Method for constructing fracture conductivity model considering hydration and Brinkman flow

Abstract

The invention provides a method for constructing a fracture conductivity model considering hydration and Brinkman flow. The method mainly comprises the following steps: 1) establishing a relational expression between fracture conductivity and fracture width; (2) carrying out an experiment of fracture conductivity test to test the conductivity loss condition of the rock core which is hydrated by introducing the KCl solution at different stress loading times; 3) establishing the relational expression between the hydration time of the deep coal rock and the fracture conductivity. The method is reasonable in conception, can accurately predict the change of the fracture conductivity, and can accurately capture the complex coupling relation between the hydration effect and the fracture conductivity as well as between the hydration effect and the effective stress, so that a scientific decision basis is provided for actual engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas reservoir exploration, and particularly relates to a method for constructing a fracture conductivity model considering hydration and Brinkman flow. BACKGROUND

[0002] Hydraulic fracturing is a key technology for extracting hydrocarbon resources from deep coal rock reservoirs. During the fracturing process, a large amount of fluid is usually retained in the fracturing cracks. These fluids retained in the cracks undergo hydration with the cracks, which seriously affects the gas well productivity. Hydration refers to the microscopic and macroscopic changes in rock structure caused by the contact between liquid and rock-soil minerals in the reservoir, which changes the mechanical properties and physical parameters of the rock, and makes the fracture conductivity show a complex decay law, thereby affecting the stability of the coal rock reservoir and the recovery rate of coalbed methane. The occurrence of hydration has a significant time effect, therefore, the artificial fracture conductivity can be directly related to the interaction time between the fracturing fluid and the rock, especially for dense reservoirs whose water distribution is controlled by capillary force and clay osmotic pressure. However, existing researches mostly focus on the influence of water-rock interaction on the mechanical properties of rock, and lack of quantitative description of the relationship between hydration time effect and fracture conductivity. Therefore, the present application proposes a fracture conductivity calculation model considering hydration and Brinkman flow.

[0003] At present, the calculation method of fracture conductivity mainly relies on the traditional Darcy law or Kozeny-Carman equation. These methods usually assume that the permeability of the fracture is proportional to the fracture width, and do not consider the viscous effect of the liquid. Especially for gas flow, the traditional model cannot fully consider the non-Darcy flow characteristics of the fluid in the fracture, especially in the high stress and low permeability fracture environment. In addition, the existing models mostly focus on the calculation based on static physical properties (such as fracture width, permeability, etc.), and ignore the dynamic changes of the fracture during the hydraulic fracturing process, especially the long-term influence of hydration on fracture width, permeability and conductivity.

[0004] In recent years, with the deepening understanding of hydration effect and non-Darcy flow characteristics, more and more researches have begun to try to introduce hydration effect, non-Darcy flow, effective stress and other factors into the model of fracture conductivity. However, the existing technology still has many limitations, especially in the coupling effect of fracture conductivity and hydration time, stress change, and no effective solution has been proposed. At the same time, the traditional fracture conductivity model mostly relies on simple static mechanical parameters, and cannot effectively cope with complex hydration effect and stress change.

[0005] The existing technology mainly has the following disadvantages:

[0006] Neglecting the long-term effect of hydration: Traditional models usually assume that the fracture width and permeability are static and unchanging, and the effect of hydration on fracture width and permeability is considered as a short-term effect. In fact, hydration is a process with significant time effect, and its effect on fracture conductivity increases with the increase of hydration time, especially under high pressure and high hydration conditions, the fracture width will shrink significantly, which in turn affects the attenuation of fracture conductivity. Therefore, the traditional model ignores the time effect of hydration, making the calculation of fracture conductivity unable to accurately reflect the change of fracture conductivity in the long-term production process, which has not been fully solved in the prior art.

[0007] Precision problem of the model: In the exploitation process of unconventional oil and gas reservoirs such as coal rock gas reservoirs, fracture conductivity is one of the key factors determining the production capacity and recoverable reserves of gas wells. The traditional fracture conductivity calculation method ignores the effect of hydration and does not fully consider the time dependence of hydration time on fracture conductivity. Existing fracture conductivity calculation models are mostly based on Darcy's law or Kozeny-Carman equation, which do not fully consider the viscous effect of liquid flow. Especially in unconventional oil and gas reservoirs, the flow of fluid is affected by complex factors such as fracture width, shape and effective stress. The prediction accuracy of traditional models in these environments is low, and they often cannot accurately predict the trend of fracture conductivity.

[0008] Cannot reflect the coupling relationship between hydration effect and stress change: The existing technology usually ignores the complex coupling relationship between hydration effect and stress change when describing the change of fracture conductivity. During hydraulic fracturing, as the fracture is closed, the stress increases, and the hydration effect further enhances the sensitivity of the fracture to stress change. Therefore, the traditional model cannot accurately reflect the interaction between hydration effect and fracture conductivity and effective stress.

[0009] In summary, it is necessary to make further innovation to the prior art. SUMMARY

[0010] In view of the technical problems in the above background art, the present application provides a method for constructing a fracture conductivity model considering hydration and Brinkman flow, which has reasonable concept and can accurately predict the change of fracture conductivity and accurately capture the complex coupling relationship between hydration and fracture conductivity and effective stress, thereby providing a scientific basis for decision-making in actual engineering.

[0011] To solve the above technical problems, the present application provides a method for constructing a fracture conductivity model considering hydration and Brinkman flow, which mainly includes the following steps:

[0012] 1) to establish a relationship between fracture conductivity and fracture width considering Brinkman flow; the specific process is as follows:

[0013] The fracture conductivity is defined by the fracture permeability and the fracture width, and the fracture conductivity is obtained by the following formula (1):

[0014] (1);

[0015] In the process of gas flow, the fracture permeability is mainly affected by the viscous shear effect of the fracture wall, and the flow field will show obvious Brinkman characteristics. Considering the change of gas permeability under Brinkman flow, the relationship between proppant filling permeability, proppant filling porosity and fracture width is represented as follows:

[0016] (2);

[0017] In the above formula (2), k f is the hydraulic fracture permeability under Brinkman seepage; k p is the proppant filling permeability; w f is the fracture width; φ p is the proppant filling porosity; and β is a unit conversion coefficient 1.01*10 15 ;

[0018] The initial state proppant filling permeability and the proppant filling porosity are calculated by the following formula (3) and formula (4) respectively, wherein the relationship between the initial state proppant filling permeability and the effective stress is shown in the following formula (3):

[0019] (3);

[0020] In the above formula (3), φ p0 represents the initial state proppant filling fracture porosity, σ0 is the initial effective stress, σ is the initial effective stress with fracture, c p is the average pore compressibility, and c p takes the value of 2*10 −4 MPa −1 ;

[0021] The relationship between the proppant filling permeability and the effective stress is shown in the following formula (4):

[0022] (4);

[0023] In the above formula (4), k p is the proppant filling permeability; and k p0 is the initial proppant filling permeability;

[0024] Initial state proppant-filled crack porosity φ p0 It can be obtained from the following formula (5):

[0025] (5);

[0026] Calculate the throat radius and channel curvature in the initial state of the crack:

[0027] (6);

[0028] (7);

[0029] In equations (5)-(7) above, r0 is the throat radius of the crack in the initial state when the closure pressure is 0; τ0 is the pore curvature of the crack in the initial state when the closure pressure is 0; and R is the proppant radius.

[0030] The initial permeability of the fracture under proppant filling is related to porosity, pore throat radius, and pore tortuosity. Substituting equations (5)-(7) into equation (8) yields the initial permeability k under proppant filling. p0 :

[0031] (8);

[0032] Based on the above formulas (3)-(4), the initial permeability k under stress-related proppant filling is obtained. p0 Initial state proppant-filled crack porosity φ p0 and average pore compressibility c p Inserting these parameters into equation (1), we obtain the relationship between crack conductivity and crack width considering Brinkman flow:

[0033] (9);

[0034] 2) Conduct experiments to test the conductivity of fractures, in order to test the loss of conductivity of coal cores under different stress loading conditions and different hydration times;

[0035] 3) Introduce the hydration sensitivity coefficient ε to establish the relationship between the hydration time of deep coal and rock and the conductivity of fractures.

[0036] The method for constructing a fracture conductivity model considering hydration and Brinkman flow, wherein the specific steps of the fracture conductivity test in step 2) are as follows:

[0037] 2.1) Load the test rock sample into the core holder, and keep the confining pressure constant for 30 minutes with an initial effective stress of 10 MPa.

[0038] 2.2) nitrogen gas is introduced into the core holder, after the gas flow is stable, the gas flow through the core of the test rock sample is monitored and recorded, and the fracture conductivity is calculated, and the fracture conductivity calculation process is as follows:

[0039] (10);

[0040] (11);

[0041] (12);

[0042] In the above formula (10)-(12), q is the gas flow measured by experiment, k is the fracture permeability, A is the cross-sectional area of the gas passing through the fracture, ΔP is the pressure difference between the injection end and the outlet end of the core holder, μ is the fluid viscosity, L is the seepage length, w is the fracture width, d is the fracture length, C f is the fracture conductivity value;

[0043] 2.3) slowly increase the effective stress in the core holder, and repeat the above steps 2.1)-2.2) when the effective stress increases by 5 MPa, until the effective reaches the maximum pressure of 40 MPa and stops increasing;

[0044] 2.4) repeat the above steps 2.1)-2.3) to test the loss of conductivity of the core introduced with KCl solution under different effective stress loading times.

[0045] The method for constructing the fracture conductivity model considering hydration and Brinkman flow, wherein: the step 2) needs to remove the irregular parts at both ends of the original core by linear cutting before the step 2) is performed, and the irregular parts are processed into a standard columnar core, and then the standard core sample is subjected to fracture induction, and 40 / 70 mesh proppant is selected for the experiment, and a core permeability test platform is independently built for the experiment.

[0046] The method for constructing the fracture conductivity model considering hydration and Brinkman flow, wherein the specific process of the step 3) is:

[0047] The fracture conductivity value measured in the step 2) is brought into the formula (9) to obtain the value of the fracture width under different hydration times, and the change of the fracture width with the effective stress is fitted based on the formula (13), and ε is the sensitivity coefficient between the fracture width and the effective stress under different hydration times.

[0048] (13);

[0049] In the formula (13) above, w f0 is the crack width calculated when the effective stress is 0; ε is the coefficient between the crack width under the hydration time and the effective stress, that is, the hydration sensitivity coefficient;

[0050] The values of ε under different hydration times are fitted to obtain the change relationship of the crack width with the hydration time under hydration as follows:

[0051] (14) ;

[0052] The crack width changes with the hydration time under different modes by bringing different ε into the formula (13), and formula (15) is further brought into the formula (9) above to obtain formula (15), wherein the crack permeability kp0 under the initial state proppant filling, the crack porosity φ p0 , the average pore compressibility c p and the initial effective stress of the crack with fractures After being determined, the change relationship of the crack conductivity with the hydration time is established by bringing the hydration sensitivity coefficient ε of the crack width change with the effective stress to obtain formula (15).

[0053] (15).

[0054] By adopting the technical scheme, the present application has the following beneficial effects:

[0055] The method for constructing the crack conductivity model considering hydration and Brinkman flow in the present application is reasonable in concept, the Brinkman flow equation and the hydration sensitivity coefficient (ε) are innovatively introduced, the technical problems that cannot be solved by the prior art are successfully solved, and a new idea and method are provided for the development of unconventional oil and gas reservoirs.

[0056] The present application successfully quantifies the time-dependent relationship between hydration and crack conductivity by defining the hydration sensitivity coefficient (ε). The hydration sensitivity coefficient (ε) is used to describe the influence of hydration on crack conductivity, especially when the hydration time changes, the change law of crack conductivity.

[0057] The present application accurately predicts the long-term change of crack conductivity: by introducing the hydration sensitivity coefficient (ε), the present application accurately describes the time-dependent influence of hydration on crack conductivity, and can quantify the long-term attenuation effect of hydration on crack conductivity, thereby providing a more accurate tool for predicting crack conductivity during gas well production.

[0058] The coupling relationship between crack conductivity and hydration time and stress change of the application: the application establishes a model capable of reflecting the evolution of crack conductivity under the influence of hydration time and effective stress by combining the Brinkman flow equation and the influence of hydration; the application can effectively reveal the complex interaction between hydration and crack conductivity and effective stress, and make up for the deficiencies of the prior art in this field.

[0059] The application considers the coupling effect of hydration and Brinkman flow, and can more accurately predict the change of crack conductivity. The application can provide a scientific basis for gas production prediction and optimization after hydraulic fracturing, and help to improve the production efficiency and ultimate recoverable reserves of gas wells.

[0060] The main advantages of the application are as follows:

[0061] (1) Crack conductivity calculation model based on Brinkman flow equation:

[0062] The application proposes a new crack conductivity calculation model, which combines the Brinkman flow equation and can consider the viscous shear effect of fluid flow in the crack, solving the problem of insufficient description of gas seepage in traditional models.

[0063] (2) Introduction and definition of hydration sensitivity coefficient (ε):

[0064] By defining the hydration sensitivity coefficient (ε), the application successfully quantifies the time-dependent relationship between hydration and crack conductivity. The coefficient is used to describe the influence of hydration on crack conductivity, especially when the hydration time changes, the change law of crack conductivity.

[0065] (3) Crack conductivity time evolution model considering hydration effect, i.e. formula (15):

[0066] Combining the hydration effect and stress loading time, a new crack conductivity time evolution model is proposed. The model can accurately predict the decay trend of crack conductivity with time under different hydration time and stress loading conditions.

[0067] (4) Application of the relationship between hydration and crack conductivity in coal rock gas reservoirs:

[0068] The application focuses on the influence of hydration on crack conductivity in unconventional oil and gas reservoirs such as coal rock gas reservoirs, and provides a model that can be applied in actual production according to the characteristics of such gas reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the specific embodiments or prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0070] Figure 1 The experimental design schematic diagram is shown in the following table:

[0071] Figure 2 The experimental results measured in the experiment are shown in the following table:

[0072] Figure 3 The fitting results of the change of the crack width with the effective stress are shown in the following table:

[0073] Figure 4 The fitting results of the value of ε under different hydration times are shown in the following table. DETAILED DESCRIPTION

[0074] The technical solutions of the present application will be described clearly and completely below in combination with the drawings. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0075] The present application will be further explained and described below in combination with specific embodiments.

[0076] The method for constructing a crack conductivity model considering hydration and Brinkman flow provided in the present embodiment mainly includes the following steps:

[0077] S100, establishing a relationship between the crack conductivity considering Brinkman flow and the crack width;

[0078] The crack conductivity calculation is shown in formula (1), and the crack conductivity is defined by the permeability and the crack width:

[0079] (1);

[0080] In the process of gas flow, the crack permeability is mainly affected by the viscous shear effect of the fracture wall, and the flow field will show obvious Brinkman characteristics, so the traditional expression has limitations in describing the equivalent permeability in the process of gas seepage. In order to overcome this defect, the change of gas permeability under Brinkman flow is considered, and the relationship between the proppant filling permeability, the proppant filling porosity and the crack width is represented:

[0081] (2);

[0082] In the above formula (2), k f is the hydraulic fracture permeability under Brinkman percolation; k p is the proppant packing permeability; w f is the fracture width; φ p is the proppant packing porosity; and β is a unit conversion coefficient 1.01*10 15 .

[0083] The initial state proppant packing permeability and the proppant packing porosity described above are calculated by the following formula (3) and formula (4), wherein the relationship formula between the initial state proppant packing permeability and the effective stress can be expressed as:

[0084] (3);

[0085] In the above formula (3), φ p0 represents the fracture porosity under the initial state proppant packing, σ0 is the initial effective stress; σ is the initial effective stress with the fracture; c p is the average pore compressibility, which is 2*10 −4 MPa −1 .

[0086] The permeability under the proppant packing and the effective stress relationship formula is shown in the following formula (4):

[0087] (4);

[0088] In the above formula (4), k p is the permeability under the proppant packing; k p0 is the initial permeability under the proppant packing;

[0089] The fracture porosity φ p0 under the initial state proppant packing is obtained from the following formula (5):

[0090] (5);

[0091] The calculation formula of the pore throat radius and the pore channel tortuosity under the initial state of the fracture is as follows:

[0092] (6);

[0093] (7);

[0094] In the above formula (5)-(7), r0 is the pore throat radius of the initial state of the fracture when the closure pressure is 0, and the unit is um; τ0 is the pore curvature of the initial state of the fracture when the closure pressure is 0, and the unit is dimensionless; R is the radius of the proppant, and the unit is um.

[0095] The initial state of the fracture permeability under proppant filling is related to the porosity, pore throat radius and pore curvature. By inserting formula (5)-(7) into formula (8), the initial permeability k p0 :

[0096] under proppant filling can be obtained.

[0097] Based on the above formula (3)-(4), the initial permeability k p0 under proppant filling under stress, the fracture porosity φ p0 under proppant filling in the initial state and the average pore compression rate c p are obtained. By inserting these parameters into formula (1), the relationship between the fracture conductivity and the fracture width under Brinkman flow can be obtained:

[0098] (9).

[0099] S200, an experiment of fracture conductivity test is performed to test the loss of the conductivity of the coal rock core under different hydration times under different stress loading conditions.

[0100] The test rock sample is selected, the irregular parts at both ends of the original core are removed by linear cutting, and the standard columnar core with a length of 5 cm and a diameter of 2.5 cm is processed, and then the Brazilian splitting method is used to induce the fracture of the standardized core sample, the 40 / 70 mesh silica proppant is selected for the experiment, and the core permeability test platform is independently built, which mainly includes a gas source, an electronic differential pressure sensor, a core holder, a confining pressure pump, an electronic diaphragm flowmeter and a pneumatic liquid pump. The experimental schematic diagram is shown in Figure 1 .

[0101] The experimental steps of the fracture conductivity test are as follows:

[0102] S210, the test rock sample is loaded into the core holder, and the test rock sample in the core holder is kept at an initial effective stress of 10 MPa as a starting point by the confining pressure pump (the pressure output by the confining pressure pump is monitored by the pressure gauge), and the confining pressure is kept unchanged for 30 min.

[0103] S220. Nitrogen gas from the gas source is introduced into the core holder containing the test rock sample using a pneumatic-liquid pump. After the gas flow stabilizes, the gas flow rate through the core sample is monitored and recorded using an electronic soap film flow meter. The fracture conductivity is then calculated. The fracture conductivity calculation method is as follows:

[0104] (10);

[0105] (11);

[0106] (12);

[0107] In equations (10)-(12) above, q is the experimentally measured gas flow rate (m³ / s). 3 / s), k is the fracture permeability (mD), and A is the cross-sectional area of ​​gas passing through the fracture (m²). 2 ), △P is the pressure difference between the injection end and the outlet end of the core holder (MPa), which is measured by an electronic differential pressure sensor; μ is the fluid viscosity (mPa·s); L is the seepage length (m); w is the fracture width (m); d is the fracture length (m); C f It is the crack conductivity value (mD·m).

[0108] S230. Slowly increase the effective stress into the core holder containing the test rock sample. Repeat steps S210-S220 every time the effective stress increases by 5 MPa, until the maximum pressure of 40 MPa is reached and then the increase is stopped.

[0109] S240. Repeat steps S210-S230 above to test the conductivity loss of core samples with KCl solution introduced under different effective stress loading times.

[0110] The experimental results are as follows Figure 2 As shown.

[0111] S300, introduce the hydration sensitivity coefficient ε to establish the relationship between the hydration time of deep coal and rock and the conductivity of fractures.

[0112] Substituting the experimentally measured crack conductivity into formula (9), the crack width values ​​under different hydration times were obtained. Simultaneously, based on formula (13), the crack width variation with effective stress was fitted. Figure 3 (dashed line), ε is the sensitivity coefficient between crack width and effective stress at different hydration times.

[0113] (13);

[0114] In the above formula (13), w f0m is the crack width calculated when the effective stress is 0; ε is the coefficient between the crack width under the hydration time and the effective stress, that is, the hydration sensitivity coefficient, 1 / Mpa.

[0115] The ε values under different hydration times are fitted, as shown in the formula (14), to obtain the relationship between the crack width under hydration and the hydration time: Figure 4

[0116] (14);

[0117] The different ε is brought into the formula (13) to obtain the change of the crack width with the hydration time under different modes, and further brought into the formula (9) to obtain the formula (15), in which the crack permeability kp0 under the initial state proppant filling, the crack porosity φ under the initial state proppant filling, the average pore compression rate c and the initial effective stress of the crack p0 p are determined. After being determined, the hydration sensitivity coefficient ε is brought in to establish the change formula of the crack conductivity with the hydration time:

[0118] (15).

[0119] The Brinkman flow equation is adopted to describe the gas flow characteristics in the crack in the application, and the viscous shear effect in the crack during the gas flow process is considered. The equation can more accurately depict the flow behavior of liquid and gas in the crack, thereby providing a more accurate crack conductivity calculation method. At the same time, the traditional crack permeability model mainly depends on single porosity and crack width, and fails to consider the viscous effect of liquid flow, resulting in large deviation of the calculation result. The Brinkman flow equation model of the application makes up for this defect and improves the accuracy of crack conductivity calculation.

[0120] The application defines the hydration sensitivity coefficient (ε) to depict the relationship between the crack conductivity and the hydration time. The hydration sensitivity coefficient reflects the influence of hydration on the crack width and further influences the crack conductivity. The introduction of the coefficient makes the attenuation law of the crack conductivity be quantitatively related to the hydration time, the effective stress and other factors, and provides a more accurate mathematical basis for subsequent production optimization.

[0121] The application establishes a time evolution model considering the mutual influence of hydration and effective stress. The model reveals the attenuation effect of hydration on the crack conductivity with the passage of time by mathematical derivation of the relationship among the crack width, the crack conductivity and the hydration time.

[0122] ​​It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for constructing a fracture conductivity model considering hydration and Brinkman flow, characterized in that... It mainly includes the following steps: 1) Establish the relationship between fracture conductivity and fracture width considering Brinkman flow; the specific process is as follows: The conductivity of a fracture is defined by the fracture permeability and the fracture width, and is obtained by the following formula (1): （1）； During gas flow, fracture permeability is mainly affected by the viscous shear effect of the fracture wall, and the flow field exhibits a distinct Brinkman-type characteristic. Considering the gas permeability variation under Brinkman flow, the relationship between proppant filling permeability, proppant filling porosity, and fracture width is characterized: （2）； In equation (2) above, k f k represents the hydraulic fracture permeability under Brinkman flow. p For proppant filling permeability; w f φ is the crack width. p The porosity of the proppant; β is the unit conversion factor 1.01*10. 15 ; The initial proppant filling permeability and proppant filling porosity are calculated using equations (3) and (4) respectively. The relationship between the initial proppant filling permeability and the effective stress is shown in equation (3) below: （3）； In equation (3) above, φ p0 This represents the crack porosity under initial proppant filling, where σ0 is the initial effective stress; σ is the initial effective stress with cracks; c p c is the average porosity compressibility. p The value is 2×10 −4 MPa −1 ; The relationship between permeability and effective stress under proppant filling is shown in equation (4) below: （4）； In equation (4) above, k p Permeability under proppant filling; k p0 The initial permeability under proppant filling; Initial state proppant-filled crack porosity φ p0 It can be obtained from the following formula (5): （5）； Calculate the throat radius and channel curvature in the initial state of the crack: （6）； （7）； In equations (5)-(7) above, r0 is the throat radius of the crack in the initial state when the closure pressure is 0; τ0 is the pore curvature of the crack in the initial state when the closure pressure is 0; and R is the proppant radius. The initial permeability of the fracture under proppant filling is related to porosity, pore throat radius, and pore tortuosity. Substituting equations (5)-(7) into equation (8) yields the initial permeability k under proppant filling. p0 : （8）； Based on the above formulas (3)-(4), the initial permeability k under stress-related proppant filling is obtained. p0 Initial state proppant-filled crack porosity φ p0 and average pore compressibility c p Inserting these parameters into equation (1), we obtain the relationship between crack conductivity and crack width considering Brinkman flow: （9）； 2) Conduct experiments to test the conductivity of fractures, in order to test the loss of conductivity of coal cores under different stress loading conditions and different hydration times; 3) Introduce the hydration sensitivity coefficient ε to establish the relationship between the hydration time of deep coal and rock and the conductivity of fractures.

2. The method for constructing a fracture conductivity model considering hydration and Brinkman flow as described in claim 1, characterized in that, The specific steps of the fracture conductivity test in step 2) are as follows: 2.1) Load the test rock sample into the core holder, and keep the confining pressure constant for 30 minutes with an initial effective stress of 10 MPa. 2.2) Nitrogen gas is introduced into the core holder. After the gas flow stabilizes, the gas flow rate through the core sample is monitored and recorded. The fracture conductivity is calculated. The calculation process for fracture conductivity is as follows: （10）； （11）； （12）； In equations (10)-(12) above, q is the experimentally measured gas flow rate, k is the fracture permeability, A is the cross-sectional area of ​​the gas passing through the fracture, ΔP is the pressure difference between the injection end and the outlet end of the core holder, μ is the fluid viscosity, L is the seepage length, w is the fracture width, d is the fracture length, and C... f This is the crack conductivity value; 2.3) Slowly increase the effective stress to the core holder. Repeat steps 2.1)-2.2) above every 5 MPa increase in effective stress until the maximum pressure of 40 MPa is reached, then stop increasing the stress. 2.4) Repeat steps 2.1) to 2.3 above to test the conductivity loss of cores with KCl solution introduced under different effective stress loading times.

3. The method for constructing a fracture conductivity model considering hydration and Brinkman flow as described in claim 1, characterized in that: Before proceeding with step 2), the selected test rock sample needs to be linearly cut to remove the irregular parts at both ends of the original core and process it into a standard columnar core. Then, the standardized core sample is subjected to fracture induction, and 40 / 70 mesh proppant is used for the experiment. The experiment uses a self-built core permeability testing platform.

4. The method for constructing a fracture conductivity model considering hydration and Brinkman flow as described in claim 1, characterized in that, The specific process of step 3) is as follows: Substitute the crack conductivity value obtained experimentally in step 2) into formula (9) to obtain the crack width value under different hydration times. At the same time, based on formula (13), the crack width is fitted with the change of effective stress. ε is the sensitivity coefficient between crack width and effective stress under different hydration times. （13）； In the above formula (13), w f0 ε is the crack width calculated when the effective stress is 0; ε is the coefficient between the crack width and the effective stress under the hydration time, i.e., the hydration sensitivity coefficient. By fitting the ε values ​​at different hydration times, the relationship between crack width and hydration time under hydration is obtained as follows: （14）； Substituting different ε values ​​into formula (13), we obtain the change in crack width with hydration time under different modes. Further substituting these values ​​into formula (9) yields formula (15). In formula (15), the crack permeability kp0 under the initial state proppant filling and the crack porosity φ under the initial state proppant filling are... p0 Average porosity c p and the initial effective stress with cracks Once determined, by incorporating the hydration sensitivity coefficient ε, which varies with effective stress as crack width, the relationship between crack conductivity and hydration time is established as follows: （15）。

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