A method for calculating the critical flow velocity of liquid in foam drainage gas wells containing condensate

Abstract

The present invention provides a method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil, and relates to the field of gas well drainage and gas production technology. Based on a gas-water two-phase liquid film flow model, the influence of foam parameters is considered to calculate the critical gas flow velocity of liquid carrying in the gas-water-foam three-phase ...

Description

Technical Field

[0001] The invention belongs to the field of gas reservoir drainage and gas production, and in particular relates to a method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil. Background Art

[0002] In the later stages of gas well production, the production of gas wells is characterized by low gas and liquid production. Moreover, many gas wells have three-phase production of gas, water and oil. The low gas production is not enough to ensure the continuous liquid carrying of gas wells, which can easily cause water flooding and shutdown. In order to effectively prevent and delay the phenomenon of liquid accumulation in gas wells, the gas field widely uses low-cost, fast-acting and easy-to-operate foam drainage gas production technology to reduce the critical liquid-carrying gas volume. The foam drainage gas production technology is a drainage measure that uses a foaming agent to mix with the gas and liquid in the wellbore to form foam, thereby inhibiting the liquid from sliding off during the flow of the wellbore fluid, changing the flow pattern, and reducing the bottom hole back pressure.

[0003] In the process of gas well production, the calculation of the critical flow velocity of liquid carrying is an important means to predict liquid accumulation. Among the commonly used critical flow velocity models of liquid carrying, the liquid film model is more practical. However, since the liquid phase in the foam drainage gas well containing condensate oil is a mixed phase of oil, water and foam, the conventional two-phase liquid film model is difficult to accurately characterize the critical flow velocity of liquid carrying in the foam drainage gas well containing condensate oil. The invention patent (CN107045671A) proposes a method for calculating the critical flow velocity of liquid carrying in gas-water two-phases based on the seepage theory, and only considers the non-Darcy seepage of gas-water two-phases; the invention patent (CN110866321A) proposes a method for calculating the critical flow velocity of liquid carrying in oil-gas-water three-phases based on the idea of ​​liquid film fall, and does not consider the application in bubble drainage wells; the invention patent (CN117973263A) obtains the expression of the critical liquid carrying gas volume of gas-water two-phases based on the liquid film inversion theory, and does not consider the influence of bubbles in the liquid film and is not suitable Used for condensate gas wells; the invention patent (CN116223837A) is based on the droplet reversal critical liquid-carrying flow rate measurement device, considering the influence of gas flow rate on critical liquid-carrying flow rate under different gas inlet angles and different droplet sizes, and establishing a new critical liquid-carrying flow rate model. There are errors in experimental measurements and the droplet model is rarely used in bubble wells, and is even less suitable for bubble wells containing condensate oil; the invention patent (CN116595905A) uses the Li Min model to calculate the critical bubble flow rate at the bottom of the bubble well, without considering the influence of condensate oil. Therefore, there is no report on the calculation of the critical liquid-carrying flow rate of the four-phase oil-gas-water-foam.

[0004] The present invention provides a method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil. The method is based on a gas-liquid two-phase liquid film flow model, takes the influence of foam parameters into consideration, calculates the critical gas flow velocity of liquid carrying in a gas-water-foam three-phase, and then uses the critical gas flow velocity of liquid carrying in the gas-water two-phase and the gas-water-foam three-phase to characterize the influence of condensate oil on the flow, thereby forming a new method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil, and providing important theoretical support for predicting the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil. Summary of the invention

[0005] The present invention aims to solve the problem that a method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil is lacking, and thus the problem that liquid accumulation in the wellbore of a foam drainage gas production well cannot be effectively predicted and process parameters cannot be optimized. A method for calculating the critical gas flow velocity of liquid carrying in a foam drainage gas well containing condensate oil is provided, providing key theoretical support for the optimization design of the foam drainage gas production process.

[0006] Step 1: Collect the dynamic production parameters of gas wells in the target research area, clarify the pressure, temperature, gas production, water production, oil production parameters of the production gas wells, and the type, factory parameters and concentration of the foaming agent, and calculate the fluid density, apparent flow rate and water content of the gas well bore. The corresponding calculation formula is as follows:

[0007] Gas density at different pressures r G Calculation formula:

[0008] ;

[0009] In the formula, r G is the gas density, kg / m 3 ; p is the pressure, MPa; M is the relative molecular mass of natural gas, g / mol; T is the temperature, K; R is the ideal gas constant, 0.008314 atm.m 3 / (kmol.K); Z is the deviation factor, dimensionless.

[0010] Calculation of apparent flow rate of gas wellbore fluid:

[0011] Gas superficial velocity v SG Calculation formula:

[0012] ;

[0013] Liquid superficial velocity v SL Calculation formula:

[0014] ;

[0015] Two-phase mixture flow rate v m Calculation formula:

[0016] ;

[0017] In the formula, v SG , v SL and v m are gas phase superficial velocity, liquid phase superficial velocity and two-phase mixture velocity, m / s, respectively; Q SC , Q SW , Q SO are respectively the gas production, water production and oil production of the gas well, m 3 / d; r SC is the gas density at normal pressure, kg / m 3 ; is the cross-sectional area of ​​the pipe, m 2 .

[0018] In condensate gas wells, the volumetric water content that characterizes the proportion of water phase in the total liquid production f W Calculation formula:

[0019] ;

[0020] In the formula, f W is the volumetric water content, dimensionless.

[0021] Step 2: Calculate the critical gas velocity of the gas-water two-phase liquid using the liquid film model v CR,2 :

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] In the formula, v CR,2 is the critical gas velocity of gas-water two-phase liquid, m / s; f i2 is the internal friction factor of gas-water two-phase flow, dimensionless; dL is the thickness of the liquid film, m; H L2 is the gas-water two-phase liquid holdup, dimensionless; r L is the liquid density, kg / m 3 ; d is the pipe diameter, m; g is the acceleration due to gravity, m / s 2 ;Re G is the gas Reynolds number, dimensionless.

[0027] Step 3: Based on the liquid film model, considering the influence of foam parameters, a new critical gas flow velocity of gas-water-foam three-phase liquid is proposed v CR,3 Calculation method:

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] ;

[0035] ;

[0036] In the formula, v CR,3 is the critical gas velocity of gas-water-foam three-phase liquid, m / s; f i3 is the internal friction factor of the air-water-foam three-phase flow, dimensionless; d F is the foam film thickness, m; r L-F is the density of the foam film, kg / m 3 ; H L3 is the gas-water-foam three-phase holdup, dimensionless; is the air void fraction, dimensionless; f g is the air content in the foam, dimensionless; H F is the foam content, dimensionless; r F is the foam density, kg / m3 .

[0037] The gas content Adopt the air content calculation method of Zhang Yuhao et al. under foam flow conditions:

[0038] ;

[0039] ;

[0040] In the formula, s is the surface tension, mN / m; c is the concentration of the foaming agent, dimensionless; Δ r is the difference between gas and liquid density, kg / m 3 , ; Re is the Reynolds number, dimensionless; i is the tilt angle, °.

[0041] Step 4: Characterize the influence of the oil phase by using the critical gas velocity of gas-water two-phase and gas-water-foam three-phase, introduce the water content parameter, and propose the critical gas velocity of liquid carrying in foam drainage gas wells containing condensate oil v CR,4 Calculation method:

[0042] ;

[0043] In the formula, v CR,4 is the critical gas velocity carrying liquid in foam drainage gas wells containing condensate, m / s.

[0044] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0045] (1) Based on the gas-water two-phase liquid film flow model and considering the influence of foam parameters, a new critical gas flow velocity for gas-water-foam three-phase liquid carrying is proposed v CR,3 Calculation method;

[0046] (2) The influence of condensate on the flow is characterized by the critical gas velocity of gas-water two-phase liquid carrying and the critical gas velocity of gas-water-foam three-phase liquid carrying. Then, the water cut parameter is introduced and a method for calculating the critical gas velocity of liquid carrying in foam drainage gas wells containing condensate is proposed, so as to better characterize the flow conditions of condensate in foam drainage gas wells.

[0047] Obviously, the above description is only an implementation idea of ​​the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1The technical roadmap is a method for calculating the critical flow velocity of liquid in a foam drainage gas well containing condensate. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0050] like Figure 1 As shown, Figure 1 The present invention provides a method for calculating the critical gas flow velocity of foam drainage gas wells containing condensate oil, which is mainly based on the transformation of the liquid film model. The key point is to characterize the influence of condensate oil on flow by using the critical gas flow velocity of gas-water two-phase liquid and the critical gas flow velocity of gas-water-foam three-phase liquid, introduce the water content parameter, and propose the critical gas flow velocity of foam drainage gas wells containing condensate oil. v CR,4 Calculation method.

[0051] The core of the calculation method provided by the present invention is to calculate the critical gas flow velocity of foam drainage gas well containing condensate oil v CR,4 .

[0052] First, calculate the critical gas flow rate of gas-water two-phase liquid v CR,2 :

[0053] ;

[0054] In the formula, v CR,2 is the critical gas velocity of gas-water two-phase liquid, m / s; d L is the thickness of the liquid film, m; f i2 is the internal friction factor of gas-water two-phase flow, dimensionless; r L is the liquid density, kg / m 3 ; r G is the gas density, kg / m 3 ; d is the pipe diameter, m; g is the acceleration due to gravity, m / s 2 .

[0055] The key lies in fitting the liquid holdup of gas-water two-phase flow H L2 Calculation formula:

[0056] ;

[0057] In the formula, vSG and v SL are gas phase superficial velocity and liquid phase superficial velocity, m / s, respectively.

[0058] Calculate the film thickness d L :

[0059] ;

[0060] The internal friction factor of gas-liquid two-phase flow is calculated using the model of Fore et al. f i2 :

[0061] ;

[0062] In the formula, Re G is the gas Reynolds number, dimensionless.

[0063] Then, calculate the critical gas velocity of the gas-water-foam three-phase liquid carrier v CR,3 :

[0064] ;

[0065] In the formula, v CR,3 is the critical gas velocity of gas-water-foam three-phase liquid, m / s; d F is the foam film thickness, m; f i3 is the internal friction factor of the air-water-foam three-phase flow, dimensionless; r L-F is the density of the foam film, kg / m 3 .

[0066] The key is to calculate the gas-water-foam three-phase holdup H L3 :

[0067] ;

[0068] In the formula, H L3 is the gas-water-foam three-phase holdup, dimensionless; is the air void fraction, dimensionless.

[0069] The gas content According to the calculation method of air content under foam flow conditions proposed by Zhang Yuhao et al.:

[0070] ;

[0071] In the formula, s is the surface tension, mN / m; c is the concentration of the foaming agent, dimensionless; v m is the flow rate of the two-phase mixture, m / s; Δ r is the difference between gas and liquid density, kg / m 3 ; Re is the Reynolds number, dimensionless; i is the tilt angle, °.

[0072] Computational foam film d F thickness:

[0073] ;

[0074] In the formula, f g is the air content in the foam, dimensionless.

[0075] Calculation of internal friction factor in air-water-foam three-phase flow f i3 And the density of the foam film r L-F :

[0076] ;

[0077] ;

[0078] In the formula, H F is the foam content, dimensionless; r F is the foam density, kg / m 3 .

[0079] Finally, the critical gas velocity of gas-water two-phase and gas-water-foam three-phase liquid carrying is used to characterize the effect of condensate oil on flow, and the water content parameter is introduced. It should be made clear that since the foaming agent cannot foam in the oil, the water content fw When it is 0%, the critical gas velocity of oil-gas-water-foam four-phase liquid v CR,4 , which is equal to the critical gas velocity of gas-water two-phase liquid v CR,2 At the same time, the experimental test results show that as the water content decreases, the critical gas flow rate of oil-gas-water-foam four-phase liquid carrying changes between the critical gas flow rate of gas-water two-phase and gas-water-foam three-phase liquid carrying, and is linearly related to the change of water content. Therefore, the critical gas flow rate of liquid carrying in foam drainage gas wells containing condensate oil is obtained. v CR,4 The calculation formula is:

[0080] ;

[0081] In the formula, v CR,4 is the critical gas velocity for liquid carrying in foam drainage gas wells containing condensate, m / s; f W is the volumetric water content, dimensionless.

Claims

1. A method for calculating the critical flow velocity of liquid in a foam drainage gas well containing condensate oil, characterized in that: The following steps are involved: Step 1: Collect the dynamic production parameters of gas wells in the target research block, clarify the pressure, temperature, gas production, water production, oil production parameters of the production gas wells, and the type, factory parameters and usage concentration of the foaming agent, and calculate the fluid density, apparent flow rate and water content of the gas well bore; Step 2: Calculate the critical gas velocity of the gas-water two-phase liquid using the liquid film model v CR,2 ; Step 3: Based on the liquid film model, considering the influence of foam parameters, a new critical gas flow velocity of gas-water-foam three-phase liquid is proposed v CR,3 Calculation method: ； ； ； ； ； ； ； ； In the formula, v CR,3 is the critical gas velocity of gas-water-foam three-phase liquid, m / s; f i3 is the internal friction factor of the air-water-foam three-phase flow, dimensionless; δ F is the foam film thickness, m; ρ L-F is the density of the foam film, kg / m 3 ; H L3 is the gas-water-foam three-phase holdup, dimensionless; is the air void fraction, dimensionless; f g is the air content in the foam, dimensionless; H F is the foam content, dimensionless; ρ F is the foam density, kg / m 3 ; ρ G is the gas density, kg / m 3 ; ρ L is the liquid density, kg / m 3 ; v SG and v SL are gas phase superficial velocity and liquid phase superficial velocity, m / s, respectively; The gas content The calculation method of air content under foam flow conditions is as follows: ； ； In the formula, σ is the surface tension, mN / m; c is the concentration of the foaming agent, dimensionless; Δ ρ is the difference between gas and liquid density, kg / m 3 , ; Re is the Reynolds number, dimensionless; θ is the tilt angle, °; v m is the flow rate of the two-phase mixture, m / s; Step 4: Characterize the influence of the oil phase by using the critical gas velocity of gas-water two-phase and gas-water-foam three-phase, introduce the water content parameter, and propose the critical gas velocity of liquid carrying in foam drainage gas wells containing condensate oil v CR,4 Calculation method: ； In the formula, v CR,2 is the critical gas velocity of gas-water two-phase liquid, m / s; v CR,4 is the critical gas velocity for liquid carrying in foam drainage gas wells containing condensate, m / s; f W is the volumetric water content, dimensionless.

Images