Method for evaluating variable flow state sand carrying capacity of ultra-deep high-pressure gas well

Abstract

The invention provides an ultra-deep high-pressure gas well variable-flow-state sand-carrying capacity evaluation method, and relates to the technical field of oil-gas exploration, and the method comprises the steps: collecting well logging data of a target gas well, constructing a gas-liquid two-phase flow parameter expression, and carrying out the quantitative analysis of key flow characteristics such as the gas content and the speed; a mathematical model is established by applying an H-K flow state judgment criterion, and numerical simulation is performed in combination with fluid dynamics simulation software, so that the flow state in the shaft is accurately identified and distinguished; then, according to high-temperature and high-pressure characteristics under actual working conditions and sand shape information monitored in a mine field, carrying out secondary correction on the resistance coefficient CD so as to improve a sand-carrying capacity prediction model; and finally, the critical sand-carrying flow velocity and yield are calculated based on the corrected model, and a scientific basis is provided for setting the sand-carrying capacity and reasonable production parameters of the gas well in different flow states. Safe and efficient development of a gas reservoir is guided, production parameter setting is optimized, and long-term stable and efficient operation of a gas well is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and in particular to a method for evaluating the variable flow state sand carrying capacity of an ultra-deep high-pressure gas well. Background Art

[0002] In the current field of oil and gas field development, ultra-deep, high-temperature, and high-pressure sandstone gas reservoirs, characterized by "three highs and one depth," possess enormous reserves and significant production potential. However, due to their great depth and extremely high reservoir temperatures and pressures, these reservoirs face a series of severe technical challenges in actual production. Specifically, due to insufficient understanding of the complex multiphase fluid flow patterns within the wellbores of ultra-deep, high-pressure gas wells, it is impossible to accurately predict the sand-carrying capacity under different flow conditions (such as bubbly flow, slug flow, and annular mist flow), which directly restricts the safe and efficient production of gas wells.

[0003] In this context, the flow characteristics of gas-liquid two-phase flow are crucial to the proper operation of vertical gas wells. Key parameters involved, such as temperature, pressure, flow rate, density, and cross-sectional gas fraction, are crucial for the safe and efficient operation of high-pressure gas wells. Existing technologies lack sufficient understanding of these key parameters and their correlation with sand-carrying capacity. This can lead to inappropriate parameter design during gas well production, impacting both production efficiency and safety.

[0004] Therefore, there is an urgent need to develop a new method specifically for evaluating the sand-carrying capacity of ultra-deep and high-pressure gas wells with variable flow regimes, so as to clarify the flow pattern distribution and conversion rules in the wellbore based on field practice, accurately evaluate the sand-carrying performance under different flow regimes, and scientifically formulate production parameters based on this, to ensure that gas wells can achieve safe and efficient long-term mining under complex working conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for evaluating the variable flow state sand carrying capacity of ultra-deep, high-temperature, and high-pressure gas wells, in view of the problem of inaccurate prediction of the sand carrying capacity under complex flow patterns in the wellbore. The method accurately evaluates the sand carrying capacity by precisely judging the wellbore flow pattern, clarifying the multiphase flow law, and correcting the resistance coefficient.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for evaluating the variable flow sand carrying capacity of an ultra-deep high-pressure gas well comprises the following steps:

[0008] S1: Data acquisition and parameter construction: Collect the target gas well logging data and construct the main parameters and calculation expressions of gas-liquid two-phase flow based on these data;

[0009] S2: Flow pattern identification: Based on the HK (Hasan & Kabir) flow pattern identification criterion, the specific flow pattern in the target gas wellbore is determined;

[0010] S3: Model establishment and numerical simulation: Based on the parameters and expressions constructed in S1 and the flow pattern determined in S2, a high-pressure gas wellbore multiphase flow model is established using fluid dynamics software; the model is run and simulation results are obtained;

[0011] S4: Based on the simulation results obtained in S3, the flow pattern conversion boundary of the high-pressure gas wellbore multiphase flow model is identified and corrected;

[0012] S5: Based on the high-pressure gas wellbore multiphase flow model obtained in S4, the sand-carrying capacity of ultra-deep gas wellbore is evaluated.

[0013] Furthermore, between steps S4 and S5, there is also a step S420: modifying the resistance coefficient of the existing gas well critical sand carrying velocity model, and modifying the flow resistance coefficient C under different flow states according to the wellbore flow type identified in S2. D Make corrections.

[0014] Furthermore, step S420 includes the following steps:

[0015] S421: Based on the empirical formula for sand carrying in gas wells under turbulent flow conditions, the first-order correction coefficient α is obtained by reverse calculation, and a calculation model for spherical sand carrying suitable for high-pressure gas wells is established;

[0016] S422: In view of the influence of non-spherical sand shape, a quadratic correction coefficient β is introduced to further correct the resistance coefficient, forming a critical sand-carrying velocity model that takes into account the influence of sand shape.

[0017] Furthermore, the existing critical sand-carrying velocity model for gas wells is:

[0018]

[0019] The calculation model for spherical sand particles carrying sand in high-pressure gas wells is:

[0020]

[0021] The critical sand-carrying velocity model established considering the wellhead sand particle shape is:

[0022]

[0023] v c —Final settling velocity of solid particles, m / s; ρ s —Solid particle density, kg / m 3 ρ f —Density of mixed fluid, kg / m 3 ;

[0024] —Pressure gradient in the wellbore, MPa / m; C D —Drag coefficient, dimensionless; g—acceleration due to gravity, m / s 2 ;α—first-order correction coefficient, dimensionless; β—second-order correction coefficient, dimensionless.

[0025] Further: in step S1, the main parameters of the gas-liquid two-phase flow are constructed, including mass flow rate, mass velocity, volume flow rate, volume flow velocity, volume phase fraction, converted velocity, gas-liquid phase real flow velocity, gas phase apparent velocity, liquid phase apparent velocity, cross-sectional gas fraction, mass gas content, mixed phase real density, and mixed phase flow density.

[0026] Furthermore: in step S3, the obtained simulation results include a gas content cloud map and a miscible phase velocity cloud map of the wellbore cross section.

[0027] Furthermore, the specific steps of step S4 are to observe the changes in the wellbore flow pattern by adjusting the gas content, and clarify the conversion boundaries of the flow pattern under different gas content; based on the cross-sectional gas content cloud map and miscible velocity cloud map data obtained by simulation, multi-data fitting is performed on the original HK (Hasan & Kabir) flow pattern discrimination formula, and then a flow pattern discrimination expression suitable for the high-pressure gas well environment is constructed.

[0028] Furthermore: In S2, the HK (Hasan & Kabir) flow state judgment criterion is:

[0029] For bubbly flow:

[0030]

[0031] For slug flow:

[0032]

[0033] when

[0034] when

[0035] For annular flow:

[0036] v sg >0.4745(998-ρ g ) 0.25 v sl

[0037] Where, v sg is the gas phase superficial velocity; v sl is the liquid phase superficial velocity; ρ l is the liquid density, unit is kg / m 3 ρ gis the gas phase density, unit is kg / m3; g is the acceleration due to gravity, unit is m / s 2 ;σ is the surface tension, unit is N / m.

[0038] Compared with the original technology, the present invention has the following beneficial effects:

[0039] 1. Accurately Identify and Predict Wellbore Flow Patterns and Sand-Carrying Capacity: This technical solution collects gas well logging data, constructs and calculates key multiphase flow parameters, and combines them with the Hasan & Kabir flow pattern discrimination criteria to establish a method that can effectively distinguish different flow patterns (such as bubbly flow, slug flow, and annular mist flow) in ultra-deep, high-pressure gas wells. By clarifying the flow patterns within the wellbore, it can more accurately evaluate the sand-carrying capacity of gas wells under different flow patterns, thus resolving the problem of inaccurate predictions caused by a lack of understanding of complex flow patterns in existing technologies.

[0040] 2. Optimizing the resistance coefficient to adapt to high-pressure environment: In view of the actual working conditions and sand production monitoring of high-pressure gas wells, the inventors optimized the flow resistance coefficient C in the existing sand carrying formula. D A secondary correction was performed by introducing a primary correction coefficient α and a secondary correction coefficient β that considers the influence of sand particle shape. This made the calculation model more able to reflect the resistance changes in the actual sand carrying process of high-pressure gas wells and improved the accuracy of the critical sand carrying velocity calculation.

[0041] 3. Guiding safe and efficient mining and production parameter setting: Based on the improved sand-carrying prediction model, the critical sand-carrying production of high-pressure gas wells under different flow states can be accurately calculated, and then production parameters can be scientifically and rationally formulated to ensure that the gas wells can effectively carry sand and ensure safe production under various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Flowchart of a method for evaluating the sand-carrying capacity of ultra-deep, high-pressure gas wells with variable flow regimes

[0043] Figure 2 Schematic diagram of the main flow patterns in the vertical gas well pipeline of the present invention;

[0044] Figure 3 Schematic diagram of bubbling flow in the wellbore of an ultra-deep high-pressure gas well according to the present invention;

[0045] Figure 4 Schematic diagram of slug flow in the wellbore of an ultra-deep high-pressure gas well according to the present invention;

[0046] Figure 5 This is a schematic diagram of the annular mist flow in the ultra-deep high-pressure gas well of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] A method for evaluating the variable flow sand carrying capacity of an ultra-deep high-pressure gas well comprises the following steps:

[0050] S1: Data acquisition and parameter construction: Collect target gas well logging data and construct the main parameters and calculation expressions of gas-liquid two-phase flow based on these data. The main parameters include mass flow rate, mass velocity, volume flow rate, volume flow velocity, volume phase holdup, converted velocity, gas-liquid phase true flow velocity, gas phase apparent velocity, liquid phase apparent velocity, cross-sectional gas holdup, mass gas holdup, miscible phase true density, and miscible phase flowing density;

[0051] S2: Flow pattern identification: Based on the HK (Hasan & Kabir) flow pattern identification criterion, the specific flow pattern in the target gas wellbore is determined;

[0052] S3: Model establishment and numerical simulation: Based on the parameters and expressions constructed in S1 and the flow pattern determined in S2, a multiphase flow model for the high-pressure gas wellbore is established using fluid dynamics software. The model is run and simulation results are obtained, including a cloud diagram of the gas fraction and miscible velocity in the wellbore cross section.

[0053] S4: Based on the simulation results obtained in S3, the flow pattern conversion boundaries of the high-pressure gas wellbore multiphase flow model are identified and corrected. The specific steps are as follows: by adjusting the gas fraction, the changes in the wellbore flow pattern are observed, and the flow pattern conversion boundaries under different gas fractions are clarified; based on the cross-sectional gas fraction cloud map and miscible phase velocity cloud map data obtained by simulation, the original HK (Hasan & Kabir) flow pattern discrimination formula is fitted with multiple data, and then a flow pattern discrimination expression suitable for the high-pressure gas well environment is constructed;

[0054] S420: Modify the resistance coefficient of the existing gas well critical sand carrying velocity model. According to the wellbore flow pattern identified in S2, the flow resistance coefficient C under different flow states is modified. D Make corrections;

[0055] S5: Based on the high-pressure gas wellbore multiphase flow model obtained in S4, the sand-carrying capacity of ultra-deep gas wellbore is evaluated.

[0056] In some embodiments: in S2, the HK (Hasan & Kabir) flow state judgment criterion is:

[0057] For bubbly flow:

[0058]

[0059] For slug flow:

[0060]

[0061] when

[0062] when

[0063] For annular flow:

[0064] v sg >0.4745(998-ρ g ) 0.25 v sl

[0065] Where, v sg is the gas phase superficial velocity; v sl is the liquid phase superficial velocity; ρ l is the liquid density, unit is kg / m 3 ρ g is the gas phase density, unit is kg / m3; g is the acceleration due to gravity, unit is m / s 2 ;σ is the surface tension, unit is N / m.

[0066] In some other embodiments, step S420 includes the following steps:

[0067] S421: Based on the empirical formula for sand carrying in gas wells under turbulent flow conditions, the first-order correction coefficient α is obtained by reverse calculation, and a calculation model for spherical sand carrying suitable for high-pressure gas wells is established;

[0068] S422: In view of the influence of non-spherical sand shape, a quadratic correction coefficient β is introduced to further correct the resistance coefficient, forming a critical sand-carrying velocity model that takes into account the influence of sand shape.

[0069] Among them: The existing critical sand-carrying velocity model of gas wells is:

[0070]

[0071] The calculation model for spherical sand particles carrying sand in high-pressure gas wells is:

[0072]

[0073] The critical sand-carrying velocity model established considering the wellhead sand particle shape is:

[0074]

[0075] v c —Final settling velocity of solid particles, m / s; ρ s —Solid particle density, kg / m 3 ρ f —Density of mixed fluid, kg / m 3 ;

[0076] —Pressure gradient in the wellbore, MPa / m; C D —Drag coefficient, dimensionless; g—acceleration due to gravity, m / s 2 ;α—first-order correction coefficient, dimensionless; β—second-order correction coefficient, dimensionless.

[0077] In one embodiment:

[0078] In S3, the dimensions of the high-pressure gas wellbore multiphase flow model are constructed based on the target gas well reservoir parameters and tubing dimensions, consistent with actual field production conditions. In this simulation, the model dimensions used are: a gas well annulus pipe of 10,000 mm, with geometric dimensions of an outer pipe inner diameter of 139.7 mm and an inner pipe outer diameter of 125.43 mm. Once the model is established, the solution is performed. The main steps include:

[0079] Load the model and perform custom mesh division;

[0080] Set up a transient flow model, use a non-coupled solver, and consider the influence of gravity;

[0081] Set the multiphase flow model and select the VOF model among the multiphase component models;

[0082] Set the standard KE turbulence model;

[0083] Set the fluid material and properties, basic phase and secondary phase, add materials from the material library, set water as the basic phase and methane as the secondary phase.

[0084] Set the inlet and outlet conditions. The mixed phase adopts the pressure inlet boundary condition and sets the gas content at the mixed phase inlet to 1. The outlet adopts the pressure outlet boundary condition and sets the hydraulic diameter of the inlet and outlet to the casing equivalent diameter.

[0085] Set the time step size, number of time step iterations, and model calculations.

[0086] In S4, based on the cross-sectional gas content cloud map and mixed phase velocity cloud map under different temperature and pressure conditions, the flow pattern of the fluid in the wellbore is observed by adjusting the gas content. The common flow pattern distribution of vertical wellbore is referred to ( Figure 2 ), A, B, and C correspond to bubble flow, slug flow, and annular mist flow, respectively, to determine the flow pattern conversion boundaries of high-pressure gas wells under different gas holdup conditions.

[0087] Based on the simulation results, it can be seen that when the gas fraction f g <0.3, the gas well flow pattern is bubbly flow ( Figure 3 ); when the gas content is 0.3 <f g <0.45, the gas well flow pattern is slug flow ( Figure 4 ); when f g When >0.45, the gas well flow pattern is annular mist flow ( Figure 5 ).

[0088] Based on the expression of the final rising velocity of bubbles in vertical wells derived by Harmathy and the simulation results of gas void fraction and velocity contour, a functional relationship between gas void fraction and miscible phase velocity was fitted using a large amount of data:

[0089] The expression for the final rising velocity of the bubble is:

[0090]

[0091] Where: v ∞ —Final rising velocity of the bubble, m / s; σ—interfacial tension, N / m; ρ l —Liquid density, kg / m3; ρ g —Gas phase density, kg / m3.

[0092] Gas fraction f g and miscibility velocity v sl 、v sg The functional relationship is:

[0093] v sg =(1.2v sl f g +v ∞ f g ) / (1-f g )

[0094] Where: v sg —Gas phase superficial velocity, m / s; v sl —Liquid phase apparent velocity, m / s; f g —Void fraction, dimensionless.

[0095] Based on the above relationship, the discriminant expression of different flow patterns in high-pressure gas wells is reconstructed:

[0096] Bubble flow:

[0097] v sg <0.514v sl +0.428[gσ(ρ l -ρ g ) / (ρ l 2 )] 0.25

[0098] Slug flow:

[0099]

[0100] Circular mist flow:

[0101] v sg >0.062g(ρ l -ρ g ) 0.25 v sl

[0102] In step 5, based on the wellbore flow pattern determined in the previous step, the flow resistance coefficient CD under different flow states is corrected. The main steps are:

[0103] Based on the existing sand-carrying formula for gas wells under turbulent flow conditions, the reasonable flow resistance coefficient of gas wells in multiple production stages is obtained by reverse deduction, and the CD correction coefficient α (see Table 1) is obtained, thus obtaining a calculation model for spherical sand-carrying sand in high-pressure gas wells.

[0104] Existing gas well critical sand-carrying velocity model:

[0105]

[0106] Calculation model of critical sand-carrying velocity based on different flow pattern corrections:

[0107]

[0108] According to the shape of sand particles in the gas well, the drag coefficient in the airflow of non-spherical particles must be corrected by the resistance correction coefficient β (see Table 1).

[0109] Table 1

[0110]

[0111] The critical sand-carrying velocity model established considering the wellhead sand grain shape is:

[0112]

[0113] Where: vc —Final settling velocity of solid particles, m / s; ρ s —Solid particle density, kg / m3; ρ f —Density of mixed fluid, kg / m3; —pressure gradient in the wellbore, MPa / m; CD—drag coefficient, dimensionless; g—acceleration due to gravity, m / s2; α—primary correction coefficient, dimensionless; β—secondary correction coefficient, dimensionless.

[0114] Based on the critical sand-carrying velocity model under different assumptions, the critical production calculation formula for high-pressure gas wells is established:

[0115]

[0116] Where: Q c —critical sand-carrying gas volume, 104m3 / d; A—cross-sectional area of ​​the oil pipe, m2; p—formation pressure, MPa; T—formation temperature, k; Z—compression factor, dimensionless.

[0117] Based on the modified model equations (25) and (28), the sand carrying particle size of the high-pressure gas wellbore under the initial formation pressure conditions was calculated (Table 2). Combined with the actual sand carrying particle size of the high-pressure gas well on site, it was found that the modified model was consistent with the actual sand production situation, and the predicted sand carrying capacity met the on-site requirements.

[0118] Table 2

[0119]

[0120] To ensure safe and stable production of subsequent gas wells, the modified model was used to predict the particle size of sand carried in the wellbore under different operating conditions (temperature, pressure, and gas content) during multiple production stages of high-pressure gas wells (Table 3). This provides theoretical support for the rational formulation of production systems for ultra-deep, high-pressure gas wells.

[0121] Table 3

[0122]

[0123] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells, characterized by: The following steps are involved: S1: Data acquisition and parameter construction: Collect the target gas well logging data and construct the main parameters and calculation expressions of gas-liquid two-phase flow based on these data; S2: Flow pattern identification: Based on the HK (Hasan & Kabir) flow pattern identification criterion, the specific flow pattern in the target gas wellbore is determined; S3: Model establishment and numerical simulation: Based on the parameters and expressions constructed in S1 and the flow pattern determined in S2, a high-pressure gas wellbore multiphase flow model is established using fluid dynamics software, and the model is run to obtain simulation results. S4: Based on the simulation results obtained in S3, the flow pattern conversion boundary of the high-pressure gas wellbore multiphase flow model is identified and corrected; S5: Based on the high-pressure gas wellbore multiphase flow model obtained in S4, the sand-carrying capacity of ultra-deep gas wellbore is evaluated.

2. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 1, characterized in that: Between step S4 and step S5, there is also step S420: modifying the resistance coefficient of the existing gas well critical sand carrying velocity model, and calculating the flow resistance coefficient C under different flow states according to the wellbore flow pattern identified in step S2. D Make corrections.

3. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 2, characterized in that: Step S420 includes the following steps: S421: Based on the empirical formula for sand carrying in gas wells under turbulent flow conditions, the first-order correction coefficient α is obtained by reverse calculation, and a calculation model for spherical sand carrying suitable for high-pressure gas wells is established; S422: In view of the influence of non-spherical sand shape, a quadratic correction coefficient β is introduced to further correct the resistance coefficient, forming a critical sand-carrying velocity model that takes into account the influence of sand shape.

4. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 3, characterized in that: The existing critical sand-carrying velocity model for gas wells is: The calculation model for spherical sand particles carrying sand in high-pressure gas wells is: The critical sand-carrying velocity model established considering the wellhead sand particle shape is: v c —Final settling velocity of solid particles, m / s; ρ s —Solid particle density, kg / m 3 ; ρ f —Density of mixed fluid, kg / m 3 ; —Pressure gradient in the wellbore, MPa / m; C D —Drag coefficient, dimensionless; g—acceleration due to gravity, m / s 2 ;α—first-order correction coefficient, dimensionless; β—second-order correction coefficient, dimensionless.

5. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 1, characterized in that: In step S1, the main parameters for constructing the gas-liquid two-phase flow include mass flow rate, mass velocity, volume flow rate, volume flow velocity, volume phase holdup, converted velocity, gas-liquid phase true flow velocity, gas phase apparent velocity, liquid phase apparent velocity, cross-sectional gas holdup, mass gas holdup, mixed phase true density, and mixed phase flow density.

6. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 1, characterized in that: In step S3, the obtained simulation results include a gas content cloud map and a miscible phase velocity cloud map of the wellbore cross section.

7. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 6, characterized in that: The specific steps of step S4 are to observe the changes in the wellbore flow pattern by adjusting the gas content, and clarify the conversion boundary of the flow pattern under different gas content; based on the cross-sectional gas content cloud map and miscible velocity cloud map data obtained by simulation, perform multi-data fitting on the original HK (Hasan & Kabir) flow pattern discrimination formula, and then construct a flow pattern discrimination expression suitable for high-pressure gas well environments.

8. The method for evaluating the variable flow sand carrying capacity of ultra-deep high-pressure gas wells according to claim 1, characterized in that: In S2, the HK (Hasan & Kabir) flow state judgment criterion is: For bubbly flow: For slug flow: when when For annular flow: v sg >0.4745(998-ρ g ) 0.25 v sl Where, v sg is the gas phase superficial velocity; v sl is the liquid phase superficial velocity; ρ l is the liquid density, unit is kg / m 3 ; ρ g is the gas phase density, unit is kg / m3; g is the acceleration due to gravity, unit is m / s 2 ;σ is the surface tension, unit is N / m.

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