High-temperature and high-pressure shaft gas-liquid two-phase flow pattern simulation and liquid holdup calculation method

Abstract

The invention discloses a high-temperature and high-pressure shaft gas-liquid two-phase flow pattern simulation and liquid holdup calculation method which comprises the following steps: establishing a shaft geometric model and a shaft gas-liquid two-phase flow field according to basic shaft parameters; constructing a local feature detection surface of the shaft, and detecting the instantaneous gas content of the cross section of the shaft; determining the gas content probability density distribution characteristics of a specific flow pattern and the influence of temperature and pressure on the transformation of different flow patterns; determining critical gas containing rates of different flow pattern transitions and boundary equations of the different flow pattern transitions; and establishing a boundary equation of flow pattern transformation of the gas-liquid two-phase flow of the high-temperature and high-pressure shaft, and determining a liquid holdup calculation method of different flow patterns. According to the invention, the defect that the high-temperature and high-pressure gas-liquid two-phase flow cannot be subjected to experimental research under the existing experimental conditions is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of gas drainage and production, and particularly relates to a method for simulating the flow pattern of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore and calculating the liquid holdup. Background Art

[0002] In the middle and later stages of gas well production, the formation pressure drops, formation water enters the wellbore, and gas-liquid two-phase flow appears in the wellbore. Especially in the Sichuan-Chongqing region, this flow phenomenon is particularly prominent, seriously affecting the stable production of gas wells and even causing the gas wells to shut down due to liquid accumulation. At present, the gas drainage and production process is usually adopted to remove the liquid accumulation in the wellbore. However, due to the lack of accurate flow pattern criteria and liquid holdup calculation models, it is difficult to achieve efficient liquid drainage, which has become the core problem restricting the stable production of gas fields.

[0003] The flow pattern transition law of gas-liquid two-phase flow in the wellbore is the premise for calculating the liquid holdup of a specific flow pattern and supports the efficient operation of the gas drainage and production process. However, nowadays, due to experimental conditions, the research of scholars on gas-liquid two-phase flow focuses on the range of normal temperature and pressure and the pressure and temperature that the experimental equipment can withstand. There is little research on high-temperature and high-pressure gas-liquid two-phase flow, and we are not clear about the flow law of gas-liquid two-phase flow in a high-temperature and high-pressure environment. Since the wellbore is in a special high-temperature and high-pressure environment, the adaptability of the flow pattern transition law of gas-liquid two-phase flow studied in the normal temperature and pressure environment to the gas-liquid two-phase flow in the production water wellbore remains to be investigated.

[0004] Therefore, it is necessary to propose a method for simulating the flow pattern of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore, deeply study the flow of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore, determine the flow pattern transition law of gas-liquid two-phase flow under different temperature and pressure conditions, establish the flow pattern transition boundary suitable for the high-temperature and high-pressure conditions of the wellbore, and establish a calculation method for the liquid holdup of a specific flow pattern to provide key technical support for the efficient development of gas reservoirs. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for simulating the flow pattern of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore and calculating the liquid holdup, so as to solve the technical problems that it is difficult to study the flow pattern transition law of gas-liquid two-phase flow in the wellbore and calculate the liquid holdup of a specific flow pattern in a high-temperature and high-pressure environment in the prior art.

[0006] The present invention is implemented by the following technical solutions: A method for simulating the flow pattern of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore and calculating the liquid holdup includes the following steps: S1: According to the basic wellbore parameters, establish a wellbore geometric model and a gas-liquid two-phase flow field in the wellbore; S2: According to the wellbore geometric model and the gas-liquid two-phase flow field in the wellbore, construct a local characteristic detection surface of the wellbore; S3: According to the local characteristic detection surface of the wellbore, detect the instantaneous gas holdup of the wellbore cross-section; S4: Determine the probability density distribution characteristics of gas holdup for specific flow patterns based on the detected instantaneous gas holdup in the wellbore cross-section; S5: Determine the influence of temperature and pressure on the transition between different flow patterns based on the probability density distribution of gas holdup; S6: Determine the critical gas holdup for the transition between different flow patterns based on the gas holdup distribution characteristics of specific flow patterns; S7: Determine the boundary equation for the transition between different flow patterns based on the critical gas holdup for the transition between different flow patterns; S8: Establish the boundary equation for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores based on the boundary equation for the transition between different flow patterns; S9: Determine the calculation method of liquid holdup for different flow patterns based on the established boundary equation for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores.

[0007] Furthermore, the basic wellbore parameters include one or more of the wellbore string structure, wellbore fluid temperature, wellbore fluid pressure, wellbore gas superficial velocity, and wellbore liquid superficial velocity.

[0008] Furthermore, step S4 includes the following sub-steps: Divide the specific flow patterns of gas-liquid two-phase flow in the wellbore, specifically including: bubble flow, bubble-slug flow, slug flow, slug-churn flow, churn flow, annular flow; Obtain the probability density distribution of gas holdup for gas-liquid two-phase flow under different working conditions by normalizing the time-history gas holdup data detected by Fluent in the wellbore cross-section; Based on the probability density distribution of gas holdup, combined with the flow cloud map of gas-liquid two-phase flow simulated by Fluent, determine the probability density distribution characteristics of gas holdup for specific flow patterns; Based on the probability density distribution characteristics of gas holdup for specific flow patterns, determine the specific flow patterns of gas-liquid two-phase flow in the wellbore.

[0009] Furthermore, step S5 is specifically: Based on the probability density distribution characteristics of gas holdup for specific flow patterns, combined with the line graph of the change of the probability density of the transitional gas holdup with the superficial gas velocity, determine the influence of temperature and pressure on the transition between different flow patterns.

[0010] Furthermore, step S6 includes the following sub-steps: Based on the gas holdup distribution of bubble flow and slug flow patterns, combined with the probability density distribution characteristics of gas holdup of bubble-slug flow pattern, determine the critical gas holdup for the transition from bubble flow to slug flow; Based on the gas holdup distribution of slug flow and churn flow patterns, combined with the probability density distribution characteristics of gas holdup of slug-churn flow pattern, determine the critical gas holdup for the transition from slug flow to churn flow; Based on the gas holdup distribution of churn flow and annular flow patterns, combined with the probability density distribution characteristics of the gas holdup in churn flow and annular flow patterns, determine the critical gas holdup for the transition from churn flow to annular flow.

[0011] Further, step S7 is specifically as follows: Based on the critical gas holdup for different flow pattern transitions, combined with the relationship between the gas holdup of gas-liquid two-phase flow and the superficial gas velocity and superficial liquid velocity, and the boundary equations for different flow pattern transitions.

[0012] Further, step S8 is specifically as follows: Based on the boundary equations for different flow pattern transitions, convert the critical gas holdup for flow pattern transitions into a function of physical properties parameters, thereby obtaining the boundary equation for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores.

[0013] Further, step S9 is specifically as follows: Based on the boundary equation for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wells, combined with the calculation formula for the liquid holdup of a specific flow pattern, through the MATLAB curve fitting tool, fit the parameters affected by the gas drift velocity for different flow patterns, and establish a calculation model for the liquid holdup of a specific flow pattern of gas-liquid two-phase flow in the wellbore.

[0014] The beneficial effects of the present invention are as follows: The present invention establishes a flow pattern simulation method for gas-liquid two-phase flow in high-temperature and high-pressure wellbores. Based on Fluent numerical simulation, considering the influence of wellbore temperature and pressure, a flow pattern simulation method for gas-liquid two-phase flow in high-temperature and high-pressure wellbores is established, local feature detection is constructed, and the dynamic characteristics of specific flow patterns of gas-liquid two-phase flow in the wellbore are accurately simulated, overcoming the drawbacks that existing experimental conditions cannot conduct experimental research on high-temperature and high-pressure gas-liquid two-phase flow.

[0015] The present invention proposes that specific flow patterns have unique probability density distribution characteristics of gas holdup, which are used as the discrimination basis for the flow patterns of gas-liquid two-phase flow in the wellbore, avoiding the influence of human subjective factors, establishing the boundary for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores, and making the flow pattern discrimination more accurate.

[0016] Based on the boundary for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores, the present invention establishes a calculation method for the liquid holdup of a specific flow pattern, which is in good agreement with the verification results of Fluent simulation and experimental data, and is convenient to calculate and has convergence. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in 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 following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0018] Figure 1This is the flow chart of the present invention; Figure 2 This is the simulation cloud chart of specific flow patterns of gas-liquid two-phase flow in the wellbore; Figure 3 This is the flow pattern chart of gas-liquid two-phase flow under normal temperature and pressure; Figure 4 This is the flow pattern chart of gas-liquid two-phase flow under high temperature and high pressure; Figure 5 This is the gas holdup distribution of bubbly flow to slug flow under normal temperature and pressure and high temperature and high pressure; Figure 6 This is the gas holdup distribution of slug flow and churn flow under normal temperature and pressure and high temperature and high pressure; Figure 7 This is the gas holdup distribution of churn flow and annular flow under normal temperature and pressure and high temperature and high pressure; Figure 8 This is the result comparison chart of Fluent simulation; Figure 9 This is the result comparison chart of the liquid holdup calculation model; Figure 10 This is the comparison chart of the liquid holdup calculation method for the specific flow pattern in the wellbore of the present invention and other calculation methods. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0020] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0021] The following will describe in detail some implementation manners of the present invention with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0022] Refer to Figure 1 , a method for simulating the flow pattern and calculating the liquid holdup of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore, comprising the following steps: S1. According to the basic wellbore parameters, establish a wellbore geometric model and a gas-liquid two-phase flow field in the wellbore; S2. According to the wellbore geometric model and the gas-liquid two-phase flow field in the wellbore, construct a local feature detection surface of the wellbore; S3. According to the local feature detection surface of the wellbore, detect the instantaneous gas holdup of the wellbore cross-section; S4. Determine the probability density distribution characteristics of gas holdup for specific flow patterns based on the instantaneous gas holdup of the wellbore cross-section. S5. Determine the influence of temperature and pressure on the transition between different flow patterns based on the probability density distribution of gas holdup. S6. Determine the critical gas holdup for the transition between different flow patterns based on the gas holdup distribution characteristics of specific flow patterns. S7. Determine the boundary equation for the transition between different flow patterns based on the critical gas holdup for the transition between different flow patterns. S8. Establish the boundary equation for the flow pattern transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore based on the boundary equation for the transition between different flow patterns. S9. Determine the calculation method for the liquid holdup of different flow patterns based on the established boundary equation for the flow pattern transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore.

[0023] In this embodiment, step S1 specifically includes the following sub-steps: S101. Based on the wellbore parameters, construct a wellbore geometric model and set the physical properties of gas and liquid fluids; the basic wellbore parameters include the wellbore string structure, wellbore fluid temperature, wellbore fluid pressure, gas superficial velocity, and liquid superficial velocity. S102. Use Fluent to simulate the gas-liquid two-phase flow pattern in the wellbore under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (90°C, 0.1 MPa) conditions, with the gas superficial velocity range (0.05 - 15 m / s) and liquid superficial velocity range (0.01 - 1 m / s).

[0024] S103. Use Fluent to simulate the gas-liquid two-phase flow pattern in the wellbore under high temperature and high pressure (100°C, 20 MPa) and normal temperature and high pressure (20°C, 20 MPa) conditions, with the gas superficial velocity range (0.05 - 10 m / s) and liquid superficial velocity range (0.01 - 1 m / s).

[0025] In this embodiment, step S2 is specifically: Construct a wellbore local feature detection surface based on the wellbore geometric model and the gas-liquid two-phase flow field in the wellbore, specifically including: Considering the full development of the gas-liquid two-phase flow field in the wellbore, construct a wellbore local feature detection surface 8 m away from the wellbore inlet.

[0026] In this embodiment, step S3 is specifically: Detect the instantaneous gas holdup of the wellbore cross-section based on the wellbore local feature detection surface, specifically including: Detect the instantaneous gas holdup of the wellbore cross-section using the area-averaged weighted method.

[0027] In this embodiment, step S4 is specifically: Determine the probability density distribution characteristics of gas holdup for specific flow patterns based on the detected instantaneous gas holdup of the wellbore cross-section, including the following sub-steps: S401, such asFigure 2 As shown in the figure, the specific flow patterns of gas-liquid two-phase flow in the wellbore are divided into: bubbly flow, bubbly-slug flow, slug flow, slug-churn flow, churn flow, and annular flow; S402. By normalizing the gas holdup data of the wellbore cross-section detected by Fluent, the probability density distribution of the gas holdup of the specific flow patterns of gas-liquid two-phase flow is obtained under the conditions of high temperature and high pressure (100 °C, 20 MPa), normal temperature and high pressure (20 °C, 20 MPa), high temperature and high pressure (100 °C, 20 MPa), and normal temperature and high pressure (20 °C, 20 MPa); S403. Based on the probability density distribution of the gas holdup of the specific flow pattern, determine the characteristics of the probability density distribution of the gas holdup of the specific flow pattern; S404. Based on the characteristics of the probability density distribution of the gas holdup of the specific flow pattern, judge the specific flow patterns of gas-liquid two-phase flow in the wellbore.

[0028] In this embodiment, step S5 is specifically as follows: According to the probability density distribution of the gas holdup, determining the influence of temperature and pressure on the transition of different flow patterns includes the following sub-steps: S501. Fix the liquid superficial velocity and draw the contour map of the probability density of the flow pattern transition gas holdup changing with the gas superficial velocity under the conditions of normal temperature and normal pressure (20 °C, 0.1 MPa), high temperature and normal pressure (90 °C, 0.1 MPa), high temperature and high pressure (100 °C, 20 MPa), and normal temperature and high pressure (20 °C, 20 MPa); specifically refer to Figure 3 、 Figure 4 As shown in the figure, where curve A is the gas holdup distribution of the bubbly flow and slug flow patterns; curve B is the gas holdup distribution of the slug flow and churn flow patterns; curve C is the churn flow and annular flow patterns.

[0029] Furthermore, the contour map of the probability density of the flow pattern transition gas holdup changing with the gas superficial velocity includes the characteristics of the probability density distribution of the gas holdup of bubbly flow, bubbly-slug flow, slug flow, slug-churn flow, churn flow, and annular flow, and can describe the transition process of different flow patterns; S502. Based on the characteristics of the probability density distribution of the gas holdup of the specific flow pattern determined in step S4, combined with the contour map of the probability density of the flow pattern transition gas holdup changing with the apparent gas velocity, determine the influence of pressure and temperature on the transition of different flow patterns; Furthermore, fixing the normal pressure at 0.1 MPa and the high pressure at 20 MPa, when the temperature rises from 20 °C to 100 °C, the three-dimensional view of the probability density of the flow pattern transition gas holdup and the contour map of the probability density of the flow pattern transition gas holdup are highly consistent, and the influence of temperature change on the flow of gas-liquid two-phase flow in the wellbore can be ignored; Furthermore, fixing the normal temperature at 20 °C and the high temperature at 100 °C, when the pressure rises from 0.1 MPa to 20 MPa, the three-dimensional view of the probability density of the flow pattern transition gas holdup and the contour map of the probability density of the flow pattern transition gas holdup change significantly; Furthermore, based on the above analysis, pressure is the dominant factor affecting the flow pattern transition of gas-liquid two-phase flow in the wellbore, and the influence of temperature on the flow pattern transition of gas-liquid two-phase flow in the wellbore can be ignored.

[0030] See Figures 5 to 7 , where Figure 5 is the gas holdup distribution diagram of bubble flow and slug flow. The left is normal temperature and pressure, and the right is high temperature and high pressure; Figure 6 is the gas holdup distribution diagram of slug flow and churn flow. The left is normal temperature and pressure, and the right is high temperature and high pressure; Figure 7 is the gas holdup distribution diagram of slug flow and annular flow. The left is normal temperature and pressure, and the right is high temperature and high pressure.

[0031] Step S6 is specifically as follows: According to the gas holdup distribution characteristics of specific flow patterns, determining the critical gas holdups for different flow pattern transitions includes the following sub-steps: S601. Based on the fact that the pressure determined in step S5 is the dominant factor affecting the flow pattern transition and the influence of temperature on the flow pattern transition can be ignored. Therefore, determine the critical gas holdups for different flow pattern transitions under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and high pressure (100°C, 20 MPa) respectively; S602. As Figure 5 shown, based on the instantaneous gas holdup data detected at the wellbore cross-section in step S3, obtain the gas holdup distribution data of specific flow patterns under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and high pressure (100°C, 20 MPa); S603. Based on the gas holdup distribution of bubble flow and slug flow patterns, and combining with the gas holdup probability density distribution characteristics of the bubble-slug flow pattern obtained in step S4, determine that the critical gas holdups for the transition from bubble flow to slug flow under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and high pressure (100°C, 20 MPa) are 0.2 and 0.25 respectively; S604. Based on the gas holdup distribution of slug flow and churn flow patterns, and combining with the gas holdup probability density distribution characteristics of the slug-churn flow pattern obtained in step S4, determine that the critical gas holdups for the transition from slug flow to churn flow under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and high pressure (100°C, 20 MPa) are 0.6 and 0.5 respectively; S605. Based on the gas holdup distribution of churn flow and annular flow patterns, and combining with the gas holdup probability density distribution characteristics of churn flow and annular flow patterns obtained in step S4, determine that the critical gas holdups for the transition from churn flow to annular flow under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and high pressure (100°C, 20 MPa) are 0.9 and 0.8 respectively; Step S7 is specifically as follows: According to the critical gas holdups for different flow pattern transitions, determining the boundary equations for different flow pattern transitions includes the following sub-steps: S701. Based on the critical gas holdups for the bubbly flow to slug flow transition at normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa) determined in step S6, and combining with the relationship between the gas holdup of bubbly flow and the superficial gas velocity and superficial liquid velocity, determine the boundary for the bubbly flow to slug flow transition; Further, the relationship between the gas holdup of bubbly flow and the superficial gas velocity and superficial liquid velocity: (1)

[0032] In the formula: is the superficial gas velocity, ; is the superficial liquid velocity, ; is the liquid density, ; is the gas density, ; is the acceleration due to gravity ; is the surface tension ; is the critical gas holdup.

[0033] Further, substitute the critical gas holdup of 0.2 for the bubbly flow to slug flow transition at normal temperature and pressure (20°C, 0.1 MPa) into equation (1) to determine the boundary equation for the bubbly flow to slug flow transition at normal temperature and pressure (20°C, 0.1 MPa): (2)

[0034] Further, substitute the critical gas holdup of 0.25 for the bubbly flow to slug flow transition at high temperature and pressure (100°C, 20 MPa) into equation (1) to determine the boundary equation for the bubbly flow to slug flow transition at high temperature and pressure (100°C, 20 MPa): (3)

[0035] S702. Based on the critical gas holdups for the slug flow to churn flow transition at normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa) determined in step S6, and combining with the relationship between the gas holdup of slug flow and the superficial gas velocity and superficial liquid velocity, determine the boundary for the slug flow to churn flow transition; Further, the relationship between the gas holdup of slug flow and the superficial gas velocity and superficial liquid velocity: (4)

[0036] In the formula: is the superficial gas velocity, ; is the superficial liquid velocity, ; is the liquid density, ; is the gas density, ; is the acceleration due to gravity ; D is the pipe diameter, ; is the critical gas holdup.

[0037] Furthermore, substituting the critical gas holdup of 0.6 for the transition from slug flow to churn flow at normal temperature and pressure (20°C, 0.1 MPa) into Equation (4) to determine the boundary equation for the transition from slug flow to churn flow at normal temperature and pressure (20°C, 0.1 MPa): (5)

[0038] Furthermore, substituting the critical gas holdup of 0.5 for the transition from slug flow to churn flow at high temperature and pressure (100°C, 20 MPa) into Equation (4) to determine the boundary equation for the transition from slug flow to churn flow at normal temperature and high temperature and pressure (100°C, 20 MPa): (6)

[0039] S703, based on the critical gas holdups for the transition from churn flow to annular flow at normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa) determined in step S6, and combining the relationship between the gas holdup in churn flow and the superficial gas velocity and superficial liquid velocity, determine the boundary for the transition from churn flow to annular flow; Furthermore, the relationship between the gas holdup in churn flow and the superficial gas velocity and superficial liquid velocity is the same as the relationship between the gas holdup in slug flow and the superficial gas velocity and superficial liquid velocity; Furthermore, substituting the critical gas holdup of 0.9 for the transition from churn flow to annular flow at normal temperature and pressure (20°C, 0.1 MPa) into Equation (4) to determine the boundary equation for the transition from churn flow to annular flow at normal temperature and pressure (20°C, 0.1 MPa): (7)

[0040] Furthermore, substituting the critical gas holdup of 0.9 for the transition from churn flow to annular flow at high temperature and pressure (100°C, 20 MPa) into Equation (4) to determine the boundary equation for the transition from churn flow to annular flow at high temperature and pressure (100°C, 20 MPa): (8)

[0041] In this embodiment, step S8 is specifically as follows: According to the boundary equations for different flow pattern transitions, establishing the boundary equations for the gas-liquid two-phase flow pattern transition in the high-temperature and high-pressure wellbore specifically includes: Based on step S7, determining the boundary equations for different flow pattern transitions, and converting the critical gas holdup of the flow pattern transition into a function of physical property parameters such as the density and surface tension of the pressure control fluid, so as to obtain the boundary equations for the gas-liquid two-phase flow pattern transition in the high-temperature and high-pressure wellbore: Boundary for the transition from bubble flow to slug flow: ; (9) Boundary equation for the transition from slug flow to churn flow: ; (10) Boundary equation for the transition from churn flow to annular flow: ; (11) In this embodiment, step S9 is specifically as follows: According to the established boundary equations for the gas-liquid two-phase flow pattern transition in the high-temperature and high-pressure wellbore, determining the calculation methods for the liquid holdup of different flow patterns includes the following sub-steps: S901, Based on the boundary equations for the gas-liquid two-phase flow pattern transition in the high-temperature and high-pressure well established in step S8, establishing a calculation model for the liquid holdup of a specific flow pattern in the wellbore gas-liquid two-phase flow; Furthermore, the calculation formula for the liquid holdup in bubble flow: Calculation of the liquid holdup in bubble flow: ; (12) Calculation of the liquid holdup in slug flow: ; (13) Calculation of the liquid holdup in churn flow: ; (14) Calculation of the liquid holdup in annular flow: ; (15)

[0042] In the formula: is the gas superficial velocity, ; is the gas-liquid mixture velocity, ; is the liquid density, ; is the gas density, ; is the gravitational acceleration ; is the surface tension ; is the pipe diameter, ; is the gas drift velocity coefficient in bubble flow; is the slug flow gas drift velocity coefficient; is the churn flow gas drift velocity coefficient; is the ratio of the frictional pressure gradient of the liquid to the frictional pressure gradient of the gas phase flow.

[0043] S902. Based on the instantaneous gas holdup data detected in the wellbore cross-section in step S3, collect the gas superficial velocity, liquid superficial velocity, and liquid holdup data under different working conditions, and use the MATLAB curve fitting tool to fit the parameters affected by the gas drift velocity 、 、 、 , and establish a liquid holdup calculation model for a specific flow pattern Bubble flow liquid holdup calculation model: ; (16) Slug flow liquid holdup calculation model: ; (17) Churn flow liquid holdup calculation model: ; (18) Annular flow liquid holdup calculation model: ; (19) Where: is the gas superficial velocity, ; is the liquid superficial velocity, ; is the gas-liquid mixture velocity, that is , ; is the liquid density, ; is the gas density, ; is the acceleration due to gravity ; is the surface tension ; is the pipe diameter, ; is the gas viscosity; is the liquid viscosity.

[0044] Use a high-temperature and high-pressure wellbore gas-liquid two-phase flow pattern simulation and liquid holdup calculation method provided by the present invention to calculate the liquid holdup of atmospheric-pressure and high-pressure gas-liquid two-phase flows, and compare it with the liquid holdup results of gas-liquid two-phase flows simulated by Fluent, as Figure 8As shown, the simulated results of the Fluent liquid holdup decrease with the increase of the superficial gas velocity and increase with the increase of the superficial liquid velocity. The variation law of the liquid holdup calculation model results is consistent with that of the Fluent liquid holdup simulation results. According to the comparison between the Fluent simulation results and the liquid holdup calculation model results under atmospheric pressure and high pressure conditions, as Figure 9 shown, the error between the liquid holdup calculation model and the Fluent simulation results is basically within 10%, indicating that the liquid holdup model proposed in this paper has good generalization ability and can realize the calculation of the liquid holdup in the wellbore gas-liquid two-phase flow under different pressure conditions.

[0045] According to the actual production data of a production well, the gas production of this well is 13221 m 3 / d; the water production is 0.04 m 3 / d; the wellhead pressure is 3.13 MPa. Use the method for simulating the flow pattern and calculating the liquid holdup of the high-temperature and high-pressure wellbore gas-liquid two-phase flow provided by the present invention to predict the pressure drop of this well. Determine the conditions such as the surface tension, water viscosity, gas density, water density, and pipe diameter in actual production. Determine the superficial gas velocity, superficial liquid velocity, and mixture velocity according to the production data and substitute them into the established liquid holdup calculation model of the wellbore gas-liquid two-phase flow to calculate the liquid holdup, so as to predict the pressure drop of this well and compare it with the existing calculation methods. As Figure 10 shown, the method for simulating the flow pattern and calculating the liquid holdup of the high-temperature and high-pressure wellbore gas-liquid two-phase flow proposed by the present invention is more consistent with actual production, and the accuracy of the model is relatively high.

[0046] For the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present application is not limited by the described action sequence, because according to the present application, some steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification belong to preferred embodiments, and the actions involved are not necessarily essential to the present application.

[0047] In the above embodiments, the basic principles, main features, and advantages of the present invention are described. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for simulating gas-liquid two-phase flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore, characterized in that: The steps include: S1: Establish the wellbore geometric model and the wellbore gas-liquid two-phase flow field according to the basic wellbore parameters; S2: Construct the local feature detection surface of the wellbore according to the wellbore geometric model and the gas-liquid two-phase flow field of the wellbore; S3: Detect the instantaneous gas content of the wellbore cross section according to the wellbore local characteristic detection surface; S4: Determine the probability density distribution characteristics of the gas content of a specific flow pattern based on the instantaneous gas content of the cross section of the detected wellbore; S5: Determine the effect of temperature and pressure on the transition of different flow patterns based on the probability density distribution of gas void fraction; S6: Determine the critical gas content of different flow patterns according to the gas content distribution characteristics of the specific flow pattern; S7: Determine the boundary equations of different flow pattern transitions according to the critical gas content of different flow pattern transitions; S8: Based on the boundary equations of different flow pattern transitions, the boundary equation of the flow pattern transition of the gas-liquid two-phase flow in the high-temperature and high-pressure wellbore is established; S9: Based on the established boundary equation for the transition of gas-liquid two-phase flow patterns in high-temperature and high-pressure wellbores, the calculation method for liquid holdup of different flow patterns is determined.

2. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: The basic wellbore parameters include one or more of the wellbore string structure, wellbore fluid temperature, wellbore fluid pressure, wellbore gas superficial velocity and wellbore liquid superficial velocity.

3. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S4 includes the following sub-steps: Classify the specific flow patterns of gas-liquid two-phase flow in the wellbore, including: bubbly flow, bubbly-slug flow, slug flow, slug-churn flow, churn flow, and annular flow; By normalizing the time-history gas content data of the wellbore cross section detected by Fluent, the probability density distribution of gas content of gas-liquid two-phase flow under different working conditions is obtained; Based on the probability density distribution of gas content, combined with the flow cloud diagram of gas-liquid two-phase flow simulated by Fluent, the probability density distribution characteristics of gas content in a specific flow pattern are determined; Based on the probability density distribution characteristics of gas content in specific flow patterns, the specific flow pattern of gas-liquid two-phase flow in the wellbore is determined.

4. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S5 specifically includes: based on the gas content probability density distribution characteristics of a specific flow pattern, combined with the flow pattern transition gas content probability density versus superficial gas velocity value line graph, determining the influence of temperature and pressure on the transition of different flow patterns.

5. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S6 includes the following sub-steps: Based on the gas content distribution of bubbly flow and slug flow, combined with the gas content probability density distribution characteristics of bubbly-slug flow, the critical gas content of the transition from bubbly flow to slug flow is determined. Based on the gas content distribution of slug flow and churning flow, combined with the gas content probability density distribution characteristics of slug-churning flow, the critical gas content of the transition from slug flow to churning flow is determined. Based on the gas void fraction distribution of turbulent flow and annular flow patterns and combined with the gas void fraction probability density distribution characteristics of turbulent flow and annular flow patterns, the critical gas void fraction for the transition from turbulent flow to annular flow is determined.

6. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S7 specifically includes: based on the critical gas content of different flow pattern transitions, combined with the relationship between the gas content of the gas-liquid two-phase flow and the gas superficial velocity and the liquid superficial velocity, the boundary equation of different flow pattern transitions is obtained.

7. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S8 specifically includes: based on the boundary equations of different flow pattern transitions, converting the critical gas content of the flow pattern transition into a function of physical property parameters, thereby obtaining the boundary equation of the high-temperature and high-pressure wellbore gas-liquid two-phase flow pattern transition.

8. A method for simulating flow patterns and calculating liquid holdup in a high-temperature and high-pressure wellbore gas-liquid two-phase flow as claimed in claim 1, characterized in that: Step S9 is specifically as follows: based on the boundary equation of the transition of the gas-liquid two-phase flow pattern in the high-temperature and high-pressure well, combined with the calculation formula of the liquid holdup of the specific flow pattern, the parameters of different flow patterns affected by the gas drift velocity are fitted through the MATLAB curve fitter, and a liquid holdup calculation model for the specific flow pattern of the wellbore gas-liquid two-phase flow is established.

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