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

Abstract

The present invention discloses 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, which includes the following steps: establishing a wellbore geometric model and a gas-liquid two-phase flow field in the wellbore according to the basic wellbore parameters; constructing a local feature detection surface in the wellbore and detecting the instantaneous gas holdup of the wellbore cross-section; determining the probability density distribution characteristics of the gas holdup of specific flow patterns and the influence of temperature and pressure on the transition between different flow patterns; determining the critical gas holdup for different flow pattern transitions and the boundary equations for different flow pattern transitions; establishing the boundary equations for the flow pattern transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore and determining the calculation method for the liquid holdup of different flow patterns. The present invention overcomes the drawback that the existing experimental conditions cannot conduct experimental research on high-temperature and high-pressure gas-liquid two-phase flow.

Description

Technical Field

[0001] The present invention relates to the technical field of gas drainage and production, and particularly 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 late 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 gas wells to shut down due to liquid accumulation. At present, the gas drainage and production process is usually used 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 normal temperature and pressure and the pressure and temperature ranges 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 method for calculating 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:

[0007] S1: According to the basic wellbore parameters, establish a wellbore geometric model and a gas-liquid two-phase flow field in the wellbore;

[0008] 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;

[0009] S3: Detect the instantaneous gas holdup of the wellbore cross-section according to the local characteristic detection surface of the wellbore;

[0010] S4: Determine the probability density distribution characteristics of the gas holdup of a specific flow regime according to the detected instantaneous gas holdup of the wellbore cross-section;

[0011] S5: Determine the influence of temperature and pressure on the transition between different flow regimes according to the probability density distribution of the gas holdup;

[0012] S6: Determine the critical gas holdup for the transition between different flow regimes according to the gas holdup distribution characteristics of a specific flow regime;

[0013] S7: Determine the boundary equation for the transition between different flow regimes according to the critical gas holdup for the transition between different flow regimes;

[0014] S8: Establish the boundary equation for the flow regime transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore according to the boundary equation for the transition between different flow regimes;

[0015] S9: Determine the calculation method of the liquid holdup for different flow regimes according to the established boundary equation for the flow regime transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore.

[0016] 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.

[0017] Furthermore, step S4 includes the following sub-steps:

[0018] Divide the specific flow regimes 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;

[0019] Obtain the probability density distribution of the gas holdup of gas-liquid two-phase flow under different working conditions by normalizing the time-history gas holdup data of the wellbore cross-section detected by Fluent;

[0020] Based on the probability density distribution of the gas holdup, combined with the flow cloud diagram of gas-liquid two-phase flow simulated by Fluent, determine the probability density distribution characteristics of the gas holdup of a specific flow regime;

[0021] Based on the probability density distribution characteristics of the gas holdup of a specific flow regime, determine the specific flow regime of gas-liquid two-phase flow in the wellbore.

[0022] Furthermore, step S5 is specifically: Based on the probability density distribution characteristics of the gas holdup of a specific flow regime, 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 regimes.

[0023] Furthermore, step S6 includes the following sub-steps:

[0024] Based on the gas holdup distribution of bubbly flow and slug flow patterns, combined with the probability density distribution characteristics of the gas holdup in the bubbly-slug flow pattern, determine the critical gas holdup for the transition from bubbly flow to slug flow;

[0025] Based on the gas holdup distribution of slug flow and churn flow patterns, combined with the probability density distribution characteristics of the gas holdup in the slug-churn flow pattern, determine the critical gas holdup for the transition from slug flow to churn flow;

[0026] 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 the churn flow and annular flow patterns, determine the critical gas holdup for the transition from churn flow to annular flow.

[0027] Furthermore, 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, the boundary equation for different flow pattern transitions.

[0028] Furthermore, step S8 is specifically as follows: Based on the boundary equation for different flow pattern transitions, convert the critical gas holdup for flow pattern transitions into a function of physical properties parameters, so as to obtain the boundary equation for the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wellbores.

[0029] Furthermore, 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 wellbores, 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.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention establishes a simulation method for the flow pattern of 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 simulation method for the flow pattern of 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.

[0032] 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.

[0033] 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, and the result is in good agreement with the verification results of Fluent simulation and experimental data, and the calculation is convenient and convergent. Description of the Drawings

[0034] 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 accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description 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.

[0035] Figure 1 This is the flowchart of the present invention;

[0036] Figure 2 This is the simulation cloud map of specific flow patterns of gas-liquid two-phase flow in the wellbore;

[0037] Figure 3 This is the flow pattern map of gas-liquid two-phase flow at normal temperature and pressure;

[0038] Figure 4 This is the flow pattern map of gas-liquid two-phase flow at high temperature and high pressure;

[0039] Figure 5 This is the gas holdup distribution of bubbly flow to slug flow at normal temperature and pressure and at high temperature and high pressure;

[0040] Figure 6 This is the gas holdup distribution of slug flow and churn flow at normal temperature and pressure and at high temperature and high pressure;

[0041] Figure 7 This is the gas holdup distribution of churn flow and annular flow at normal temperature and pressure and at high temperature and high pressure;

[0042] Figure 8 This is the result comparison chart of Fluent simulation;

[0043] Figure 9 This is the result comparison chart of the liquid holdup calculation model;

[0044] Figure 10 This is the comparison chart of the liquid holdup calculation method for specific flow patterns in the wellbore of the present invention and other calculation methods. Detailed implementation manners

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with 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. Usually, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0046] 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.

[0047] The following will, in conjunction with the accompanying drawings, elaborate on some embodiments of the present invention. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0048] See Figure 1 , 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, comprising the following steps:

[0049] S1. Based on the basic wellbore parameters, establish a wellbore geometric model and a gas-liquid two-phase flow field in the wellbore;

[0050] 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;

[0051] S3. According to the local feature detection surface of the wellbore, detect the instantaneous gas holdup of the wellbore cross-section;

[0052] S4. According to the detected instantaneous gas holdup of the wellbore cross-section, determine the gas holdup probability density distribution characteristics of a specific flow pattern;

[0053] S5. According to the gas holdup probability density distribution, determine the influence of temperature and pressure on the transition between different flow patterns;

[0054] S6. According to the gas holdup distribution characteristics of a specific flow pattern, determine the critical gas holdup for the transition between different flow patterns;

[0055] S7. According to the critical gas holdup for the transition between different flow patterns, determine the boundary equation for the transition between different flow patterns;

[0056] S8. According to the boundary equation for the transition between different flow patterns, establish the boundary equation for the transition of the gas-liquid two-phase flow pattern in the high-temperature and high-pressure wellbore;

[0057] S9. According to the established boundary equation for the transition of the gas-liquid two-phase flow pattern in the high-temperature and high-pressure wellbore, determine the calculation method for the liquid holdup of different flow patterns.

[0058] In this embodiment, step S1 specifically includes the following sub-steps:

[0059] S101. Based on the wellbore parameters, construct a wellbore geometric model and set the physical properties of the gas and liquid fluids; the basic wellbore parameters include the wellbore string structure, the wellbore fluid temperature, the wellbore fluid pressure, the gas superficial velocity, and the liquid superficial velocity;

[0060] S102. Use Fluent to simulate the gas-liquid two-phase flow pattern in the wellbore with the gas superficial velocity range (0.05~15 m / s) and the liquid superficial velocity range (0.01~1 m / s) under the conditions of normal temperature and pressure (20°C, 0.1 MPa) and high temperature and normal pressure (90°C, 0.1 MPa).

[0061] S103. Use Fluent to simulate the flow patterns of gas-liquid two-phase flow 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 the liquid superficial velocity range (0.01 - 1 m / s).

[0062] In this embodiment, step S2 is specifically as follows: According to the wellbore geometric model and the gas-liquid two-phase flow field in the wellbore, construct a wellbore local feature detection surface, which specifically includes: 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.

[0063] In this embodiment, step S3 is specifically as follows: According to the wellbore local feature detection surface, detect the instantaneous gas holdup of the wellbore cross-section, which specifically includes: Detect the instantaneous gas holdup of the wellbore cross-section by using the area-averaged weighted method.

[0064] In this embodiment, step S4 is specifically as follows: According to the detected instantaneous gas holdup of the wellbore cross-section, determine the gas holdup probability density distribution characteristics of specific flow patterns, including the following sub-steps:

[0065] S401, as Figure 2 shown, divide the specific flow patterns of gas-liquid two-phase flow in the wellbore, which specifically includes: bubble flow, bubble-slug flow, slug flow, slug-churn flow, churn flow, annular flow;

[0066] S402. By normalizing the time-history gas holdup data detected by Fluent for the wellbore cross-section, obtain the gas holdup probability density distribution of specific flow patterns of gas-liquid two-phase flow under 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) conditions;

[0067] S403. Based on the gas holdup probability density distribution of specific flow patterns, determine the gas holdup probability density distribution characteristics of specific flow patterns;

[0068] S404. Based on the gas holdup probability density distribution characteristics of specific flow patterns, determine the specific flow patterns of gas-liquid two-phase flow in the wellbore.

[0069] In this embodiment, step S5 is specifically as follows: According to the gas holdup probability density distribution, determine the influence of temperature and pressure on the transition between different flow patterns, including the following sub-steps:

[0070] S501. Fix the apparent liquid velocity and plot the contour maps of the probability density of the gas holdup at the flow pattern transition varying with the apparent gas velocity under the conditions of normal temperature and pressure (20°C, 0.1 MPa), high temperature and 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). For details, see Figure 3 , Figure 4 as shown. Among them, 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.

[0071] Furthermore, the contour map of the probability density of the gas holdup at the flow pattern transition varying with the apparent gas velocity includes the probability density distribution characteristics of the gas holdup in the 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;

[0072] S502. Based on the probability density distribution characteristics of the gas holdup of a specific flow pattern determined in step S4, combined with the contour map of the probability density of the gas holdup at the flow pattern transition varying with the apparent gas velocity, determine the influence of pressure and temperature on the transition of different flow patterns;

[0073] Furthermore, fix the pressure at 0.1 MPa under normal pressure and 20 MPa under high pressure, and increase the temperature from 20°C to 100°C. The three-dimensional view of the probability density of the gas holdup at the flow pattern transition and the contour map of the probability density of the gas holdup at the flow pattern transition are highly consistent. The change in temperature has a negligible impact on the flow of the gas-liquid two-phase flow in the wellbore;

[0074] Furthermore, fix the temperature at 20°C under normal temperature and 100°C under high temperature, and increase the pressure from 0.1 MPa to 20 MPa. The three-dimensional view of the probability density of the gas holdup at the flow pattern transition and the contour map of the probability density of the gas holdup at the flow pattern transition change significantly;

[0075] Furthermore, based on the above analysis, pressure is the dominant factor affecting the transition of the gas-liquid two-phase flow pattern in the wellbore, and the influence of temperature on the transition of the gas-liquid two-phase flow pattern in the wellbore can be ignored.

[0076] See Figures 5 to 7 , where Figure 5 is the gas holdup distribution diagram of the bubbly 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 the 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 the slug flow and annular flow. The left is normal temperature and pressure, and the right is high temperature and high pressure.

[0077] Step S6 is specifically as follows: Determine the critical gas holdup for the transition of different flow patterns according to the gas holdup distribution characteristics of a specific flow pattern, including the following sub-steps:

[0078] S601. Based on the pressure determined in step S5 being the dominant factor affecting the flow pattern transition, the influence of temperature on the flow pattern transition can be ignored. Therefore, the critical gas holdups for different flow pattern transitions are determined separately under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa);

[0079] S602. As shown in Figure 5 , based on the instantaneous gas holdup data detected for the wellbore cross-section in step S3, the gas holdup distribution data for specific flow patterns under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa) are obtained;

[0080] S603. Based on the gas holdup distributions of the bubbly flow and slug flow patterns, and combining with the gas holdup probability density distribution characteristics of the bubbly-slug flow pattern obtained in step S4, the critical gas holdups for the transition from bubbly flow to slug flow under normal temperature and pressure (20°C, 0.1 MPa) and high temperature and pressure (100°C, 20 MPa) are determined to be 0.2 and 0.25 respectively;

[0081] S604. Based on the gas holdup distributions of the 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, 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 pressure (100°C, 20 MPa) are determined to be 0.6 and 0.5 respectively;

[0082] S605. Based on the gas holdup distributions of the churn flow and annular flow patterns, and combining with the gas holdup probability density distribution characteristics of the churn flow and annular flow patterns obtained in step S4, 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 pressure (100°C, 20 MPa) are determined to be 0.9 and 0.8 respectively;

[0083] 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:

[0084] S701. Based on the critical gas holdups for the transition from bubbly flow to slug flow under 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, the boundary for the transition from bubbly flow to slug flow is determined;

[0085] Furthermore, the relationship between the gas holdup of bubbly flow and the superficial gas velocity and superficial liquid velocity:

[0086] (1)

[0087] 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.

[0088] Furthermore, substituting the critical gas holdup of 0.2 for the transition from bubbly flow to slug flow at normal temperature and pressure (20°C, 0.1 MPa) into Equation (1) to determine the boundary equation for the transition from bubbly flow to slug flow at normal temperature and pressure (20°C, 0.1 MPa):

[0089] (2)

[0090] Furthermore, substituting the critical gas holdup of 0.25 for the transition from bubbly flow to slug flow at high temperature and pressure (100°C, 20 MPa) into Equation (1) to determine the boundary equation for the transition from bubbly flow to slug flow at high temperature and pressure (100°C, 20 MPa):

[0091] (3)

[0092] S702. Based on the critical gas holdups for the transition from slug flow to churn 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 of slug flow and the superficial gas velocity and superficial liquid velocity, determine the boundary for the transition from slug flow to churn flow;

[0093] Furthermore, the relationship between the gas holdup of slug flow and the superficial gas velocity and superficial liquid velocity:

[0094] (4)

[0095] Wherein: 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.

[0096] Further, substitute 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):

[0097] (5)

[0098] Further, substitute 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 pressure (100°C, 20 MPa):

[0099] (6)

[0100] 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 with 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;

[0101] Further, the relationship between the gas holdup in churn flow and the superficial gas velocity and superficial liquid velocity is the same as that between the gas holdup in slug flow and the superficial gas velocity and superficial liquid velocity;

[0102] Further, substitute 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):

[0103] (7)

[0104] Further, substitute 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):

[0105] (8)

[0106] In this embodiment, step S8 is specifically as follows: According to the boundary equations for different flow pattern transitions, establishing the boundary equation for the flow pattern transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore specifically includes: Based on the boundary equations for different flow pattern transitions determined in step S7, converting the critical gas holdup for 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 equation for the flow pattern transition of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore:

[0107] Boundary for the transition from bubble flow to slug flow:

[0108] ; (9)

[0109] Slug flow to churn flow transition boundary equation:

[0110] ; (10)

[0111] Churn flow to annular flow transition boundary equation:

[0112] ; (11)

[0113] In this embodiment, step S9 is specifically as follows: According to the established boundary equations for the flow pattern transitions of gas-liquid two-phase flow in high-temperature and high-pressure wellbores, determining the calculation methods for the liquid holdup of different flow patterns includes the following sub-steps:

[0114] S901, based on the boundary equations for the flow pattern transitions of gas-liquid two-phase flow in high-temperature and high-pressure wells established in step S8, establish a calculation model for the liquid holdup of a specific flow pattern of gas-liquid two-phase flow in the wellbore;

[0115] Furthermore, the calculation formula for the liquid holdup in bubble flow:

[0116] Calculation of liquid holdup in bubble flow:

[0117] ; (12)

[0118] Calculation of liquid holdup in slug flow:

[0119] ; (13)

[0120] Calculation of liquid holdup in churn flow:

[0121] ; (14)

[0122] Calculation of liquid holdup in annular flow:

[0123] ; (15)

[0124] Where: is the superficial gas velocity, ; is the gas-liquid mixture velocity, ; 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 drift velocity coefficient for bubbly flow; is the gas drift velocity coefficient for slug flow; is the gas drift velocity coefficient for churn flow; is the ratio of the frictional pressure gradient of the liquid to the frictional pressure gradient of the gas-phase flow.

[0125] 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

[0126] Liquid holdup calculation model for bubbly flow:

[0127] ; (16)

[0128] Liquid holdup calculation model for slug flow:

[0129] ; (17)

[0130] Liquid holdup calculation model for churn flow:

[0131] ; (18)

[0132] Liquid holdup calculation model for annular flow:

[0133] ; (19)

[0134] In the formula: 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.

[0135] Using 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 provided by the present invention, the liquid holdup of gas-liquid two-phase flow under normal pressure and high pressure is calculated and compared with the liquid holdup results of gas-liquid two-phase flow simulated by Fluent. As Figure 8 shown, the simulated results of the liquid holdup by Fluent decrease with the increase of the gas superficial velocity and increase with the increase of the liquid superficial velocity. The variation law of the results of the liquid holdup calculation model is consistent with that of the simulated results of the liquid holdup by Fluent. According to the comparison between the simulated results by Fluent and the results of the liquid holdup calculation model under normal pressure and high pressure conditions, as Figure 9 shown, the error between the liquid holdup calculation model and the simulated results by Fluent is basically within 10%, indicating that the liquid holdup model proposed in this paper has good generalization and can realize the calculation of the liquid holdup of gas-liquid two-phase flow in the wellbore under different pressure conditions.

[0136] 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. Using 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 provided by the present invention, the pressure drop of this well is predicted. Determine the conditions such as the surface tension, water viscosity, gas density, water density, and pipe diameter in actual production. According to the production data, determine the gas superficial velocity, liquid superficial velocity, and mixture velocity and substitute them into the established liquid holdup calculation model of gas-liquid two-phase flow in the wellbore 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, 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 proposed by the present invention is more consistent with actual production, and the accuracy of the model is relatively high.

[0137] 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 this application is not limited by the described action sequence, because according to this 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 this application.

[0138] In the above embodiments, the basic principles, main features, and advantages of the present invention are described. Those skilled in the art 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 principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

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, characterized in that, It includes the following steps: S1: Establish a wellbore geometric model and a wellbore gas-liquid two-phase flow field according to the basic wellbore parameters; S2: Construct a wellbore local feature detection surface according to the wellbore geometric model and the wellbore gas-liquid two-phase flow field; S3: Detect the instantaneous gas holdup of the wellbore cross-section according to the wellbore local feature detection surface; S4: Determine the gas holdup probability density distribution characteristics of a specific flow pattern according to the detected instantaneous gas holdup of the wellbore cross-section; Step S4 includes the following sub-steps: Divide the specific flow patterns of the wellbore gas-liquid two-phase flow, specifically including: bubble flow, bubble-slug flow, slug flow, slug-churn flow, churn flow, annular flow; By normalizing the time-history gas holdup data of the wellbore cross-section detected by Fluent, obtain the gas holdup probability density distribution of the gas-liquid two-phase flow under different working conditions; Based on the gas holdup probability density distribution, combined with the Fluent-simulated gas-liquid two-phase flow cloud map, determine the gas holdup probability density distribution characteristics of a specific flow pattern; Based on the gas holdup probability density distribution characteristics of a specific flow pattern, judge the specific flow pattern of the wellbore gas-liquid two-phase flow; S5: Determine the influence of temperature and pressure on the transition between different flow patterns according to the gas holdup probability density distribution; Step S5 is specifically: Based on the gas holdup probability density distribution characteristics of a specific flow pattern, combined with the line graph of the change of the gas holdup probability density of the flow pattern transition with the superficial gas velocity, determine the influence of temperature and pressure on the transition between different flow patterns; S6: Determine the critical gas holdup of the transition between different flow patterns according to the gas holdup distribution characteristics of a specific flow pattern; S7: Determine the boundary equation of the transition between different flow patterns according to the critical gas holdup of the transition between different flow patterns; S8: Establish the boundary equation of the flow pattern transition of the high-temperature and high-pressure wellbore gas-liquid two-phase flow according to the boundary equation of the transition between different flow patterns; S9: Determine the calculation method of the liquid holdup of different flow patterns according to the established boundary equation of the flow pattern transition of the high-temperature and high-pressure wellbore gas-liquid two-phase flow.

2. The 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 according to claim 1, wherein 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 the flow pattern and calculating the liquid holdup of gas-liquid two-phase flow in a high-temperature and high-pressure wellbore according to claim 1, characterized in that, Step S6 includes the following sub-steps: Based on the gas holdup distributions of the bubble flow and slug flow patterns, combined with the gas holdup probability density distribution characteristics of the bubble-slug flow pattern, determine the critical gas holdup for the transition from bubble flow to slug flow; Based on the gas holdup distributions of the slug flow and churn flow patterns, combined with the gas holdup probability density distribution characteristics of the slug-churn flow pattern, determine the critical gas holdup for the transition from slug flow to churn flow; Based on the gas holdup distributions of the churn flow and annular flow patterns, combined with the gas holdup probability density distribution characteristics of the churn flow and annular flow patterns, determine the critical gas holdup for the transition from churn flow to annular flow.

4. 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 according to claim 1, characterized in that, Step S7 is specifically: Based on the critical gas holdup of the transition between different flow patterns, combined with the relationship between the gas holdup of the gas-liquid two-phase flow and the superficial gas velocity and superficial liquid velocity, determine the boundary equation of the transition between different flow patterns.

5. The 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 according to claim 1, characterized in that, Step S8 is specifically: Based on the boundary equation of the transition between different flow patterns, convert the critical gas holdup of the flow pattern transition into a function of physical properties parameters, so as to obtain the boundary equation of the high-temperature and high-pressure wellbore gas-liquid two-phase flow pattern transition.

6. The 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 according to claim 1, wherein Step S9 specifically is as follows: Based on the boundary equation of the flow pattern transition of gas-liquid two-phase flow in high-temperature and high-pressure wells, combined with the calculation formula of the liquid holdup of a specific flow pattern, through the MATLAB curve fitter, the parameters affected by the gas drift velocity of different flow patterns are fitted, and a calculation model of the liquid holdup of a specific flow pattern of gas-liquid two-phase flow in the wellbore is established.

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