Method for constructing a model of fracture conductivity accounting for hydration and brinkman flow

Abstract

The application provides a method for constructing a fracture conductivity model considering hydration and Brinkman flow, which mainly comprises the following steps: 1) establishing a relationship between fracture conductivity and fracture width; 2) performing a fracture conductivity test experiment to test the fracture conductivity loss of a core subjected to hydration by passing KCl solution under different stress loading times; and 3) establishing a relationship between deep coal rock hydration time and fracture conductivity. The application has reasonable concept, can accurately predict the change of fracture conductivity, can accurately capture the complex coupling relationship between hydration and fracture conductivity and effective stress, and thus provides a scientific decision basis for actual engineering.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir exploration technology, specifically to a method for constructing a fracture conductivity model that considers hydration and Brinkman flow. Background Technology

[0002] Hydraulic fracturing is a key technology for extracting hydrocarbon resources from deep coal and rock reservoirs. During fracturing, a large amount of fluid is usually trapped in the fractures. This trapped fluid undergoes hydration with the fractures, severely impacting gas well productivity. Hydration refers to the microscopic and macroscopic changes in rock structure caused by fluid contact with rock and soil minerals, altering rock mechanical properties and physical parameters, resulting in a complex attenuation law of fracture conductivity, thus affecting the stability of coal and rock reservoirs and the recovery rate of coalbed methane. Hydration exhibits a significant time effect; therefore, the conductivity of artificial fractures can be directly correlated with the interaction time between fracturing fluid and rock, especially for tight reservoirs where water distribution is controlled by capillary forces and clay osmotic pressure. However, existing research mostly focuses on the impact of water-rock interaction on rock mechanical properties, lacking a quantitative description of the relationship between the hydration time effect and fracture conductivity. Therefore, this invention proposes a fracture conductivity calculation model that considers hydration and Brinkman flow.

[0003] Currently, methods for calculating fracture conductivity mainly rely on traditional Darcy's law or the Kozeny-Carman equation. These methods typically assume that fracture permeability is proportional to fracture width and do not consider the viscous effects of fluids. Especially for gas flow, traditional models cannot adequately account for the non-Darcy flow characteristics of fluids in fractures, particularly in high-stress and low-permeability fracture environments. Furthermore, existing models often focus on calculations based on static physical properties (such as fracture width and permeability), neglecting the dynamic changes in fractures during hydraulic fracturing, particularly the long-term effects of hydration on fracture width, permeability, and conductivity.

[0004] In recent years, with a deeper understanding of hydration effects and non-Darcy flow characteristics, more and more studies have begun to attempt to incorporate factors such as hydration effects, non-Darcy flow, and effective stress into models of fracture conductivity. However, existing techniques still have many limitations, especially regarding the coupling effect between fracture conductivity and hydration time and stress changes, for which no effective solution has yet been proposed. Furthermore, traditional fracture conductivity models often rely on simple static mechanical parameters, which cannot effectively address complex hydration effects and stress variations.

[0005] The existing technology has the following main drawbacks:

[0006] Ignoring the long-term effects of hydration: Traditional models typically assume that fracture width and permeability are statically constant, treating the effects of hydration on fracture width and permeability as short-term effects. In reality, hydration is a process with a significant time effect; its impact on fracture conductivity intensifies with increasing hydration time. Especially under high pressure and high hydration conditions, fracture width will shrink significantly, thus affecting the attenuation of fracture conductivity. Therefore, traditional models neglect the time effect of hydration, making it impossible to accurately reflect changes in fracture conductivity during long-term production. This problem has not been adequately addressed in existing technologies.

[0007] Accuracy issues with the model: In the development 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. Traditional methods for calculating fracture conductivity neglect the influence of hydration and fail to fully consider the time dependence of hydration time on fracture conductivity. Existing fracture conductivity calculation models are mostly based on Darcy's law or the Kozeny-Carman equation, failing to fully consider the viscous effect of fluid flow. Especially in unconventional oil and gas reservoirs, fluid flow is complexly affected by factors such as fracture width, morphology, and effective stress. Traditional models have low prediction accuracy in these environments and often cannot accurately predict the changing trend of fracture conductivity.

[0008] Existing techniques often fail to reflect the coupling relationship between hydration and stress changes when describing changes in fracture conductivity. During hydraulic fracturing, as the fracture closes, stress continuously increases, and hydration further enhances the fracture's sensitivity to stress changes. Therefore, traditional models cannot accurately reflect the interaction between hydration, fracture conductivity, and effective stress.

[0009] In conclusion, it is necessary to further innovate existing technologies. Summary of the Invention

[0010] To address the technical problems existing in the background art, this invention proposes a method for constructing a fracture conductivity model that considers hydration and Brinkman flow. The method is reasonable and can accurately predict changes in fracture conductivity. It can accurately capture the complex coupling relationship between hydration, fracture conductivity, and effective stress, thereby providing a scientific basis for decision-making in practical engineering.

[0011] To address the aforementioned technical problems, this invention provides a method for constructing a fracture conductivity model that considers hydration and Brinkman flow, which mainly includes the following steps:

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

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

[0014] (1);

[0015] 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:

[0016] (2);

[0017] 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 ;

[0018] 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:

[0019] (3);

[0020] 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 ;

[0021] The relationship between permeability and effective stress under proppant filling is shown in equation (4) below:

[0022] (4);

[0023] In equation (4) above, k p Permeability under proppant filling; k p0 The initial permeability under proppant filling;

[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 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:

[0039] (10);

[0040] (11);

[0041] (12);

[0042] 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;

[0043] 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.

[0044] 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.

[0045] The method for constructing a fracture conductivity model that considers hydration and Brinkman flow includes: before 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, fracture induction is performed on the standardized core sample, and 40 / 70 mesh proppant is used for the experiment. The experiment uses a self-built core permeability testing platform.

[0046] The method for constructing a fracture conductivity model that considers hydration and Brinkman flow, wherein step 3) specifically involves the following process:

[0047] 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.

[0048] (13);

[0049] 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.

[0050] By fitting the ε values ​​at different hydration times, the relationship between crack width and hydration time under hydration is obtained as follows:

[0051] (14);

[0052] 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:

[0053] (15).

[0054] By adopting the above technical solution, the present invention has the following beneficial effects:

[0055] The method of constructing a fracture conductivity model that considers hydration and Brinkman flow in this invention is well-conceived. By innovatively introducing the Brinkman flow equation and the hydration sensitivity coefficient (ε), it successfully solves the technical problems that existing technologies cannot address, and provides a new approach and method for the development of unconventional oil and gas reservoirs.

[0056] This invention successfully quantifies the time dependence between hydration and fracture conductivity by defining a hydration sensitivity coefficient (ε). This hydration sensitivity coefficient (ε) is used to characterize the effect of hydration on fracture conductivity, especially the variation of fracture conductivity with changes in hydration time.

[0057] This invention accurately predicts long-term changes in fracture conductivity: By introducing a hydration sensitivity coefficient (ε), this invention accurately characterizes the time-dependent influence of hydration on fracture conductivity, and can quantify the long-term attenuation effect of hydration on fracture conductivity, thus providing a more accurate tool for predicting fracture conductivity during gas well production.

[0058] This invention addresses the coupling relationship between fracture conductivity and hydration time and stress changes: By combining the Brinkman flow equation and the influence of hydration, this invention establishes a model that reflects the evolution of fracture conductivity caused by hydration time and effective stress. This invention effectively reveals the complex interaction between hydration and fracture conductivity and effective stress, thus overcoming the shortcomings of existing technologies in this field.

[0059] This invention considers the coupling effect of hydration and Brinkman flow, enabling more accurate prediction of changes in fracture conductivity. This invention provides a scientific basis for gas production prediction and optimization after hydraulic fracturing, helping to improve gas well production efficiency and ultimate recoverable reserves.

[0060] The main advantages of this invention are reflected in the following aspects:

[0061] (1) Calculation model of fracture conductivity based on Brinkman flow equation:

[0062] This invention proposes a novel model for calculating the conductivity of fractures. This model incorporates the Brinkman flow equation and can take into account the viscous shear effect of fluid flow in fractures, thus solving the problem of insufficient description of gas seepage by traditional models.

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

[0064] By defining a hydration sensitivity coefficient (ε), this invention successfully quantifies the time dependence between hydration and fracture conductivity. This coefficient is used to characterize the effect of hydration on fracture conductivity, especially the variation of fracture conductivity with changes in hydration time.

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

[0066] A novel time-dependent evolution model for fracture conductivity is proposed, combining the hydration effect and stress loading time. This model can accurately predict the decay trend of fracture conductivity over time under different hydration times and stress loading conditions.

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

[0068] This invention focuses on the impact of hydration on fracture conductivity in unconventional oil and gas reservoirs such as coal-rock gas reservoirs, and provides a model that can be applied in actual production, tailored to the characteristics of this type of gas reservoir. Attached Figure Description

[0069] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0070] Figure 1 This is a schematic diagram of the experimental design;

[0071] Figure 2 These are the experimental results obtained from the experiment;

[0072] Figure 3 The results are the fitting of crack width as a function of effective stress.

[0073] Figure 4 The results show the fitting of ε values ​​under different hydration times. Detailed Implementation

[0074] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] The present invention will be further explained below with reference to specific embodiments.

[0076] This embodiment provides a method for constructing a fracture conductivity model that considers hydration and Brinkman flow, which mainly includes the following steps:

[0077] S100. Establish the relationship between fracture conductivity and fracture width, taking into account Brinkman flow;

[0078] The fracture conductivity is calculated as shown in formula (1). The fracture conductivity is defined by the permeability and the fracture width:

[0079] (1);

[0080] During gas flow, fracture permeability is primarily influenced by the viscous shear effect of the fracture walls, resulting in a distinct Brinkman-type flow field. Therefore, traditional methods for describing equivalent permeability during gas seepage have limitations. To overcome this limitation, this study considers the gas permeability variation under Brinkman flow conditions, characterizing the relationship between proppant-filled permeability, proppant-filled porosity, and fracture width:

[0081] (2);

[0082] 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 .

[0083] The initial proppant filling permeability and proppant filling porosity are calculated using equations (3) and (4), where the relationship between the initial proppant filling permeability and the effective stress can be expressed as:

[0084] (3);

[0085] 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 The average porosity is taken as 2 × 10⁻⁶. −4 MPa −1 .

[0086] The relationship between permeability and effective stress under proppant filling is shown in equation (4) below:

[0087] (4);

[0088] In equation (4) above, k p Permeability under proppant filling; k p0 The initial permeability under proppant filling;

[0089] Initial state proppant-filled crack porosity φ p0 It can be obtained from the following formula (5):

[0090] (5);

[0091] The formulas for calculating the throat radius and channel curvature in the initial state of the crack are as follows:

[0092] (6);

[0093] (7);

[0094] In equations (5)-(7) above, r0 is the throat radius of the crack in the initial state when the closing pressure is 0, in μm; τ0 is the pore curvature of the crack in the initial state when the closing pressure is 0, in dimensionless form; and R is the proppant radius, in μm.

[0095] 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 :

[0096] (8);

[0097] 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 By inserting these parameters into formula (1), we can obtain the relationship between crack conductivity and crack width under Brinkman flow:

[0098] (9);

[0099] S200, An experiment was conducted to test the conductivity of fractures, in order to assess the loss of conductivity in coal core samples under different stress loading conditions and hydration times;

[0100] Test rock samples were selected, and irregular portions at both ends of the original core were removed using a linear cutting method. The resulting core samples were then processed into standard columnar cores, 5 cm in length and 2.5 cm in diameter. The Brazilian splitting method was then used to induce fractures in the standardized core samples. 40 / 70 mesh silica proppant was used for the experiments. A self-built core permeability testing platform was employed, comprising a gas source, electronic differential pressure sensor, core holder, confining pressure pump, electronic soap film flow meter, and pneumatic-liquid pump. A schematic diagram of the experiment is shown below. Figure 1 As shown.

[0101] The experimental steps for testing the conductivity of cracks are as follows:

[0102] S210. Load the test rock sample into the core holder, and use the confining pressure pump (monitor the pressure output of the confining pressure pump through the pressure gauge) to maintain the confining pressure on the test rock sample in the core holder for 30 minutes with an initial effective stress of 10 MPa.

[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 f0ε is the crack width calculated when the effective stress is 0, in meters; ε is the coefficient between the crack width and the effective stress under the hydration time, i.e., the hydration sensitivity coefficient, in 1 / MPa.

[0115] The ε values ​​at different hydration times were fitted, such as... Figure 4 As shown, the relationship between crack width and hydration time under hydration is obtained:

[0116] (14);

[0117] Substituting different ε values ​​into formula (13), we obtain the change in crack width with hydration time under different modes. 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, the relationship between fracture conductivity and hydration time is established:

[0118] (15).

[0119] This invention employs the Brinkman flow equation to describe the gas flow characteristics in fractures, taking into account the viscous shear effect within the fracture during gas flow. This equation can more accurately characterize the flow behavior of liquids and gases in fractures, thus providing a more precise method for calculating fracture conductivity. Meanwhile, traditional fracture permeability models often rely solely on porosity and fracture width, failing to consider the viscous effect of liquid flow, leading to significant deviations in calculation results. The Brinkman flow equation model of this invention overcomes this deficiency, improving the accuracy of fracture conductivity calculation.

[0120] This invention characterizes the relationship between fracture conductivity and hydration time by defining a hydration sensitivity coefficient (ε). The hydration sensitivity coefficient reflects the influence of hydration on fracture width, which in turn affects fracture conductivity. The introduction of this coefficient allows for a quantitative correlation between the attenuation law of fracture conductivity and factors such as hydration time and effective stress, providing a more accurate mathematical basis for subsequent production optimization.

[0121] This invention establishes a time evolution model that considers the interaction between hydration and effective stress. Through mathematical derivation of the relationship between crack width, crack conductivity, and hydration time, this model reveals the attenuation effect of hydration on crack conductivity over time.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of constructing a model of fracture conductivity accounting for hydration and Brinkman flow, characterized by , comprising the following steps: 1) establishing a relationship between the fracture conductivity and the fracture width considering Brinkman flow; the specific process is as follows: The fracture conductivity is defined by the fracture permeability and the fracture width, and the fracture conductivity is obtained by the following formula (1): （1）； In the process of gas flow, the fracture permeability is 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 the proppant filling permeability, the proppant filling porosity and the fracture width is represented as follows: （2）； In the above equation (2), k f is the hydraulic fracture permeability under Brinkman percolation; k p is the proppant pack permeability; w f is the fracture width; φ p is the proppant pack porosity; and β is a unit conversion factor of 1.01*10 15 ; The initial state of the 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 of the proppant filling permeability and the effective stress is shown in the following formula (3): （3）； In the above formula (3), φ p0 represents the fracture porosity under the initial state proppant filling, σ0 is the initial effective stress; σ is the initial effective stress with cracks; c p is the average pore compression rate, c p takes a value of ; The relationship between the proppant filling permeability and the effective stress is shown in the following formula (4): （4）； In the above equation (4), k p is the permeability under proppant packing; k p0 is the initial permeability under proppant packing; Initial fracture porosity φ with proppant pack p0 is obtained from the following equation (5): （5）； The pore throat radius and the pore tortuosity of the initial state of the fracture are calculated as follows: （6）； （7）； 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; τ0 is the pore tortuosity of the initial state of the fracture when the closure pressure is 0; R is the radius of the proppant; The initial fracture permeability with proppant filling is related to the porosity, pore throat radius and pore tortuosity. The above equations (5) - (7) are inserted into the above equation (8) to obtain the initial permeability k p0 : （8）； Based on the above equations (3)-(4), the initial permeability k of the fracture filled with proppant related to stress is obtained p0 , the initial fracture porosity φ filled with proppant p0 , and the average pore compressibility c p , by inserting these parameters into equation (1), the relationship between the fracture conductivity and the fracture width under the consideration of Brinkman flow is obtained: （9）； 2) performing an experiment of testing the fracture conductivity to test the loss of the coal rock core conductivity under different stress loading conditions and different hydration times; 3) introducing a hydration sensitivity coefficient ε to establish a relationship between the deep coal rock hydration time and the fracture conductivity; the specific process is as follows: The fracture width values under different hydration times are obtained by bringing the fracture conductivity values measured in the experiment in step 2) into formula (9), and the change of the fracture width with the effective stress is fitted based on formula (13), and ε is the sensitivity coefficient between the fracture width and the effective stress under different hydration times; （13）； In the above equation (13), w f0 is the crack width calculated when the effective stress is 0; ε is the coefficient between the crack width at the hydration time and the effective stress, i.e., the hydration sensitivity coefficient; The ε values under different hydration times are fitted to obtain the change relationship of the fracture width with the hydration time under hydration as follows: （14）； The different ε is brought into formula (13), and the change of the fracture width with hydration time under different modes is obtained, and the above formula (9) is further brought into formula (15), wherein the fracture permeability kp0 under the initial state of proppant filling, the fracture porosity φ under the initial state of proppant filling, the average pore compression rate c and the initial effective stress of the fracture with cracks p0 , the average pore compression rate c p and the initial effective stress of the fracture with cracks After being determined, the hydration sensitivity coefficient ε changing with the fracture width changing with the effective stress is brought in, and the change relationship formula of the fracture conductivity with the hydration time is established as follows: （15）。 2. The method of constructing a model of fracture conductivity that accounts for hydration and Brinkman flow of claim 1, wherein, The specific steps of the experiment of testing the fracture conductivity in step 2) are as follows: 2.1) The test rock sample is loaded into the core holder, and the test rock sample in the core holder is taken as the starting point with an initial effective stress of 10 MPa, and the confining pressure is kept unchanged for 30 min; 2.2) Nitrogen is introduced into the core holder, and 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 calculation process is as follows: （10）； （11）； （12）； In the above equations (10) - (12), q is the experimentally measured gas flow rate, k is the fracture permeability, A is the cross-sectional area of the fracture through which the gas is flowing, ΔP is the pressure differential between the injection end and the outlet end of the core holder, μ is the fluid viscosity, L is the length of the permeameter, w is the fracture width, d is the fracture length, and C f is the fracture conductivity value. 2.3) The effective stress of the core holder is slowly increased, and when the effective stress is increased by 5 MPa, the above steps 2.1)-2.2) are repeated until the effective stress reaches the maximum pressure of 40 MPa and stops increasing; 2.4) The above steps 2.1)-2.3) are repeated to test the loss of the conductivity of the core into which KCl solution is introduced under different effective stress loading times.

3. The method of constructing a model of fracture conductivity that accounts for hydration and Brinkman flow of claim 1, wherein: Before step 2), the selected test rock sample is processed into a standard columnar core by removing the irregular parts at both ends of the original core in a linear cutting manner, and then the standardized 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.

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