Method, device and equipment for determining flow pattern transformation limit of gas well shaft

Abstract

The invention discloses a method, device and equipment for determining a gas well shaft flow pattern transformation limit, the method comprises the steps that multiple sets of experimental data of shaft flow patterns are obtained, the shaft flow patterns comprise annular flow, quasi-annular flow, quasi-slug flow, slug flow and bubble flow, and the experimental data comprise the liquid flow speed, the gas flow speed and the pipeline inner diameter corresponding to the shaft flow patterns; according to a liquid membrane inversion theory and experimental data, determining a transformation limit of the annular flow and the quasi-annular flow; according to the experimental data, a flow pattern chart is constructed, and the flow pattern chart is used for representing the corresponding relation between the wellbore flow pattern and the liquid flow velocity, the airflow velocity and the pipeline inner diameter; and according to the flow pattern chart, fitting the transformation boundaries of the quasi-annular flow, the quasi-slug flow, the slug flow and the bubble flow to obtain the transformation boundaries among the quasi-annular flow, the quasi-slug flow, the slug flow and the bubble flow. Through the technical scheme provided by the invention, the transformation limit of the wellbore flow pattern can be accurately predicted.

Description

Technical Field

[0001] This application belongs to the field of gas reservoir drainage and gas production, and particularly relates to a method, apparatus and equipment for determining the flow pattern transition boundary of a gas well. Background Technology

[0002] During natural gas extraction, formation water often flows into the bottom of the gas well. As the reservoir energy gradually decreases, the well's lifting capacity weakens, and the wellbore's liquid holdup increases, thus affecting the wellbore flow pattern. Flow pattern, also known as flow structure or flow morphology, generally refers to the distribution of gas and liquid during flow and is an important indicator reflecting the production status of a gas well. For example, when the flow pattern is bubbly, the wellbore pressure drop is high, and the gas well production is low; when the flow pattern is slug flow, the wellbore pressure drop is high, and gas well production is unstable; when the flow pattern is agitated flow (also known as transitional flow), the wellbore liquid holdup and pressure drop decrease; when the flow pattern is annular flow, the wellbore liquid holdup and pressure drop decrease, and gas well production is stable. Therefore, accurate prediction of the gas well's flow pattern can provide guidance for the optimized design of drainage and gas production processes, effectively improving the final recovery rate of the gas well and increasing the economic benefits of a single well.

[0003] Currently, the prediction of gas wellbore flow patterns can be divided into empirical models and theoretical models. Flow pattern charts generated by empirical models cannot fully cover the range of gas well production parameters, leading to some data points falling outside the chart during field applications, and the overall prediction accuracy does not meet engineering requirements. While theoretical models can accurately predict the transition boundary between annular and agitated flow, the other two types of transition boundaries are complex and variable, making simplified theoretical models difficult to predict, and their practical application performance is far inferior to empirical models. Therefore, how to accurately predict the flow pattern of gas wells is a problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The embodiments of this application provide a method, apparatus, and equipment for determining the flow pattern transition boundary of a gas well shaft, which can achieve accurate prediction of the flow pattern of a gas well shaft.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to a first aspect of the present application, a method for determining the transition boundary of a gas wellbore flow pattern is provided, comprising: acquiring multiple sets of experimental data on wellbore flow patterns, wherein the wellbore flow patterns include annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, and the experimental data includes the liquid velocity, gas velocity, and pipe inner diameter corresponding to the wellbore flow pattern; determining the transition boundary between the annular flow and the pseudo-annular flow based on the liquid film reversal theory and the experimental data; constructing a flow pattern chart based on the experimental data, the flow pattern chart being used to characterize the correspondence between the wellbore flow pattern and the liquid velocity, the gas velocity, and the pipe inner diameter; and fitting the transition boundaries of the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubbly flow based on the flow pattern chart to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubbly flow.

[0007] In some embodiments of this application, based on the foregoing scheme, constructing a flow pattern chart based on the experimental data includes: drawing a statistical chart of the wellbore flow pattern based on the experimental data, wherein the vertical axis of the statistical chart is... The x-axis is Where, ρ l ρ is the density of the liquid phase. g v is the gas phase density. SL v is the apparent flow rate of the liquid phase. SG denoted as the apparent velocity of the gas phase, g is the acceleration due to gravity, and D is the pipe diameter.

[0008] In some embodiments of this application, based on the foregoing scheme, fitting the transition boundary between the pseudo-annular flow and the pseudo-slug flow according to the flow pattern diagram includes: fitting a transition boundary formula between the pseudo-annular flow and the pseudo-slug flow according to the flow pattern diagram; wherein, the transition boundary formula between the pseudo-annular flow and the pseudo-slug flow is:

[0009]

[0010] a, b, c, and d are the fitting coefficients.

[0011] In some embodiments of this application, based on the foregoing scheme, fitting the transition boundary between the pseudo-slug flow and the slug flow according to the flow pattern map includes: fitting a transition boundary formula between the pseudo-slug flow and the slug flow according to the flow pattern map; wherein, the transition boundary formula between the pseudo-slug flow and the slug flow is:

[0012]

[0013]

[0014] n, m, g, h, and Z1 are the fitting coefficients.

[0015] In some embodiments of this application, based on the foregoing scheme, fitting the transition boundary between the slug flow and the bubbly flow according to the flow pattern diagram includes: fitting a formula for the transition boundary between the slug flow and the bubbly flow according to the flow pattern diagram; wherein, the formula for the transition boundary between the slug flow and the bubbly flow is:

[0016]

[0017]

[0018] p, q, j, k, and Z2 are the fitting coefficients.

[0019] In some embodiments of this application, based on the foregoing scheme, determining the transition boundary between the annular flow and the pseudo-annular flow according to the liquid film reversal theory and the experimental data includes: performing a force analysis on the liquid film on the pipe wall according to the liquid film reversal theory and the experimental data; determining that the transition boundary between the annular flow and the pseudo-annular flow corresponds to the wall shear force of the liquid film being zero.

[0020] In some embodiments of this application, based on the foregoing scheme, determining the transition boundary between the annular flow and the pseudo-annular flow when the wall shear force of the liquid film is zero includes: determining the gas flow velocity corresponding to the zero wall shear force of the liquid film as the transition boundary between the annular flow and the pseudo-annular flow; wherein, the gas flow velocity corresponding to the zero wall shear force of the liquid film is determined based on the following formula:

[0021]

[0022] v SG,R ρ is the gas velocity corresponding to the zero wall shear force of the liquid film. L Let g be the liquid density, g be the gravitational acceleration, δ be the liquid film thickness, and r be the liquid film density. o f is the pipe radius. i ρ is the internal friction factor. c This represents the core density.

[0023] In some embodiments of this application, based on the foregoing scheme, constructing a flow pattern chart based on the experimental data includes: drawing a statistical chart of the wellbore flow pattern based on the experimental data, wherein the vertical axis of the statistical chart is... The x-axis is Where, ρ l ρ is the density of the liquid phase. g v is the gas phase density. SL v is the apparent flow rate of the liquid phase. SGdenoted as the apparent velocity of the gas phase, g is the acceleration due to gravity, and D is the pipe diameter.

[0024] In some embodiments of this application, based on the foregoing scheme, the method further includes: acquiring production data of the target gas well; and determining the flow pattern category of the target gas well based on the production data and the flow pattern chart.

[0025] According to a second aspect of the present application, a device for determining the flow pattern transition boundary of a gas well is provided, comprising: an experimental data acquisition module, used to acquire multiple sets of experimental data of the well flow pattern, wherein the well flow pattern includes annular flow, pseudo-annular flow, pseudo-slug flow, slug flow and bubbly flow, and the experimental data includes the liquid flow velocity, gas flow velocity and pipe inner diameter corresponding to the well flow pattern;

[0026] The theoretical limit determination module is used to determine the transition limit between the annular flow and the pseudo-annular flow based on the liquid film reversal theory and the experimental data.

[0027] The flow pattern diagram construction module is used to construct a flow pattern diagram based on the experimental data. The flow pattern diagram is used to characterize the correspondence between the wellbore flow pattern and the fluid velocity, the gas velocity, and the pipe inner diameter.

[0028] The fitting boundary determination module is used to fit the transition boundaries of the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow according to the flow pattern diagram, so as to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow.

[0029] According to a third aspect of the present application, an apparatus for determining the flow pattern transition limit of a gas wellbore is provided, comprising a processor and a memory, wherein the memory stores computer program instructions executable by the processor, and when the processor executes the computer program instructions, it implements the steps of the method described in any of the first aspects above.

[0030] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided, wherein computer program instructions are stored therein, and when executed by a processor, the computer program instructions cause the processor to perform the steps of the method as described in any of the first aspects above.

[0031] According to a fifth aspect of the embodiments of this application, a multiphase pipe flow experimental platform is provided, including a supply device, a measurement and control device, and a test pipe section. The supply device provides a stable gas flow rate and liquid flow rate to the multiphase pipe flow experimental platform. The measurement and control device is used to record experimental data such as gas flow rate, liquid flow rate, and pipe inner diameter in real time during the experiment. The test pipe section is used to observe the gas-liquid two-phase flow pattern.

[0032] The multiphase pipe flow experimental platform is used to combine the dynamic characteristics of gas well production, use the fluid mechanics similarity criterion to determine experimental parameters, and carry out gas-liquid two-phase flow pattern experiments to observe the flow pattern characteristics under different experimental conditions. Then, the wellbore flow pattern is determined, and the experimental data corresponding to the flow pattern transition boundary is recorded. This experimental data is used to implement the method described in any of the first aspects above.

[0033] In this application, based on the occurrence of liquid slugging in the wellbore, the turbulent flow is subdivided into pseudo-annular flow and pseudo-slug flow. Experimental parameters corresponding to various wellbore flow patterns, such as pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, are obtained through experiments to construct a flow pattern chart that comprehensively considers factors such as gas velocity, liquid velocity, and pressure. This allows for fitting the flow pattern transition boundaries and determining the relationships between the transition boundaries of different flow patterns, including pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow. Furthermore, the flow pattern transition boundaries between annular flow and pseudo-annular flow are determined using the liquid film reversal theory. Thus, by combining theoretical and empirical models, the expression for the transition boundaries of wellbore flow patterns is clarified, enabling accurate prediction of gas wellbore flow patterns.

[0034] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0036] Figure 1 A schematic diagram of the system architecture of a multiphase pipe flow experimental platform in one embodiment is shown;

[0037] Figure 2 A flowchart illustrating a method for determining the flow pattern transition boundary of a gas wellbore in one embodiment is shown.

[0038] Figure 3 A flow pattern diagram of a wellbore flow pattern is shown in one embodiment;

[0039] Figure 4 A block diagram of a device for determining the flow pattern transition boundary of a gas wellbore is shown in one embodiment;

[0040] Figure 5 A schematic diagram of a device for determining the flow pattern transition boundary of a gas wellbore is shown in one embodiment.

[0041] 1-Air compressor, 2-Air tank, 3-Gas flow meter, 4-Sliding support frame, 5-Experimental observation section, 6-Pressure gauge, 7-Valve, 8-Gas-water separator, 9-Water tank, 10-Centrifugal pump, 11-Turbine liquid flow meter, 12-Paperless recorder, 13-Computer. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0044] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0045] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0046] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.

[0047] Currently, the prediction of flow patterns in gas wellbore can be divided into empirical models and theoretical models. Empirical models typically involve conducting physical simulation experiments of gas-liquid two-phase pipe flow under normal or low-pressure conditions. Methods such as experimental observation, particle image velocimetry, and wire mesh sensors are used to record the flow patterns in the wellbore, identify the transition boundaries between different flow patterns, and optimize the dimensionless similarity criterion. Two-dimensional flow pattern diagrams are then created to achieve flow pattern similarity conversion between low-pressure experiments and high-pressure gas wells.

[0048] For example, Hewitt-Roberts conducted 128 flow pattern experiments under different pressure conditions and created flow pattern diagrams considering the pressure effect by combining flow snapshots. Aziz introduced correction factors X and Y to create flow pattern diagrams for vertical pipes in gas-liquid two-phase mixed flow, classifying the flow patterns as bubbly flow, slug flow, agitated flow, annular flow, and mist flow. Duns & Ros conducted approximately 4000 gas-liquid two-phase flow experiments in a vertical pipe loop at a height of approximately 56.4 m using air-water as the flow medium under normal pressure, obtaining nearly 20,000 data points, and created two-phase flow pattern diagrams suitable for vertical pipes using dimensionless gas and liquid phase velocity quanta. Gould conducted gas-liquid two-phase flow experiments in a 25 mm diameter wellbore using air and water as the flow medium and created flow pattern diagrams.

[0049] However, when the prediction methods of empirical models are applied in the field, it is found that some data points fall outside the chart and the overall prediction accuracy does not meet engineering requirements. The reason for this is that empirical charts are biased towards large liquid volumes and small gas volumes, and cannot fully cover the range of gas well production parameters.

[0050] Furthermore, the Mandhane and Goiver charts are based on air-water small-diameter (Φ<40mm) experiments, and depict the horizontal flow pattern. Gould conducted two-phase flow pattern experiments using a 25mm pipe diameter and obtained the flow pattern chart for the inclined section. The Baker chart is derived from experimental data of large-diameter (Φ150~250mm). Due to the predominantly stratified flow under high gas-liquid ratio conditions in gas wells, the pressure drop in the horizontal section is relatively small, and the test tubing size differs significantly from that of commonly used gas well tubing, resulting in limited field application of horizontal flow pattern charts.

[0051] The theoretical model conducts force analysis based on the phase interface characteristics of different flow patterns. Among them, the shear force of the liquid film on the pipe wall is zero, which is regarded as the transition boundary between annular flow and turbulent flow; the transition mechanism between turbulent flow and slug flow is not yet unified, and can be divided into inlet effect theory, wake effect theory, bubble merging theory and flooding theory; when the size of a single bubble or the liquid holdup in the wellbore reaches a critical value, it is regarded as the transition boundary between slug flow and bubbly flow.

[0052] For example, Taitel, based on the physical mechanisms of flow pattern transitions, comprehensively considered the influence of fluid properties and pipe diameter on flow patterns, and established a flow pattern prediction chart for gas-liquid two-phase flow in vertical pipes. Hasan & Kabir, using hydrodynamic principles, analyzed the mechanisms of gas-liquid two-phase flow pattern transitions, deriving the criteria and methods for identifying each flow pattern, and synthesized their research results to provide flow pattern charts predicting four flow patterns: bubbly flow, slug flow, agitated flow, and annular flow. Orkiszewski, based on measured data from 148 wells, compared and analyzed multiple vertical pipe gas-liquid two-phase pipe flow models, selected the best for different flow patterns, and provided the boundary relationships for the formation of bubbly flow, slug flow, agitated flow, and mist flow in vertical pipes.

[0053] Among them, the annular flow exhibits a distinct gas-liquid interface, clear structural characteristics, and high accuracy in calculating wall shear force, resulting in a small prediction error for the transition boundary between annular and agitated flows. Therefore, the transition boundary between annular and agitated flows can be accurately predicted. However, the other two types of transition boundaries are complex and variable. The theoretical models based on simplification are far less effective in practical applications than empirical models, and the auxiliary closure equations are established based on experimental test data, which limits the applicability of the models.

[0054] To address the aforementioned issues, research has revealed that the dynamic characteristics of gas well production can be considered, and gas-liquid two-phase physical simulation experiments can be conducted. Based on the occurrence of liquid plugs in the wellbore, the turbulent flow can be further subdivided into pseudo-annular flow and pseudo-slug flow. A wellbore flow pattern diagram can be drawn, and the transition boundary expression of the wellbore flow pattern can be clarified by combining theoretical and empirical models, thereby achieving accurate prediction of the wellbore flow pattern.

[0055] To address the difficulty in accurately predicting the transition boundaries of flow patterns in gas wells, this application proposes a method for determining these transition boundaries, combining the advantages of physical simulation experiments and theoretical analysis. This method provides guidance for the optimized design of gas well drainage and production processes. The method utilizes a multiphase pipe flow experimental platform to conduct gas-liquid two-phase flow pattern experiments. Experimental parameters corresponding to various wellbore flow patterns, such as pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, are obtained to plot flow pattern diagrams that comprehensively consider factors such as gas velocity, liquid velocity, and pressure. The transition boundaries of these flow patterns are then fitted, and the relationships between the transition boundaries of different flow patterns are determined. Furthermore, the transition boundaries between annular and pseudo-annular flow patterns are determined using liquid film reversal theory to accurately predict the flow patterns in gas wells.

[0056] Figure 1 A schematic diagram of the system architecture of a multiphase pipe flow experimental platform according to one embodiment of this application is shown. The multiphase pipe flow experimental platform is mainly divided into a supply device, a measurement and control device, and a test pipe section.

[0057] The supply system provides a stable gas and liquid flow rate for the multiphase pipe flow experimental platform. For example, an air compressor provides the gas source, while a water storage tank and a water pump provide the liquid flow.

[0058] like Figure 1 As shown, the multiphase pipe flow experimental platform may include an air compressor 1 and an air storage tank 2 that can provide an air source, a water tank 9 and a centrifugal pump 10 that can provide liquid volume, and a valve 7 that can control the fluid flow rate. Optionally, during the experiment, the fluid flow rate can be controlled by adjusting the valve opening using a needle valve.

[0059] The measurement and control device provides the experimental parameters for the multiphase pipe flow experimental platform. These experimental parameters can be gas velocity, liquid velocity, pressure, etc. For example, gas flow meters and liquid flow meters measure the flow velocities of gas and liquid, respectively.

[0060] like Figure 1 As shown, the multiphase pipe flow experimental platform may include a gas flow meter 3 capable of measuring gas flow velocity, a turbine liquid flow meter 11 capable of measuring liquid flow velocity, and a pressure gauge 6 capable of measuring pressure.

[0061] In addition, the multiphase pipe flow experimental platform may also include a paperless recorder 12 and a computer 13 (or other electronic devices that allow users to read experimental parameters). Data measured by the gas flow meter 3, turbine liquid flow meter 11, and pressure gauge 6 can be transmitted to the paperless recorder 12 via cable. The paperless recorder 12 then transmits the data signals to the computer 13 to record the readings of the gas flow meter, liquid flow meter, pressure gauge, etc., in real time during the experiment. Thus, the user can read the experimental parameters measured during the experiment via the computer.

[0062] The test pipe section serves as a multiphase pipe flow experimental platform for conducting gas-liquid two-phase physical simulation experiments to observe the flow patterns of the gas and liquid phases under specific pipe diameter conditions. The test pipe section may include a transparent plexiglass pipe section and a gas-liquid mixing device. It is understood that a gas-water mixing section exists before gas and water are injected into the wellbore in an oilfield, and this gas-liquid mixing device is developed based on this principle. During the experiment, users can observe the gas-liquid two-phase flow patterns through the glass tube.

[0063] like Figure 1 As shown, the multiphase pipe flow experimental platform may include a test pipe section on a fixed sliding support frame 4, which includes an experimental observation section 5 for observing the flow pattern. Optionally, pressure gauges 6 may be installed at both ends of the experimental observation section 5 to measure the pressure drop corresponding to each pipe segment in the test pipe section.

[0064] In addition, the multiphase pipe flow experimental platform may also include a gas-liquid separator 8 for separating the gas-liquid mixture into separate gases and liquids.

[0065] Thus, when gas enters the gas-liquid mixing device of the test tube section through gas flow meter 3, and liquid (such as water) enters the gas-liquid mixing device of the test tube section through turbine liquid flow meter 11, the two phases of gas and liquid can flow through the gas-liquid mixing device through the experimental observation section 5 of the test tube section, and then flow into the gas-liquid separator 8 for gas-liquid separation. The separated gas is vented after passing through the valve, and the separated liquid flows into the water tank 9. The liquid in the water tank is pumped back into the test tube section by centrifugal pump 10 to form a complete experimental loop, realizing the recycling of liquid.

[0066] In this embodiment of the application, based on the above-mentioned multiphase pipe flow experimental platform, the experimental parameters can be determined by combining the dynamic characteristics of gas well production and using the fluid mechanics similarity criteria. After conducting gas wellbore flow pattern experiments, the flow pattern characteristics under different experimental conditions can be observed, the wellbore flow pattern can be determined, and the gas flow velocity, liquid flow velocity and tubing inner diameter corresponding to the flow pattern transition boundary can be recorded, providing data support for establishing the expression of the gas wellbore flow pattern transition boundary.

[0067] In this embodiment of the application, the wellbore flow pattern can be determined based on the following flow pattern characteristics.

[0068] Among them, the flow state of the annular flow is stable, and the ripples on the surface of the liquid film are continuously upward.

[0069] As the airflow velocity decreases, it is observed that when the liquid film adhering closely to the pipe wall slides downwards, the liquid film reverses direction but does not form a bridge, resulting in a pseudo-annular flow. Since the annular flow is stable, a theoretical model can be used to construct the boundary between the flow patterns of annular and pseudo-annular flows. Specifically, the wall shear force can characterize the fall of the liquid film adhering to the pipe wall. When the liquid film and gas flow direction are the same, the wall shear force hinders the liquid film flow and is negative; conversely, when the liquid film and gas flow direction are opposite, the wall shear force provides an upward force to the liquid film and is positive. Therefore, when the wall shear force is zero, it corresponds to the boundary between the flow patterns of annular and pseudo-annular flows.

[0070] During the process of liquid film fallback and accumulation, bridging occurs but Taylor bubbles do not appear, which is called pseudo-slug flow. When bridging transitions to liquid plug and Taylor bubbles form, it becomes slug flow. When Taylor bubbles break down and form dispersed small bubbles in a continuous liquid phase, it is called bubbly flow.

[0071] Figure 2 A flowchart illustrating a method for determining the flow pattern transition boundary of a gas wellbore according to one embodiment of this application is shown. Figure 2 As shown, the table method may include steps 201 to 204.

[0072] In step 201, multiple sets of experimental data for wellbore flow patterns are obtained. The wellbore flow patterns include annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubble flow. The experimental data include the liquid velocity, gas velocity, and pipe inner diameter corresponding to the wellbore flow pattern.

[0073] In this embodiment, a physical simulation experiment of the flow pattern in the gas wellbore can be conducted based on the flow pattern involved in the gas well production process. The inner diameter of the test pipe section is consistent with the inner diameter of the actual oil tubing.

[0074] Specifically, this application subdivides turbulent flow into pseudo-slug flow and pseudo-annular flow, thus the flow patterns involved in this application include annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow. Wellbore flow patterns were obtained under experimental conditions such as different fluid flow rates, gas flow rates, and tubing inner diameters. To ensure the accuracy and repeatability of the experiment, the gas and fluid flow rates were stabilized for three minutes before observation and recording began. The experiment was repeated three times and cross-validated.

[0075] The specific experimental procedure is as follows: First, the sealing performance of the test pipe section on the multiphase pipe flow experimental platform is tested, and the safety of equipment such as the air compressor, water pump, and monitoring and control device is checked. The instruments are adjusted to appropriate parameter ranges. Then, the liquid flow rate and gas flow rate of the target experimental parameters are adjusted. The target experimental parameters can be target pressure, target gas density, target deviation factor, etc.

[0076] Optionally, the range of experimental parameters can be determined by combining the production dynamic characteristics of the target gas well with the fluid dynamics similarity criteria, and then a physical simulation experiment of the gas wellbore flow pattern can be carried out based on the corresponding experimental parameter conditions.

[0077] For example, the daily gas production of the target gas well is in the range of 1×10 4 m 3 / d~3×10 4 m 3 When / d, it can be 1×10 4 m 3 / d~3×10 4 m 3 Five values ​​between / d were selected as the liquid inflow parameters for the experiment.

[0078] During the experiment, once the flow in the wellbore stabilized, the gas-liquid two-phase distribution characteristics could be observed. The liquid film adhering closely to the pipe wall reversed and gradually accumulated downwards, causing the liquid film to thicken, but without bridging, indicating a pseudo-annular flow. During the liquid film's fall and accumulation, bridging formed but Taylor bubbles did not appear, indicating a pseudo-slug flow. The bridging transitioned to a liquid plug and Taylor bubbles formed, indicating a slug flow. The Taylor bubbles broke down, forming dispersed small bubbles in the liquid phase, indicating a bubbly flow.

[0079] Meanwhile, during the observation process, experimental data such as gas flow rate, liquid flow rate, and tubing inner diameter corresponding to the flow pattern transition boundary were recorded.

[0080] In this way, multiple sets of experimental data on the wellbore flow pattern can be collected during the experiment. This data includes different liquid flow velocities, gas flow velocities, and pipe inner diameters, as well as the corresponding wellbore flow patterns. The pipe inner diameter can be either the pipe diameter itself or the pipe radius. Optionally, the experimental data may also include liquid phase density, gas phase density, and pipe pressure.

[0081] Step 202: Based on the liquid film reversal theory and the experimental data, determine the transition boundary between the annular flow and the pseudo-annular flow.

[0082] After obtaining the experimental data, the transition boundaries of different wellbore flow patterns can be determined by combining the experimental data. Since annular flow is stable, a theoretical model can be used to construct the transition boundary between annular and quasi-annular flow patterns. The theoretical model is based on the stress analysis of the phase interface characteristics of different flow patterns.

[0083] In this application, the transition boundary between the annular flow and the pseudo-annular flow is determined based on the liquid film reversal theory and the experimental data. That is, when the shear force on the liquid film wall of the pipe is zero, it can be considered as the transition boundary between the annular flow and the pseudo-annular flow.

[0084] It can be understood that the wall shear force of the liquid film adhering to the pipe wall can characterize the reversal and fall of the liquid film adhering to the pipe wall. When the liquid film and gas flow direction are the same, the wall shear force hinders the liquid film flow and is negative; when the liquid film and gas flow direction are opposite, the wall shear force provides an upward force to the liquid film and is positive. Therefore, when the wall shear force is zero, it corresponds to the boundary between annular and quasi-annular flow patterns. The specific determination process of the boundary between annular and quasi-annular flow patterns will be described below.

[0085] First, a force analysis is performed on the liquid film in cylindrical coordinates. The specific expression is as follows:

[0086]

[0087] In the formula, v z g is the velocity of the liquid film, in m / s; g is the acceleration due to gravity, in m. 2 / s;μ L The viscosity of the liquid phase is Pa·s; ρ L The density of the liquid phase is kg / m³. 3 r is the radius, in meters; p is the pressure, in Pa.

[0088] Since the boundary between annular and quasi-annular flow patterns is defined by zero wall shear force, the solution boundary conditions near the pipe wall are:

[0089]

[0090] In the formula, τ w The wall shear force is Pa; r o The radius of the pipeline (oil pipe) is in meters (m).

[0091] Since the force is zero, the velocity of the liquid film on the pipe wall is zero. The boundary conditions near the pipe wall are:

[0092]

[0093] At the other end of the liquid film, near the air core, the air core provides an upward drag force to the liquid film, specifically expressed as:

[0094]

[0095] In the formula, τ i δ represents the drag force, Pa; δ represents the liquid film thickness, m.

[0096] Therefore, ignoring the pressure gradient, equation (1) can be simplified to:

[0097]

[0098] By combining expressions (3), (4), and (5) and performing integration, the velocity distribution expression of the liquid film along the gas core direction is obtained as follows:

[0099]

[0100] The liquid film flow rate can be obtained by radially integrating the liquid film velocity:

[0101]

[0102] In the formula, Q f For liquid film flow rate, m 3 / s.

[0103] Using Taylor expansion to simplify equation (7), we obtain the expression for the liquid film flow rate as follows:

[0104]

[0105] Therefore, the expression for the liquid film thickness can be derived from equation (8):

[0106]

[0107] During the flow of annular flow, the gas core entrains liquid droplets, therefore the expression for the liquid film flow rate is:

[0108] Q f =Q L ·(1-fE (10)

[0109] In the formula, Q L For the influent volume, m 3 / s;f E denoted as droplet entrainment rate, a decimal.

[0110] From the force analysis, it can be seen that to avoid the shear force being zero, the air core drag force is equal to the gravity:

[0111] τ i =δρ L g; (11)

[0112] The internal shear force is expressed by the equation concerning the airflow velocity:

[0113]

[0114] In the formula, f i ρ is the internal friction factor, which is dimensionless; c The density of the air core is kg / m³. 3 ;v SG It is the apparent velocity or equivalent velocity of the gas phase (gas), in m / s.

[0115] The internal friction factor is selected from the empirical expression proposed by Fore:

[0116]

[0117] In the formula, Re G — Gas Reynolds number, dimensionless.

[0118] From equations (9), (11) and (12), the corresponding airflow velocity when the liquid film reverses can be obtained:

[0119]

[0120] In the formula, v SG,R The airflow velocity is the airflow velocity corresponding to the zero wall shear force.

[0121] In this way, the transition boundary between the annular flow and the pseudo-annular flow can be determined.

[0122] Step 203: Based on the experimental data, construct a flow pattern diagram, which is used to characterize the correspondence between the wellbore flow pattern and the fluid velocity, the gas velocity, and the pipe inner diameter.

[0123] Because the transition boundaries between pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow are complex and variable, the practical application results of simplified theoretical models are far inferior to those of empirical models. Therefore, in order to accurately predict the transition boundaries between pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, this application adopts the prediction method of empirical models.

[0124] Specifically, after obtaining the experimental data, the experimental results of wellbore flow patterns with different gas flow rates, liquid flow rates and pipe inner diameters (oil tubing sizes) can be recorded in the statistical chart to draw the flow pattern chart of the wellbore flow pattern.

[0125] In this application, the vertical axis of the statistical graph is... The x-axis is

[0126] Where, ρ l ρ is the density of the liquid phase. g v is the gas phase density. SL v is the apparent velocity or equivalent velocity of the liquid phase. SG denoted as the apparent velocity of the gas phase, g is the acceleration due to gravity, and D is the pipe diameter.

[0127] It is understandable that gas wellbore pressures are extremely high, reaching tens or even hundreds of megapascals. Existing visualization experimental conditions are insufficient to replicate such high pressures, thus making it impossible to fully simulate wellbore conditions and predict wellbore flow patterns. For high-pressure gas wells and medium-to-low-pressure experiments, the biggest difference lies in the gas density, which changes with pressure. Therefore, this application constructs a dimensionless criterion through flow similarity, based on the density ratio between the gas and liquid phases, combined with the kinetic energy ρv. 2 The flow pattern was created by taking into account the pipe diameter and then taking the square root. This resulted in a flow pattern chart that comprehensively considered factors such as gas velocity, liquid velocity, and pressure. Thus, in the application of this method in a real well, by calculating the density of the gas well under different pressures and gas volumes, a similarity criterion was calculated. Using this similarity criterion value, the corresponding apparent gas velocity at normal pressure was calculated, and the flow pattern chart was then used to obtain the gas well flow pattern.

[0128] Step 204: Based on the flow pattern diagram, fit the transition boundaries of the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow.

[0129] After obtaining the flow pattern chart, the distribution area of ​​different wellbore flow patterns in the statistical chart can be observed to determine the transition boundary between different wellbore flow patterns. The empirical relationship between the transition of different wellbore flow patterns can be fitted to obtain the expression of the transition boundary between different wellbore flow patterns.

[0130] Specifically, to determine the transition boundary between the pseudo-annular flow and the pseudo-slug flow, we can first observe the distribution areas of the pseudo-annular flow and the pseudo-slug flow in the statistical graph, determine the flow pattern transition boundary between the pseudo-annular flow and the pseudo-slug flow, and fit the coefficients a, b, c, d of the empirical relation of the flow pattern transition boundary to obtain the expression of the flow pattern transition boundary between the pseudo-annular flow and the pseudo-slug flow.

[0131] The expression for the flow pattern transition boundary between pseudo-annular flow and pseudo-slug flow is as follows:

[0132]

[0133] In the formula, a, b, c, and d are the fitting coefficients of the transition boundary expression between pseudo-annular flow and pseudo-slug flow.

[0134] To determine the transition boundary between the pseudo-slug flow and the slug flow, we can first observe the distribution areas of the pseudo-slug flow and the slug flow in the statistical chart, determine the flow pattern transition boundary between the pseudo-slug flow and the slug flow in the flow pattern chart, and fit the coefficients n, m, g, h and Z1 of the empirical relation of the flow pattern transition boundary to obtain the expression of the flow pattern transition boundary between the pseudo-slug flow and the slug flow.

[0135] The expression for the flow pattern transition boundary between pseudo-slug flow and slug flow is as follows:

[0136]

[0137]

[0138] In the formula, n, m, g, h, and Z1 are the fitting coefficients of the transition boundary expression between pseudo-slug flow and slug flow.

[0139] To determine the transition boundary between slug flow and bubble flow, we can first observe the distribution areas of slug flow and bubble flow in the statistical chart, determine the flow pattern transition boundary between slug flow and bubble flow in the flow pattern chart, and fit the coefficients p, q, j, k and Z2 of the empirical relation of the flow pattern transition boundary to obtain the expression of the flow pattern transition boundary between slug flow and bubble flow.

[0140] The expression for the flow pattern transition boundary between slug flow and bubbly flow is as follows:

[0141]

[0142] In the formula, p, q, j, k, and Z2 are the fitting coefficients of the transition boundary expression between slug flow and bubbly flow.

[0143] In summary, the transition boundaries between pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow have been determined, enabling accurate prediction of wellbore flow patterns in gas wells.

[0144] In this embodiment, experimental parameters can be determined by combining the production dynamic characteristics of the target gas well with the fluid mechanics similarity criteria, and gas-liquid two-phase flow pattern experiments can be carried out to observe the flow pattern characteristics under different experimental conditions, determine the wellbore flow pattern, and record the gas flow velocity, liquid flow velocity, and tubing inner diameter corresponding to the flow pattern transition boundary. Through the above-mentioned method for determining the flow pattern transition boundary of the gas well, the expression for the flow pattern transition boundary of the target gas well is established, thereby achieving accurate prediction of the wellbore flow pattern of the target gas well.

[0145] In some embodiments, after constructing the flow pattern chart, it can be verified using example wells. Specifically, production data of example wells, such as the target gas well, can be obtained, including daily gas production, daily fluid production, wellhead oil pressure, wellhead temperature, and tubing temperature; then, based on the production data and the flow pattern chart, the flow pattern category of the target gas well can be determined.

[0146] Specifically, the flow pattern in the wellbore can be determined using the fluid dynamics similarity principle in step 204. Specifically, the apparent gas velocity v can be calculated based on production data. SG and apparent flow rate v of the liquid phase SL Then, the apparent gas velocity v was obtained through calculation. SG and apparent flow rate v of the liquid phase SL ,calculate and Then, by combining the flow pattern diagram, the flow pattern of the gas well can be obtained.

[0147] Among them, the apparent flow rate v of the liquid phase SL The calculation formula is: In the formula, Q SL Gas well production rate, m 3 / s; A is the cross-sectional area of ​​the oil pipe, m 2 .

[0148] Gas density ρ under different pressure conditions G The calculation formula is as follows: In the formula, p is the pressure (MPa), M is the relative molecular mass of natural gas (g / mol), T is the temperature (K), and R is the ideal gas constant, 0.008314 atm·m. 3 / (kmol·K), where Z is the deviation factor and has no dimension;

[0149] apparent gas flow rate v SG The calculation formula is: In the formula, Q SG For gas production, m 3 / s.

[0150] In this way, the wellbore flow pattern of the example well can be accurately predicted.

[0151] The method for determining the flow pattern transition boundary in gas wells provided in this application utilizes a multiphase pipe flow experimental platform to conduct gas-liquid two-phase flow pattern experiments. Experimental parameters for pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow are obtained through these experiments. A flow pattern chart comprehensively considering factors such as gas velocity, liquid velocity, and pressure is plotted, and the flow pattern transition boundary is fitted to determine the relationship between the transition boundaries of different flow patterns. The flow pattern transition boundary between annular flow and pseudo-annular flow is determined using the liquid film reversal theory. This enables accurate prediction of the flow pattern in gas wells, providing guidance for the optimized design of gas well drainage and gas production processes.

[0152] The following is a specific embodiment to illustrate the method for determining the flow pattern transition boundary of a gas wellbore provided in this application.

[0153] First, based on the flow patterns involved in gas well production, namely annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, physical simulation experiments of gas wellbore flow patterns were conducted. The inner diameter of the test pipe section was consistent with the inner diameter of the actual tubing, and wellbore flow patterns with different liquid flow velocities, gas flow velocities, and tubing inner diameters were obtained. To ensure the accuracy and repeatability of the experiment, the gas flow rate and liquid flow rate were stabilized, and observation and recording began after three minutes. The experiment was repeated three times and cross-validated. Some experimental results are shown in Table 1.

[0154] Table 1. Statistical Table of Experimental Flow Patterns

[0155]

[0156]

[0157] Then, the boundary between annular and pseudo-annular flow patterns was determined. A theoretical model was used to conduct a force analysis on the liquid film. The gas-liquid velocity corresponding to zero wall shear force was taken as the boundary for the transition. The specific calculation is as follows:

[0158] The force analysis is carried out in cylindrical coordinates with the liquid film as the research object, and the specific expression is given in Equation (1). The boundary between annular flow and quasi-annular flow is that the wall shear force is zero. Therefore, the solution boundary conditions near the pipe wall are given in Equation (2).

[0159] Since the force is zero, the flow velocity of the liquid film on the pipe wall is zero. The boundary conditions for solving near the pipe wall are shown in equation (3).

[0160] At the other end of the liquid film, near the air core, the air core provides an upward drag force to the liquid film, as detailed in equation (4). Therefore, ignoring the pressure gradient, equation (1) can be simplified to equation (5).

[0161] By combining expressions (3), (4) and (5) and performing integration, the velocity distribution expression of the liquid film along the gas core direction is obtained, as shown in equation (6).

[0162] The liquid film flow rate can be obtained by radial integration of the liquid film velocity, as shown in Equation (7). Simplifying Equation (7) using the Taylor expansion yields the liquid film flow rate expression, as shown in Equation (8). Furthermore, the liquid film thickness expression is derived from Equation (8), as shown in Equation (9). During the annular flow, the gas core carries liquid droplets; therefore, the liquid film flow rate expression is shown in Equation (10).

[0163] From the force analysis, it can be seen that to avoid the shear force being zero, the air core drag force is equal to the gravity, see equation (11). The internal shear force is an equation about the air velocity, see equation (12). The internal friction factor adopts the empirical expression proposed by Fore, see equation (13).

[0164] The corresponding airflow velocity when the liquid film reverses can be obtained from equations (9), (11) and (12), see equation (14).

[0165] Then, the flow pattern transition boundary between pseudo-annular flow and pseudo-slug flow was determined. The experimental results of wellbore flow patterns with different gas flow velocities, fluid flow velocities, and tubing sizes were recorded in a statistical graph. The vertical axis of the statistical graph is... The x-axis is By observing the distribution regions of pseudo-annular flow and pseudo-slug flow in the statistical graph, the flow pattern transition boundary between pseudo-annular flow and pseudo-slug flow is determined, and the coefficients of the empirical relationship for the flow pattern transition are fitted. The expression for the flow pattern transition boundary between pseudo-annular flow and pseudo-slug flow is as follows:

[0166]

[0167] Then, the flow pattern transition boundary between pseudo-slug flow and slug flow is determined. The distribution areas of pseudo-slug flow and slug flow in the statistical chart are observed. The flow pattern transition boundary between pseudo-slug flow and slug flow in the flow pattern chart is determined. The coefficients of the empirical relational expression for the flow pattern transition are fitted. The expression for the flow pattern transition boundary between pseudo-slug flow and slug flow is as follows:

[0168]

[0169] Then, the flow pattern transition boundary between slug flow and bubbly flow is determined. The distribution areas of slug flow and bubbly flow in the statistical chart are observed. The flow pattern transition boundary between slug flow and bubbly flow in the flow pattern chart is determined, and the coefficients of the empirical relational formula for flow pattern transition are fitted. The expression for the flow pattern transition boundary between slug flow and bubbly flow is as follows:

[0170]

[0171] Assume the production data of the gas wells (example wells) in the target block are: daily gas production 1.68 × 10⁻⁶. 4 m 3 / d, Daily liquid production 3.1m 3 The parameters were: wellhead oil pressure 3.17 MPa, wellhead temperature 23℃, and tubing inner diameter 42.8 mm. The experimental parameter range was determined using the principle of fluid mechanics similarity, and the calculation results are shown in Table 2.

[0172] Table 2 Experimental parameter range

[0173]

[0174]

[0175] Based on the defined experimental parameter range, the above-mentioned gas-liquid two-phase flow pattern experiments were carried out, and a wellbore flow pattern diagram of the target block gas well was constructed (e.g., Figure 3 (As shown) After combining the production data of the gas wells in the target block with the constructed gas wellbore flow pattern diagram, it can be seen that the flow pattern of the gas well is mainly annular flow, such as Figure 3 As shown.

[0176] The following describes an embodiment of the apparatus described in this application, which can be used to execute the method for determining the flow pattern transition boundary of a gas wellbore in the above embodiments of this application. For details not disclosed in the apparatus embodiments of this application, please refer to the embodiments of the method for determining the flow pattern transition boundary of a gas wellbore described above in this application.

[0177] Figure 4 A block diagram of a device for determining the flow pattern transition boundary of a gas wellbore according to an embodiment of this application is shown. Figure 4 As shown in the embodiment of this application, the device for determining the transition boundary of gas well flow pattern includes: an experimental data acquisition module 401, used to acquire multiple sets of experimental data of well flow patterns, wherein the well flow patterns include annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubbly flow, and the experimental data includes the liquid velocity, gas velocity, and pipe inner diameter corresponding to the well flow pattern; a theoretical boundary determination module 402, used to determine the transition boundary between the annular flow and the pseudo-annular flow based on the liquid film reversal theory and the experimental data; a flow pattern map construction module 403, used to construct a flow pattern map based on the experimental data, the flow pattern map being used to characterize the correspondence between the well flow pattern and the liquid velocity, the gas velocity, and the pipe inner diameter; and a fitting boundary determination module 404, used to fit the transition boundaries of the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubbly flow based on the flow pattern map, to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubbly flow.

[0178] In some embodiments of this application, based on the foregoing scheme, the flow pattern diagram construction module 403 is further configured to draw a statistical chart of the wellbore flow pattern according to the experimental data, wherein the vertical axis of the statistical chart is... The x-axis is Where, ρ l ρ is the density of the liquid phase. g v is the gas phase density. SL v is the apparent flow rate of the liquid phase. SG denoted as the apparent velocity of the gas phase, g is the acceleration due to gravity, and D is the pipe diameter.

[0179] In some embodiments of this application, based on the foregoing scheme, the fitting boundary determination module 404 is further configured to fit the transition boundary formula between the pseudo-annular flow and the pseudo-slug flow according to the flow pattern diagram; wherein, the transition boundary formula between the pseudo-annular flow and the pseudo-slug flow is:

[0180]

[0181] a, b, c, and d are the fitting coefficients.

[0182] In some embodiments of this application, based on the foregoing scheme, the fitting boundary determination module 404 is further configured to fit the transition boundary formula between the pseudo-slug flow and the slug flow according to the flow pattern diagram; wherein, the transition boundary formula between the pseudo-slug flow and the slug flow is:

[0183]

[0184]

[0185] n, m, g, h, and Z1 are the fitting coefficients.

[0186] In some embodiments of this application, based on the foregoing scheme, the fitting boundary determination module 404 is further configured to fit the transition boundary formula between the slug flow and the bubbly flow according to the flow pattern diagram; wherein, the transition boundary formula between the slug flow and the bubbly flow is:

[0187]

[0188]

[0189] p, q, j, k, and Z2 are the fitting coefficients.

[0190] In some embodiments of this application, based on the aforementioned scheme, the theoretical limit determination module 402 is further used to perform a force analysis on the liquid film on the pipe wall according to the liquid film reversal theory and the experimental data; and to determine the transition limit between the annular flow and the pseudo-annular flow when the wall shear force of the liquid film is zero.

[0191] In some embodiments of this application, based on the foregoing scheme, the theoretical limit determination module 402 is further configured to determine the gas flow velocity corresponding to the zero wall shear force of the liquid film as the transition limit between the annular flow and the pseudo-annular flow; wherein, the gas flow velocity corresponding to the zero wall shear force of the liquid film is determined based on the following formula:

[0192]

[0193] v SG,R Let ρ be the first airflow velocity. L Let g be the liquid density, g be the gravitational acceleration, δ be the liquid film thickness, and r be the liquid film density. o f is the pipe radius. i ρ is the internal friction factor. c This represents the core density.

[0194] In some embodiments of this application, based on the foregoing scheme, the device further includes a prediction module (not shown) for acquiring production data of the target gas well; and determining the flow pattern category of the target gas well based on the production data and the flow pattern chart.

[0195] Based on the same inventive concept, this application also provides a device for determining the flow pattern transition boundary of a gas wellbore, see reference. Figure 5 The diagram shows a schematic of the structure of a device for determining the flow pattern transition limit of a gas well shaft according to an embodiment of this application. The device for determining the flow pattern transition limit of a gas well shaft includes one or more memories 504, one or more processors 502, and at least one computer program (computer program instructions) stored in the memory 504 and executable on the processor 502. When the processor 502 executes the computer program, it implements the method described above.

[0196] Among them, Figure 5In this document, a bus architecture (represented by bus 500) is used. Bus 500 may include any number of interconnected buses and bridges, linking various circuits including one or more processors represented by processor 502 and memory represented by memory 504. Bus 500 may also link various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. Bus interface 505 provides an interface between bus 500 and receiver 501 and transmitter 503. Receiver 501 and transmitter 503 may be the same element, i.e., a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 502 is responsible for managing bus 500 and general processing, while memory 504 can be used to store data used by processor 502 during operation.

[0197] Based on the same inventive concept, embodiments of this application provide a computer-readable storage medium storing computer program instructions, which, when executed by a processor, cause the processor to perform the steps of the method described above.

[0198] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Other examples and embodiments are within the scope and spirit of this application and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Furthermore, the functional units may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit.

[0199] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0200] The units described as separate components may or may not be physically separate. Similarly, the components of the control device may or may not be physical units; they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0201] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing computer program instructions, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0202] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for determining the flow pattern transition boundary of a gas wellbore, characterized in that, include: Multiple sets of experimental data for wellbore flow patterns were obtained, including annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubble flow. The experimental data included the fluid velocity, gas velocity, and pipe inner diameter corresponding to the wellbore flow pattern. Based on the liquid film reversal theory and the experimental data, the transition boundary between the annular flow and the pseudo-annular flow was determined. Based on the experimental data, a flow pattern diagram is constructed, which is used to characterize the correspondence between the wellbore flow pattern and the fluid velocity, the gas velocity, and the pipe inner diameter; Based on the flow pattern diagram, the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow are fitted to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow.

2. The method according to claim 1, characterized in that, The step of constructing a manifold chart based on the experimental data includes: Based on the experimental data, a statistical graph of the wellbore flow pattern was plotted, with the vertical axis of the statistical graph being... The x-axis is where p l is the liquid density, p g is the gas density, v SL is the liquid superficial velocity, v SG is the gas superficial velocity, g is the gravitational acceleration, and D is the pipe diameter.

3. The method according to claim 2, characterized in that, The fitting of the transition boundary between the pseudo-annular flow and the pseudo-slug flow based on the flow pattern diagram includes: Based on the flow pattern diagram, a transition boundary formula between the pseudo-annular flow and the pseudo-slug flow is fitted; wherein, the transition boundary formula between the pseudo-annular flow and the pseudo-slug flow is: a, b, c, and d are the fitting coefficients.

4. The method according to claim 2, characterized in that, The step of fitting the transition boundary between the pseudo-slug flow and the slug flow based on the flow pattern diagram includes: Based on the flow pattern diagram, a transition boundary formula between the pseudo-slug flow and the slug flow is fitted; wherein, the transition boundary formula between the pseudo-slug flow and the slug flow is: n, m, g, h, and Z1 are the fitting coefficients.

5. The method according to claim 2, characterized in that, The step of fitting the transition boundary between the slug flow and the bubbly flow based on the flow pattern diagram includes: Based on the flow pattern diagram, a transition boundary formula between the slug flow and the bubbly flow is fitted; wherein, the transition boundary formula between the slug flow and the bubbly flow is: p, q, j, k, and Z2 are the fitting coefficients.

6. The method according to claim 1, characterized in that, The determination of the transition boundary between the annular flow and the pseudo-annular flow based on the liquid film reversal theory and the experimental data includes: Based on the liquid film reversal theory and the experimental data, the force analysis of the liquid film on the tube wall is performed. When the wall shear force of the liquid film is determined to be zero, it corresponds to the transition boundary between the annular flow and the pseudo-annular flow.

7. The method according to claim 6, characterized in that, The determination that the wall shear force of the liquid film is zero corresponds to the transition boundary between the annular flow and the pseudo-annular flow, including: The gas flow velocity corresponding to zero wall shear force of the liquid film is determined as the transition boundary between the annular flow and the pseudo-annular flow; wherein, the gas flow velocity corresponding to zero wall shear force is determined based on the following formula: v SG,R is the gas flow rate corresponding to the wall shear force of zero, p L is the liquid phase density, g is the gravitational acceleration, δ is the liquid film thickness, r o is the pipe radius, f i is the internal friction factor, p c is the gas core density.

8. The method according to any one of claims 1-7, characterized in that, The method further includes: Obtain production data from the target gas well; Based on the production data and the flow pattern chart, the flow pattern category of the target gas well is determined.

9. A device for determining the flow pattern transition boundary of a gas wellbore, characterized in that, The device includes: The experimental data acquisition module is used to acquire multiple sets of experimental data for wellbore flow patterns, including annular flow, pseudo-annular flow, pseudo-slug flow, slug flow, and bubble flow. The experimental data includes the liquid velocity, gas velocity, and pipe inner diameter corresponding to the wellbore flow pattern. The theoretical limit determination module is used to determine the transition limit between the annular flow and the pseudo-annular flow based on the liquid film reversal theory and the experimental data. The flow pattern diagram construction module is used to construct a flow pattern diagram based on the experimental data. The flow pattern diagram is used to characterize the correspondence between the wellbore flow pattern and the fluid velocity, the gas velocity, and the pipe inner diameter. The fitting boundary determination module is used to fit the transition boundaries of the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow according to the flow pattern diagram, so as to obtain the transition boundaries between the pseudo-annular flow, the pseudo-slug flow, the slug flow, and the bubble flow.

10. A device for determining the flow pattern transition boundary of a gas wellbore, comprising a processor and a memory, characterized in that, The memory stores computer program instructions that can be executed by the processor, and when the processor executes the computer program instructions, it implements the steps of the method as described in any one of claims 1 to 8.

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