Gas well TPC curve determination method under influence of wellbore effusion

Abstract

The invention belongs to the field of gas field development, and particularly relates to a method for determining a gas well TPC curve under the influence of wellbore effusion. In the invention, in order to eliminate the influence of the accumulated liquid on the calculation of the flow pressure, a shaft is divided into a liquid accumulation section and a non-liquid accumulation section, a shaft pressure drop model considering the influence of the accumulated liquid is established, and the gas well TPC curve determination method under the influence of the shaft accumulated liquid is provided. The method has theoretical rationality and practical production application value in practical application of gas reservoir extraction.

Description

Technical Field

[0001] The present invention belongs to the field of gas field development, and particularly relates to a method for determining the TPC curve of a gas well under the influence of wellbore liquid accumulation. Background Art

[0002] Currently, the commonly used wellbore multiphase flow pressure drop models do not consider the influence of liquid accumulation when calculating the wellbore pressure drop. However, the liquid accumulation phenomenon in shale gas wells is obvious, which leads to the result of calculating the bottom hole flowing pressure using the conventional multiphase pipe flow pressure drop model being often less than the actual bottom hole flowing pressure, affecting the reasonable gas production allocation and process application in the later stage of gas wells. Therefore, we divide the wellbore into a liquid accumulation section and a non-liquid accumulation section, establish a wellbore pressure drop model considering the influence of liquid accumulation, and propose a method for determining the TPC curve of a gas well under the influence of wellbore liquid accumulation. This method has theoretical rationality and practical production application value in the actual application of gas reservoir production. Summary of the Invention

[0003] The purpose of the present invention is to solve the practical application problem of wellbore liquid accumulation pressure drop in the process of gas reservoir development. By establishing the pressure drop models of the liquid accumulation section and the non-liquid accumulation section of the gas well, the wellbore pressure drop under different gas production requirements is calculated and determined. The new method in the present invention can effectively determine the TPC curve after wellbore liquid accumulation in shale gas wells, which helps the subsequent gas field development design, formulates a reasonable production plan, and provides technical support for formulating an effective development plan.

[0004] To achieve the above purpose, the present invention provides a method for determining the TPC curve of a gas well under the influence of wellbore liquid accumulation, which includes the following steps: The first step is to determine the formation gas production, formation water production, wellhead pressure, tubing inner diameter, bottom hole and wellhead temperature, time step parameter, and the liquid accumulation height of the wellbore liquid accumulation section at the previous moment according to the on-site production data , and the liquid accumulation volume ; The second step is to calculate the water production that meets the liquid carrying requirement at the liquid accumulation height from the wellhead downwards according to the formation gas production and the formation water production ; The third step is to calculate the liquid accumulation volume of the liquid accumulation section by comparing ; ; The fourth step is to calculate the initial value of the liquid accumulation height according to the formula ; The fifth step is to calculate the pressure distributions of the non-liquid accumulation section and the liquid accumulation respectively when the liquid accumulation height is ; The sixth step is to calculate the liquid accumulation volume of the liquid accumulation section according to the formula , verify and whether it meets the accuracy requirements. If not, let , and repeat step (5) until the accuracy requirements are met; Step 7: Recalculate the water production volume that meets the liquid-carrying requirement when the liquid accumulation height is at : , verify and whether it meets the accuracy requirements. If not, let be brought into step (3) for continuous calculation until is basically unchanged; Step 8: Draw the TPC curve of the gas well considering the influence of liquid accumulation.

[0005] Compared with the prior art, the present invention has the following beneficial effects: (1) It has a wide range of applications and can be applied to gas reservoirs under different conditions; (2) The calculation method is convenient and effective, with high work efficiency; (3) The calculation method is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In the drawings: Figure 1 is the technical roadmap of this method; Figure 2 is the calculation flow chart. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present invention will be further described below in conjunction with the embodiments and the drawings; The present invention provides a method for determining the TPC curve of a gas well affected by wellbore liquid accumulation. This method includes the following steps: S100: Determine the formation gas production volume , the formation water production volume , the wellhead pressure, the wellbore inner diameter, the bottom-hole and wellhead temperatures, the time-step parameter, and the liquid accumulation height of the wellbore liquid accumulation section at the previous moment , the liquid accumulation volume ; S200: Calculate the water production volume that meets the liquid-carrying requirement when the liquid accumulation height is at from the wellhead downwards according to the formation gas production volume: In the formula is the liquid production volume that meets the liquid-carrying requirement at the current gas production volume, with the unit of ; is the gas production volume, with the unit of ; z is the gas compressibility factor, dimensionless; T is the temperature, with the unit of K; is the gas density in the wellbore, with the unit of ; is the friction coefficient at the apparent gas velocity, dimensionless; is the surface tension, with the unit of ; is the liquid density in the wellbore, with the unit of ; A is the cross-sectional area of the wellbore, with the unit of ; p is the wellhead pressure, with the unit of MPa; S300: Calculate the liquid accumulation volume 、 in the liquid accumulation section according to the comparison ; S400: Calculate the initial value of the liquid accumulation height according to the formula ; S500: Calculate the pressure distributions in the non-liquid accumulation section and the liquid accumulation section respectively according to the liquid accumulation height of : Liquid accumulation section: , where is the pressure gradient, with the unit of MPa / m; is the density of the mixed fluid in the wellbore, with the unit of ; g is the acceleration due to gravity, taking 9.8 ; is the angle between the wellbore and the horizontal plane, with the unit of degrees; is the friction coefficient, dimensionless; is the flow velocity of the mixed fluid, with the unit of ; D is the inner diameter of the wellbore, with the unit of m; Non-liquid accumulation section: where is the total pressure drop, with the unit of MPa; g is the acceleration due to gravity, taking 9.8 ; is the unit conversion coefficient, dimensionless, which is 1 in the International System of Units; is the gas density in the wellbore, with the unit of ; h is the depth, with the unit of m; is the friction coefficient, dimensionless; G is the mass flow rate (mass flow per unit area), with the unit of ; D is the inner diameter of the wellbore, with the unit of m; is the density of the mixed fluid in the wellbore, with the unit of ; is the density of the mixed fluid at the wellhead, with the unit of ; is the gas void fraction (gas volume fraction), dimensionless, ranging from 0 to 1; S600: Calculate the liquid holdup in the liquid accumulation section according to the formula : In the formula and are the liquid holdups in the non-liquid accumulation well section and the liquid accumulation well section, respectively, measured by on-site experiments, dimensionless; is the liquid accumulation position, in m; is the liquid holdup in the liquid accumulation section of the previous day, in m 3 ; is the change in the liquid holdup in the liquid accumulation section, in m 3 ; H is the wellbore depth, in m; A is the cross-sectional area of the wellbore, in ; h is the depth, in m; Verify and meet the accuracy requirements. If not, let , and repeat step S500 until the accuracy requirements are met, with an error less than 5%; S700: Recalculate the water production rate at which the liquid carrying requirement is met at the liquid accumulation height , verify and meet the accuracy requirements, with an error less than 5%. If not, let be substituted into step S300 for continuous calculation until remains unchanged; S800: Plot the TPC curve considering the influence of liquid accumulation with the wellbore pressure drop as the ordinate and the gas production rate as the abscissa.

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) It has a wide range of applications and can be applied to gas wells under different conditions; (2) The calculation method is convenient and effective, with high work efficiency; (3) The calculation method is easy to promote.

[0009] 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 of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A method for determining a TPC curve of a gas well under the influence of wellbore liquid loading, characterized in that: The method comprises the following steps: S100: Determine formation gas production based on field production data , formation water production , wellhead pressure, wellbore inner diameter, wellhead and bottom hole temperature, time step parameters, and the height of the liquid accumulation section of the wellbore at the previous moment , effusion volume ; S200: According to the formation gas production and formation water production, the liquid accumulation height is calculated from the wellhead downward. The water production that meets the liquid carrying requirements : In the formula It is the liquid production that meets the liquid carrying requirement under the current gas production, in units of ; is the gas production, in units of ; z is the gas compressibility coefficient, dimensionless; T is the temperature, in K; is the gas density in the wellbore, in units of ; is the friction coefficient at the gas phase apparent velocity, dimensionless; is the surface tension, in units of ; is the density of the liquid in the wellbore, in units of ; A is the wellbore cross-sectional area, in ; p is the wellhead pressure, in MPa; S300: According to the comparison , Size, calculate the amount of fluid accumulation in the effusion section ; S400: According to the formula Calculate the initial value of the effusion height ; S500: According to the height of the accumulated liquid Calculate the pressure distribution of the non-fluid accumulation section and the fluid accumulation section separately: Effusion section: ， In the formula is the pressure gradient, in MPa / m; is the density of the mixed fluid in the wellbore, in units of ; g is the acceleration due to gravity, take 9.8 ; is the angle between the wellbore and the horizontal plane, in degrees; is the friction coefficient, dimensionless; is the mixed fluid flow rate, in units of ; D is the inner diameter of the wellbore, in m; Non-effusion segment: In the formula is the total pressure drop, in MPa; g is the acceleration due to gravity, which is 9.8 ; is the unit conversion factor, dimensionless, and is 1 in the International System of Units; is the gas density in the wellbore, in units of ; h is the depth, in meters; is the friction coefficient, dimensionless; G is the mass flow rate, that is, the mass flow rate per unit area, in units of ; D is the inner diameter of the wellbore, in m; is the density of the mixed fluid in the wellbore, in units of ; is the density of the mixed fluid at the wellhead, in units of ; is the gas phase void ratio, also known as the gas phase volume fraction, dimensionless, between 0 and 1; S6 00: Calculate the amount of fluid accumulation in the fluid accumulation section according to the formula : In the formula , is the liquid holdup rate of the non-liquid-filled well section and the liquid-filled well section, measured by field experiments, dimensionless; is the effusion position, in m; The volume of fluid in the previous day's effusion segment, in m 3 ; is the change in the amount of liquid accumulation in the liquid accumulation section, in m 3 ; H is the wellbore depth in m; A is the wellbore cross-sectional area, in ; h is the depth, in meters; verify and Whether it meets the accuracy requirements, if not, a new , repeat step S500 until the accuracy requirement is met and the error is less than 5%; S700: Recalculate the liquid accumulation height Water production that meets liquid carrying requirements ,verify and Whether the accuracy requirement is met, the error is less than 5%, if not, Bring it into step S300 and continue calculating until constant; S800: The TPC curve considering the effect of liquid accumulation is drawn with the wellbore pressure drop as the vertical axis and the gas production as the horizontal axis.

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