Prediction method for diffusion range of grouting slurry in coal seam floor area

Abstract

The invention provides a method for predicting the diffusion range of grouting slurry in a coal seam floor area. The method comprises the following steps: acquiring a slurry flooding model containing well field stratum parameters and grouting drilling parameters in the coal seam floor area; based on a Navier Stokes equation and a Darcy law, obtaining a Brinkman equation used for describing incompressible fluid flow caused by the reinforcing material in the porous medium; wherein the Brinkman equation comprises a viscosity item and a pressure gradient item; the grouting pressure, the slurry density, the dynamic viscosity, the porous medium permeability and the porous medium porosity serve as influence factors of slurry diffusion, and various parameter combinations of the influence factors and levels are obtained; and simulating a slurry diffusion process based on the slurry flooding model by using a plurality of parameter combinations and utilizing the Brinkman equation so as to obtain an optimal parameter combination and a corresponding slurry diffusion range. According to the method, the slurry diffusion range can be scientifically and accurately predicted, and the consistency and reliability of the grouting treatment effect are improved.

Description

Technical Field

[0001] The present application belongs to the technical field of mine water hazard prevention and control, and in particular relates to a method for predicting the diffusion range of grouting slurry in a coal seam floor area. Background Art

[0002] The coal seam floors of the Carboniferous and Permian coalfields in northern my country are mostly deposited with 2 to 14 layers of thin interlayer limestone of coal measures and thick layers of Ordovician or Cambrian limestone with a thickness of up to 200 to 800 meters. These strata are one of the main sources of water inrush faced by deep mines and lower coal mining. When the thickness of the coal seam floor aquifer is insufficient and it is in a strong runoff zone or a rich water-conducting geological structure zone, the carbonate rock aquifer in the coal seam floor is prone to cause water inrush disasters. Such disasters usually present the characteristics of high water pressure, abundant water sources, strong concealment and great destructiveness, and have become one of the main disasters faced by deep mining in North China coalfields. Grouting technology is the main means of preventing and controlling karst confined water hazards in the coal seam floor. Its basic principle is to strengthen the floor aquifer through ground regional governance or local grouting, transform the aquifer into a relative aquifer, and block the original fissures, faults, sinkholes and other water-conducting channels in the stratum. Thereby, the transformed rock stratum meets the thickness requirement of the waterproof layer, the comprehensive water-blocking capacity of the rock stratum of the coal seam floor is improved, and water damage caused by water inrush from the floor is prevented.

[0003] Although Chinese scholars have conducted a lot of research on the diffusion law of grouting slurry in fractured rock mass and the regional management of water hazards in coal seam floors, and have achieved certain theoretical and practical results, the existing technology still has shortcomings when facing complex geological conditions such as deep complex stress, hydrodynamics and structure. Especially in the complex engineering background of vertical holes, inclined holes and ultra-long horizontal holes, the grouting transformation effects of thin limestone and Ordovician thick limestone under different hydrogeological conditions are significantly different. Existing grouting technology mostly relies on idealized models and field experience, and the main control factors of slurry diffusion and the effective management range under complex conditions are still not fully understood, which makes it difficult to accurately predict and control the management effect, limiting its promotion and application in actual engineering. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a method for predicting the diffusion range of grouting slurry in the coal seam floor area. This method takes into account the macroscopic viscosity effect and the pressure gradient in each pore channel, and can scientifically and accurately predict the slurry diffusion range, overcome the shortcomings of traditional methods that mainly rely on field experience, and improve the consistency and reliability of grouting treatment effects, providing a scientific basis for achieving efficient treatment of deep and highly pressurized aquifers.

[0005] The present application provides a method for predicting the diffusion range of grouting slurry in a coal seam floor area, comprising:

[0006] Obtain a slurry water displacement model for the coal seam floor area including well field formation parameters and grouting drilling parameters;

[0007] Based on the Navier-Stokes equations and Darcy's law, a Brinkman equation is obtained to describe the flow of incompressible fluid caused by the reinforcing material in the porous medium; wherein the Brinkman equation includes a viscosity term and a pressure gradient term;

[0008] Grouting pressure, slurry density, dynamic viscosity, porous medium permeability, and porous medium porosity are used as influencing factors of slurry diffusion, and multiple parameter combinations of each influencing factor and level are obtained;

[0009] Using a variety of parameter combinations and utilizing the Brinkman equation, the slurry diffusion process is simulated based on the slurry water displacement model to obtain an optimal parameter combination and a corresponding slurry diffusion range.

[0010] Furthermore, the well field formation parameters include: regional division information of each well field formation and geological parameter information of each well field formation; wherein the geological parameter information includes: porosity, permeability and thickness;

[0011] The grouting drilling parameters include: location information and segmentation information of the grouting drilling, and the drill bit diameter of each segment.

[0012] Furthermore, in the simulation of slurry diffusion, the following assumptions are met:

[0013] (1) The flow of the slurry is continuous;

[0014] (2) The slurry is an isotropic, incompressible fluid, and the bulk density of the slurry remains unchanged during the flow process, and the flow rate is stable;

[0015] (3) The side wall of the slurry satisfies a no-slip boundary;

[0016] (4) The diffusion mode of the slurry is complete displacement diffusion, and the mixing of water and slurry at the slurry-water interface is not considered;

[0017] (5) The flow of the slurry is laminar flow.

[0018] Furthermore, the Brinkmann equation for describing the incompressible fluid flow caused by the reinforcement material in porous media is obtained in the following way:

[0019] Use the Navier-Stokes equations to describe the motion of viscous incompressible fluids;

[0020] Adding Darcy drag terms to the Navier-Stokes equations to simulate the resistance of the solid skeleton to the fluid when flowing in porous media;

[0021] The porosity used to correct the density term is introduced to describe the fluid flowing only in the pore space of the porous medium;

[0022] Based on the premise that the porous medium is isotropic, the viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor, respectively, and the Brinkman equation is obtained to describe the incompressible fluid flow caused by the reinforcing material in the porous medium.

[0023] Furthermore, the Navier-Stokes equation is expressed as:

[0024]

[0025] In the formula, ρ represents the fluid density; u represents the fluid velocity; p represents the fluid pressure; μ represents the fluid dynamic viscosity; f represents the external force acting on the fluid; Represents the gradient operator.

[0026] Furthermore, the Darcy drag term f d It is expressed as:

[0027]

[0028] Where -μ / κ·u represents the linear resistance based on Darcy's law; -βρ|u|u represents the nonlinear resistance introduced due to the increase in flow velocity, which usually dominates under high flow rate conditions; β represents a constant related to the fluid and porous media, reflecting the degree of nonlinear resistance.

[0029] Furthermore, the fluid flowing only in the pore space of the porous medium is described by the following equation:

[0030]

[0031] In the formula, ε p represents the porosity of porous media, represents the viscosity term, represents the pressure gradient term.

[0032] Furthermore, the viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor respectively by the following equations:

[0033]

[0034]

[0035] In the formula, represents the velocity gradient; represents the transpose of the velocity gradient; pI represents the pressure tensor, where I is the unit tensor;

[0036] The Brinkmann equation is expressed as:

[0037]

[0038]

[0039] Furthermore, the initial grouting parameters of the slurry flooding model are set as follows:

[0040] The initial grouting pressure is 9MPa and the initial slurry density is 1200kg / m 3 The initial slurry dynamic viscosity is 3mPa·s, and the permeability of the grouting transformation rock formation is 1.2E-11m 2 , grouting transformation experience once the porosity was 0.05, the fault zone permeability was 0.5m 2 , the porosity of the fault zone is 0.01.

[0041] Furthermore, the optimal parameter combination and the corresponding slurry diffusion range are obtained by the following method:

[0042] Obtaining multiple parameter combinations and the slurry diffusion ranges corresponding to the multiple parameter combinations obtained through multi-physics field coupling numerical simulation;

[0043] Based on multiple parameter combinations and their corresponding slurry diffusion ranges, the variance analysis method was used to analyze the influence of single factors on the slurry diffusion range, and the main and secondary factors were determined.

[0044] Based on the main and secondary factors, and the influence characteristics of each factor on the slurry diffusion range, the optimal parameter combination is determined, and the predicted slurry diffusion range is obtained by using the Brinkman equation and the slurry water displacement model.

[0045] The present application provides a method for predicting the diffusion range of grouting slurry in the coal seam floor area. The method takes into account the macroscopic viscosity effect and the pressure gradient in each pore channel, and can scientifically and accurately predict the slurry diffusion range, overcome the deficiency of traditional methods that mainly rely on field experience, and improve the consistency and reliability of grouting treatment effects, providing a scientific basis for achieving efficient treatment of deep and highly pressurized aquifers. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A flow chart showing a method for predicting the diffusion range of grouting slurry in a coal seam floor area provided in an embodiment of the present application is shown;

[0047] Figure 2 A schematic diagram of a slurry water flooding model provided in an embodiment of the present application is shown;

[0048] Figure 3A graph showing a trend of the estimated boundary average value provided by the embodiment of the present application with the grouting pressure;

[0049] Figure 4 A graph showing a trend of the estimated boundary average value provided by the embodiment of the present application with the slurry density;

[0050] Figure 5 A graph showing a trend of the estimated boundary average value provided in the embodiment of the present application with the slurry dynamic viscosity;

[0051] Figure 6 A graph showing a trend of the estimated boundary average value provided by the embodiment of the present application with the permeability of the porous medium;

[0052] Figure 7 A graph showing the variation trend of the estimated boundary average value provided in the embodiment of the present application with the porosity of the porous medium is shown. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the technical solution more clear, the technical solution is further described in detail below in conjunction with specific implementation methods. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the technical solution.

[0054] At present, the advanced regional control of coal seam floor water hazards mainly relies on field experience. Faced with complex geological conditions such as deep complex stress, hydrodynamics, and structure, and the complex engineering background of vertical holes, inclined holes, and super-long horizontal holes, the grouting transformation effects of thin-layer limestone and Ordovician thick limestone (abbreviated as "Ordovician limestone") under different hydrogeological conditions are quite different, and the slurry diffusion law and effective control range are difficult to accurately predict.

[0055] In addition, usually during the grouting process, the displaced phase cannot be completely discharged from the pores, and a layer of residual wetting fluid will be left on the solid surface, keeping the two incompatible fluids at the contact interface. This two-phase seepage simulation involves the flow of slurry and groundwater, which have different volume fractions in a specific spatial region, but the sum of their volume fractions is always 1. Therefore, although the ratio of slurry to groundwater will change, the total volume remains unchanged. That is, in the initial state, the porous medium is completely filled with water, and as the slurry is displaced, the volume fraction of water gradually decreases until it is completely replaced.

[0056] In porous media phase transfer, the complex behavior of two-phase flow needs to be described by specific equations. The relevant two-phase flow equation can be expressed as the following formula (1):

[0057]

[0058] In the formula, ε pis the porosity of the porous medium; is the density of the corresponding phase; S i is the volume fraction of the corresponding phase; N i is the flux phase; Q Si is the mass source term of the corresponding phase; u i is the Darcy velocity of the corresponding phase; κ rSi is the relative permeability of the corresponding phase; μ Si is the dynamic viscosity of the corresponding phase; κ is the permeability of the porous medium; p Si is the pressure of the corresponding phase fluid; p v is the pressure of the phase calculated according to the volume constraint; p cSi is the capillary pressure provided by the phase; ▽· is the divergence operator; ▽ is the gradient operator.

[0059] When coupling free medium and porous medium flows, Darcy's law is often introduced into the Navier-Stokes equations for solution. Although this method is numerically easy to solve, it does not take into account the viscous effect in the free medium flow, which is still very important in the free-porous interface region.

[0060] In view of this, this application proposes a method for predicting the diffusion range of grouting slurry in the coal seam floor area, please refer to Figure 1 , Figure 1 FIG. 1 is a flow chart of a method for predicting the diffusion range of grouting slurry in a coal seam floor area provided in an embodiment of the present application. Figure 1 As shown, the method includes:

[0061] S101. Obtain a slurry water displacement model for the coal seam floor region including well field formation parameters and grouting drilling parameters.

[0062] In this step, the slurry water displacement model is used to provide a simulation environment for the grouting process. Under high pressure, the slurry displaces the groundwater, forming a two-phase unstable seepage in the porous medium. The slurry and groundwater interact with each other as two immiscible fluids and flow simultaneously. By simulating the grouting process, the grouting effect and the slurry diffusion range can be predicted, thereby providing a scientific basis for grouting design, optimizing the design scheme, and improving engineering quality and efficiency.

[0063] Among them, the well field formation parameters include: regional division information of each well field formation and geological parameter information of each well field formation; wherein the geological parameter information includes: porosity, permeability and thickness; the grouting drilling parameters include: grouting drilling location information and segmentation information, and the drill bit diameter of each segment.

[0064] As an example, see Figure 2 , Figure 2 FIG. 2 is a schematic diagram of a slurry water displacement model provided in an embodiment of the present application. Figure 2As shown in Figure 1, the slurry flooding model is divided into multiple wellfield strata from top to bottom, including: Quaternary, Upper Shihezi Formation, Lower Shihezi Formation, Shanxi Formation, 9# coal seam, Taiyuan Formation, 16# coal seam, Zhuozishan Formation. The geological parameter information of each wellfield stratum is shown in Table 1. The width, length and height of the model are 1000 meters, 1000 meters and 877.53 meters respectively. Furthermore, the area below the 16# coal seam and above the Zhuozishan Formation is determined as the location of the grouting transformation rock stratum, and the following is obtained: Figure 2 The location information and segmentation information of the grouting drilling holes shown specifically include: vertical well section, inclined section and horizontal section. The length of the horizontal section is 200 meters. The drill bit diameter of the first vertical well section of the well body is 311.15 mm, the drill bit diameter of the second inclined section is 215.9 mm, and the drill bit diameter of the third horizontal section is 152.4 mm.

[0065] Table 1. Geological parameter information of each well field stratum

[0066]

[0067] S102. Based on the Navier-Stokes equations and Darcy's law, the Brinkman equation is obtained to describe the flow of incompressible fluid caused by reinforcing materials in porous media.

[0068] The Brinkmann equation includes a viscosity term and a pressure gradient term.

[0069] In a specific implementation, the Brinkmann equation for describing the incompressible fluid flow caused by the reinforcement material in the porous medium is obtained in the following way:

[0070] Step 1021: Use the Navier-Stokes equations to describe the motion of a viscous incompressible fluid.

[0071] Specifically, the Navier-Stokes equation is expressed as:

[0072]

[0073] In the formula, ρ represents the fluid density; u represents the fluid velocity; p represents the fluid pressure; μ represents the fluid dynamic viscosity; f represents the external force acting on the fluid; Represents the gradient operator.

[0074] Step 1022: Add the Darcy resistance term to the Navier-Stokes equations to simulate the resistance of the solid skeleton to the fluid when flowing in the porous medium.

[0075] Specifically, the Darcy drag term f d It is expressed as:

[0076]

[0077] Where -μ / κ·u represents the linear resistance based on Darcy's law; -βρ|u|u represents the nonlinear resistance introduced due to the increase in flow velocity, which usually dominates under high flow rate conditions; β represents a constant related to the fluid and porous media, reflecting the degree of nonlinear resistance.

[0078] Step 1023: The porosity for correcting the density term is introduced again to describe the fluid flowing only in the pore space of the porous medium.

[0079] Specifically, the fluid flowing only in the pore space of the porous medium is described by the following equation:

[0080]

[0081] In the formula, ε p represents the porosity of porous media, represents the viscosity term, represents the pressure gradient term.

[0082] Step 1024: Based on the premise that the porous medium is isotropic, the viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor, respectively, and the Brinkman equation for describing the flow of incompressible fluid caused by the reinforcement material in the porous medium is obtained.

[0083] Specifically, the viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor, respectively, by the following equations:

[0084]

[0085] In the formula, represents the velocity gradient; represents the transpose of the velocity gradient; pI represents the pressure tensor, where I is the unit tensor;

[0086] Here, we use formulas (5) and (6) to replace the viscosity term and pressure gradient term in formula (4), and assume that the fluid flow is slow and further ignore the inertia term. Finally, we get the Brinkmann equation.

[0087] The Brinkmann equation is expressed as:

[0088]

[0089] S103. Taking grouting pressure, slurry density, dynamic viscosity, porous medium permeability, and porous medium porosity as influencing factors of slurry diffusion, and obtaining a plurality of parameter combinations of the influencing factors and levels.

[0090] In this step, considering that the diffusion of slurry in karst media is affected by multiple factors, studying these factors helps to better understand and control the diffusion process, thereby improving grouting efficiency. A comprehensive analysis of the factors affecting slurry diffusion in the advanced regional management of coal seam floor water hazards is conducted, and they are divided into three categories: external dynamics, slurry properties, and formation properties. Among them, external dynamics include grouting pressure; slurry properties include slurry density and dynamic viscosity; formation properties include porous medium permeability and porous medium porosity.

[0091] In order to fully cover the situations that may be encountered in actual engineering, the embodiment of the present application designs an orthogonal experiment, which can achieve better experimental results with fewer experiments and significantly optimize the experimental process. This orthogonal experiment includes 5 factors, each of which has 5 levels, and its specific selection is shown in Table 2.

[0092] Table 2. Selection of influencing factors and levels

[0093]

[0094] Furthermore, according to the orthogonal design principle, at least 21 tests are required based on the above parameter combinations. To meet the test requirements, the L25 (56) orthogonal table is selected, which contains 25 groups of test configurations, that is, 25 parameter combinations that can cover all factors and levels to ensure test flexibility and data integrity. The control indicator of the test is the diffusion range of the grouting slurry in the coal seam floor area.

[0095] S104, using a variety of parameter combinations and the Brinkman equation to simulate the slurry diffusion process based on the slurry water displacement model to obtain an optimal parameter combination and a corresponding slurry diffusion range.

[0096] Among them, in the simulation of slurry diffusion process, the following assumptions are met:

[0097] (1) The flow of the slurry is continuous;

[0098] (2) The slurry is an isotropic, incompressible fluid, and the bulk density of the slurry remains unchanged during the flow process, and the flow rate is stable;

[0099] (3) The side wall of the slurry satisfies a no-slip boundary;

[0100] (4) The diffusion mode of the slurry is complete displacement diffusion, and the mixing of water and slurry at the slurry-water interface is not considered;

[0101] (5) The flow of the slurry is laminar flow.

[0102] At the same time, the initial grouting parameters of the slurry flooding model are set as follows:

[0103] The initial grouting pressure is 9MPa and the initial slurry density is 1200kg / m 3 The initial slurry dynamic viscosity is 3mPa·s, and the permeability of the grouting transformation rock formation is 1.2E-11m 2 , grouting transformation experience once the porosity was 0.05, the fault zone permeability was 0.5m 2 , the porosity of the fault zone is 0.01.

[0104] In this step, the slurry water displacement model is used as the simulation environment, the Brinkman equation is used as the solution equation of the slurry water displacement model, and a variety of parameter combinations are used to simulate the slurry diffusion process to complete the orthogonal experiment. By analyzing the results of the orthogonal experiment, the optimal parameter combination and the corresponding slurry diffusion range are obtained.

[0105] In specific implementation, the optimal parameter combination and the corresponding slurry diffusion range are obtained by the following method:

[0106] Step 1041, obtaining a plurality of parameter combinations, and slurry diffusion ranges corresponding to the plurality of parameter combinations obtained through multi-physical field coupling numerical simulation.

[0107] As an example, 25 parameter combinations and their corresponding slurry diffusion ranges are shown in Table 3:

[0108]

[0109] Step 1042: Based on the various parameter combinations and the corresponding slurry diffusion ranges, the variance analysis method is used to analyze the influence of a single factor on the slurry diffusion range, and the main factor and the secondary factor are determined.

[0110] In this step, the variance analysis method can distinguish the experimental differences caused by factors, level changes and errors, and provide reliable quantitative estimates. At the same time, SPSS statistical software is widely used in the fields of natural sciences and social sciences, and can efficiently perform data analysis. Therefore, the embodiment of the present application uses SPSS software to perform variance analysis.

[0111] Here, a one-way analysis is performed by introducing estimated marginal means before performing the ANOVA:

[0112] Estimating marginal mean means estimating the mean value of a specific variable under the influence of other related variables for data analysis. This application calculates the estimated marginal mean values ​​under the specific variables of grouting pressure, slurry density, slurry dynamic viscosity, porous medium permeability, and porous medium porosity, and draws a trend chart of the estimated marginal mean value with the specific variables to analyze the influence of various factors on the slurry diffusion range, specifically:

[0113] (1) Please refer to Figure 3The estimated boundary average value provided by the embodiment of the present application is shown as a trend diagram of the change of grouting pressure. Figure 3 As shown in Figure 1, as the grouting pressure gradually increases from 3 MPa to 15 MPa, the slurry diffusion range expands significantly. In the lower grouting pressure stage (A1 to A3), the increase in the slurry diffusion range is particularly significant, with the increase from A1 (88.189m 3 ) to A2(287.574m 3 ) increased by 199.385m 3 The increase from A2 to A3 is 356.972m 3 However, at higher pressure stages, the increase gradually decreases: from A3 to A4, the increase decreases to 137.96m 3 , from A4 to A5 is only 22.745m 3 This trend shows that the slurry diffusion range has a higher responsiveness in the lower grouting pressure stage and gradually becomes stable in the high pressure stage.

[0114] Therefore, it can be determined that there is a positive correlation between the slurry diffusion range and the grouting pressure, that is, the greater the grouting pressure, the wider the slurry diffusion range; the smaller the grouting pressure, the smaller the slurry diffusion range. However, as the grouting pressure continues to increase, the slurry gradually fills the pores of the porous medium. After reaching saturation, the effect of further increasing the pressure on diffusion gradually weakens, resulting in a decrease in the increase in the increase.

[0115] (2) Please refer to Figure 4 The estimated boundary average value provided by the embodiment of the present application is shown as a trend diagram of the change of slurry density. Figure 4 As shown in the figure, as the slurry density increases from 1200kg / m 3 Gradually increase to 1500kg / m 3 The slurry diffusion range showed a clear decreasing trend. From B1 to B2, the slurry diffusion range decreased by 20.769m 3 , from B2 to B3, it descends 14.394m 3 , and from B3 to B4, the drop is 19.395m 3 , and finally from B4 to B5, the descent is 3.625m 3 In general, as the slurry density continues to increase, the decline in the slurry diffusion range gradually decreases, especially in the higher density range, where the decline slows down significantly.

[0116] Therefore, it can be determined that there is a negative correlation between the slurry diffusion range and the slurry density, that is, the lower the slurry density, the wider the slurry diffusion range; the higher the slurry density, the smaller the slurry diffusion range.

[0117] (3) Please refer to Figure 5The estimated boundary average value provided by the embodiment of the present application is shown as a trend diagram of the change of the slurry dynamic viscosity. Figure 5 As shown in Figure 2, as the slurry dynamic viscosity gradually increases from 3 mPa·s to 6 mPa·s, the slurry diffusion range shows a significant downward trend. Specifically, from C1 to C2, the slurry diffusion range decreases by 67.079 m 3 ; From C2 to C3, a reduction of 46.789m 3 ; From C3 to C4, the drop is 98.925m 3 ; From C4 to C5, the reduction is 18.095m 3 In general, as the dynamic viscosity of the slurry increases, the diffusion range of the slurry continues to decrease, but the extent of decrease varies in different viscosity ranges. In particular, in the lower viscosity range (3mPa·s to 4mPa·s), the decrease is large, while in the higher viscosity range (5mPa·s to 6mPa·s), the decrease is significantly reduced.

[0118] Therefore, it can be determined that there is a negative correlation between the slurry diffusion range and the slurry dynamic viscosity, that is, the lower the slurry dynamic viscosity, the wider the slurry diffusion range; the higher the slurry dynamic viscosity, the smaller the slurry diffusion range.

[0119] (4) Please refer to Figure 6 The estimated boundary average value provided by the embodiment of the present application is shown as a trend diagram of the change of the porous medium permeability. Figure 6 As shown, as the permeability of the porous medium increases from 6.5×10-13m 2 Gradually increase to 1.2×10-11m 2 The slurry diffusion range shows an obvious increasing trend. 3 ) to D2(229.176m 3 ), the diffusion range increased by 175.307m 3 , indicating that in low permeability media, the flow resistance of slurry is large and the diffusion range increases relatively slowly; from D2 to D3 (514.244m 3 ), the diffusion range increased by 285.068m 3 ; From D3 to D4 (829.202m 3 ), the diffusion range increased by 314.958m 3 , indicating that in the medium permeability stage (such as D2 to D4), the permeability improvement significantly enhanced the diffusion capacity of the slurry; from D4 to D5 (981.575m 3 ), the diffusion range increased by 152.376m 3Although the diffusion range continues to increase, the growth rate has slowed down. This trend shows that when the permeability of the porous medium reaches a certain level, the diffusion capacity of the slurry tends to be saturated, and the effect of further increasing the permeability of the porous medium on the diffusion range gradually weakens.

[0120] Therefore, it can be determined that there is a positive correlation between the slurry diffusion range and the permeability of the porous medium, that is, the higher the permeability, the wider the slurry diffusion range; the lower the permeability, the smaller the slurry diffusion range. However, as the permeability continues to increase, the slurry gradually fills the pores of the porous medium and tends to be saturated. After that, the effect of further increasing the permeability on diffusion gradually weakens, and the increase gradually decreases.

[0121] (5) Please refer to Figure 7 The estimated boundary average value provided by the embodiment of the present application is shown as a trend diagram of the change of the porosity of the porous medium. Figure 7 As shown in Figure 2, as the porosity of the porous medium gradually increases from 0.05 to 0.4, the slurry diffusion range shows an obvious decreasing trend. Specifically, from E1 (813.526m 3 ) to E2(72.984m 3 ), the slurry diffusion range decreased by 40.542m 3 ; From E2 to E3 (471.799m 3 ), a decrease of 301.185m 3 ; From E3 to E4 (385.196m 3 ), a decrease of 86.603m 3 ; From E4 to E5 (164.563m 3 ), a decrease of 220.633m 3 Overall, as the porosity of the porous medium increases, the slurry diffusion range gradually decreases, but the extent of decrease varies in different intervals. Especially in the higher porosity stage (such as E4 to E5), the increase in porosity significantly limits the diffusion of the slurry, indicating that the pore structure of the medium has formed a significant obstacle to the penetration and diffusion of the slurry.

[0122] Therefore, it can be determined that there is a negative correlation between the slurry diffusion range and the porosity of the porous medium: the smaller the porosity, the wider the slurry diffusion range; the larger the porosity, the smaller the slurry diffusion range.

[0123] Furthermore, single factor analysis was performed using ANOVA:

[0124] Table 4. ANOVA table

[0125]

[0126]

[0127] It can be seen from Table 4 that the significance of slurry density and slurry dynamic viscosity are 0.965 and 0.253 (both greater than 0.05), respectively, and have no significant effect on the test results; while the significance of grouting pressure, porous medium permeability and porous medium porosity are 0.010, 0.003 and 0.006 (all less than 0.05), respectively, indicating that they have a significant impact on the test results. Combining the significance analysis results of each factor, it can be determined that porous medium permeability, porous medium porosity and grouting pressure are the main factors affecting the change of slurry diffusion range, while slurry dynamic viscosity and slurry density have relatively little effect on them.

[0128] Step 1043: Based on the main factors and the secondary factors, and the influence characteristics of each factor on the slurry diffusion range, determine the optimal parameter combination, and use the Brinkman equation and the slurry water displacement model to obtain the predicted slurry diffusion range.

[0129] In this step, different levels of different factors have different effects on the test results. The optimal parameter combination can be determined based on the analysis results of the influence of the above single factors on the slurry diffusion range.

[0130] As an example, the grouting pressure is 15 MPa and the slurry density is 1200 kg / m 3 The dynamic viscosity of the slurry is 3 MPa·s, and the permeability of the porous medium is 1.2×10-11m 2 ,The parameter combination with the porous medium porosity of 0.05 has the greatest influence on the change of the slurry diffusion range. Therefore, the above parameter combination is determined as the optimal parameter combination. Further, the optimal parameter combination is used to simulate the slurry diffusion process based on the slurry water displacement model using the Brinkman equation to obtain the predicted slurry diffusion range.

[0131] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, many changes can be made in the specific implementation methods and application scopes based on the ideas of the present technical content. As long as these changes do not deviate from the concept of the present invention, they all fall within the scope of protection of this patent.

Claims

1. A method for predicting the diffusion range of grouting slurry in the coal seam floor area, characterized in that: The method comprises: Obtain a slurry water displacement model for the coal seam floor area including well field formation parameters and grouting drilling parameters; Based on the Navier-Stokes equations and Darcy's law, a Brinkman equation is obtained to describe the flow of incompressible fluid caused by the reinforcing material in the porous medium; wherein the Brinkman equation includes a viscosity term and a pressure gradient term; Grouting pressure, slurry density, dynamic viscosity, porous medium permeability, and porous medium porosity are used as influencing factors of slurry diffusion, and multiple parameter combinations of each influencing factor and level are obtained; Using a variety of parameter combinations and utilizing the Brinkman equation, the slurry diffusion process is simulated based on the slurry water displacement model to obtain an optimal parameter combination and a corresponding slurry diffusion range.

2. The method according to claim 1, characterized in that The well field formation parameters include: regional division information of each well field formation and geological parameter information of each well field formation; wherein the geological parameter information includes: porosity, permeability and thickness; The grouting drilling parameters include: location information and segmentation information of the grouting drilling, and the drill bit diameter of each segment.

3. The method according to claim 1, characterized in that In the simulation of slurry diffusion, the following assumptions are met: (1) The flow of the slurry is continuous; (2) The slurry is an isotropic, incompressible fluid, and the bulk density of the slurry remains unchanged during the flow process, and the flow rate is stable; (3) The side wall of the slurry satisfies a no-slip boundary; (4) The diffusion mode of the slurry is complete displacement diffusion, and the mixing of water and slurry at the slurry-water interface is not considered; (5) The flow of the slurry is laminar flow.

4. The method according to claim 1, characterized in that The Brinkmann equations for describing the incompressible flow of fluids in porous media induced by reinforcement materials are obtained as follows: Use the Navier-Stokes equations to describe the motion of viscous incompressible fluids; Adding Darcy drag terms to the Navier-Stokes equations to simulate the resistance of the solid skeleton to the fluid when flowing in porous media; The porosity used to correct the density term is introduced to describe the fluid flowing only in the pore space of the porous medium; Based on the premise that the porous medium is isotropic, the viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor, respectively, and the Brinkman equation is obtained to describe the incompressible fluid flow caused by the reinforcing material in the porous medium.

5. The method according to claim 4, characterized in that The Navier-Stokes equations are expressed as: In the formula, ρ represents the fluid density; u represents the fluid velocity; p represents the fluid pressure; μ represents the fluid dynamic viscosity; f represents the external force acting on the fluid; ▽ represents the gradient operator.

6. The method according to claim 5, characterized in that The Darcy drag term f d It is expressed as: Where -μ / κ·u represents the linear resistance based on Darcy's law; -βρ|u|u represents the nonlinear resistance introduced due to the increase in flow velocity, which usually dominates under high flow rate conditions; β represents a constant related to the fluid and porous media, reflecting the degree of nonlinear resistance.

7. The method according to claim 6, characterized in that Fluid flow only within the pore spaces of a porous medium is described by the following equation: In the formula, ε p represents the porosity of porous media, represents the viscosity term, represents the pressure gradient term.

8. The method according to claim 7, characterized in that The viscosity term and the pressure gradient term are expressed as the divergence form of the viscous stress tensor and the pressure tensor, respectively, by the following equations: In the formula, represents the velocity gradient; represents the transpose of the velocity gradient; pI represents the pressure tensor, where I is the unit tensor; The Brinkmann equation is expressed as:

9. The method according to claim 1, characterized in that The initial grouting parameters of the slurry flooding model are set as follows: The initial grouting pressure is 9MPa and the initial slurry density is 1200kg / m 3 The initial slurry dynamic viscosity is 3mPa·s, and the permeability of the grouting transformation rock formation is 1.2E-11m 2 , grouting transformation experience once the porosity was 0.05, the fault zone permeability was 0.5m 2 , the porosity of the fault zone is 0.

01.

10. The method according to claim 1, characterized in that The optimal parameter combination and the corresponding slurry diffusion range are obtained by the following method: Obtaining multiple parameter combinations and the slurry diffusion ranges corresponding to the multiple parameter combinations obtained through multi-physics field coupling numerical simulation; Based on multiple parameter combinations and their corresponding slurry diffusion ranges, the variance analysis method was used to analyze the influence of single factors on the slurry diffusion range, and the main and secondary factors were determined. Based on the main and secondary factors, and the influence characteristics of each factor on the slurry diffusion range, the optimal parameter combination is determined, and the predicted slurry diffusion range is obtained by using the Brinkman equation and the slurry water displacement model.

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