Experimental method for evaluating reverse wetting water seal splitting recovery potential of flooded gas well

Abstract

The invention relates to an experimental method for evaluating the reverse wetting water seal splitting recovery potential of a flooded gas well, and belongs to the field of oil-gas field development. According to the technical scheme, the scientific analysis method for evaluating the water seal breaking effect of the flooded gas well based on wetting reversal is established. According to the technical scheme, the method comprises the steps that well circumference pressure gradient distribution data of a target gas well under the current productivity are obtained; respectively obtaining wetting angles of the reservoir core before and after wetting reversal and corresponding well periphery breakthrough pressure gradient distribution data; comparing the three types of distribution data, evaluating the recovery potential of the reverse wetting measure on the water seal removal of the target gas well according to the comparison result, and quickly and intuitively evaluating the application effect of the reverse wetting agent; the method is good in practical application effect, reliable in result and high in generalizability.

Description

Technical Field

[0001] This invention relates to an experimental method for evaluating the potential of water-flooded gas wells to break water seals and resume production, belonging to the field of oil and gas field development. Background Technology

[0002] As natural gas field development deepens, water has been commonly encountered in many old gas reservoirs, leading to increasingly serious problems of water intrusion and flooding in gas wells. Water intrusion refers to the invasion of formation water into the gas reservoir during development, resulting in increased water production rate, a sharp decline in gas phase permeability, and even water flooding of gas wells, causing production shutdowns. Injecting wetting reversal agents to break the water seal is a common field practice. Wetting reversal agents can change the wettability of rock surfaces, changing them from hydrophilic to hydrophobic, reducing water phase retention, and enhancing gas flow capacity. Therefore, quantitatively evaluating the potential for water seal breaking and production recovery in water-flooded gas wells through wetting reversal is beneficial for optimizing drainage and gas production processes and accurately tapping the potential of remaining gas.

[0003] Based on extensive research, the "Method for Unblocking and Resuming Production of Sealed Gas Wells" (application number CN201911199216.4) utilizes coiled tubing technology and chemical unblocking agents to specifically unblock polymer and inorganic contaminants within the wellbore, improving reservoir seepage conditions near the well bottom. The "A Diagnostic Method for the Resumption Capacity of Water-Producing Gas Wells After Shutdown" (application number CN202410013710.1) is based on gas well node analysis theory. By establishing inflow and outflow dynamic curves and combining them with critical fluid-carrying flow rates, it diagnoses the natural resumption capacity of water-producing gas wells after shutdown. The "An Experimental Evaluation Method for Water Lock Damage in Gas Reservoirs" (application number CN202011527150.X) uses centrifuges to control water saturation, converts mercury intrusion curves into capillary pressure, measures gas permeability changes, and calculates the damage severity coefficient.

[0004] In general, there are many methods for resuming production of water-flooded gas wells after water seal is broken, but most of them focus on on-site operation, production dynamic diagnosis or damage assessment. There are few methods for quantitatively evaluating the potential for breaking water seal based on wetting reversal. There is a need for a method that considers the impact of wetting reversal on the wellbore breakthrough pressure gradient under wetting reversal agent treatment, and can conveniently evaluate the potential for resuming production of water-flooded gas wells after water seal is broken. Summary of the Invention

[0005] The purpose of this invention is to establish a scientific analytical method for evaluating the water-sealing effect of wetting reversal on water-flooded gas wells. This invention obtains the wellbore pressure gradient distribution data of the target gas well under its current production capacity; it obtains the wetting angle and corresponding wellbore breakthrough pressure gradient distribution data of the reservoir core before and after wetting reversal; it compares the above three types of distribution data, and evaluates the production recovery potential of wetting reversal measures for water-sealing in the target gas well based on the comparison results, and quickly and intuitively assesses the application effect of wetting reversal agents; this invention has good practical application results, reliable results, and strong scalability.

[0006] To achieve the above objectives, this invention provides an experimental method for evaluating the potential for water-flooded gas wells to break water seals and resume production. This method includes the following steps: S100: Obtain the wellbore pressure gradient distribution data of the target gas well under the current production capacity; S200, obtain the wetting angle and wellbore breakthrough pressure gradient distribution data of the target gas well reservoir core before wetting reversal; S300, obtain the wetting angle and wellbore breakthrough pressure gradient distribution data of the target gas well reservoir core after wetting reversal; S400 compares the wellbore pressure gradient distribution data, the wellbore breakthrough pressure gradient distribution data before wetting reversal, and the wellbore breakthrough pressure gradient distribution data after wetting reversal, and evaluates the potential for wetting reversal to break the water seal and restore production of the target gas well based on the comparison results.

[0007] In the above-mentioned experimental method for evaluating the potential for water-flooded gas wells to break water seals and resume production, the step of obtaining the wellbore pressure gradient distribution data of the target gas well under the current production capacity involves collecting the production parameters and reservoir parameters of the target gas well and substituting them into the wellbore pressure gradient calculation formula. The wellbore pressure gradient distribution data of the target gas well under the current production capacity is obtained, where, This represents the pressure gradient, in MPa / m. Gas well production, in meters (m³) 3 / d; Reservoir temperature, in Kelvin (K). This is the gas compressibility factor, and its unit is dimensionless. The average viscosity of the gas is expressed in mPa·s. Reservoir permeability, in mD; The reservoir thickness is expressed in meters (m). Mean formation pressure, in MPa; The radius of the well is in meters (m).

[0008] In the above-mentioned experimental method for evaluating the potential of water-flooded gas wells to break water seal and resume production, the method for obtaining the wetting angle of the target gas well reservoir core before and after wetting reversal is to test the wetting angle of the outlet end face of the target gas well reservoir core under reservoir temperature and pressure conditions using a wetting angle measuring instrument.

[0009] In the above-mentioned experimental method for evaluating the potential of water-flooded gas wells to break water seals and resume production, the acquisition of the corresponding wellbore breakthrough pressure gradient distribution data involves first performing a centrifugal dehydration experiment on the core sample of the target gas well reservoir, and then, according to the formula... Converting the rotational speed to the wellbore radius yields the wellbore water saturation distribution data. Then, a gas breakthrough pressure experiment is conducted on the target gas well reservoir core to obtain water saturation and breakthrough pressure gradient data. Finally, a mapping relationship between the wellbore radius and the breakthrough pressure gradient is established to obtain the corresponding wellbore breakthrough pressure gradient distribution data. Where, The radius of the well is in meters. Gas well production, in meters (m³) 3 / d; Reservoir temperature, in Kelvin (K). This is the gas compressibility factor, and its unit is dimensionless. The average viscosity of the gas is expressed in mPa·s. Reservoir permeability, in mD; The reservoir thickness is expressed in meters (m). Mean formation pressure, in MPa; This refers to the density of formation water, expressed in kg / m³. 3 ; Rotational speed, in rpm; This refers to the centrifugal radius of the centrifuge, expressed in meters (m). This represents the core length, in meters (m).

[0010] In the above-mentioned experimental method for evaluating the potential of water-flooded gas wells to revert to wetted conditions and break water seals for production recovery, the final establishment of the mapping relationship between the well radius and the breakthrough pressure gradient is as follows: for data points with the same water saturation in the same interval, the well radius and breakthrough pressure gradient are directly matched to establish the mapping relationship; for data points with different water saturation in the same interval, conformal interpolation is performed to the same point and then matched to establish the mapping relationship; and for data points with different water saturation in different intervals, curve fitting is performed to establish the mapping relationship.

[0011] In the above-mentioned experimental method for evaluating the potential of water seal breaking and production recovery of water-flooded gas wells by wetting reversal, the evaluation of the production recovery potential of the target gas well by wetting reversal based on the comparison results is as follows: if the wellbore pressure gradient is lower than the breakthrough pressure gradient before wetting reversal but higher than the breakthrough pressure gradient after wetting reversal, then the water seal breaking and production recovery effect of wetting reversal is significant; if the wellbore pressure gradient is lower than both the wellbore breakthrough pressure gradient before and after wetting reversal, then the water seal breaking and production recovery effect of wetting reversal is not significant; if the wellbore pressure gradient is higher than both the wellbore breakthrough pressure gradient before and after wetting reversal, then wetting reversal has an improving effect on gas well production.

[0012] Compared with the prior art, the present invention has the following advantages: (1) It combines theory with practice to quickly and intuitively evaluate the water seal potential of gas wells under different wetting angles; (2) The testing process is simple and easy to use; (3) It has strong scalability. Attached Figure Description

[0013] In the attached diagram: Figure 1 It is a methodology and technology roadmap.

[0014] Figure 2 This is a chart evaluating the potential for resuming production after the water seal is broken in the X-12# water-flooded gas well.

[0015] Figure 3 This is a chart evaluating the potential for resuming production after the water seal is broken in the X-19# water-flooded gas well. Detailed Implementation

[0016] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0017] This invention provides an experimental method for evaluating the potential for regeneration and recovery of water-flooded gas wells by wetting reversal and water seal breaking. Figure 1 This is a technical roadmap for the method, which includes the following steps: S100: Obtain the wellbore pressure gradient distribution data of the target gas well under the current production capacity; S200, obtain the wetting angle and wellbore breakthrough pressure gradient distribution data of the target gas well reservoir core before wetting reversal; S300, obtain the wetting angle and wellbore breakthrough pressure gradient distribution data of the target gas well reservoir core after wetting reversal; S400 compares the wellbore pressure gradient distribution data, the wellbore breakthrough pressure gradient distribution data before wetting reversal, and the wellbore breakthrough pressure gradient distribution data after wetting reversal, and evaluates the potential for wetting reversal to break the water seal and restore production of the target gas well based on the comparison results.

[0018] Furthermore, the method for obtaining the wellbore pressure gradient distribution data of the target gas well under the current production capacity involves collecting the production parameters and reservoir parameters of the target gas well and inputting them into the wellbore pressure gradient calculation formula to obtain the wellbore pressure gradient distribution data of the target gas well under the current production capacity. The specific steps are as follows: S101, substituted the parameters of average gas viscosity, gas well production, reservoir temperature, reservoir permeability, gas compressibility factor, average formation pressure, and reservoir thickness into the wellbore pressure gradient calculation formula. We obtain a discrete dataset of the wellbore pressure gradient with respect to the wellbore radius under the current production capacity, where, This represents the pressure gradient, in MPa / m. Gas well production, in meters (m³) 3 / d; Reservoir temperature, in Kelvin (K). This is the gas compressibility factor, and its unit is dimensionless. The average viscosity of the gas is expressed in mPa·s. Reservoir permeability, in mD; The reservoir thickness is expressed in meters (m). Mean formation pressure, in MPa; The radius of the well is in meters (m).

[0019] Furthermore, the method for obtaining the wetting angle of the target gas well reservoir core before and after wetting reversal is as follows: using a wetting angle measuring instrument, the wetting angle of the outlet end face of the target gas well reservoir core is tested under reservoir temperature and pressure conditions.

[0020] Furthermore, the specific steps for obtaining the corresponding wellbore breakthrough pressure gradient distribution data are as follows: S201. After cleaning the core, dry it in a constant temperature drying oven and record the dry weight. Then, vacuum the core, saturate it with formation water and record the wet weight. Calculate the core saturation using the weighing method according to the formula. S202, put the core saturated with formation water into the centrifuge tube of a centrifuge for centrifugation dehydration experiment, record the rotation speed at this time, calculate the water saturation at this time by weighing method, and then gradually increase the rotation speed for centrifugation dehydration. Repeat this step to obtain the data of water saturation of the core before wetting reversal with respect to rotation speed. S203, according to the formula, Converting the rotational speed to the well circumference radius yields the well circumference water saturation distribution data, where, The radius of the well is in meters. Gas well production, in meters (m³) 3 / d; Reservoir temperature, in Kelvin (K). This is the gas compressibility factor, and its unit is dimensionless. The average viscosity of the gas is expressed in mPa·s. Reservoir permeability, in mD; The reservoir thickness is expressed in meters (m). Mean formation pressure, in MPa; This refers to the density of formation water, expressed in kg / m³. 3 ; Rotational speed, in rpm; This refers to the centrifugal radius of the centrifuge, expressed in meters (m). This refers to the core length, in meters (m). S204, after cleaning the core, it is dried in a constant temperature drying oven, then vacuumed, and then the core is resaturated with formation water. S205. The core is placed in a core holder with temperature control, and confining pressure is applied. The experimental temperature is the formation temperature, and the outlet pressure is set to be 0.1 MPa~1.0 MPa higher than the saturated vapor pressure of formation water. The gas source is connected to the inlet end of the core, and the inlet pressure is gradually increased. When the outlet flow meter just shows a non-zero and constant value, the pressure difference between the inlet and outlet is recorded and divided by the core length. This is the gas breakthrough pressure gradient of the core. The core is then removed, and the water saturation at this time is calculated using the weighing method. S206, the core was centrifuged and dehydrated to reduce the water saturation of the core. The gas breakthrough pressure experiment was repeated to obtain data on the breakthrough pressure gradient of the core before wetting reversal with respect to water saturation. S207 Finally, the mapping relationship between the wellbore radius and the breakthrough pressure gradient is established to obtain the corresponding wellbore breakthrough pressure gradient distribution data.

[0021] Furthermore, the specific steps for establishing the mapping relationship between the wellbore radius and the breakthrough pressure gradient are as follows: S301, for points in the data of centrifugal dehydration experiment and gas breakthrough pressure experiment where the water saturation value is the same, by data matching, the corresponding breakthrough pressure gradient and well radius are associated to obtain the mapping relationship of breakthrough pressure gradient with respect to well radius; S302, for the data of centrifugal dehydration experiment and gas breakthrough pressure experiment, for the points in the overlapping interval of water saturation, the conformal interpolation method is used to interpolate the data points to unify the data to the same water saturation value, and then through data matching, the mapping relationship of breakthrough pressure gradient with respect to well radius is established within the interval; S303. For the points outside the overlapping interval of water saturation in the data of centrifugal dehydration experiment and gas breakthrough pressure experiment, the logarithmic curve equation is obtained by logarithmic fitting of the centrifugal dehydration experiment data and the exponential curve equation is obtained by exponential fitting of the gas breakthrough pressure experiment data with the natural constant as the base. By solving the two equations simultaneously, the mapping relationship of the breakthrough pressure gradient outside the interval with respect to the well radius is obtained.

[0022] Furthermore, the evaluation of the potential for water seal reversal in the target gas well to restore production based on the comparison results is as follows: if the wellbore pressure gradient is lower than the breakthrough pressure gradient before water seal reversal but higher than the breakthrough pressure gradient after water seal reversal, then the water seal reversal effect of water seal restoration is significant; if the wellbore pressure gradient is lower than both the breakthrough pressure gradient before and after water seal reversal, then the water seal restoration effect of water seal restoration is not significant; if the wellbore pressure gradient is higher than both the breakthrough pressure gradient before and after water seal reversal, then water seal reversal has an improving effect on gas well production.

[0023] Taking X-12# and X-19# as examples, core samples No. 1 from X-12# and No. 2 from X-19# were used to conduct an evaluation experiment on the potential for water-flooded gas wells to break the water seal and resume production. The average formation pressure of X-12# was 27.18 MPa, the reservoir temperature was 379.62 K, the average gas viscosity was 0.020164 mPa·s, the gas compressibility factor was 0.99138, the reservoir thickness was 30.86 m, the reservoir permeability was 0.4 mD, and the daily production of X-12# was 6089 m³. 3 / d, X-19# average formation pressure 6.5 MPa, X-19# reservoir temperature 379.62 K, X-19# gas average viscosity 0.014539 mPa·s, X-19# gas compressibility factor 0.96696, X-19# reservoir thickness 30.86 m, X-19# reservoir permeability 3.25 mD, X-19# daily production 83521 m³ / d. 3 / d, core geometric parameters and other detailed parameters are shown in Table 1.

[0024] Table 1 Detailed Parameter Table By substituting the parameters of average gas viscosity, gas well production, reservoir temperature, reservoir permeability, gas compressibility factor, average formation pressure, and reservoir thickness into the wellbore pressure gradient calculation formula, the wellbore pressure gradient distribution data of the target gas well under the current production capacity is obtained. The specific data are shown in Table 2.

[0025] Table 2. Wellbore pressure gradient distribution data of the target gas well at current production capacity. Wetting angle tests, centrifugal dehydration experiments, and gas breakthrough pressure experiments were conducted to obtain the wetting angle and corresponding wellbore breakthrough pressure gradient distribution data of the target gas well reservoir cores before wetting reversal. Among them, the wetting angle of core No. 1 of X-12# before wetting reversal was 43.023°, and the wetting angle of core No. 2 of X-19# before wetting reversal was 45.827°. Specific data are shown in Tables 3, 4, 5, and 6.

[0026] Table 3. Centrifugation and breakthrough pressure test data of core No. 1 of X-12# before wetting and reversal. Table 4. Distribution of perimeter breakthrough pressure gradient before wetting reversal at X-12# wellhead. Table 5. Centrifugation and breakthrough pressure test data of core No. 2 of X-19# before wetting and reversal. Table 6. Distribution of perimeter breakthrough pressure gradient before wetting reversal of X-19# wellhead. The core was displaced using a wetting reversal agent, and the wetting angle at the core outlet was tested. The wetting angle after wetting reversal and the corresponding wellbore breakthrough pressure gradient distribution data were obtained. The wetting angle after wetting reversal of core No. 1 of X-12# was 83.926°, and the wetting angle after wetting reversal of core No. 2 of X-19# was 86.321°. Specific data are shown in Tables 7, 8, 9 and 10.

[0027] Table 7. Centrifugation and breakthrough pressure test data of core No. 1 of X-12# after wetting reversal. Table 8. Wellbore breakthrough pressure gradient distribution data after wetting reversal at X-12# Table 9. Centrifugation and breakthrough pressure test data of core No. 2 of X-19# after wetting reversal. Table 10. Wellbore breakthrough pressure gradient distribution data after wetting reversal of X-19# The wellbore pressure gradient distribution data, the wellbore breakthrough pressure gradient distribution data before wetting reversal, and the wellbore breakthrough pressure gradient distribution data after wetting reversal are compared. Based on the comparison results, the potential for wetting reversal to restore production in the target gas well by breaking the water seal is evaluated. Figure 2 and Figure 3 ,exist Figure 2 The pressure gradient around well X-12# remained consistently lower than the breakthrough pressure gradient, resulting in insignificant water seal release and production recovery due to wetting reversal, making production recovery difficult. Figure 3 The wetting reversal of the X-19# gas well has an improving effect on gas well production, increasing the wellbore control radius. Figure 2 and Figure 3 This allows for a direct and rapid evaluation of the potential for water-sealed gas wells to resume production under different wetting angles, providing a basis for decision-making regarding wetting reversal measures.

[0028] Compared with the prior art, the present invention has the following advantages: (1) It combines theory with practice, and the pressure response characteristic curve chart is more convenient and faster; (2) The testing process is simple and easy to use; (3) It has strong scalability.

[0029] 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 evaluating the potential of a watered-out gas well for re-production by reversing the water seal and wetness reversal, characterized in that, The method comprises the following steps: S100, acquiring wellbore pressure gradient distribution data of a target gas well under current deliverability; S200, acquiring a wetting angle of a reservoir core of the target gas well before wetting reversal and wellbore breakthrough pressure gradient distribution data before wetting reversal; S300, acquiring a wetting angle of the reservoir core of the target gas well after wetting reversal and wellbore breakthrough pressure gradient distribution data after wetting reversal; S400, comparing the wellbore pressure gradient distribution data, the wellbore breakthrough pressure gradient distribution data before wetting reversal and the wellbore breakthrough pressure gradient distribution data after wetting reversal, and evaluating the production potential of the target gas well after wetting reversal according to the comparison result.

2. The method of claim 1, wherein, The wellbore pressure gradient distribution data of the target gas well under current productivity is obtained by collecting production parameters and reservoir parameters of the target gas well and bringing them into a wellbore pressure gradient calculation formula , obtaining the wellbore pressure gradient distribution data of the target gas well under current productivity, wherein, is a pressure gradient, with a unit of MPa / m; is a gas well production, with a unit of m 3 / d; is a reservoir temperature, with a unit of K; is a gas compressibility factor, with a unit of dimensionless; is a gas average viscosity, with a unit of mPa·S; is a reservoir permeability, with a unit of mD; is a reservoir thickness, with a unit of m; is an average formation pressure, with a unit of MPa; is a wellbore radius, with a unit of m.

3. The method of claim 1, wherein: The method for acquiring the wetting angle of the reservoir core of the target gas well before wetting reversal in S200 and the wetting angle of the reservoir core of the target gas well after wetting reversal in S300 is that a wetting angle measuring instrument is used to test the wetting angle of an outlet end surface of the reservoir core under reservoir temperature and pressure conditions.

4. The method of claim 1, wherein: The wellbore breakthrough pressure gradient distribution data before wetting reversal in S200 and the wellbore breakthrough pressure gradient distribution data after wetting reversal in S300 are obtained by first performing centrifugal dehydration experiments on the core of the target gas well reservoir, according to the formula... Converting the rotational speed to the wellbore radius yields the wellbore water saturation distribution data. Then, a gas breakthrough pressure experiment is conducted on the target gas well reservoir core to obtain water saturation and breakthrough pressure gradient data. Finally, a mapping relationship between the wellbore radius and the breakthrough pressure gradient is established to obtain the corresponding wellbore breakthrough pressure gradient distribution data. Where, The radius of the well is in meters. Gas well production, in meters (m³) 3 / d; Reservoir temperature, in Kelvin (K). This is the gas compressibility factor, and its unit is dimensionless. The average viscosity of the gas is expressed in mPa·s. Reservoir permeability, in mD; The reservoir thickness is expressed in meters (m). Mean formation pressure, in MPa; This refers to the density of formation water, expressed in kg / m³. 3 ; Rotational speed, in rpm; This refers to the centrifugal radius of the centrifuge, expressed in meters (m). This represents the core length, in meters (m).

5. The method of claim 4, wherein: The mapping relationship between the wellbore radius and the breakthrough pressure gradient is established by directly matching the wellbore radius and the breakthrough pressure gradient corresponding to the data points with the same water saturation in the same interval, by matching the wellbore radius and the breakthrough pressure gradient corresponding to the data points with different water saturations in the same interval after shape-preserving interpolation to the same point, and by curve fitting the wellbore radius and the breakthrough pressure gradient corresponding to the data points with different water saturations in different intervals.

6. The method of claim 1, wherein: The evaluation of the production potential of the target gas well after wetting reversal according to the comparison result is that if the wellbore pressure gradient is lower than the breakthrough pressure gradient before wetting reversal but higher than the breakthrough pressure gradient after wetting reversal, the effect of wetting reversal on the production of the target gas well is remarkable, if the wellbore pressure gradient is lower than the wellbore breakthrough pressure gradient before wetting reversal and after wetting reversal, the effect of wetting reversal on the production of the target gas well is not remarkable, and if the wellbore pressure gradient is higher than the wellbore breakthrough pressure gradient before wetting reversal and after wetting reversal, the effect of wetting reversal on the production of the target gas well is improved.

Images