A method for phase transition water shutoff in a water-containing reservoir

Abstract

The application discloses a method for water plugging of a water-containing reservoir by phase change. The method comprises the following steps: according to engineering requirements, the type of temperature-sensitive water plugging material used in a water-containing target well is selected; the amount of a preflush is determined according to reservoir data and well basic data; the distance between the water plugging material-displacement fluid interface and the wellbore is determined according to the direction of water in the target well; the amount of displacement fluid is determined according to the distance between the position of the water plugging material-displacement fluid interface and the wellbore, the volume of the wellbore and the filtration of the displacement fluid to the formation; the plugging length and the amount of water plugging material are determined in combination with the early liquid production data of the target well, the fracturing reconstruction data and the water plugging demand of the target well. According to the determined amounts of the preflush, the water plugging material and the displacement fluid, the preflush, the water plugging material and the displacement fluid are injected into the target well in sequence, and well shut-in is performed for a preset time length, and then flowback is performed. The application provides guidance for inverse temperature phase change water plugging design and construction, expands the application of water plugging materials in the oil and gas industry and improves the development efficiency of oil and gas reservoirs.

Description

Technical Field

[0001] This invention relates to the field of petroleum development technology, and in particular to a method for phase change water shut-off in aquifer reservoirs. Background Technology

[0002] During water injection development of sandstone reservoirs, due to factors such as reservoir heterogeneity, natural fracture orientation, and fracturing fracture scale, injected water or reservoir edge and bottom water can rapidly flow into oil wells along the high-permeability channels of natural and artificial fractures, leading to water flooding of oil wells. This results in problems such as reduced water drive sweep volume, decreased oil displacement efficiency, premature water breakthrough in oil wells, and persistently high water cut, thereby reducing the oil recovery rate and severely restricting the efficient and sustainable development of oil reservoirs. Therefore, water shut-off of oil wells is of great significance for oil reservoir development.

[0003] Currently, conventional oil well water shut-off technology mainly utilizes particulate plugging agents and non-particulate plugging agents such as gels and jelly. However, the following problems exist: First, the design and construction process of water shut-off schemes are complex, the injection rate is low, and the construction period is long; second, for high-permeability channels such as artificial fractures, conventional water shut-off materials have limited sealing range and sealing strength, resulting in unsatisfactory overall water shut-off effect. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method for phase change water shut-off in aquifers that overcomes or at least partially solves the above problems.

[0005] In a first aspect, embodiments of the present invention provide a method for phase change water shut-off in an aquifer, comprising:

[0006] Based on the project requirements, select the type of temperature-sensitive plugging material to be used in the target well containing water;

[0007] Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off;

[0008] Based on the direction of water in the target well determined through prior analysis, the location of the water-plugging material-displacement fluid interface and the distance between it and the wellbore are determined.

[0009] The amount of displacement fluid used is determined based on the distance between the water-blocking material-displacement fluid interface and the wellbore, the volume of the wellbore, and the amount of displacement fluid lost to the formation.

[0010] Based on the target well's pre-production fluid data, fracturing stimulation data, and water shut-off requirements, determine the sealing length of the water shut-off material; determine the amount of water shut-off material to be used based on the sealing length of the water shut-off material.

[0011] Based on the determined amounts of the pre-flush fluid, the displacement fluid, and the water-blocking material, the corresponding amounts of the pre-flush fluid, the water-blocking material, and the displacement fluid are injected into the target well in sequence, and the well is shut in for a preset time before being flushed back.

[0012] In one embodiment, if the target well is an oil well, the direction of water flow in the target well is determined in advance by the following method:

[0013] Based on the dynamic data analysis of injection and production wells, it is determined whether the target well is directly connected to the injection well. If the target well is directly connected to the injection well, then the water in the target well is determined to come from the injected water.

[0014] If not, the reservoir geological data of the target well are used to analyze whether there is edge water, bottom water or intra-layer water in the reservoir, and the direction of the water is determined to be edge water, bottom water or intra-layer water based on the analysis results of the reservoir geological data.

[0015] If the target well is a gas well, the direction of water flow in the target well is determined in advance by the following method:

[0016] Based on the reservoir geological data of the target well, the presence of edge water, bottom water, or intra-layer water in the gas reservoir is analyzed, and the direction of water origin is determined to be edge water, bottom water, or intra-layer water according to the analysis results of the reservoir geological data.

[0017] In one embodiment, the amount of displacement fluid used is determined based on the distance between the location of the water-blocking material-displacement fluid interface and the wellbore, the volume of the wellbore, and the filtration loss of displacement fluid into the formation, including:

[0018] The amount of displacement fluid, Q3, is calculated using the following formula:

[0019]

[0020] Δt x = xΔt; n is an integer, ranging from 100 to 1000;

[0021] In the formula: L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; r1 is the tubing inner diameter, in meters; H is the well depth, in meters; C3 is the displacement fluid filtration coefficient, in m / min. 0.5 h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture proppant in decimal form; t3 is the time from the start of the displacement fluid entering the fracture to the end of the displacement fluid injection in minutes.

[0022] In one embodiment, if it is determined that the water in the target well comes from injected water or edge water, then the distance L3 between the location of the plugging material-displacement fluid interface and the wellbore is taken as 25m to 0m.

[0023] If the water in the target well comes from bottom water or intra-layer water, the distance L3 between the location of the plugging material-displacement fluid interface and the wellbore is 10m to 20m.

[0024] In one embodiment, the displacement liquid is a guar gum-based liquid with a viscosity greater than that of the temperature-sensitive water-blocking material.

[0025] In one embodiment, the type of temperature-sensitive plugging material used in the target well containing water is selected based on engineering requirements and the phase transition temperature of the temperature-sensitive plugging material, including:

[0026] From a variety of temperature-sensitive water-blocking materials, one or more water-blocking materials are selected based on the phase transition temperature of each material, the original formation temperature, and the maximum temperature in the wellbore after the pre-fluid injection.

[0027] The phase transition temperature of the selected water-blocking material must meet the following temperature conditions required by the project: the original formation temperature T3 is greater than the phase transition temperature T2 of the water-blocking material, and the maximum temperature T1 in the wellbore after the pre-fluid injection is less than the phase transition temperature T2.

[0028] In one embodiment, the temperature-sensitive water-plugging material is a phase change fracturing fluid.

[0029] In one embodiment, determining the amount of pre-flush fluid required for water shut-off based on the reservoir data and well foundation data of the target well includes:

[0030] Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off. The following conditions must be met: the maximum temperature T1 in the wellbore after the pre-flush fluid is injected must be less than the phase transition temperature T2 of the water shut-off material, and the amount of pre-flush fluid must be less than or equal to a preset volume value.

[0031] In one embodiment, if the determined amount of pre-flushing liquid is greater than a preset volume value given the selected water-blocking material, the process returns to the step of selecting the type of temperature-sensitive water-blocking material until a water-blocking material that meets the temperature conditions and the amount of pre-flushing liquid are selected.

[0032] In one embodiment, determining the amount of water-blocking material used based on the sealing length of the water-blocking material includes:

[0033] The amount of the water-blocking material Q2 is calculated by the following formula:

[0034]

[0035] Δt y = yΔt; m is an integer, ranging from 200 to 1000;

[0036] In the formula: L2 is the sealing length of the water-plugging material; L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture-filling proppant, a decimal; t2 is the time from the start of timing when the temperature-sensitive water-plugging material enters the high-permeability fracture channel to the end of the displacement fluid injection, in minutes; C2 is the filtration loss coefficient of the temperature-sensitive water-plugging material in m / min. 0.5 .

[0037] In one embodiment, the larger the production of the target well, the more positively correlated it is with the value of L2, which is between 10m and 20m.

[0038] In one embodiment, based on the determined dosage of the pre-flush fluid, the displacement fluid, and the water-blocking material, corresponding amounts of the pre-flush fluid, the water-blocking material, and the displacement fluid are sequentially injected into the target well, including:

[0039] In the target well, sequentially inject 2.0–3.0 m... 3 Inject pre-fluid at a flow rate of 1.0–2.0 m³ / min. 3 Inject temperature-sensitive plugging material at a flow rate of 1.0–2.0 m / min. 3 The displacement fluid is injected at a rate of / min.

[0040] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0041] The water-blocking method for phase change in water-bearing reservoirs provided in this invention fully utilizes the natural variation law of the wellbore-formation temperature field during construction and combines the characteristics of temperature-sensitive water-blocking materials. It provides a way to select suitable temperature-sensitive materials, a method to determine the dosage of pre-flush fluid, displacement fluid, and water-blocking materials, and a specific construction procedure to achieve water blocking of the target well. It provides sufficient guidance for the design and construction of inverse temperature phase change water blocking in fractured water-flooded wells in water-injection oil reservoirs, expands the application of temperature-sensitive water-blocking materials in the oil and gas industry, and improves the development efficiency of oil or gas reservoirs.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0045] Figure 1 This is a flowchart of the water-blocking method for phase change in aquifers in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram illustrating the relationship between the displacement fluid, the water-plugging material, its cross-section, and the wellbore in an embodiment of the present invention.

[0047] Figure 3 This is a simplified flowchart of a phase change water shut-off construction method for aquifers in an embodiment of the present invention. Detailed Implementation

[0048] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0049] The inventors of this invention have discovered that, based on the problems existing in the granular plugging agents and non-granular plugging agents such as gels and jelly, a new type of temperature-sensitive water-blocking material has emerged. This temperature-sensitive water-blocking material has the characteristic of reverse temperature phase change, that is, it is a liquid phase under low temperature conditions during construction and becomes a solid phase when heated after construction. At the same time, the temperature-sensitive water-blocking material has low viscosity, high injection rate, and simple construction procedures, and can quickly form a large-area, high-strength sealing zone, solving the drawbacks of conventional water-blocking technology. However, conventional water-blocking methods cannot be applied to reverse temperature phase change water-blocking with temperature-sensitive water-blocking materials. Therefore, it is necessary to study the construction method of phase change water-blocking of the water-bearing reservoir of the target well using temperature-sensitive water-blocking materials, so as to more scientifically guide the water-blocking design and construction of the target well.

[0050] Based on this, the inventors of this invention, combining the situation of temperature-sensitive water-blocking materials and the analysis of relevant data on high water-cut target wells, provide a phase change water-blocking method applicable to water-bearing reservoirs of high water-cut target wells.

[0051] The method for phase change water shut-off in aquifer reservoirs provided in this embodiment of the invention refers to... Figure 1 The flowchart shown includes:

[0052] S11. Select the type of temperature-sensitive plugging material to be used in the target well containing water, based on the project requirements;

[0053] S12. Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off;

[0054] S13. Based on the direction of water in the target well obtained from the pre-analysis, determine the position of the water-plugging material-displacement fluid interface and the distance between it and the wellbore.

[0055] S14. Determine the amount of displacement fluid to be used based on the location of the water-plugging material-displacement fluid interface and the distance between it and the wellbore, the volume of the wellbore, and the loss of displacement fluid to the formation.

[0056] S15. Based on the target well's early production data, fracturing stimulation data, and water shut-off requirements, determine the sealing length of the water shut-off material; determine the amount of water shut-off material to be used based on the sealing length of the water shut-off material.

[0057] S16. Based on the determined amount of pre-flush fluid, displacement fluid, and water-blocking material, inject the corresponding amounts of pre-flush fluid, water-blocking material, and displacement fluid into the target well in sequence, and then shut the well in for a preset time before backflow.

[0058] In this embodiment of the invention, the target well includes oil wells, gas wells, etc., and correspondingly, the reservoir includes oil reservoirs, gas reservoirs, etc.

[0059] The water-blocking method for phase change in water-bearing reservoirs provided in this invention fully utilizes the natural variation law of the wellbore-formation temperature field during construction and combines the characteristics of temperature-sensitive water-blocking materials. It provides a way to select suitable temperature-sensitive materials, a method to determine the dosage of pre-flush fluid, displacement fluid, and water-blocking material, and a specific construction procedure to achieve water blocking of the target well. It provides sufficient guidance for the design and construction of inverse temperature phase change water blocking in fractured water-flooded wells in water-injection oil reservoirs, expands the application of temperature-sensitive water-blocking materials in the petroleum industry, and improves the development efficiency of oil and gas reservoirs.

[0060] The following will provide a more detailed explanation of each of the above steps using specific examples.

[0061] In one embodiment, in step S11 above, the type of temperature-sensitive water-blocking material can be selected in the following manner:

[0062] From a variety of temperature-sensitive water-blocking materials, one or more water-blocking materials are selected based on the phase transition temperature of each material, the original formation temperature, and the maximum temperature in the wellbore after the pre-fluid injection.

[0063] The selected water-blocking material's phase transition temperature needs to meet the following temperature conditions: the original formation temperature T3 is greater than the water-blocking material's phase transition temperature T2, and the maximum temperature T1 in the wellbore after the pre-fluid injection is less than the phase transition temperature T2.

[0064] In one embodiment, the temperature-sensitive water-plugging material can be a phase change fracturing fluid.

[0065] Existing phase change fracturing fluids can be classified into various types based on their phase change temperature. For example, in the "Phase Change Fracturing Fluid System for Phase Change Fracturing (Patent Application No. CN201610534192.3)", phase change fracturing fluids FfP1, FfP2, and FfP3 have phase change temperatures T2 of 80℃ to 90℃, 90℃ to 100℃, and 70℃ to 80℃ respectively. ℃. For example, "A temperature-responsive phase change fracturing fluid and its application method (patent application number CN201911399069.5)" provides four functional oil phases. The phase change temperature T2 of functional oil phase GOP1 is 80℃~90℃, the phase change temperature T2 of functional oil phase GOP2 is 90℃~100℃, the phase change temperature T2 of functional oil phase GOP3 is 60℃~80℃, and the phase change temperature T2 of functional oil phase GOP4 is 110℃~120℃.

[0066] Phase change fracturing fluids contain components such as supramolecular building blocks, supramolecular functional units, surfactants, inorganic salts, oxidants, co-solvents, and solvents. They can be classified into different types of phase change fracturing fluids based on their components. For a detailed description of the specific types of phase change fracturing fluids, please refer to the existing technology, which will not be elaborated here.

[0067] If the original formation temperature T3 is greater than the phase transition temperature T2, and the maximum temperature T1 in the wellbore after the pre-fluid injection is less than the phase transition temperature T2, then one or more water-blocking materials can be selected.

[0068] In one embodiment, in step S12 above, the amount of pre-flush fluid required for water shut-off can be determined based on the reservoir data and well foundation data of the target well. The following conditions must be met: the maximum temperature T1 in the wellbore after the pre-flush fluid is injected is less than the phase change temperature T2 of the water shut-off material, and the amount of pre-flush fluid is less than or equal to a preset volume value.

[0069] If, given the selected water-blocking material, the determined amount of pre-fluid is greater than the preset volume value, then return to the step of selecting the type of temperature-sensitive water-blocking material in S11 above, until a water-blocking material that meets the aforementioned temperature conditions (i.e., the original formation temperature T3 is greater than the phase change temperature T2, and the maximum temperature T1 in the wellbore after the pre-fluid is injected is less than the phase change temperature T2) and the amount of pre-fluid are selected.

[0070] In one embodiment, the preset volume value of the pre-fluid can be obtained through experience, for example, it can be 150m. 3 In other words, the amount of pre-fluid used usually needs to be less than 150m³.3 .

[0071] In one embodiment, the calculation method for the maximum temperature T1 in the wellbore after the pre-fluid injection can refer to existing technologies, such as the calculation method for T mentioned in "A Temporary Plugging and Diversion Method for Realizing Liquid-Solid-Liquid Phase Transformation Using Natural Geothermal Field (Patent Application No. CN201811179675.1)". m The method, namely:

[0072] Based on the temperature data of the modified reservoir, the temperature distribution within the wellbore is calculated, and the temperature T of the fluid inside the tubing is used as the reference. f The temperature distribution curve inside the wellbore (calculated using the basic parameters of conventional guar gum fracturing fluid to determine the temperature distribution curve inside the wellbore during fluid injection) yields the maximum value T of the fluid temperature inside the tubing. f This is the highest point of temperature change at the bottom of the well, T. m .

[0073] The highest point of temperature change at the bottom of the well is T. m This refers to the maximum temperature T1 in the wellbore after the pre-fluid has been injected in this embodiment of the invention.

[0074] Of course, the embodiments of the present invention are not limited to the above method for obtaining the maximum temperature T1 in the wellbore after the pre-fluid injection.

[0075] In one embodiment, the direction of water flow in the target well can be determined in advance by the following method:

[0076] If the target well is an oil well, then the dynamic data of the injection and production wells are analyzed to determine whether the target well is directly connected to the water injection well. If the target well is directly connected to the water injection well, then the water in the target well is determined to come from the injected water.

[0077] If not, analyze the reservoir geological data of the target well to determine whether there is edge water, bottom water, or intra-layer water in the reservoir, and further determine the source of the water as edge water, bottom water, or intra-layer water based on the analysis results of the reservoir data.

[0078] If the target well is a gas well, the direction of water flow in the target well is determined in advance by the following method:

[0079] Based on the reservoir geological data of the target well, the presence of edge water, bottom water, or intra-layer water in the gas reservoir is analyzed, and the direction of water origin is determined to be edge water, bottom water, or intra-layer water according to the analysis results of the reservoir geological data.

[0080] In one embodiment, the distance between the location of the plugging material-displacement fluid interface and the wellbore, determined in S13 above based on the pre-analyzed direction of water in the target well, can be obtained in the following manner:

[0081] If it is determined that the water in the target well comes from injected water or edge water, the distance L3 between the location of the plugging material-displacement fluid interface and the wellbore can be 25m to 0m.

[0082] If the water in the target well comes from bottom water or intra-layer water, the distance L3 between the location of the plugging material-displacement fluid interface and the wellbore can be 10m to 20m.

[0083] Reference Figure 2 As shown, the displacement fluid (the shaded part in the figure) consists of three parts: the part in the wellbore, the part in the fracture, and the part that is filtered out into the formation.

[0084] The displacement fluid and the water-blocking material are immiscible, thus creating a clear interface.

[0085] Figure 2 The area marked "interface" is the interface between the displacement liquid and the phase change plugging material, as shown in the image. Figure 2 As shown, the distance from the interface to the wellbore sidewall, L3, represents the distance between the location of the water-plugging material-displacement fluid interface and the wellbore.

[0086] The distance L3 between the water shut-off material-displacement fluid interface and the wellbore, the wellbore volume, and the fluid loss to the formation can be calculated using the following formula (1):

[0087]

[0088] Δt x = xΔt; n is an integer, ranging from 100 to 1000.

[0089] In formula (1): Q3 is the amount of displacement fluid used; L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; r1 is the inner diameter of the tubing, in meters; H is the well depth, in meters; C3 is the displacement fluid filtration coefficient, in m / min. 0.5 h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture proppant in decimal form; t3 is the time from the start of the displacement fluid entering the fracture to the end of the displacement fluid injection in minutes.

[0090] The aforementioned replacement liquid can be a guar gum-based liquid, whose viscosity is slightly greater than that of temperature-sensitive water-blocking materials.

[0091] Guar gum-based fluids are viscous liquids formed primarily of guar gum, and are widely used in oil and gas extraction and other fields. Guar gum-based fluids have very high viscosity, capable of forming high-viscosity solutions at low concentrations, which gives them excellent suspension and transport capabilities when carrying proppant and other substances into formations.

[0092] In one embodiment, in step S15 above, generally speaking, the larger the oil well production, the larger the value of L2, which is generally 10m to 20m.

[0093] Furthermore, the amount of the aforementioned water-blocking material, Q2, can be calculated, for example, by the following formula (2):

[0094]

[0095] Δt y = yΔt; m is an integer, ranging from 200 to 1000;

[0096] In formula (2): L2 is the sealing length of the water-plugging material; L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture proppant in decimal form; t2 is the time from the start of timing when the temperature-sensitive water-plugging material enters the high-permeability fracture channel to the end of the displacement fluid injection in minutes; C2 is the filtration loss coefficient of the temperature-sensitive water-plugging material in m / min. 0.5 .

[0097] In one embodiment, in step S16 above, the injection of the pre-fluid, the water-blocking material, and the displacement fluid are completed sequentially in the following manner:

[0098] Towards, successively 2.0–3.0m 3 Inject pre-fluid at a flow rate of 1.0–2.0 m³ / min. 3 Inject temperature-sensitive plugging material at a flow rate of 1.0–2.0 m / min. 3 The displacement fluid is injected at a rate of / min.

[0099] A simplified flowchart of the construction method for phase change plugging in aquifer reservoir can be found here. Figure 3 As shown.

[0100] In this embodiment of the invention, an oil well is used as an example for illustration. First, the source of the water produced by the oil well is determined. Then, based on the reservoir data and basic data of the oil well, a temperature-sensitive water-blocking material is selected. Next, the pre-fluid volume Q1 is designed. The pre-fluid volume must meet the following requirements: the original formation temperature T3 is greater than the phase transition temperature T2 of the water-blocking material; the maximum temperature T1 in the wellbore after pre-fluid injection is less than the phase transition temperature T2; and the pre-fluid volume Q1 must be less than 150 m³. 3If the condition is met, proceed to the next step; otherwise, return to the step of selecting temperature-sensitive plugging material and reselect the plugging material until the condition is met. The next step is to design the displacement fluid volume Q3, then design the temperature-sensitive plugging material usage Q2, and finally carry out on-site construction by sequentially injecting the pre-flush fluid, plugging material, and displacement fluid, and then shutting in the well for a preset time before backflow.

[0101] The following is a specific example illustrating the water-blocking method for phase change in aquifers provided in this embodiment of the invention.

[0102] Taking Well A, an advanced water injection development reservoir on a slope in a basin, as the target for water shut-off, the water-bearing reservoir phase change water shut-off method provided in this embodiment of the invention is used for scheme design and on-site construction.

[0103] Step S1: Based on reservoir geological data and well baseline data analysis, this reservoir is a reverse nine-point water injection development well pattern with edge water present; well A initially had a water cut of 10.8% and a production volume of 3.5 m³. 3 / d; After a short period of production, the water cut of well A rapidly increased to 98.5%, with a production volume of 10.8m³. 3 / d; After stopping injection into the surrounding wells, the production of well A decreased significantly to 1.8m. 3 / d, and the water cut also decreased to 56.9%; after water injection was resumed in the injection wells around Well A, the production of fluid in Well A increased to 10.2m. 3 / d, the water cut also rose to 97.7%; dynamic data analysis of injection and production wells showed that well A was connected to the water injection well, and well A was 6.8km away from the reservoir boundary. Therefore, it was determined that the water in well A came from the water injection well, that is, the water came from the injection water.

[0104] In step S2, with the initial formation temperature T3 at 85℃, pure phase change fracturing fluid FfP3 from the patent application CN201610534192.3 ("A Phase Change Fracturing Fluid System for Phase Change Fracturing") was selected, with a filtration loss coefficient C2 of 0.7 × 10⁻⁶. -3 m / min 0.5 The phase transition temperature T2 is 70℃~80℃, and the sealing strength is 69.8MPa.

[0105] Step S3, the pre-fluid volume Q1 is 50m 3 , at 2.5m 3 The injection pre-fluid at a flow rate of / min was used to inject the pre-fluid. After the pre-fluid was injected, the maximum temperature T1 in the wellbore was 48℃, which was lower than the phase transition temperature T2.

[0106] In steps S4 and L3, the values ​​are 30m and n is 300. Based on the pre-fracturing data of well A, the fracture height h is 33.2m, the fracture width w is 0.025m, the porosity φ of the fracture proppant is 0.4, the tubing inner diameter r1 is 0.031m, the well depth H is 1910m, and the displacement fluid loss coefficient C3 is 0.55 × 10⁻⁶. -3 m / min 0.5 , at 1.5m 3 The displacement fluid was injected at a rate of / min, t3 was 12.9min, and the displacement fluid volume Q3 was 25m³. 3 .

[0107] In steps S5 and L2, the value is 15m, and the value of m is 450, with 1.5m as the base. 3 The injection temperature-sensitive plugging material has a displacement of / min, t2 is 20.9min, and the amount of temperature-sensitive plugging material used, Q2, is 12m³. 3 .

[0108] Step S6: Organize on-site construction, proceeding in 2.5m increments. 3 Inject pre-fluid at a flow rate of / min, at a flow rate of 1.5m 3 Inject temperature-sensitive plugging material at a flow rate of / min, at a depth of 1.5m. 3 Inject displacement fluid at a rate of / min, and then backflow after shutting in the well for 10 hours.

[0109] Analysis of water shut-off effect: Before the water shut-off operation, well A produced 10.2m³ of fluid. 3 / d, water content 97.7%, oil yield 0.23m 3 / d; After water shut-off construction using the water-bearing reservoir phase change water shut-off method provided in the embodiments of the present invention, well A produced 2.4m³ of fluid. 3 / d, water content 9.8%, oil yield 2.16m 3 / d. The above data shows that the water-bearing reservoir phase change plugging method proposed in this embodiment of the invention makes good use of the inverse phase change characteristics of temperature-sensitive plugging materials, which not only effectively reduces the fluid production and water cut of well A, but also greatly increases the oil production, and the technical effect is very significant.

[0110] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for phase change water shut-off in an aquifer, characterized in that, include: Based on the project requirements, select the type of temperature-sensitive plugging material to be used in the target well containing water; Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off; Based on the direction of water in the target well determined through prior analysis, the location of the water-plugging material-displacement fluid interface and the distance between it and the wellbore are determined. The amount of displacement fluid used is determined based on the distance between the location of the water-blocking material-displacement fluid interface and the wellbore, the volume of the wellbore, and the amount of displacement fluid lost to the formation. Based on the target well's pre-production fluid data, fracturing stimulation data, and water shut-off requirements, determine the sealing length of the water shut-off material; determine the amount of water shut-off material to be used based on the sealing length of the water shut-off material. Based on the determined amounts of the pre-flush fluid, the displacement fluid, and the water-blocking material, the corresponding amounts of the pre-flush fluid, the water-blocking material, and the displacement fluid are injected into the target well in sequence, and the well is shut in for a preset time before being flushed back.

2. The method as described in claim 1, characterized in that, If the target well is an oil well, the direction of water flow in the target well is determined in advance by the following method: Based on the dynamic data analysis of injection and production wells, it is determined whether the target well is directly connected to the injection well. If the target well is directly connected to the injection well, then the water in the target well is determined to come from the injected water. If not, the reservoir geological data of the target well are used to analyze whether there is edge water, bottom water or intra-layer water in the reservoir, and the direction of the water is determined to be edge water, bottom water or intra-layer water based on the analysis results of the reservoir geological data. If the target well is a gas well, the direction of water flow in the target well is determined in advance by the following method: Based on the reservoir geological data of the target well, the presence of edge water, bottom water, or intra-layer water in the gas reservoir is analyzed, and the direction of water origin is determined to be edge water, bottom water, or intra-layer water according to the analysis results of the reservoir geological data.

3. The method as described in claim 2, characterized in that, The amount of displacement fluid used is determined based on the distance between the water-blocking material-displacement fluid interface and the wellbore, the volume of the wellbore, and the filtration loss of displacement fluid into the formation, including: The amount of displacement fluid, Q3, is calculated using the following formula: Δt x = xΔt; n is an integer, ranging from 100 to 1000; In the formula: L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; r1 is the tubing inner diameter, in meters; H is the well depth, in meters; C3 is the displacement fluid filtration coefficient, in m / min. 0.5 h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture proppant in decimal form; t3 is the time from the start of the displacement fluid entering the fracture to the end of the displacement fluid injection in minutes.

4. The method as described in claim 3, characterized in that, If it is determined that the water in the target well comes from injected water or edge water, then the distance L3 between the location of the water-plugging material-displacement fluid interface and the wellbore is taken as 25m to 0m; If the water in the target well comes from bottom water or intra-layer water, the distance L3 between the location of the plugging material-displacement fluid interface and the wellbore is 10m to 20m.

5. The method as described in claim 3, characterized in that, The displacement liquid is a guar gum-based liquid, and its viscosity is greater than that of the temperature-sensitive water-blocking material.

6. The method as described in claim 1, characterized in that, Based on engineering requirements, select the type of temperature-sensitive plugging material to be used in the target well containing water, including: From a variety of temperature-sensitive water-blocking materials, one or more water-blocking materials are selected based on the phase transition temperature of each material, the original formation temperature, and the maximum temperature in the wellbore after the pre-fluid injection. The phase transition temperature of the selected water-blocking material must meet the following temperature conditions required by the project: the original formation temperature T3 is greater than the phase transition temperature T2 of the water-blocking material, and the maximum temperature T1 in the wellbore after the pre-fluid injection is less than the phase transition temperature T2.

7. The method as described in claim 6, characterized in that, The temperature-sensitive water-blocking material is a phase change fracturing fluid.

8. The method as described in claim 6, characterized in that, Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off, including: Based on the reservoir data and well foundation data of the target well, determine the amount of pre-flush fluid required for water shut-off. The following conditions must be met: the maximum temperature T1 in the wellbore after the pre-flush fluid is injected must be less than the phase transition temperature T2 of the water shut-off material, and the amount of pre-flush fluid must be less than or equal to a preset volume value.

9. The method as described in claim 8, characterized in that, If, given the selected water-blocking material, the determined amount of pre-flushing liquid exceeds the preset volume value, then return to the step of selecting the type of temperature-sensitive water-blocking material until a water-blocking material that meets the temperature conditions and the amount of pre-flushing liquid are selected.

10. The method as described in claim 8, characterized in that, The amount of water-blocking material used is determined based on the sealing length of the water-blocking material, including: The amount of the water-blocking material Q2 is calculated by the following formula: Δt y = yΔt; m is an integer, ranging from 200 to 1000; In the formula: L2 is the sealing length of the water-plugging material; L3 is the distance between the water-plugging material-displacement fluid interface and the wellbore; h is the fracture height in meters; w is the fracture width in meters; φ is the porosity of the fracture-filling proppant, a decimal; t2 is the time from the start of timing when the temperature-sensitive water-plugging material enters the high-permeability fracture channel to the end of the displacement fluid injection, in minutes; C2 is the filtration loss coefficient of the temperature-sensitive water-plugging material in m / min. 0.5 .

11. The method as described in claim 10, characterized in that, The higher the production of the target well, the more positively correlated it is with the value of L2, which ranges from 10m to 20m.

12. The method as described in claim 10, characterized in that, Based on the determined dosages of the pre-fluid, the displacement fluid, and the plugging material, corresponding amounts of the pre-fluid, the plugging material, and the displacement fluid are sequentially injected into the target, including: In the target well, sequentially inject 2.0–3.0 m... 3 Inject pre-fluid at a flow rate of 1.0–2.0 m³ / min. 3 Inject temperature-sensitive plugging material at a flow rate of 1.0–2.0 m / min. 3 The displacement fluid is injected at a rate of / min.

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