kg / m 3 ; f is the friction coefficient, dimensionless; v r is the relative flow velocity between the fluid and the pipeline, m / s.

[0092] According to the generalized Hooke's law, the axial internal force T of the pipeline can be expressed as follows:

[0093]

[0094] Where E is the elastic modulus of the pipeline, GPa; μ is the Poisson's ratio; ε h is the circumferential strain; σ x is the axial stress, MPa; D is the inner diameter of the pipeline, m; δ is the wall thickness, m; A p is the cross-sectional area of the pipeline, m 2 ; μ* is μ is the Poisson's ratio; E* is A f is the flow-through area of the pipeline, m 2; ε x is the axial strain of the pipeline, dimensionless.

[0095] The relationship between shear force and bending moment can be as follows:

[0096] Q = M' = -EI p θ”; (Equation 7)

[0097] Where Q is the shear force, N; M is the bending moment, N·m; E is the elastic modulus of the pipeline, Pa; I p is the moment of inertia of the pipeline cross-section, mm 4 ; θ p is the deflection curve.

[0098] According to Equations 1 - 4 and Equation 7, the axial vibration equation of the test pipeline can be as follows:

[0099]

[0100] The transverse vibration equation of the test pipeline can be as follows:

[0101]

[0102] Where m p is the mass of the test pipeline, kg; m f is the mass of the fluid, kg; is the axial velocity of the test pipeline, m / s; is the axial acceleration of the test pipeline, m / s 2 ; u' is the first derivative of the axial displacement of the test pipeline with respect to the coordinate; u” is the second derivative of the axial displacement of the test pipeline with respect to the coordinate; v f is the fluid velocity, m / s; is the fluid acceleration, m / s 2 ; v' f is the first derivative of the fluid velocity with respect to the coordinate; w' is the first derivative of the transverse displacement of the test pipeline with respect to the coordinate; w” is the second derivative of the transverse displacement of the test pipeline with respect to the coordinate; w”' is the third derivative of the transverse displacement of the test pipeline with respect to the coordinate; E is the elastic modulus of the test pipeline, Pa; A p is the cross-sectional area of the pipeline, m 2 ; A f is the cross-sectional area of the pipeline through which the fluid flows, m 2 ; I p is the moment of inertia of the pipeline cross-section, mm 4 ; μ* is μ is the Poisson's ratio; E* is c a , c t are the axial and transverse structural damping coefficients.

[0103] S12: Based on the vibration model of the ground test pipeline, a multiphase flow model considering the influence of different water contents in the pipeline and solid-phase erosion wear on the vibration response of the test pipeline can be established. Based on the multiphase flow model, a three-phase continuity equation and a three-phase mixed momentum equation are established to calculate the fluid velocity distribution in the test pipeline. Among them, as Figure 3 shown, the length of the entire fluid microelement section is dz. According to the law of conservation of mass, the mass change of the control unit is the input mass of the control unit minus the output mass. For the gas phase, the input mass of the microelement section is:

[0104] ρ g ν g E g Adt + q g dtdz; (Equation 10)

[0105] The output mass of the control unit is:

[0106]

[0107] The internal mass change caused by the change in gas void fraction is:

[0108]

[0109] Therefore, the multiphase flow model in the microelement section is derived as:

[0110]

[0111] Among them, the three-phase continuity equation can include:

[0112] Gas-phase continuity equation:

[0113]

[0114] Liquid-phase continuity equation:

[0115]

[0116] Solid-phase continuity equation:

[0117]

[0118] According to the law of conservation of momentum, the gas-liquid-solid three-phase mixed momentum equation can be obtained as follows:

[0119]

[0120] Among them, ρ g , ρ l , ρ s are the densities of the gas, liquid, and solid in the pipeline, kg / m 3 ; v g, v l , v s are the velocities of the gas, liquid, and solid inside the pipe, respectively, in m / s; A is the cross-sectional area of the pipe, in m² 2 ; E g , E l , E s are the gas holdup, liquid holdup, and solid fraction in the cross-sectional area of the pipe; r H is the hydrate decomposition rate, in m 3 / s; P is the pressure inside the pipe, in Pa.

[0121] Here, based on Equations 14 - 17, the momentum conservation equation considering hydrate decomposition inside the pipe can be established. After the hydrate decomposes, it will affect the temperature and pressure inside the pipe; after the temperature and pressure change, the velocities of the gas phase, liquid phase, and solid phase in the equation will change. Here, the volumetric gas holdup, cross-sectional gas holdup, and slip velocity ratio with different degrees of slip between multiphase flows in the gas-liquid two-phase flow can be as follows:

[0122]

[0123] where ε g is the volumetric gas holdup in the two-phase flow; α g is the cross-sectional gas holdup; K is the slip velocity ratio in the multiphase flow; Q g is the volumetric gas flow rate, in m 3 / s; Q l is the volumetric liquid flow rate, in m 3 / s; A g is the cross-sectional area occupied by the gas phase, in m 2 ; A l is the cross-sectional area occupied by the liquid phase, in m 2 ; U ig is the true gas velocity inside the pipe, in m / s; U il is the true liquid velocity inside the pipe, in m / s.

[0124] If the volumetric gas holdup, cross-sectional gas holdup, and slip velocity ratio with different degrees of slip between multiphase flows satisfy the following relationship:

[0125]

[0126] then the pressure equation at the end of the pipeline can be as follows:

[0127] P z = ρ e RT e ; (Equation 20)

[0128] where, where ε g is the volumetric gas holdup in the two-phase flow; α gis the cross-sectional gas holdup; K is the slip velocity ratio in the multiphase flow; P Z is the outlet pressure at the end of the test pipeline, MPa; ρ e is the natural gas density at the blowout outlet, kg / m 3 ; R is the gas constant of air, J / (Kg k); T e is the temperature at the end of the test pipeline, °C.

[0129] Furthermore, the mass and flow rate of each phase in the pipe can be as follows;

[0130] M g = ρ g A g = ρ g α g A i ; (Equation 21)

[0131] M l = ρ l A l = ρ l (1 - a g )A i ; (Equation 22)

[0132]

[0133]

[0134] Among them, M g , M l are the mass of gas and liquid per unit length in the pipe, kg / m; U ig is the true gas velocity in the pipe, m / s; U il is the true liquid velocity in the pipe, m / s; ε g is the volumetric gas holdup in the two-phase flow; α g is the cross-sectional gas holdup; Q g is the volumetric gas flow rate, m 3 / s; Q l is the volumetric liquid flow rate, m 3 / s; A g is the cross-sectional area occupied by the gas, m 2 ; A l is the cross-sectional area occupied by the liquid, m 2 .

[0135] Under standard conditions, the density of air can be as follows:

[0136]

[0137] Therefore, the natural gas density at the end of the test pipeline can be as follows:

[0138]

[0139] The temperature at the end of the pipeline being the critical temperature can be as follows:

[0140]

[0141] Where ρ a is the air density under standard conditions, kg / m 3 ; ρ e is the natural gas density at the blowout outlet, kg / m 3 ; ρ is ρ a Δ, kg / m 3 (Δ is the relative density of natural gas, dimensionless); T0 is the stagnation temperature, K; T e is the critical temperature at the blowout outlet, K; k is the adiabatic index of natural gas, dimensionless.

[0142] S13: Establish a friction analysis method for different flow patterns and sand contents in the test pipeline, and set the two-phase flow hydraulic friction coefficient:

[0143]

[0144] Where λ m is the two-phase flow friction coefficient, dimensionless; Re is the Reynolds number.

[0145] Among them, the calculation formula for the C value of the two-phase flow hydraulic friction coefficient can be as follows:

[0146]

[0147] Where R l is the volume liquid holdup.

[0148] Substitute the two-phase flow hydraulic friction coefficient into the natural gas mass flow calculation equation for iterative calculation to obtain the initial internal pressure of the test pipeline. The natural gas mass flow calculation equation can be as follows:

[0149]

[0150] Where M is the mass flow of natural gas, kg / s; P Q is the internal pressure at the initial end of the pipeline, MPa; A is the cross-sectional area of the pipeline, m 2 ; Z is the compressibility factor of natural gas; T is the stagnation temperature, K; λ m is the hydraulic friction coefficient of the mixed fluid; L is the length of the blowout pipeline, m; D is the inner diameter of the pipeline, m.

[0151] Furthermore, the compressibility factor Z is unknown and can be obtained through iterative calculation. Its iterative calculation formula can be as follows:

[0152]

[0153] Among them, Z is the natural gas compression factor, dimensionless; P is the average pressure of natural gas, MPa.

[0154] In this exemplary embodiment, obtaining the along - the - way hydraulic friction during the flow of natural gas at different flow rates in test pipelines of different sizes and lengths may include the following steps:

[0155] S21: For the equivalent length L of valves, tees or elbows under compressible or incompressible fluid conditions, the comparative test method is specifically used for measurement. Other parameters such as the pipe roughness coefficient, pipe inner diameter, flow rate, and fluid type are not important and can be ignored. Calculate the equivalent length of valves, tees or elbows under compressible or incompressible fluid conditions. As Figure 4 shown, for the equivalent length L of valves, tees or elbows under compressible or incompressible fluid conditions, the comparative test method is specifically used for measurement. Other parameters such as the pipe roughness coefficient, pipe inner diameter, flow rate, and fluid type are not important and can be ignored. The formula for calculating the equivalent length can be as follows:

[0156]

[0157] Among them, L1 is the equivalent length of the test section of the pipeline before and after the elbow, m; L2 is the length of the test pipe in the straight - pipe measurement section, m; L eq is the equivalent length of the elbow, m; P is the gas pressure in the pipeline, Pa; ΔP1 is the pressure difference in the elbow measurement section, Pa; ΔP2 is the pressure difference in the straight - pipe measurement section, Pa.

[0158] S22: Combine the equivalent length to calculate the along - the - way hydraulic friction during the flow of natural gas at the same flow rate in test pipelines of different sizes and lengths:

[0159]

[0160] Among them, ΔP is the along - the - way hydraulic friction of the pipeline, MPa; ρ is the density of the fluid in the pipe, kg / m 3 ; L is the equivalent length of the blow - down pipeline, m; D is the inner diameter of the pipe, m.

[0161] Here, the mathematical model of the temperature and pressure of the surface flow test pipeline may include the outlet pressure at the end of the test pipeline and the internal pressure at the initial end of the test pipeline in S12 and S13.

[0162] In this exemplary embodiment, the pressure at the end of the test pipeline (end - point pressure) can be the internal pressure at the initial end of the test pipeline minus the along - the - way hydraulic friction, that is

[0163] P o = P Q -ΔP; (Equation 34)

[0164] Among them, P o is the pressure at the end of the test pipeline, in MPa; P Q is the internal pressure at the initial end of the test pipeline, in MPa; ΔP is the hydraulic friction along the pipeline, in MPa.

[0165] In this exemplary embodiment, the steps for back-calculating the pressure at the initial end of the test pipeline may include:

[0166] First, calculate the two-phase flow hydraulic friction coefficient:

[0167]

[0168] Among them, λ m is the two-phase flow hydraulic friction coefficient, C is a coefficient, dimensionless; Re is the fluid Reynolds number at this time.

[0169] Calculate the compressibility factor Z:

[0170]

[0171] The average pressure P can be calculated by the following formula:

[0172]

[0173] Using the natural gas mass flow formula, the internal pressure at the initial end of the test pipeline is iteratively calculated. The natural gas mass flow formula is as follows:

[0174]

[0175] Furthermore, the change in internal hydrate characteristics can be calculated by the three-phase continuity equations in Equations 14 - 16. Specifically, the internal hydrate will decompose, and after decomposition, the temperature, pressure, and the content of each phase inside the pipeline will change; then, combining the three-phase continuity equations (Equations 14 - 16) with the law of conservation of momentum, the three-phase mixed momentum equation (Equation 17) can be deduced, and the change in the velocity of each phase inside the pipeline can be deduced through the three-phase mixed momentum equation.

[0176] In this exemplary embodiment, the steps for determining the limit production threshold of the test pipeline may include: setting the inner and outer diameters and the length of the blowdown pipeline, assuming the limit production Qd, calculating the production Qd and the outlet pressure, average pressure of the blowdown pipeline and the compressibility factor at this time under the separator pressure, and combining the hydraulic friction coefficient and the natural gas mass flow formula to obtain the production Qd2 at this time. When Qd2 is greater than the assumed limit production Qd, the iteration ends, and thus the limit production threshold at this time is determined.

[0177] Second Exemplary Embodiment

[0178] This exemplary embodiment provides a system for calculating the limit production threshold of a test pipeline.

[0179] In this exemplary embodiment, the system for calculating the limit production threshold of a test pipeline mainly includes a first calculation unit, a second calculation unit, a third calculation unit, and a limit production threshold calculation unit. The first calculation unit, the second calculation unit, the third calculation unit, and the fourth calculation unit are connected to the limit production threshold calculation unit. Among them, the first calculation unit is configured to establish a ground test pipeline vibration model. Based on the ground test pipeline vibration model, a multiphase flow model considering the influence of different water contents and solid-phase erosion wear in the pipeline on the pipeline vibration is established. A three-phase continuity equation is established through the multiphase flow model, the fluid velocity distribution in the test pipeline is calculated, the internal fluid flow characteristics of the test pipeline are analyzed, and a calculation equation for the outlet pressure at the end of the test pipeline is derived in combination with the pipeline length and size data and the multiphase flow model. The second calculation unit is configured to establish a friction resistance analysis method for different flow patterns and sand contents in the test pipeline, and establish a calculation equation for the internal pressure at the initial end of the test pipeline in combination with the internal fluid flow resistance conditions of the test pipeline. The third calculation unit is configured to establish a calculation equation for the hydraulic friction resistance along the test pipeline based on the pressure loss of natural gas during the flow process in test pipelines of different sizes and lengths under different flow rates. The fourth calculation unit is configured to derive the pressure at the end of the test pipeline by combining the calculation equations established by the second calculation unit and the third calculation unit, that is, the calculation equation for the internal pressure at the initial end of the test pipeline and the calculation equation for the hydraulic friction resistance along the test pipeline. The limit production threshold calculation unit is configured to, according to the equation established by the third calculation unit and the fourth calculation unit, that is, the calculation equation for the hydraulic friction resistance along the test pipeline and the calculation equation for the pressure at the end of the test pipeline, and in combination with the change in the hydrate characteristics in the test pipeline, calculate the initial pressure at the current test pipeline initial end by inverse calculation, and compare the initial pressure with the maximum allowable working pressure of the test separator to determine the limit production threshold of test pipelines of different lengths and sizes.

[0180] Third Exemplary Embodiment

[0181] This exemplary embodiment provides a computer-readable storage medium storing a computer program.

[0182] When the computer-readable storage medium is executed by a processor, the processor executes a computer program for the method of calculating the limit production threshold of a test pipeline according to the present invention. The computer-readable recording medium is any data storage device capable of storing data read by a computer system. Examples of computer-readable recording media include: read-only memory, random access memory, compact disc read-only memory, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data transmission via the Internet through a wired or wireless transmission path).

[0183] Fourth Exemplary Embodiment

[0184] This exemplary embodiment provides a computer device. The computer device includes a processor and a memory. The memory is used to store a computer program. The computer program is executed by the processor such that the processor executes the computer program for calculating the limit production threshold of the test pipeline according to the present invention.

[0185] The fifth exemplary embodiment

[0186] This exemplary embodiment provides a ground test system.

[0187] Figure 5 The schematic flow diagram of a well ground test system according to an exemplary embodiment of the present invention is shown. The following will describe the ground test system of this exemplary embodiment in conjunction with Figure 5 to describe the ground test system of this exemplary embodiment.

[0188] In this exemplary embodiment, as Figure 5 shown in, the ground test system mainly includes a diverter manifold 2, a choke manifold 3, a combustion pit 5, a separator 7, a test pipeline 12 and a drain pit 4. Among them, one end of the diverter manifold 2 is connected to the Christmas tree 1 through a wellhead high-pressure pipeline, and the other end is connected to the choke manifold 3 through a high-pressure pipeline. One end of the heat exchanger 6 is connected to the choke manifold 3 through the test pipeline 12, and the other end is connected to the separator 7 through the test pipeline 12. The separator 7 is connected to the combustion pit 5 through the test pipeline 12. At the same time, a safety valve relief pipeline 11 is also provided between the separator 7 and the combustion pit 5. The diverter manifold 2 and the combustion pit 5 can be directly connected through a direct discharge pipeline 9. A pipeline branch can also be provided on the direct discharge pipeline 9 between the diverter manifold 2 and the combustion pit 5 to be connected in series with the drain pit 4. In addition, a drain pipeline 10 can be provided between the separator 7 and the drain pit 4.

[0189] In this exemplary embodiment, as Figure 5 shown in, a power source 13 can also be provided, for example, a boiler provides energy for the operation of the ground test system. At the same time, a control terminal 14 can also be provided to control the operating state of the natural gas in the pipeline, for example, it can include an ESD control panel.

[0190] In this exemplary embodiment, as Figure 5 shown in, the separator 7 can also include a flowmeter 71, such as a Daniel flowmeter.

[0191] In this exemplary embodiment, as Figure 5As shown in the figure, the high-voltage lines may include high-voltage line #181 and high-voltage line #282. One end of high-voltage line #181 and high-voltage line #282 is connected to the gas production tree 1 at the same time, and the other end is connected to the wellhead high-pressure pipeline 86 at the same time. An emergency shutdown valve 83 may be provided at the gas inlet end of high-voltage line #1 and high-voltage line #2. Throttle valves 85 may be provided at the connection ends of high-voltage line #181 and high-voltage line #282 with the wellhead high-pressure pipeline respectively. In addition, a chip catcher 84 may also be provided on high-voltage line #181.

[0192] In the present exemplary embodiment, as Figure 5 shown in the figure, the gas production tree opens the valve to supply gas to high-pressure pipe #181. Through the choke manifold 3 and the swivel manifold 2, after passing through the separator 7, the gas is discharged through the test pipeline 12 by blowout. The liquid is discharged into the liquid drainage pit 4 through the direct drainage pipeline 9. After a period of stability, record the working pressure of the separator 7 and the flowmeter value at different times. Combining the size and length of the blowout pipeline and the relative density of natural gas, iteratively calculate the test production at the working pressure of the separator at this time and compare it with the field situation. When the working pressure of the separator is selected to its maximum value, the predicted production of the test pipeline calculated at this time is the limit production.

[0193] To better understand the above exemplary embodiment, the following further illustrates and elaborates on the above first exemplary embodiment in conjunction with Example 1.

[0194] Example 1

[0195] Figure 4 shows a schematic diagram of the equivalent length of an elbow according to an exemplary embodiment of the present invention; Figure 5 shows a schematic diagram of the process of a well surface test system according to an exemplary embodiment of the present invention; Figure 6 shows a comparative analysis diagram of the initial end pressure and separator pressure of a well test pipeline according to an exemplary embodiment of the present invention; Figure 7 shows a schematic diagram of the working pressure of a well separator according to an exemplary embodiment of the present invention. The following combines Figures 4 to 7 to describe the calculation method of this example.

[0196] The calculation steps in this example are the same as the method for calculating the limit production threshold of the test pipeline in the first exemplary embodiment. Taking the test operation process of a well as an example, analyze the initial end pressure and test production of the pipeline during the test operation process, and compare them with the three-item separator pressure and the actual field test production, and analyze the error. Among them, as Figure 5 shown in the figure, the surface test process of the present invention may include: after the test is stable for a period of time, record the working pressure of the separator 7 and the flowmeter value at different times. Use as Figure 4Calculate the equivalent lengths of the structural elbows and tees shown, and combine the blowout prevention pipeline dimensions, blowout prevention pipeline length, and relative density of natural gas to iteratively obtain the test production at the working pressure of the separator at this time and compare it with the actual on-site test production to analyze the error.

[0197] As Figure 6 shown, the initial pressure at the test pipeline end calculated is highly similar to the separator pressure, with an error within 5%. As Figure 7 shown, the calculated test production is highly similar to the actual production measured on-site, with an error within 5%. Furthermore, as shown in Table 1, in Table 1, the working pressure of the separator is the value on the pressure gauge during the on-site test. Characterize the change in the separator pressure during the test operation, and predict the test production at this time through this pressure, which is called the predicted test production. There will be a flowmeter at the blowout prevention pipeline on-site, which can measure the test production at this time, called the on-site test production. According to the comparison between the on-site test production and the predicted test production, the relative error of the predicted test production compared with the actual on-site production is less than 3.2%. In summary, the method for calculating the limit test threshold of the test pipeline described in the present invention has high reliability.

[0198] Due to the high innovation and difficulty of the theoretical model, it is very difficult for competitors to make a theoretical breakthrough in a short time, that is, it is very difficult to form an effective competitiveness against the present invention. The well testing operation is an indispensable link in oil and gas field development and is very important in the oil and gas exploration process. Therefore, to ensure the safe and efficient progress of the test operation, it is necessary to have a thorough understanding of the influence laws of the above parameters on the pipeline limit threshold during the test operation, which cannot be avoided. At the same time, the innovative achievement of the present invention, the method for calculating the limit test threshold under different fluid components during the test operation, has broad application prospects. There is no relevant patent in China at present, so the present invention will occupy the dominant position within three years after it is made public. Due to the high difficulty and innovation of the mathematical model applied in the present invention, it is very difficult for competitors to replicate it in a short time.

[0199] Table 1 Comparison of Test Production of a Certain Well

[0200]

[0201]

[0202] In summary, the advantages of the present invention may include at least one of the following:

[0203] (1) The calculation model provided by the present invention combines several different types of complex situations existing in the pipeline, and the obtained production calculation results are more accurate, which can provide theoretical guidance for the selection of on-site test pipelines and equipment;

[0204] (2) The calculation method provided by the present invention is based on the test results obtained under the coupling action of complex working conditions of the surface process, and can take into account the ultimate production threshold of natural gas under different flow rates in test pipelines of different sizes and lengths, with wide applicability;

[0205] (3) The model provided by the present invention has a high degree of innovation and is forward-looking, which can ensure the safe and efficient progress of the test operation process;

[0206] (4) The calculation method provided by the present invention can detect the ultimate production threshold under different fluid components in the test operation, and has broad application prospects.

[0207] Although the method and system for calculating the ultimate production threshold of a test pipeline of the present invention have been described above by combining exemplary embodiments, those skilled in the art should clearly understand that various modifications and changes can be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for calculating the threshold of the ultimate production of a test pipeline, characterized in that, The method includes the following steps: S1: Establish a ground test pipeline vibration model. On the basis of the ground test pipeline vibration model, establish a multiphase flow model considering the influence of different water contents in the pipeline and solid-phase erosion wear on the pipeline vibration. Establish a three-phase continuity equation through the multiphase flow model, calculate the fluid velocity distribution in the test pipeline, analyze the internal fluid flow characteristics of the test pipeline, and combine the pipeline length and size data and the multiphase flow model to deduce and establish a calculation equation for the outlet pressure at the end of the test pipeline; S2: Establish a friction resistance analysis method for different flow patterns and sand contents in the test pipeline, and establish a calculation equation for the internal pressure at the initial end of the test pipeline in combination with the internal fluid flow resistance conditions of the test pipeline; S3: Establish a calculation equation for the hydraulic friction resistance along the test pipeline according to the pressure loss of natural gas during the flow process in test pipelines with different sizes and lengths under different flow rates; S4: Deduce the pressure at the end of the test pipeline by combining the equations established in S2 and S3; S5: Inverse calculate the initial pressure of the current test pipeline by combining the equations established in S3 - S4 and the change of hydrate characteristics in the test pipeline; S6: Compare the initial pressure of the test pipeline in S5 with the maximum allowable working pressure of the test separator to determine the limit production threshold of test pipelines with different lengths and sizes.

2. The method for calculating the threshold value of the ultimate production of the test pipeline according to claim 1, wherein The ground test pipeline vibration model includes a pipeline axial vibration equation and a pipeline lateral vibration equation. The pipeline axial vibration equation is as follows: The pipeline lateral vibration equation is as follows: where, m p is the mass of the test pipeline, kg; m f is the mass of the fluid, kg; is the axial velocity of the test pipeline, m / s; is the axial acceleration of the test pipeline, m / s 2 ; u' is the first derivative of the axial displacement of the test pipeline with respect to the coordinate; u” is the second derivative of the axial displacement of the test pipeline with respect to the coordinate; v f is the fluid velocity, m / s; is the fluid acceleration, m / s 2 ; v' f is the first derivative of the fluid velocity with respect to the coordinate; w' is the first derivative of the lateral displacement of the test pipeline with respect to the coordinate; w” is the second derivative of the lateral displacement of the test pipeline with respect to the coordinate; w”' is the third derivative of the lateral displacement of the test pipeline with respect to the coordinate; E is the elastic modulus of the test pipeline, Pa; A p is the cross-sectional area of the pipeline, m 2 ; A f is the flow-through area of the pipeline, m 2 ; I p is the moment of inertia of the pipeline cross-section, mm 4 ; μ* is μ is the Poisson's ratio; E* is c a , c t are the axial and lateral structural damping coefficients.

3. The method for calculating the threshold of the ultimate production rate of a test pipeline according to claim 1, characterized in that The three-phase continuity equation is as follows: Gas-phase continuity equation: Liquid-phase continuity equation: Solid-phase continuity equation: Among them, ρ g , ρ l , ρ s are the densities of the gas, liquid, and solid in the pipe, respectively, kg / m 3 ; v g , v l , v s are the velocities of the gas, liquid, and solid in the pipe, respectively, m / s; A is the cross-sectional area of the pipe, m / s 2 ; E g , E l , E s are the gas holdup, liquid holdup, and solid fraction of the cross-sectional area of the pipe; r H is the hydrate decomposition rate, m 3 / s.

4. The method for calculating the threshold value of the ultimate production rate of the test pipeline according to claim 3, wherein According to the three-phase mixed continuity equation and combining the law of conservation of momentum, establish a gas-liquid-solid three-phase mixed momentum equation. The gas-liquid-solid three-phase mixed momentum equation is as follows: where ρ g , ρ l , ρ s are the densities of the gas, liquid, and solid in the pipe, respectively, in kg / m 3 ; v g , v l , v s are the velocities of the gas, liquid, and solid in the pipe, respectively, in m / s; E g , E l , E s are the gas holdup, liquid holdup, and solid fraction of the pipe cross-sectional area, respectively; is the frictional pressure drop in the pipe, in Pa.

5. The method for calculating the threshold of the ultimate production rate of a test pipeline according to claim 1, characterized in that If the volume gas holdup, cross-sectional gas holdup in the two-phase flow in the test pipeline and the slip velocity ratio of different degrees of slip between the multiphase flows satisfy the following formula: where ε g is the volumetric gas holdup; α g is the cross-sectional gas holdup, and K is the slip velocity ratio Then the equation for the outlet pressure at the end of the test pipeline: P z = ρ e RT e ; Among them, P Z is the outlet pressure at the end of the test pipeline, MPa; ρ e is the natural gas density at the blowout outlet, kg / m 3 ; R is the gas constant of air, J / (Kg k); T e is the temperature at the end of the test pipeline, °C.

6. The method for calculating the threshold of the ultimate production of the test pipeline according to claim 1, characterized in that, The method for establishing the friction resistance analysis method for different flow patterns and sand contents in the test pipeline includes the following steps: Establish a two-phase flow hydraulic friction coefficient: where λ m is the two-phase flow hydraulic friction coefficient; C is a dimensionless coefficient; Re is the fluid Reynolds number at this time; Use the natural gas mass flow formula to iteratively calculate the internal pressure at the initial end of the test pipeline. The natural gas mass flow formula is as follows: where, M is the mass flow rate of natural gas, kg / s; P Q is the internal pressure at the initial end of the pipeline, MPa; A is the cross-sectional area of the pipeline, m 2 ²; Z is the compressibility factor of natural gas; T is the stagnation temperature, K; λ m is the hydraulic friction coefficient of the mixed fluid; L is the length of the blowout preventer line, m; D is the inner diameter of the pipeline, m.

7. The method for calculating the threshold of the ultimate production of the test pipeline according to claim 1, characterized in that, The calculation equation for the hydraulic friction resistance along the test pipeline is as follows: Among them, ΔP k is the hydraulic friction along the pipeline, in MPa; ρ is the density of the fluid in the pipe, in kg / m 3 ; L eq is the equivalent length of the blowout prevention pipeline, in m; D is the inner diameter of the pipeline, in m.

8. The method for calculating the threshold value of the ultimate production of the test pipeline according to claim 1, wherein The process of calculating the pressure at the end of the test pipeline includes: The density calculation of air under standard conditions can be obtained from the state equation: Where, R is the gas constant of air, and T is the temperature under standard conditions, °C; The calculation equation for the density of natural gas at the blowout outlet is as follows: The calculation equation for the temperature at the blowout outlet being the critical temperature is as follows: Therefore, the state equation of the end point pressure at the blowout pipeline outlet is obtained: P z = ρ e RT e ; where ρ a is the air density under standard conditions, kg / m 3 ; ρ e is the natural gas density at the blowout outlet, kg / m 3 ; ρ is ρ a Δ, kg / m 3 , where Δ is the relative density of natural gas, dimensionless; T0 is the stagnation temperature, K; T e is the critical temperature at the blowout outlet, K; k is the adiabatic index of natural gas, dimensionless.

9. The method for calculating the threshold of the ultimate production of the test pipeline according to claim 1, characterized in that, The inverse calculation steps for the initial pressure of the test pipeline include: First, calculate the two-phase flow hydraulic friction coefficient. The calculation equation is as follows: where λ m is the two-phase flow hydraulic friction coefficient; C is a dimensionless coefficient; Re is the fluid Reynolds number at this time; Calculate the compressibility factor Z. The calculation equation is as follows: Calculate the average pressure P. The calculation equation is as follows: Use the natural gas mass flow formula to iteratively calculate the internal pressure at the initial end of the test pipeline. The natural gas mass flow formula is as follows: Among them, M is the mass flow rate of natural gas, kg / s; P Q is the internal pressure at the initial end of the pipeline, MPa; A is the cross-sectional area of the pipeline, m 2 ; Z is the compressibility factor of natural gas; T is the stagnation temperature, K; λ m is the hydraulic friction coefficient of the mixed fluid; L is the length of the blowout prevention pipeline, m; D is the inner diameter of the pipeline, m.

10. The method for calculating the threshold of the ultimate production of the test pipeline according to claim 1, characterized in that The comparison steps for determining the limit production threshold of test pipelines with different lengths and sizes include: Set the inner and outer diameters and length of the flow line. Assume the limit production rate \(Q_d\), calculate the production rate \(Q_d\), the outlet pressure, average pressure of the flow line at the separator pressure at this time, and the compressibility factor at this time. Combine the hydraulic friction coefficient and the natural gas mass flow formula to obtain the production rate \(Q_d2\) at this time. End the iteration after meeting the conditions, so as to determine the limit production rate threshold at this time and complete the comparison of the limit production rate thresholds of test pipelines with different lengths and sizes.

11. A system for calculating the threshold of the ultimate production of a test pipeline, characterized in that, The system for calculating the limit production rate threshold of the test pipeline includes a first calculation unit, a second calculation unit, a third calculation unit and a limit production rate threshold calculation unit. The first calculation unit, the second calculation unit, the third calculation unit and the fourth calculation unit are connected to the limit production rate threshold calculation unit. Among them, The first calculation unit is configured to establish a ground test pipeline vibration model. Based on the ground test pipeline vibration model, establish a multiphase flow model considering the influence of different water contents and solid particle erosion wear conditions in the pipeline on the pipeline vibration. Establish a three-phase continuity equation through the multiphase flow model, calculate the fluid velocity distribution in the test pipeline, analyze the internal fluid flow characteristics of the test pipeline, and combine the pipeline length and size data and the multiphase flow model to derive and establish a calculation equation for the outlet pressure at the end of the test pipeline; The second calculation unit is configured to establish a friction analysis method for different flow patterns and sand contents in the test pipeline, and establish a calculation equation for the internal pressure at the initial end of the test pipeline in combination with the internal fluid flow resistance conditions of the test pipeline; The third calculation unit is configured to establish a calculation equation for the hydraulic friction along the test pipeline based on the pressure loss of natural gas during the flow process in test pipelines with different sizes and lengths under different flow rates; The fourth calculation unit is configured to derive a calculation equation for the pressure at the end of the test pipeline by combining the calculation equations established by the second calculation unit and the third calculation unit; The limit production rate threshold calculation unit is configured to, according to the equations established by the third calculation unit and the fourth calculation unit, combine the change of hydrate characteristics in the test pipeline to back-calculate the initial pressure of the current test pipeline, and compare the initial pressure with the maximum allowable working pressure of the test separator to determine the limit production rate thresholds of test pipelines with different lengths and sizes.

12. A computer device, characterized in that, The computer device includes a processor and a memory. When the computer program is executed by the processor, it implements the method for calculating the limit production rate threshold of the test pipeline as described in any one of claims 1 to 10.

13. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for calculating the limit production rate threshold of the test pipeline as described in any one of claims 1 to 10.

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