Method for determining installation distance of liquid-accumulation-free tubular column of normal-pressure shale gas well

Abstract

The invention relates to a method for determining the installation distance of a liquid-accumulation-free tubular column of a normal-pressure shale gas well. The problems that an existing liquid-accumulation-free pipe column drainage gas recovery process is not clear in application limit, not clear in process tripping-in position and the like are solved. According to the technical scheme, the method comprises the steps that the liquid accumulation state of a gas well is calculated according to the gas production rate and the water production rate of the gas well, whether a liquid-accumulation-free tubular column needs to be put down or not is judged, if the gas well is subjected to liquid accumulation, the height of a liquid-carrying production section and the number of installed liquid-accumulation-free valves are calculated according to the actual minimum conveying pressure after the liquid-accumulation-free valves are installed, and the installation distance of the liquid-accumulation-free tubular column is determined; according to the method for determining the installation distance of the liquid-accumulation-free tubular column of the normal-pressure shale gas well, the influence of the liquid production capacity and the pressure of the gas well on the tripping-in position of the liquid-accumulation-free tubular column is considered, and the application effect of the liquid-accumulation-free tubular column under the conditions of high liquid yield and low pressure of the normal-pressure shale gas well is improved.

Description

Technical Field

[0001] This invention relates to a method for determining the installation distance of the tubing string in atmospheric pressure shale gas wells without liquid accumulation, and belongs to the field of shale gas well development. Background Technology

[0002] Atmospheric shale gas wells have low pressure coefficients, low production capacity, and poor production stability. They are also prone to water production due to fracturing fluid flowback, often leading to well shutdowns caused by fluid accumulation. Therefore, drainage and gas production technologies are needed to maintain continuous production in atmospheric shale gas wells. However, given the insufficient bottomhole pressure and low gas production, traditional methods such as optimized tubing strings, plunger pump lifting, and gas lift are inefficient in this situation. Therefore, there is an urgent need to develop a novel drainage and gas production technology designed specifically for the characteristics of low-pressure, low-yield, and easily fluid-accumulating atmospheric shale gas wells to solve current production challenges.

[0003] There are currently some studies on novel drainage and gas production technologies using non-accumulating tubing strings. For example, patent application No. 202211230225.7, entitled "Oil and Gas Well Non-Accumulating Device System," designs a non-accumulating valve system for oil and gas wells. This system utilizes the well's own energy to drain fluid, making it difficult for effective fluid to accumulate in the wellbore. Another utility model patent, application No. 2022201057416, entitled "Non-Accumulating Valve," elaborates on the valve's internal structure design and operating mechanism, further revealing key technical details for improving drainage efficiency. Nevertheless, liquid-free tubing is still in the experimental and analytical stage. It has been initially applied in some atmospheric shale gas wells and low-pressure water-producing gas wells. The main challenge is that the liquid-free tubing has a complex structure and complex gas-liquid two-phase flow law in the wellbore, which leads to unclear installation distance of the liquid-free tubing for drainage and gas production. The drainage and gas production effect of some test wells is not good, which affects the large-scale application of liquid-free tubing. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of unclear application boundaries and unclear insertion points of the current liquid-free tubing drainage gas production process, and to facilitate the application of drainage gas production technology in atmospheric pressure shale gas wells.

[0005] To achieve the above objectives, the present invention provides a method for determining the installation distance of the tubing string in atmospheric pressure shale gas wells without liquid accumulation, the method comprising the following steps: S100. Prepare parameters for atmospheric pressure shale gas wells, including gas production, water production, tubing inner diameter, bottom hole flowing pressure, average wellbore temperature, minimum transmission pressure, well depth, natural gas density at average temperature and pressure, and water density. S200. Calculate the height of the production section with fluid in the wellbore when no fluid-free tubing string is available, and determine whether a fluid-free tubing string is necessary. The steps are as follows: S201, Based on empirical formulas Calculate the liquid holdup in the liquid-containing production section ;in The liquid holdup in the production section is dimensionless; D is the inner diameter of the tubing, in meters. The density of natural gas at average temperature and pressure is expressed in kg / m³. The apparent velocity in the gas phase is expressed in m / s. S202, According to the formula Calculate the pressure gradient in the liquid-containing production section; where This is the density of water, expressed in kg / m³. This is the acceleration due to gravity, expressed in kg·m / s². S203, According to the formula Calculate the height of the production section with fluid in the wellbore when there is no fluid-free tubing string. ,like If the value is less than zero, it indicates that the gas well can carry liquid for production, and the liquid-free tubing string is not applicable; therefore, further calculations are not performed. A value greater than zero indicates that the gas well has a production section with liquid present; if If the depth is greater than the well depth, then set it to equal the well depth; where The height of the fluid-bearing production section of the wellbore without a fluid-free tubing string, in meters; This refers to the bottom hole flowing pressure, expressed in MPa. Gas production is expressed in m³ / d; Z is the natural gas deviation factor, dimensionless; T is the wellbore average temperature, in K; A is the tubing cross-sectional area, in m². The critical liquid-carrying velocity is expressed in m / s. Pressure under standard conditions, expressed in MPa; Temperature under standard conditions, in Kelvin (K). The pressure gradient in the liquid-containing production section is expressed in Pa / m. S300. Calculate the height of the liquid-carrying production section after installing the anti-liquidation valve. The steps are as follows: S301, according to Liquid holdup in liquid-carrying production section HLC; where Liquid holdup in the liquid-carrying production section, dimensionless; The apparent flow rate of the liquid phase is expressed in m / s. The proportion of liquid phase in the gas core to the total liquid phase is dimensionless. S302, according to Calculate the pressure gradient in the liquid-carrying production section; where is Friction coefficient, dimensionless; S303, According to the formula Calculate the height of the liquid-carrying production section after installing the liquid-free valve. ,in The height of the liquid-carrying production section after installing the liquid-free valve; This is the minimum transmission pressure, expressed in MPa. This represents the pressure gradient in the liquid-carrying production section, expressed in Pa / m. The depth is measured in meters (m). S400. Calculate the minimum number of liquid-free valves to be installed. The steps are as follows: S401, According to the formula Calculate the height of the liquid-carrying production section below the non-accumulating valve, where The drag coefficient is dimensionless. The average diameter of the droplet is in meters. S402, According to the formula Calculate the minimum number of liquid-free valves to be installed, where The minimum number of liquid-free valves to be installed, an integer, dimensionless. The height of the liquid-carrying production section below the liquid-free valve is measured in meters. S500, according to the formula Calculate the minimum installation distance for the liquid-free tubing string, where Minimum installation distance for tubing to prevent liquid accumulation, in meters.

[0006] The method of this invention can calculate the insertion position of the liquid-free valve, taking into account the gas well production rate and pressure, which helps to improve the application effect of the liquid-free tubing string under high production and low pressure conditions in atmospheric shale gas wells. Attached Figure Description

[0007] Figure 1 This is the technical roadmap for this method; Figure 2 This is a cross-sectional view of the liquid-free tubing column; Figure 3 This is a wellbore pressure distribution diagram after the fluid-free tubing string was installed in well Z1. Detailed Implementation

[0008] The invention will now be further described with reference to the accompanying drawings.

[0009] This invention provides a method for determining the installation distance of the tubing string in atmospheric pressure shale gas wells without liquid accumulation. Figure 1 The technical roadmap for this method mainly includes the following steps: Step 1: Prepare parameters for atmospheric shale gas wells, including gas production, water production, tubing inner diameter, bottom hole flowing pressure, average wellbore temperature, minimum delivery pressure, well depth, and the density of natural gas and water at average temperature and pressure. Step 2: Calculate the liquid holdup rate in the liquid-containing production section. and pressure gradient in liquid production section , bring in If the height of the fluid-bearing production section in the wellbore is obtained without a fluid-free tubing string, If the value is less than zero, it indicates that the gas well can carry liquid for production, and the liquid-free tubing string is not applicable; therefore, further calculations are not performed. A value greater than zero indicates that the gas well has a production section with liquid in it; in, The liquid holdup in the production section is dimensionless; D is the inner diameter of the tubing, in meters. The density of natural gas at average temperature and pressure is expressed in kg / m³. The apparent velocity in the gas phase is expressed in m / s. This is the density of water, expressed in kg / m³. This is the acceleration due to gravity, expressed in kg·m / s². The height of the fluid-bearing production section of the wellbore without a fluid-free tubing string, in meters; This refers to the bottom hole flowing pressure, expressed in MPa. Gas production is expressed in m³ / d; Z is the natural gas deviation factor, dimensionless; T is the wellbore average temperature, in K; A is the tubing cross-sectional area, in m². The critical liquid-carrying velocity is expressed in m / s. Pressure under standard conditions, expressed in MPa; Temperature under standard conditions, in Kelvin (K). The pressure gradient in the liquid-containing production section is expressed in Pa / m. The third step is to calculate the liquid holdup in the liquid-carrying production section. Pressure gradient in liquid-carrying production section Substitute the calculation results into The height of the liquid-carrying production section after the installation of the liquid-free valve is obtained; in Liquid holdup in the liquid-carrying production section, dimensionless; The apparent flow rate of the liquid phase is expressed in m / s. The proportion of liquid phase in the gas core to the total liquid phase is dimensionless. The coefficient of friction is dimensionless. The height of the liquid-carrying production section after installing the liquid-free valve; This is the minimum transmission pressure, expressed in MPa. This represents the pressure gradient in the liquid-carrying production section, expressed in Pa / m. The depth is measured in meters (m). The fourth step is to calculate the height of the liquid-carrying production section below the non-accumulating valve. To obtain the minimum number of liquid-free valves capable of carrying liquid. ; in The drag coefficient is dimensionless. The average diameter of the droplet is in meters. The minimum number of liquid-free valves to be installed, an integer, dimensionless. The height of the liquid-carrying production section below the liquid-free valve is measured in meters. Fifth step, according to the formula The minimum installation distance for the liquid-free valve is obtained based on the height of the liquid-bearing production section in the wellbore when no liquid-free valve is available.

[0010] Taking well Z1 as an example, well Z1 is a shale gas well in a domestic atmospheric pressure shale gas field. On November 5, 2023, the well's daily gas production was 1.1×104 m3 / d, water production was 10.1 m3 / d, bottom hole flowing pressure was 8.8 MPa, the well's tubing inner diameter was 0.0503 m, the wellbore average temperature was 325.15 K, the minimum transmission pressure was 3.0 MPa, the well depth was 2110 m, and under the average temperature and pressure conditions, the density of natural gas was 32.0 kg / m3, and the density of water was 1050 kg / m3. The pressure gradient of the fluid-carrying production section is calculated to be 6135 Pa / m according to the formula, and the pressure gradient of the fluid-carrying production section is 1208 Pa / m. Without a fluid-free tubing string, the height of the fluid-carrying production section in the wellbore is 675.0 m. According to the formula, the height of the fluid-carrying production section below a single fluid-free tubing valve is 24.6 m. Fluid-free tubing strings are applicable. The minimum number of fluid-free valves to be installed is 2, and the maximum installation distance is 337.5 m.

[0011] Compared with the prior art, the present invention has the following advantages: the method takes into account the influence of pressure, gas production and water production before and after the installation of the liquid-free tubing valve on the liquid accumulation height in the wellbore, and establishes a method for determining the installation distance of the liquid-free tubing string, so that on-site personnel can easily determine the lowering position of the liquid-free tubing string.

[0012] Finally, it should be noted that the above embodiments are only used to illustrate and not 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 modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for determining the installation distance of a liquid-free tubing string in an atmospheric pressure shale gas well, characterized in that, The method includes the following steps: S100. Prepare parameters for atmospheric pressure shale gas wells, including gas production, water production, tubing inner diameter, bottom hole flowing pressure, average wellbore temperature, minimum transmission pressure, well depth, natural gas density at average temperature and pressure, and water density. S200. Calculate the height of the production section with fluid in the wellbore when there is no fluid-free tubing string. The steps are as follows: S201, Based on empirical formulas Calculate the liquid holdup in the liquid-containing production section ;in The liquid holdup in the liquid-carrying production section is dimensionless. D This refers to the inner diameter of the oil pipe, in meters (m). The density of natural gas at average temperature and pressure, in kg / m³. 3 ; The apparent velocity in the gas phase is expressed in m / s. S202, According to the formula Calculate the pressure gradient in the liquid-containing production section; where This is the density of water, expressed in kg / m³. 3 ; This is the acceleration due to gravity, with units of kg·m / s². 2 ; S203, According to the formula Calculate the height of the production section with fluid in the wellbore when there is no fluid-free tubing string. ,like If the value is less than zero, it indicates that the gas well can carry liquid for production, and the liquid-free tubing string is not applicable; therefore, further calculations are not performed. A value greater than zero indicates that the gas well has a production section with liquid present; if If the depth is greater than the well depth, then set it to equal the well depth; where The height of the fluid-bearing production section of the wellbore without a fluid-free tubing string, in meters; This refers to the bottom hole flowing pressure, expressed in MPa. Gas production, in m³ 3 / d; Z The natural gas deviation factor is dimensionless. T The average temperature of the wellbore is expressed in Kelvin (K). A This refers to the cross-sectional area of ​​the oil pipe, in meters (m²). 2 ; The critical liquid-carrying velocity is expressed in m / s. Pressure under standard conditions, expressed in MPa; Temperature under standard conditions, in Kelvin (K). The pressure gradient in the liquid-containing production section is expressed in Pa / m. S300. Calculate the height of the liquid-carrying production section after installing the anti-liquidation valve. The steps are as follows: S301, according to Liquid holdup in liquid-carrying production section H LC ;in Liquid holdup in the liquid-carrying production section, dimensionless; The apparent flow rate of the liquid phase is expressed in m / s. The proportion of liquid phase in the gas core to the total liquid phase is dimensionless. S302, according to Calculate the pressure gradient in the liquid-carrying production section; where is Friction coefficient, dimensionless; S303, According to the formula Calculate the height of the liquid-carrying production section after installing the liquid-free valve. ,in The height of the liquid-carrying production section after the installation of the liquid-free valve, in meters; This is the minimum transmission pressure, expressed in MPa. This represents the pressure gradient in the liquid-carrying production section, expressed in Pa / m. The depth is measured in meters (m). S400, calculate the minimum number of liquid-free valves to be installed, the steps are as follows: S401, According to the formula Calculate the height of the liquid-carrying production section below the non-accumulating valve, where The drag coefficient is dimensionless. The average diameter of the droplet is in meters. S402, According to the formula Calculate the minimum number of liquid-free valves to be installed, where The minimum number of liquid-free valves to be installed, an integer, dimensionless. The height of the liquid-carrying production section below the liquid-free valve is measured in meters. S500, according to the formula Calculate the minimum installation distance for the liquid-free tubing string, where Minimum installation distance for tubing to prevent liquid accumulation, in meters.

Images