Shale gas well oil pipe size optimization method considering hydrops influence

Abstract

The invention relates to a shale gas well oil pipe size optimization method considering liquid accumulation influence. The problems of serious liquid accumulation influence, difficulty in optimizing the size of an oil pipe and the like in the whole production period of the shale gas well are solved; according to the technical scheme, according to a wellbore pressure drop calculation method considering the liquid accumulation influence, the daily wellbore pressure drop and the liquid accumulation amount of oil pipes of different sizes in the whole production cycle of a gas well are predicted, the influence of the wellbore pressure drop and the liquid accumulation amount in the whole production cycle is comprehensively considered, and the comprehensive utility value of the oil pipes of different sizes is obtained through calculation. By comparing the comprehensive utility values of the oil pipes with different sizes, the optimal oil pipe size is optimized; according to the shale gas well oil pipe size optimization method considering the liquid accumulation influence, the influence of the change of the liquid production capacity of the shale gas well in the whole production period on the oil pipe liquid accumulation is considered, and efficient and stable production of the shale gas well in the whole production period is promoted.

Description

Technical Field

[0001] The invention relates to a method for optimizing the size of a shale gas well oil pipe taking into account the influence of liquid accumulation, and belongs to the field of shale gas well development. Background Art

[0002] The production and pressure of shale gas wells change rapidly during the entire production cycle. In the early stage, the liquid production of shale gas wells is large. If the oil pipe is lowered too early, it is easy to cause liquid accumulation in the gas well and affect production. In the later stage, the pressure of shale gas wells is low and the gas production is low, which is also easy to cause liquid accumulation in the oil pipe and increase the pressure drop. In view of the complex influence of liquid accumulation on the wellbore pressure drop during the entire production cycle of shale gas wells, how to optimize the size of the oil pipe, optimize the pressure loss of the gas well, and reduce the impact of liquid accumulation is the key to efficient and stable production of shale gas wells throughout the entire production cycle.

[0003] At present, there have been some relevant studies on the optimization of shale gas well tubing strings, such as the patent application "A method for optimizing shale gas well production based on optimized tubing strings" with application number CN202310061510.9, which constructs a shale gas well bore pressure drop model. By calculating the law of pressure drop of different tubing inner diameters as the gas production changes, the tubing inner diameter is optimized to produce at the minimum pressure drop point to ensure that the shale gas well is produced with the minimum pressure drop loss. At present, the research on the optimization of shale gas well tubing strings mainly considers the impact of wellbore pressure drop, but there is no method for optimizing tubing strings that considers the impact of liquid accumulation during the entire production cycle. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of serious impact of liquid accumulation in the whole production cycle of shale gas wells and difficulty in optimizing the size of oil pipes, so as to help shale gas wells to produce efficiently and stably and reduce the pressure loss of shale gas wells.

[0005] To achieve the above object, the present invention provides a method for optimizing the size of a shale gas well oil pipe taking into account the influence of liquid accumulation, the method comprising the following steps: S100: preparing a gas well gas production decreasing relationship, a water production decreasing relationship and a bottom hole pressure decreasing relationship, and preparing gas well depth data; S200: Based on the gas production decline relationship, water production decline relationship and bottom hole pressure decline relationship of the gas well, the daily gas production, water production and bottom hole pressure predicted in the whole production cycle are obtained. The whole production cycle is from the start of gas well production to the gas production decreasing to 1000m 3 the entire production phase; S300: According to the wellbore pressure drop calculation method considering the effect of liquid accumulation, the wellbore pressure drop and liquid accumulation of different sizes of oil pipes during the full production cycle of the gas well are calculated every day. The wellbore pressure drop calculation method considering the effect of liquid accumulation has the following steps: ① Input t The daily gas production, water production, bottom hole pressure and t-1 day's effusion volume, where the effusion volume on day 0 is 0; ② Divide the wellbore into n Well sections, assuming that there is no liquid accumulation in each wellbore section; ③ The theoretical wellbore pressure drop of each section is calculated based on the wellbore pressure drop equation considering the effect of liquid accumulation. ;D p i For the i Wellbore pressure drop, MPa; g is the acceleration due to gravity, m / s 2 ; f i For the i The friction coefficient of the wellbore section is dimensionless; v sg is the gas superficial velocity, m / s; D H is the height of each section of the wellbore, m; q wci For the i Liquid carrying capacity of section wellbore, m 3 ; q w is the water production, m 3 ; V w is the volume of fluid accumulated on the previous day, m 3 ; ρ mi For the i Mixture density of section wellbore, kg / m 3 ; D is the tubing size, m; ④Calculate the t Liquid carrying capacity per wellbore section per day ;in A is the cross-sectional area of ​​the oil pipe, m 2 ;D T time step, d; ⑤Calculate the t Liquid holdup per wellbore section per day ;in H Li For the i The liquid holdup of the wellbore section is dimensionless; X is the Lockhart-Martinelli coefficient, dimensionless; v ∞T is the Taylor bubble limiting ascent velocity, m / s; ⑥ Recalculate the actual wellbore pressure drop in each section according to the wellbore pressure drop equation considering the effect of liquid accumulation, and compare the theoretical wellbore pressure drop in each section with the actual wellbore pressure drop in each section. If the accuracy requirement is met, proceed to the next step. If not, repeat steps ③ to ⑥ until the accuracy requirement is met; ⑦Calculate the amount of effusion and output thet The wellbore pressure drop of the day; the wellbore pressure drop is the sum of the actual wellbore pressure drops in each section; S400: Based on the comprehensive utility value equation Calculate the comprehensive utility value of oil pipes of various sizes, and the oil pipe with the smallest comprehensive utility value is the optimal oil pipe; E j For the j The comprehensive utility value of the oil pipe, dimensionless; For the j Average wellbore pressure drop during the entire production cycle of this type of tubing, MPa; No. j Average liquid accumulation during the entire production cycle of this type of oil pipe, m 3 .

[0006] Furthermore, the formula for calculating the density of the mixture in the i-th section of the wellbore in S300 is: ,in ρ g is the gas density, kg / m 3 ; ρ w is the density of water, kg / m 3 .

[0007] Furthermore, the calculation formula for the amount of fluid accumulation in S300 is: . BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the attached picture: Figure 1 It is the technical roadmap of this method.

[0009] Figure 2 This is the prediction chart of gas production, water production and bottom hole pressure of N1 well.

[0010] Figure 3 This is the wellbore pressure drop prediction diagram for the N1 well during the entire production cycle for different sizes of tubing.

[0011] Figure 4 This is a prediction chart of liquid accumulation during the entire production cycle of tubings of different sizes in the N1 well. DETAILED DESCRIPTION

[0012] The present invention will be further described below in conjunction with the accompanying drawings.

[0013] To achieve the above object, the present invention provides a method for optimizing the size of a shale gas well oil pipe taking into account the influence of liquid accumulation, the method comprising the following steps: To achieve the above object, the present invention provides a method for optimizing the size of a shale gas well oil pipe taking into account the influence of liquid accumulation, the method comprising the following steps: S100: preparing a gas well gas production decreasing relationship, a water production decreasing relationship and a bottom hole pressure decreasing relationship, and preparing gas well depth data; S200: Based on the gas production decline relationship, water production decline relationship and bottom hole pressure decline relationship of the gas well, the daily gas production, water production and bottom hole pressure predicted in the whole production cycle are obtained. The whole production cycle is from the start of gas well production to the gas production decreasing to 1000m 3 the entire production phase; S300: According to the wellbore pressure drop calculation method considering the effect of liquid accumulation, the wellbore pressure drop and liquid accumulation of different sizes of oil pipes during the full production cycle of the gas well are calculated every day. The wellbore pressure drop calculation method considering the effect of liquid accumulation has the following steps: ① Input t The daily gas production, water production, bottom hole pressure and t -1 day's effusion volume, where the effusion volume on day 0 is 0; ② Divide the wellbore into n Well sections, assuming that there is no liquid accumulation in each wellbore section; ③ The theoretical wellbore pressure drop of each section is calculated based on the wellbore pressure drop equation considering the effect of liquid accumulation. ;D p i For the i Wellbore pressure drop, MPa; g is the acceleration due to gravity, m / s 2 ; f i For the i The friction coefficient of the wellbore section is dimensionless; v sg is the gas superficial velocity, m / s; D H is the height of each section of the wellbore, m; q wci For the i Liquid carrying capacity of section wellbore, m 3 ; q w is the water production, m 3 ; V w is the volume of fluid accumulated on the previous day, m 3 ; ρ mi For the i Mixture density of section wellbore, kg / m 3 ; D is the tubing size, m; ④Calculate the t Liquid carrying capacity per wellbore section per day ;in A is the cross-sectional area of ​​the oil pipe, m 2 ;D Ttime step, d; ⑤Calculate the t Liquid holdup per wellbore section per day ;in H Li For the i The liquid holdup of the wellbore section is dimensionless; X is the Lockhart-Martinelli coefficient, dimensionless; v ∞T is the Taylor bubble limiting ascent velocity, m / s; ⑥ Recalculate the actual wellbore pressure drop in each section according to the wellbore pressure drop equation considering the effect of liquid accumulation, and compare the theoretical wellbore pressure drop in each section with the actual wellbore pressure drop in each section. If the accuracy requirement is met, proceed to the next step. If not, repeat steps ③ to ⑥ until the accuracy requirement is met; ⑦Calculate the amount of effusion and output t The wellbore pressure drop of the day; the wellbore pressure drop is the sum of the actual wellbore pressure drops in each section; S400: Based on the comprehensive utility value equation Calculate the comprehensive utility value of oil pipes of various sizes, and the oil pipe with the smallest comprehensive utility value is the optimal oil pipe; E j For the j The comprehensive utility value of the oil pipe, dimensionless; For the j Average wellbore pressure drop during the entire production cycle of this type of tubing, MPa; No. j Average liquid accumulation during the entire production cycle of this type of oil pipe, m 3 .

[0014] Furthermore, the formula for calculating the density of the mixture in the i-th section of the wellbore in S300 is: ,in ρ g is the gas density, kg / m 3 ; ρ w is the density of water, kg / m 3 .

[0015] Furthermore, the calculation formula for the amount of fluid accumulation in S300 is: .

[0016] Take Well N1 as an example. Well N1 is a shale gas well in a normal-pressure shale gas field in China. The wellbore is 3150m. It was put into production on November 5, 2024. The gas production, water production and bottom hole pressure decreasing equations of the well were obtained based on the production data of adjacent wells on the same platform. The predicted daily gas production, water production and bottom hole pressure of Well N1 during the entire production cycle were calculated. The results are as follows: Figure 2Three commonly used sizes of tubing (with inner diameters of 0.043m, 0.050m, and 0.062m) were selected for prediction. The gas production, water production, and bottom hole pressure were brought into the wellbore pressure drop calculation method based on the consideration of the effect of liquid accumulation. The wellbore pressure drop and liquid accumulation of tubings of different sizes were calculated every day during the full production cycle of the gas well. The results are shown in the figure below. Figure 3 , Figure 4 The average tubing pressure and average effusion volume of tubings of various sizes are substituted into the comprehensive utility value calculation equation, and the comprehensive utility value of tubing with a size of 0.043 m is 0.30, the comprehensive utility value of tubing with a size of 0.050 m is 0.28, and the comprehensive utility value of tubing with a size of 0.062 m is 0.42. The tubing with a size of 0.050 m is preferred.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the method takes into account the influence of changes in liquid production during the entire production cycle of a shale gas well on liquid accumulation in the oil pipe, and establishes a shale gas well oil pipe size optimization method that takes into account the influence of liquid accumulation, so that production site personnel can easily and quickly determine the optimal oil pipe size for a shale gas well.

[0018] Finally, it should be noted that the above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for optimizing the size of oil pipes in shale gas wells considering the influence of liquid accumulation, characterized in that: The method comprises the following steps: S100: preparing a gas well gas production decreasing relationship, a water production decreasing relationship and a bottom hole pressure decreasing relationship, and preparing gas well depth data; S200: Based on the gas production decline relationship, water production decline relationship and bottom hole pressure decline relationship of the gas well, the daily gas production, water production and bottom hole pressure predicted in the whole production cycle are obtained. The whole production cycle is from the start of gas well production to the gas production decreasing to 1000m 3 the entire production phase; S300: According to the wellbore pressure drop calculation method considering the effect of liquid accumulation, the wellbore pressure drop and liquid accumulation of different sizes of oil pipes during the full production cycle of the gas well are calculated every day. The wellbore pressure drop calculation method considering the effect of liquid accumulation has the following steps: ① Input t The daily gas production, water production, bottom hole pressure and t -1 day's effusion volume, where the effusion volume on day 0 is 0; ② Divide the well into n Well sections, assuming that there is no liquid accumulation in each wellbore section; ③ The theoretical wellbore pressure drop of each section is calculated based on the wellbore pressure drop equation considering the effect of liquid accumulation. ;D p i For the i Wellbore pressure drop, MPa; g is the acceleration due to gravity, m / s 2 ; f i For the i The friction coefficient of the wellbore section is dimensionless; v sg is the gas superficial velocity, m / s; D H is the height of each section of the wellbore, m; q wci For the i Liquid carrying capacity of section wellbore, m 3 ; q w is the water production, m 3 ; V w is the volume of fluid accumulation on the previous day, m 3 ; ρ mi For the i Mixture density of section wellbore, kg / m 3 ; D is the tubing size, m; ④Calculate the t Liquid carrying capacity per wellbore section per day ;in A is the cross-sectional area of ​​the oil pipe, m 2 ;D T time step, d; ⑤Calculate the t Liquid holdup per wellbore section per day ;in H Li For the i The liquid holdup of the wellbore section is dimensionless; X is the Lockhart-Martinelli coefficient, dimensionless; v ∞T is the Taylor bubble limiting ascent velocity, m / s; ⑥ Recalculate the actual wellbore pressure drop in each section according to the wellbore pressure drop equation considering the effect of liquid accumulation, and compare the theoretical wellbore pressure drop in each section with the actual wellbore pressure drop in each section. If the accuracy requirement is met, proceed to the next step. If not, repeat steps ③ to ⑥ until the accuracy requirement is met; ⑦Calculate the amount of effusion and output t The wellbore pressure drop is the sum of the actual wellbore pressure drops in each section. S4 00: According to the comprehensive utility value equation Calculate the comprehensive utility value of oil pipes of various sizes, and the oil pipe with the smallest comprehensive utility value is the optimal oil pipe; E j For the j The comprehensive utility value of the oil pipe, dimensionless; For the j Average wellbore pressure drop during the entire production cycle of this type of tubing, MPa; No. j Average liquid accumulation during the entire production cycle of this type of oil pipe, m 3 .

2. The method for optimizing the size of oil pipes in shale gas wells considering the influence of liquid accumulation according to claim 1, characterized in that: The formula for calculating the density of the mixture in the i-th section of the wellbore in S300 is: ,in ρ g is the gas density, kg / m 3 ; ρ w is the density of water, kg / m 3 .

3. The method for optimizing the size of oil pipes in shale gas wells considering the influence of liquid accumulation according to claim 1, characterized in that: The calculation formula of the amount of fluid accumulation in S300 is: .

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