Sedimentary basin mine water geological storage suitability evaluation method

Abstract

The invention provides a sedimentary basin mine water geological storage suitability evaluation method. The method comprises the following steps: establishing a geological conceptual model based on geological parameters of a sedimentary basin mine; determining an evaluation index for evaluating the storage suitability of the mine water in the sedimentary basin based on the geological conceptual model; establishing a hierarchical structure of storage suitability evaluation based on an analytic hierarchy process, and calculating an evaluation index weight; and evaluating the geological storage suitability of the mine water based on the evaluation index system and the weight of the evaluation index obtained by using an analytic hierarchy process. According to the method, a more reliable and accurate result can be provided for mine water geological storage site selection of the coal-endowed sedimentary basin.

Description

Technical Field

[0001] The present invention belongs to the field of treatment of mine water in coal mines in sedimentary basins, and particularly relates to a method for evaluating the suitability of geological storage of mine water in sedimentary basins. Background Art

[0002] The water environment problems in coal mining areas mainly include mine water gushing out during coal mining, coal washing wastewater, and domestic sewage in coal mining areas. With the increasingly strict environmental protection laws and regulations in China and the continuous improvement of treatment processes, the coal washing process can basically achieve closed-loop recycling of washing water; and the amount of domestic sewage generated in the mining area is small, and after being treated by the municipal domestic sewage treatment process, it can meet the reclaimed water reuse standards for greening, cleaning, etc. and realize reuse. Therefore, the core content of the water environment problem in coal mining areas is how to treat and utilize the mine water gushing out during coal mining.

[0003] In terms of time dimension, coal mine water gushing can be divided into the stored old goaf water generated after mine closure and the newly added mine water generated during coal mine production. The common treatment technologies for old goaf water mainly include physical methods, chemical methods, and biological methods, etc. Among them, the mainstream technologies are the use of underground permeable reactive walls and lime neutralization treatment methods. In recent years, units such as Taiyuan University of Technology have also carried out practices on the advanced treatment of old goaf water using constructed wetlands, adsorption methods, etc., and all have achieved good treatment effects. For the newly added mine water generated during coal mine production, through mine dewatering, it is pumped to the target area for further treatment, and in this process, problems such as treatment costs and land occupation area are generated.

[0004] In terms of spatial dimension, for traditional mine water treatment, the mine water first needs to be lifted to the ground for treatment. Part of it is directly reused on the ground, and part is returned to the underground for reuse. This treatment method has disadvantages such as large floor area, high capital construction costs, operation costs, lifting costs, and corresponding pipeline laying costs. Moreover, it inevitably causes secondary pollution. In addition, pumping a large amount of mine water to the ground for treatment leads to surface subsidence in some areas, causing ecological problems. Therefore, in recent years, many scientific researchers have tried to directly reuse the mine water after in-situ treatment underground. This can not only overcome the above disadvantages but also generate significant economic, environmental, and ecological benefits. Therefore, the existing underground mine water treatment processes have limited options and small treatment capacities, while the ground treatment has a large floor area and high operation costs. Discharging the treated mine water to the surface will also incur high drainage fees. In some regions of China, the method of recharging the mine water into the formation in a different location has achieved good results. Sun Yajun (in 2022) proposed the technical idea of mine water recharge and storage in a different location, and Zhang Chunhui (in 2023) proposed a utilization model for coal mine mine water treatment based on the linkage of "deep earth - underground - ground". However, there is no unified standard for how to select the site and evaluate the suitability. Therefore, there is an urgent need to provide a method for evaluating the suitability of mine water recharge in a different location at the site level to improve the accuracy of screening the target layer for mine water recharge and storage in a different location, and at the same time, to quantitatively characterize the weights of evaluation indicators and the evaluation results. Summary of the Invention

[0005] In view of the underground recharge of mine water, the present invention provides an evaluation method for geological storage of mine water in sedimentary basins to improve the accuracy of mine water storage and at the same time quantitatively characterize the weights of evaluation indicators and the evaluation results.

[0006] The technical solution of the present invention is as follows:

[0007] An evaluation method for the suitability of geological storage of mine water in sedimentary basins, comprising the following steps:

[0008] Establish a geological conceptual model based on the geological parameters of the mine in the sedimentary basin;

[0009] Determine the evaluation indicators for the evaluation of the suitability of mine water storage in the sedimentary basin based on the geological conceptual model;

[0010] Establish a hierarchical structure for the evaluation of storage suitability based on the analytic hierarchy process and calculate the weights of the evaluation indicators;

[0011] Evaluate the suitability of geological storage of mine water based on the evaluation index system and the weights of the evaluation indicators obtained by using the analytic hierarchy process.

[0012] Furthermore, the geological parameters include the necessary reservoir parameters and fluid parameters of the target reservoir;

[0013] Furthermore, the necessary reservoir parameters include: seismic basic intensity value, primary tectonic area, depth, peak ground acceleration of the main body of the tectonic unit, general situation of active faults, geological characteristics of the reservoir-caprock, geothermal gradient, type of hydraulic driving force, flow depth, formation water salinity, coal mine distribution, regional resource exploitation degree, and resource potential.

[0014] Furthermore, the evaluation indexes for the geological storage suitability of mine water include primary indexes and secondary indexes;

[0015] The primary indexes include geological stability, storage potential, hydrogeological conditions, and social and economic capabilities; the secondary indexes include seismic intensity, primary tectonic area, peak ground acceleration of the main body, active faults, physical properties of the reservoir, lithology of the reservoir, sedimentary facies of the reservoir, thickness of the reservoir, burial depth of the reservoir, physical properties of the caprock, lithology of the caprock, thickness of the caprock, geothermal gradient, driving force type, flow depth, water quality, coal mine distribution density, exploitation degree, and resource potential.

[0016] Furthermore, the calculation of the weights of the evaluation indexes is specifically as follows:

[0017] For the primary index layer and the secondary index layer, construct the corresponding primary index layer set A = f(B1, B2, B3, B4), and secondary index layer sets B1 = g1(C1, C2, C3, C4), B2 = g2(C5, C6, C7, C8, C9, C10, C11, C12, C13), B3 = g3(C14, C15, C16), B4 = g4(C17, C18, C19);

[0018] According to the Saaty scale method, compare and quantitatively represent the relative importance of any two indexes in each primary index layer set and secondary index layer set, and create the corresponding judgment matrix based on the comparison results of pairwise indexes in each set. The judgment matrix of set A is U, the judgment matrix of set B1 is X, the judgment matrix of set B2 is Y, the judgment matrix of set B3 is Z, and obtain the weight vector u = (u1, u2, u3) of judgment matrix U T , the weight vector x = (x1, x2, x3, x4) of judgment matrix X T , the weight vector y = (y1, y2,... y9) of judgment matrix Y T , the weight vector z = (z1, z2, z3) of judgment matrix Z T , the weight vector d = (d1, d2, d3) of judgment matrix D T The elements of each weight vector are the weights of the corresponding indexes in each set;

[0019] The weight vectors x, y, z, and d of the secondary necessary index layer are composed into a matrix U. By calculating the matrix U and the weight vector F of the primary necessary index layer, the weight vector W=(w1, w2, w3... w 19 ) T is obtained. Then, the final weights of the indexes in the secondary index layer are w1, w2, w3... w 19 , and further, the weights of all indexes in the secondary necessary index layer with respect to the weight layer are obtained.

[0020] Furthermore, the evaluation index system includes 5 levels: suitable, relatively suitable, generally suitable, relatively unsuitable, and unsuitable. In this regard, the alternative set is taken as V={suitable, relatively suitable, moderately suitable, less suitable, unsuitable}, and the numericalized alternative set is V j ={9, 7, 5, 3, 1}. Based on this score and the weights of each evaluation index with respect to the target layer obtained by using the analytic hierarchy process, the geological storage suitability of mine water is evaluated.

[0021] Furthermore, the calculation formula for evaluating the geological storage suitability of mine water based on this score and the weights of each evaluation index with respect to the target layer obtained by using the analytic hierarchy process is as follows:

[0022]

[0023] where: S is the comprehensive score for evaluating the geological storage suitability of mine water in the sedimentary basin, V i and W i are the scores of different evaluation indexes and their weight values with respect to the target layer respectively, i = 1, 2, 3... n, j = 1, 2... 5

[0024] Furthermore, when the comprehensive score for evaluating the storage suitability of mine water is greater than 7.5, the suitability degree of this tectonic unit is "suitable"; when the comprehensive score for evaluating the storage suitability of mine water is between 7.5 and 6.5, the suitability degree of this tectonic unit is "moderately suitable"; when the comprehensive score for evaluating the storage suitability of mine water is between 6.5 and 5.5, the suitability degree of this tectonic unit is "generally suitable"; when the comprehensive score for evaluating the storage suitability of mine water is less than 5.5, the suitability degree of this tectonic unit is "unsuitable".

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] Based on the established suitability evaluation index system, the present invention realizes the quantitative description of all indexes, solves the problem of multiple solutions in the suitability evaluation results caused by the qualitative analysis of evaluation indexes in previous evaluations, realizes the quantitative characterization of the suitability evaluation results, and improves the accuracy and scientificity of the results. The index system structure of this solution is clear, the logic is easy to understand, and the calculation process is simple, which is convenient for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings illustrate various embodiments by way of example rather than limitation, and together with the specification and the claims are used to explain the embodiments of the invention. Where appropriate, the same reference numerals are used in all the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the device or method.

[0028] Figure 1 The schematic diagram of the weight calculation model of the necessary index system of the embodiment of the present invention is shown;

[0029] Figure 2 The schematic flow diagram of the evaluation method of the present invention is shown. Detailed implementation manners

[0030] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0031] An embodiment discloses a method for evaluating the geological storage suitability of mine water in a sedimentary basin. The method uses the analytic hierarchy process to evaluate the geological storage suitability of mine water, as Figure 2 shown, and includes the following steps:

[0032] Establish a geological conceptual model based on the geological parameters of the mine in the sedimentary basin;

[0033] Determine the evaluation indexes for evaluating the geological storage suitability of mine water in the sedimentary basin based on the geological conceptual model;

[0034] Establish a hierarchical structure for evaluating the storage suitability based on the analytic hierarchy process and calculate the weights of the evaluation indexes;

[0035] Evaluate the geological storage suitability of mine water based on the evaluation index system and the weights of the evaluation indexes obtained by using the analytic hierarchy process.

[0036] The specific calculation process of establishing a hierarchical structure for evaluating the storage suitability based on the analytic hierarchy process and calculating the weights of the evaluation indexes is as follows:

[0037] First, construct a weight calculation model for the necessary index system, as Figure 1As shown, the model includes a weight layer, a first-level necessary index layer, and a second-level necessary index layer. An index set is formed for the first-level necessary index layer and the second-level necessary index layer of the model, that is, the first-level necessary index layer set A = f(B1, B2, B3, B4), and the second-level index layer sets B1 = g1(C1, C2, C3, C4), B2 = g2(C5, C6, C7, C8, C9, C10, C11, C12, C13), B3 = g3(C14, C15, C16), B4 = g4(C17, C18, C19). According to the Saaty scale method, the relative importance of any two indexes in each index set is compared and quantitatively represented. For example, if index A i and index A j have the same importance, then a ij is assigned 1. If A i is extremely important compared to A j , then a ij is assigned 9, and vice versa, the reciprocal is taken. The principle of the Saaty scale method is relatively mature and will not be elaborated here. The judgment matrix of each set is created by synthesizing the comparison results of pairwise indexes in the set. The judgment matrix of set A is U, the judgment matrix of set B1 is X, the judgment matrix of set B2 is Y, the judgment matrix of set B3 is Z, and the judgment matrix of set B4 is D. The expression forms of each judgment matrix are as follows:

[0038]

[0039] In the formula, aij represents the degree of importance of index ui compared to uj when ui and uj are compared.

[0040] Calculating the importance order: The eigenvector W corresponding to the largest eigenvalue of the judgment matrix A is obtained. W = (W1, W2,..., Wn) is the weight of each index sought, and Wi is calculated according to the following formula.

[0041]

[0042] Consistency test: Calculate the largest eigenvalue λmax of the judgment matrix A, as shown in the formula.

[0043]

[0044] Among them, (AW)i represents the i-th element of the vector. Then the consistency test index of the judgment matrix is the formula:

[0045]

[0046] Among them, To define the consistency index, RI is the random consistency index of the judgment matrix. The corresponding relationship between the RI value and the order n is as follows: when n = (1, 2, 3, 4, 5, 6, 7, 8), the RI values are RI = (0, 0, 0.58, 0.90, 1.12, 1.24, 1.32, 1.41)

[0047] When CR ≤ 0.1, it is generally considered that the judgment matrix has satisfactory consistency, indicating that the determined weights of each index are reasonable. Otherwise, the judgment matrix needs to be adjusted until it has satisfactory consistency.

[0048] The weight calculation of the first-level indicators uses the 1-9 scale method to quantitatively score the first-level indicators and constructs the A-B judgment matrix to obtain the first level. The weight vector WBi (i = 1 - 4) of the first-level evaluation indicators is (0.1406, 0.3479, 0.3479, 0.1636). The maximum eigenvalue λmax of the judgment matrix A is 5.01. The defined consistency index CI is 0.0025, the random consistency index RI of the judgment matrix is 1.12, and the consistency test index CR of the judgment matrix is 0.0022, which is less than 0.1. Therefore, the result is reasonable. Similarly, the weight analysis method of the second-level indicators is similar and will not be specifically described below.

[0049] Based on the judgment matrix, the weight vector U of the judgment matrix U is calculated using the eigenvalue method: U = (0.1406, 0.3479, 0.3479, 0.1636) T ; the weight vector x of the judgment matrix X is x = (0.2, 0.2, 0.2, 0.4) T ; the weight vector y of the judgment matrix Y is

[0050] (0.2954, 0.2041, 0.0841, 0.0841, 0.0841, 0.1356, 0.0528, 0.0352, 0.02478) T . The weight vector z of the judgment matrix Z is z = (0.1429, 0.1429, 0.7143) T , the weight vector d of the judgment matrix D is d = (0.5, 0.25, 0.25) T .

[0051] Perform consistency tests on each weight vector. The consistency ratios are all less than 0.1, indicating satisfactory consistency, and the obtained weights are acceptable.

[0052] After obtaining the weight vector U of the evaluation index layer relative to the target layer and the weight vectors x, y, z, d of the evaluation index relative to the index layer, the weight vector w of the evaluation index relative to the target layer is calculated as w = (0.0281, 0.0281, 0.0281, 0.0562, 0.1028, 0.0710, 0.0292, 0.0292, 0.0292, 0.0472, 0.0184, 0.0122, 0.0086, 0.0497, 0.0497, 0.2485, 0.0818, 0.0409, 0.0409). T , and then the weight of the evaluation index relative to the target layer is obtained.

[0053] Similarly, a consistency test is performed on the weight vector w. The consistency ratio is less than 0.1, and the consistency test is passed, so the obtained weight is acceptable.

[0054] An evaluation index system for the geological storage suitability of mine water is established, as shown in Table 1. This system includes 4 primary evaluation index layers and 19 secondary evaluation indexes. At the same time, the 19 evaluation indexes are respectively divided into 5 grades: suitable, relatively suitable, generally suitable, relatively unsuitable, and unsuitable.

[0055] Table 1 Evaluation Index System for the Geological Storage Suitability of Mine Water

[0056]

[0057]

[0058] The scores corresponding to the 5 grades of the evaluation index are 9, 7, 5, 3, and 1 respectively. V = {9 7 5 3 1}. Based on this score and the established evaluation index system, the quantitative characterization of the evaluation results of the geological storage adaptability of mine water in sedimentary basins is realized. The formula is as follows:

[0059]

[0060] Among them: S is the comprehensive score of the evaluation of the geological storage suitability of mine water in sedimentary basins, V j and W i are the scores of different evaluation indexes and their weights of the target layer respectively, i = 1, 2, 3... n, j = 1, 2... 5.

[0061] When the S value is greater than 7.5, the suitability of this tectonic unit is "suitable"; when the S value is between 7.5 and 6.5, the suitability of this tectonic unit is "moderately suitable"; when the S value is between 6.5 and 5.5, the suitability of this tectonic unit is "generally suitable"; when the S value is less than 5.5, the suitability of this tectonic unit is "unsuitable". When the data difference is not large, the greater the value, the stronger the adaptability.

[0062] The above method is used to evaluate the suitability of mine water geological storage in the Majiagou Formation of the northern Shaanxi slope in the Ordos Basin. The relevant parameters of this formation are as follows: the area of the tectonic unit is 109,000 km 2 , the peak ground acceleration of the main body is 0.05, there is no regional major fault. The physical property porosity of the reservoir is %, the lithology of the reservoir is limestone and dolomite, the sedimentary facies of the reservoir is marine, the thickness of the reservoir is 310 m, the burial depth of the reservoir is 2,826 m, the reservoir pressure coefficient is 0.76, the lithology of the caprock is bauxite and altered tuff, the thickness of the caprock is 50 m, the geothermal gradient is 2.9, the driving force type is weak, the flow depth is 2,900, the water quality (salinity) is 35.12 g / l. The distribution density of coal mines is relatively high and the exploitation degree is relatively high. Finally, the comprehensive score of the evaluation of the suitability of this saline water is 6.69, which is suitable for mine water geological storage and is consistent with the actual situation of the mine site.

[0063] As mentioned above, it is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for evaluating the geological storage suitability of mine water in sedimentary basins, characterized in that, It includes the following steps: Establish a geological conceptual model based on the geological parameters of the mine in the sedimentary basin; Determine the evaluation indexes for the evaluation of the suitability of mine water storage in the sedimentary basin based on the geological conceptual model; Establish a hierarchical structure for the evaluation of storage suitability based on the analytic hierarchy process and calculate the weights of the evaluation indexes; Evaluate the geological storage suitability of mine water based on the evaluation index system and the weights of the evaluation indexes obtained by using the analytic hierarchy process.

2. The method for evaluating the geological storage suitability of mine water in sedimentary basins according to claim 1, characterized in that, The geological parameters include the necessary reservoir parameters and fluid parameters of the target reservoir.

3. The method for evaluating the geological storage suitability of mine water in sedimentary basins according to claim 2, characterized in that, The necessary reservoir parameters include: seismic basic intensity value, primary tectonic area, depth, peak ground acceleration of the main body of the tectonic unit, general situation of active faults, geological characteristics of the reservoir-cap rock, geothermal gradient, type of hydraulic driving force, flow depth, formation water salinity, coal mine distribution, regional resource exploitation degree, and resource potential.

4. The geological storage suitability evaluation method for mine water in sedimentary basins according to claim 1, characterized in that, The evaluation indexes for the geological storage suitability of mine water include primary indexes and secondary indexes; the primary indexes include geological stability, storage potential, hydrogeological conditions, and social and economic capabilities; the secondary indexes include seismic intensity, primary tectonic area, peak ground acceleration of the main body, active faults, physical properties of the reservoir, lithology of the reservoir, sedimentary facies of the reservoir, thickness of the reservoir, buried depth of the reservoir, physical properties of the cap rock, lithology of the cap rock, thickness of the cap rock, geothermal gradient, driving force type, flow depth, water quality, coal mine distribution density, exploitation degree, and resource potential.

5. The geological storage suitability evaluation method for mine water in sedimentary basins according to claim 1, characterized in that, The calculation of the weights of the evaluation indexes is specifically as follows: Construct the corresponding primary index layer set A = f(B1, B2, B3, B4) for the primary index layer and secondary index layer, and secondary index layer sets B1 = g1(C1, C2, C3, C4), B2 = g2(C5, C6, C7, C8, C9, C10, C11, C12, C13), B3 = g3(C14, C15, C16), B4 = g4(C17, C18, C19); According to the Saaty scale method, the relative importance of any two indicators in each set of first-level indicator layers and second-level indicator layers is compared and quantitatively represented. The judgment matrices corresponding to them are created by synthesizing the results of pairwise comparisons of indicators in each set. The judgment matrix of set A is F, the judgment matrix of set B1 is X, the judgment matrix of set B2 is Y, the judgment matrix of set B3 is Z, and the judgment matrix of set B4 is D. The weight vector u=(u1, u2, u3, u4) of the judgment matrix U is obtained T , the weight vector x=(x1, x2, x3, x4) of the judgment matrix X T , the weight vector y=(y1, y2, …… y9) of the judgment matrix Y T , the weight vector z=(z1, z2, z3) of the judgment matrix Z T , the weight vector d=(d1, d2, d3) of the judgment matrix D T The elements of each weight vector are the weights of the corresponding indicators in each set; Form a matrix U with the weight vectors x, y, z, and d of the secondary necessary index layer, and use the combined weights of the elements of the weight vector F of the primary necessary index layer as weights to calculate the weighted sum of each element of the corresponding secondary index judgment matrix U. The result obtained is the combined weight of the target layer element, and the weight vector W = (w1, w2, w3... w19) is obtained. T , then the final weights of the indicators in the secondary index layer are w1, w2, w3... w19, and further the weights of all indicators in the secondary necessary index layer for the weight layer are obtained.

6. The method for evaluating the geological storage suitability of mine water in sedimentary basins according to claim 1, characterized in that, The evaluation index system includes 5 levels: suitable, relatively suitable, generally suitable, relatively unsuitable, and unsuitable. The corresponding numerical alternative set is V = {9, 7, 5, 3, 1}. Based on this score and the weights of each evaluation index for the target layer obtained by using the analytic hierarchy process, the weighted scoring method is used to evaluate the geological storage suitability of mine water.

7. The evaluation method for the geological storage suitability of mine water in sedimentary basins according to claim 6, characterized in that, The calculation formula for evaluating the geological storage suitability of mine water based on this score and the weights of each evaluation index for the target layer obtained by using the analytic hierarchy process is: Where: S is the comprehensive score of the geological storage suitability evaluation of mine water in sedimentary basins, V i and W i are the scores of different evaluation indicators and their weights of the target layer respectively, where i = 1, 2, 3... n and j = 1, 2...

5.

8. The method for evaluating the geological storage suitability of mine water in sedimentary basins according to claim 7, characterized in that, When the comprehensive score of the evaluation of the suitability of mine water storage is greater than 7.5, the suitability degree of this tectonic unit is "suitable"; when the comprehensive score of the evaluation of the suitability of mine water storage is between 7.5 and 6.5, the suitability degree of this tectonic unit is "moderately suitable"; when the comprehensive score of the evaluation of the suitability of mine water storage is between 6.5 and 5.5, the suitability degree of this tectonic unit is "generally suitable"; when the comprehensive score of the evaluation of the suitability of mine water storage is less than 5.5, the suitability degree of this tectonic unit is "unsuitable".

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