A method for calculating the liquid holdup of a high-pressure gas well

Abstract

The application provides a high-pressure gas well wellbore liquid holdup calculation method, which is based on a drift flux model, introduces a dimensionless phase superficial velocity in the form of Froude similarity parameter for pressure scaling, and is fitted through normal pressure experimental test data under a wide gas-liquid flow velocity range to accurately characterize the change rule of the liquid holdup with the dimensionless phase superficial velocity, and further forms an effective method suitable for high-pressure gas well wellbore liquid holdup calculation. The key parameter in the application is a multiplication coefficient of the dimensionless gas phase superficial velocity, which can accurately capture the distribution rule of the gas-liquid two-phase flow in a wide liquid flow velocity range, so that the method can ensure the calculation accuracy of high and low pressure pipe flow, does not need complex drift parameter implicit calculation and gas-liquid two-phase flow type judgment, is simple in form and convenient to operate, provides a convenient and efficient gas well wellbore liquid holdup prediction means for field operators and engineering and technical personnel in the oil and gas field development field, and has potential popularization and application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of gas reservoir drainage gas recovery, and particularly relates to a high-pressure gas well wellbore liquid holdup calculation method. TECHNICAL BACKGROUND

[0002] Wellbore liquid holdup refers to the proportion of liquid in the wellbore of the target well section under the production state of the water-producing gas well to the total volume thereof, and is one of important parameters for gas-liquid two-phase pipe flow pressure drop calculation. Accurate prediction of the liquid holdup is the core technology for optimizing the production system and drainage and recovery process parameters of the gas well. During the development of oil and gas fields, there are a large number of wellbore gas-liquid two-phase flows of high-pressure gas wells, and it is difficult to measure the real liquid holdup. Large-scale physical simulation experiments are often used to measure the liquid holdup under normal pressure flow conditions by relying on conductivity probes, wire mesh sensors, electrical capacitance or resistance tomography, fast valve flow sampling and other technologies. Limited by the two-phase flow experimental simulation size, equipment pressure-bearing capacity and operation safety and other factors, it is also difficult to obtain high-pressure test data of the gas-liquid two-phase pipe flow with equal proportions or large scales. However, the existing high-pressure liquid holdup calculation methods directly apply normal pressure experimental data or use high-pressure numerical simulation results to fit parameters, and the obtained liquid holdup calculation correlations cannot represent high-pressure flow or need to carry out complex flow pattern classification and modeling calculation respectively, and the implicit iteration also increases the engineering application difficulty of the model.

[0003] The invention patent (CN113685165B) relates to a liquid holdup calculation formula for a low gas-liquid ratio high-pressure gas well, which is a function of gas-liquid ratio and gas deviation factor. Since the gas deviation factor involves complex pressure and temperature iterative calculation, and the method needs to judge the flow state, there is a large subjective error, and it is difficult to promote and apply in the field. The invention patent (CN120046544B) provides a high temperature and high pressure wellbore liquid holdup calculation method, which divides the flow into bubbly flow, slug flow, churn flow and annular flow, involves three relatively complex flow pattern transition boundaries and corresponds to four liquid holdup calculation expressions. In essence, it uses the conventional drift model calculation method, fixes the distribution coefficient and uses high-pressure numerical simulation results to fit four drift velocities, but the confidence of the Fluent software simulation results is not high. The invention patent (CN117371345A) discloses a gas well liquid holdup calculation method, which has a similar model form to the Hagedorn & Brown (1965) model commonly used in the field of oil and gas field development engineering. The model fitting coefficients are as many as 20, and there is a relatively complex high-order polynomial. In addition, the invention patent (CN117332723B) relates to a liquid holdup expression based on experimental gas-liquid apparent velocity fitting, the invention patent (CN117454063B) proposes a set of liquid holdup calculation related expressions for the six flow patterns in oil-gas-water three-phase flow, and the invention patent (CN114818535B) provides a three-parameter liquid holdup iterative calculation related expression based on flow pattern transition boundaries, which is only related to gas flow velocity. These methods all have problems such as pressure limitation, narrow application range or complex form, which are difficult to apply.

[0004] Therefore, the present application provides a high-pressure gas well wellbore liquid holdup calculation method, which is based on the drift flux model, introduces the dimensionless phase apparent velocity in the form of the Froude similarity criterion, and is fitted by normal pressure experimental test data in a wide range of gas-liquid flow velocity to accurately represent the change law of liquid holdup with dimensionless phase apparent velocity. An effective method for calculating the wellbore liquid holdup of high-pressure gas wells is formed. This method ensures the accuracy of high and low pressure pipe flow calculation without complex drift parameter implicit calculation and gas-liquid two-phase flow state judgment, and has simple form and convenient operation. It provides a convenient and efficient gas well wellbore liquid holdup prediction means for field operators and engineering and technical personnel in the field of oil and gas field development, and has potential application value. SUMMARY

[0005] The purpose of the present application is to solve the problems of difficult acquisition of high-pressure gas well wellbore liquid holdup data and lack of theoretical calculation method or difficulty in engineering promotion and application, and to provide a simple method for calculating the wellbore liquid holdup of high-pressure gas wells, which provides a convenient and efficient gas well wellbore liquid holdup prediction means for field operators and engineering and technical personnel in the field of oil and gas field development.

[0006] The high-pressure gas well wellbore liquid holdup calculation method provided by the application mainly comprises the following steps:

[0007] Step one: collect target gas well production dynamic parameters, determine gas well pressure, temperature, gas production, and liquid production parameters, calculate gas wellbore gas density and fluid superficial velocity, and the corresponding calculation formulas are as follows:

[0008] (1.1) gas density calculation formula under different pressure conditions: , wherein p G is the gas density (kg / m 3 ), g g is the relative density of natural gas, taken as 0.5-0.7, p is the pressure (MPa), Z is the natural gas deviation factor, R is the ideal gas constant, taken as 0.008314 MPa·m 3 / (kmol·K), T is the temperature (K);

[0009] (1.2) gas well wellbore fluid superficial velocity calculation: gas phase superficial velocity v SG calculation formula: , liquid phase superficial velocity v SL calculation formula: , wherein v SG , v SL are the gas phase superficial velocity and the liquid phase superficial velocity (m / s), respectively, Q SC , Q SL are the gas production and the liquid production (m 3 / d), respectively, p SC is the normal pressure gas density (kg / m 3 ), A is the pipeline cross-sectional area (m 2 );

[0010] Step two: use the proposed Froude similarity criterion form, introduce the phase density and pipe diameter parameters, and calculate the dimensionless phase velocity: dimensionless gas phase superficial velocity N GV calculation formula: ; dimensionless liquid phase superficial velocity N LV calculation formula: Dimensionless gas real flow rate N RGV Calculation formula: Wherein v G is the gas real flow rate (m / s), , H L is the vertical section volume or cross-sectional liquid holdup, p L is the liquid density, g is the gravitational acceleration (m / s 2 ), D is the pipe diameter (m).

[0011] Step three: build the relationship between the dimensionless real gas flow rate and the dimensionless phase superficial velocity: Wherein , a , b , c is the experimental fitting coefficient.

[0012] Step four: based on the form of the drift flux model, the relationship in step two and step three is obtained simultaneously, and the calculation formula of the vertical section wellbore liquid holdup of the high-pressure gas well is obtained: .

[0013] Step five: add the angle correction term in the liquid holdup formula in step four to calculate the liquid holdup under the specific inclination angle of the inclined or horizontal pipeline of the high-pressure gas well: Wherein H θ is the liquid holdup under the certain horizontal direction inclination q angle, c 1, c 2, c 3 is the experimental fitting coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the technical roadmap of the present application;

[0015] Figure 2 is the change relationship diagram of the dimensionless real gas flow rate N RGV with the dimensionless gas phase superficial velocity N GV ;

[0016] Figure 3 is the change relationship diagram of the dimensionless real gas flow rate N RGV with the dimensionless liquid phase superficial velocity N LV . DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with reference to the drawings.

[0018] As Figure 1 shown, Figure 1 is the technical roadmap of the present application. The present application provides a wellbore liquid holdup rate calculation method for high-pressure gas wells, mainly based on the drift flux model, introducing flow similarity criteria, and combining with the data rule of normal pressure experiment to construct a new liquid holdup rate calculation model; the core of the method is to construct the relationship between dimensionless real gas flow rate and dimensionless phase superficial velocity based on experimental data in a wide range of gas-liquid flow rates, and the experimental fitting coefficients involved can be tested according to the gas well parameters of the target oil and gas field block. The experimental test results are re-fitted to improve the adaptability of the model to the specific production block gas well and improve the calculation accuracy, which specifically includes the following steps:

[0019] (1) Collect the production parameters of the target gas well, determine the given average pressure and average temperature of the calculated well section, and calculate the gas density p G and gas and liquid phase superficial velocity v SG , v SL ; here, the liquid density is considered as a fixed value of 1000 kg / m 3 ;

[0020] (2) Convert the calculated gas and liquid phase superficial velocity into dimensionless form, and according to the basic relationship of two-phase flow , substitute into the dimensionless real gas flow rate expression , and rearrange to obtain the dimensionless form of the liquid holdup rate relationship ;

[0021] (3) Construct the relationship between dimensionless real gas flow rate and dimensionless phase superficial velocity: , wherein , a , b , c are experimental fitting coefficients;

[0022] (4) Substitute the dimensionless real gas flow rate expression constructed in step (3) into the liquid holdup rate relationship in step (2) to obtain the high-pressure gas well vertical section wellbore liquid holdup rate calculation formula: ;

[0023] (5) Add an angle correction term to the liquid holdup rate formula in step (4) to calculate the liquid holdup rate under a specific inclination angle of the high-pressure gas well inclined or horizontal pipeline: , wherein Hθ for a certain inclination angle in horizontal direction q under the condition of c 1, c 2, c 3 is the experimental fitting coefficient.

[0024] As Figure 2 shown, Figure 2 is the dimensionless real gas flow rate N RGV with the dimensionless gas phase superficial flow rate N GV The relationship between the dimensionless real gas flow rate N RGV and N GV There are two kinds of change relationships: one is under the condition of low liquid flow rate, N RGV and N GV a clear quadratic relationship; two is under the condition of high liquid flow rate, N RGV and N GV a linear relationship. Therefore, the relationship between the dimensionless real gas flow rate N RGV and the dimensionless gas phase superficial flow rate N GV is constructed, and the expression of the front coefficient A is composed of two terms, the first term can capture the quadratic change rule under the condition of low liquid flow rate, and the second term can capture the linear change rule under the condition of high liquid flow rate, and the parameter A The denominator part of each term in the expression is actually the weighted coefficient of the liquid flow rate, and under the given liquid flow rate, A only one term plays a decisive role. In the figure, the vertical coordinate N RGV - N GV can make the above change relationship more intuitive, and in the modeling process, N GV can be moved to the quadratic or linear relationship that plays a major role, so that N RGV and N GV the change rule remains unchanged.

[0025] As Figure 3 shown, Figure 3 is the dimensionless real gas flow rate N RGV with the dimensionless liquid phase superficial flow rate N LVThe change relationship diagram of the liquid holdup. Under the given gas flow rate condition, N RGV With N LV The quadratic term relationship is presented, thus the dimensionless true gas flow rate N RGV The change law with the dimensionless liquid phase superficial flow rate.

[0026] Compared with the defects and deficiencies of the prior art, the present application has the following beneficial effects:

[0027] (1) The liquid holdup calculation relationship formula proposed in the present application realizes pressure scaling through the Froude similarity criterion, is suitable for a wide range of gas-liquid flow rates, and can represent the wellbore flow conditions of high-pressure gas wells.

[0028] (2) The newly proposed liquid holdup calculation relationship formula in the present application does not need complex implicit calculation of drift parameters and judgment of gas-liquid two-phase flow types, and is simple in form and easy to operate.

[0029] (3) The key parameter A in the present application is related to the dimensionless phase superficial flow rate, can accurately capture the distribution law of gas-liquid two-phase flow in a wide liquid flow rate range, avoids the iterative calculation of complex drift parameters in the drift model, and at the same time improves the calculation accuracy of the model.

[0030] Obviously, the above description only represents the implementation idea of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating the liquid holdup in the wellbore of a high pressure gas well, characterized in that, The method comprises the following steps: Step 1: Collect the production dynamic parameters of the target gas well, and determine the parameters of the gas well pressure, temperature, gas production, and liquid production; calculate the gas density and apparent flow velocity of the wellbore, and the corresponding calculation formulas are as follows: (1.1) Gas density calculation formula under different pressure conditions: wherein ρ G is the gas density, with the unit of kg / m 3 ; γ g is the relative density of natural gas, taken between 0.5~0.7; p is the pressure, with the unit of MPa; Z is the deviation factor of natural gas; R is the ideal gas constant, taken 0.008314 MPa·m 3 / (kmol·K); T is the temperature, with the unit of K; (1.2) Gas well borehole fluid superficial velocity calculation: gas phase superficial velocity v SG Calculation formula: , liquid phase superficial velocity v SL Calculation formula: , wherein v SG , v SL The gas phase superficial velocity and the liquid phase superficial velocity are respectively, and the unit is m / s; Q SC , Q SL The gas well gas production and the liquid production are respectively, and the unit is m 3 / d; ρ SC The normal pressure gas density; A The pipe cross-sectional area is m 2 ; Step two: Using the proposed form of Froude similarity criterion, introduce phase density and pipe diameter parameters, calculate dimensionless phase flow rate: Dimensionless gas phase superficial velocity N GV Calculation formula: Dimensionless liquid phase superficial velocity N LV Calculation formula: Dimensionless gas phase real velocity N RGV Calculation formula: , wherein v G is the gas phase real velocity, unit: m / s, ; H L is the vertical section volume or cross-sectional liquid holdup; ρ L is the liquid density; g is the gravitational acceleration, unit: m / s 2 ; D is the pipe diameter, unit: m; Step three: Construct the relationship between the dimensionless real gas flow rate and the dimensionless phase superficial flow rate: wherein , a , b , c is the experimental fitting coefficient; Step four: Based on the form of drift-flux model, the relationship between step two and step three is obtained, and the liquid holdup calculation formula of vertical section of high-pressure gas well is obtained: ; Step five: add the angle correction term in the holdup formula in step four to calculate the holdup rate of high-pressure gas wells at a specific angle of inclined or horizontal pipe: where H θ is the holdup rate of a certain angle θ along the horizontal direction under the condition of c 1、 c 2、 c 3 is the experimental fitting coefficient.

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