Analytical methods for coal seam metamorphism types and their combinations in coal mining areas

Abstract

The present invention relates to an analysis method for coal seam metamorphism types and combinations thereof in coal mining areas, and belongs to the field of gas monitoring technology. The method includes the following steps: sorting out the coal rank distribution characteristics of coal mining areas or mines; judging the deep metamorphism type, and clarifying whether there are other metamorphism types in addition to the deep metamorphism type; further judging whether there is magmatic metamorphism, hydrothermal metamorphism and dynamic metamorphism on the basis of the deep metamorphism type, and judging whether there is dynamic metamorphism. The present invention realizes the comprehensive and effective prediction of coal and gas outburst hazards of coal seams in coal mining areas or mines, the comprehensive and effective assessment of the degree of outburst hazard, the comprehensive and effective division of outburst hazard areas, and the effective adoption of outburst prevention measures based on the main controlling factors of outburst hazard from the source.

Description

Technical Field

[0001] The invention belongs to the technical field of gas monitoring and relates to an analysis method of coal seam metamorphism types and combinations thereof in a coal mining area. Background Art

[0002] Based on on-site production experience, significant differences often exist in coal seam ranks between different mines, geological units, and coal seams within a mining area, as well as between different parts of the same mine and coal seams. It is well known that coal seams are formed by the peatification and coalification of original coal-forming materials (diagenesis and coalification). Furthermore, coal seams are metamorphosed into different ranks due to the different combinations of formation temperature, pressure, and time experienced during their formation. Differences in coal ranks directly affect the generation and adsorption capacity of coal seam gas, as well as the pore structure and strength of the coal body, and other basic coal seam gas characteristics. These basic characteristics, in turn, determine the different coal seam gas occurrence characteristics and the degree of coal and gas outburst hazard. At the same time, the formation temperature and pressure experienced by coal seams during their formation process have multiple sources. Currently, coal seam metamorphism is divided into four types based on the sources of formation temperature and pressure: deep metamorphism, dynamic metamorphism, magmatic metamorphism (regional magmatic metamorphism + contact metamorphism), and hydrothermal metamorphism. Different types of metamorphism have significant differences in the coal rank and coal rank combination characteristics, coal body structure, stress environment, and occurrence characteristics (thickness + occurrence). These factors comprehensively restrict the occurrence characteristics of coal seam gas and the degree of coal and gas outburst hazard. Therefore, clarifying the coal seam metamorphism type and combination pattern in coal mining areas or mines is crucial for the occurrence characteristics of coal seam gas and the prediction of coal and gas outburst hazard, the assessment of outburst hazard degree, the division of outburst hazard areas, and the identification of the main controlling factors of outburst hazard. This has practical guiding significance for the efficient control of coal seam gas and the implementation of effective measures to prevent coal and gas outburst hazard.

[0003] However, currently, when it comes to coal mining area or mine gas prevention and control, as well as coal and gas outburst prevention and control, there is little comprehensive and effective prediction of coal seam gas distribution patterns and coal and gas outburst hazards at the source, comprehensive and effective assessment of outburst hazard levels, comprehensive and effective categorization of outburst hazard zones, and comprehensive and effective identification of key controlling factors for outburst hazards, based on the perspective of coal seam metamorphism types and their combined characteristics. Instead, based on the measurement of a series of parameters such as coal seam gas content, coal seam gas pressure, and coal seam solidity coefficient, the coal and gas outburst hazard of each working face is gradually predicted, the degree of coal and gas outburst hazard of each working face is assessed, and coal and gas outburst hazard zones are categorized for each working face, with prevention measures then implemented face by face. This lack of comprehensiveness, foresight, and efficiency in coal and gas outburst hazard prevention and control efforts has been compromised. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for analyzing the types and combinations of coal seam metamorphism in coal mining areas, so as to analyze and clarify the types and combination patterns of coal seam metamorphism in coal mining areas or mines.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for analyzing coal seam metamorphism types and combinations in a coal mining area, the method comprising the following steps:

[0007] S1: Combing the coal rank distribution characteristics of coal mining areas or mines;

[0008] S2: Determine the type of deep-seated metamorphism and clarify whether other metamorphic types exist besides the deep-seated metamorphism type;

[0009] S3: For the maximum metamorphic temperature T max Significantly greater than the formation temperature t at the historical maximum burial depth of the coal seam max The unit is judged based on the type of deep-seated metamorphism to determine whether it has magmatic metamorphism, hydrothermal metamorphism and dynamic metamorphism; among them, magmatic metamorphism includes regional magmatic metamorphism and contact metamorphism;

[0010] S4: On the basis of the deep metamorphism of each unit, for units with regional magmatic metamorphism, units with contact metamorphism, units with hydrothermal metamorphism, units with regional magmatic metamorphism + contact metamorphism, units with regional magmatic metamorphism + hydrothermal metamorphism, units with contact metamorphism + hydrothermal metamorphism, and units with regional magmatic metamorphism + contact metamorphism + hydrothermal metamorphism, further determine whether they also have dynamic metamorphism.

[0011] Furthermore, the S1 is specifically:

[0012] Based on the perspectives of different mines, different geological units or different parts of the mine, different horizontal coal rank areas are horizontally sorted and divided, and numbered A, B, C, etc. in sequence, which are the horizontal coal rank area numbers; the number of horizontal coal rank division units is consistent with the number of horizontal coal ranks;

[0013] Based on the perspectives of different coal seams or coal seam groups, the horizontal coal rank division units are again longitudinally sorted and divided one by one, and numbered a, b, c... from top to bottom according to the burial depth, which is the vertical coal rank area number, among which the number of vertical coal rank division units divided in each horizontal coal rank division unit is consistent with the number of vertical coal ranks, the number of vertical coal rank division units divided in each horizontal coal rank division unit is ≥1, and the number of vertical coal rank division units divided in each horizontal coal rank division unit is not necessarily the same.

[0014] Furthermore, the S2 is specifically:

[0015] Take coal samples of each coal rank unit according to industry standards and measure the maximum vitrinite reflectance Ro of each coal rank unit max ;

[0016] According to Barker's formula: T max =(lnRo max +1.2) / 0.0078, calculate the maximum metamorphic temperature T of each coal rank unit max ;

[0017] Obtain the development thickness of the regional strata, the age of the regional strata, the time of tectonic subsidence-uplift, the number of tectonic subsidence-uplift, and the amount of tectonic uplift erosion of each coal rank unit, and use basin simulation software to simulate and obtain the historical maximum burial depth H of the coal seam where each coal rank unit is located. max ;

[0018] Obtain the coal seam settlement of each coal rank unit to H max The regional geothermal gradient at the time of H max Regional geothermal gradient, calculate the formation temperature t at the historical maximum burial depth of each coal rank unit max ;

[0019] Successive comparative analysis of each coal rank unit T max and the coal seam where it is located max :

[0020] For T max -t max For units with a temperature of ≤20°C, the coal seam metamorphism type is plutonic metamorphism;

[0021] For T max -t max For units with a temperature greater than 20℃, the coal seam metamorphism types include, in addition to deep-seated metamorphism, one or more of dynamic metamorphism, magmatic metamorphism, and hydrothermal metamorphism.

[0022] Furthermore, the S3 is specifically:

[0023] Establish a comprehensive discrimination condition combination characteristic table for magmatic metamorphism and hydrothermal metamorphism, namely Table 1;

[0024] The table header includes condition combination classification, feature details and corresponding qualitative action type;

[0025] The combination classification includes the first condition combination, the second condition combination and the third condition combination;

[0026] The characteristics of the first condition combination include: the metamorphic area where the unit is located has hydrothermal quartz veins and calcite veins; the area of ​​the metamorphic area where the unit is located is greater than a certain value, has regional characteristics, and the coal rank zoning in the metamorphic area is generally ring-shaped; the rocks in the metamorphic area where the unit is located are altered; the coal rank in the metamorphic area where the unit is located is high, and there are graphite belts, high metamorphic anthracite belts, medium metamorphic anthracite belts, and low metamorphic anthracite belts; the unit has a high metamorphic gradient, and its Ro max The gradient of change is greater than 0.1% / hm; the corresponding metamorphism type is regional magmatic metamorphism;

[0027] The characteristics of the second conditional combination include: the unit develops intrusive igneous rocks; the metamorphic area where the unit is located is centered on intrusive igneous rocks and is localized or narrow; the metamorphic area where the unit is located has a coke rock mixed zone, a natural coke zone, a coke coal mixed zone, and a thermally altered coal zone, with the intrusive igneous rocks as the center. The rocks in the metamorphic area where the unit is located are altered, and high-medium-low temperature alteration zones are developed from the inside to the outside, with the intrusive igneous rocks as the center. The corresponding metamorphic type is contact metamorphism.

[0028] The characteristics of the third condition combination include: the metamorphic area where the unit is located has regional and boundary deep fault zones; hot springs are developed around the metamorphic area where the unit is located; the area of ​​the metamorphic area where the unit is located is less than a certain value, showing local characteristics;

[0029] The corresponding metamorphism types include magmatic metamorphism, hydrothermal metamorphism and dynamic metamorphism; the corresponding metamorphism type is hydrothermal metamorphism;

[0030] For T max -t max For units with a temperature greater than 20°C, geological survey and analysis are conducted on Table 1:

[0031] When a coal rank unit meets the first combination of conditions, then the coal rank unit has regional magmatic metamorphism superimposed on plutonic metamorphism;

[0032] When a coal rank unit meets the second combination of conditions, the coal rank unit has contact metamorphism superimposed on magmatic metamorphism on the basis of deep-seated metamorphism;

[0033] When a coal rank unit meets the third combination of conditions, the coal rank unit has hydrothermal metamorphism superimposed on deep-seated metamorphism;

[0034] When a coal rank unit meets both the first and second condition combinations, then the coal rank unit has both regional magmatic metamorphism and contact metamorphism superimposed on the plutonic metamorphism.

[0035] When a coal rank unit meets both the first and third condition combinations, then the coal rank unit has both regional magmatic metamorphism and hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism.

[0036] When a coal rank unit meets both the second and third condition combinations, then the coal rank unit has both contact metamorphism of magmatic metamorphism and hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism.

[0037] When a coal rank unit meets the first, second and third condition combinations at the same time, then the coal rank unit has not only regional magmatic metamorphism and contact metamorphism of magmatic metamorphism, but also hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism;

[0038] When a coal rank unit does not meet any of the first, second, and third condition combinations, the coal rank unit is subjected to dynamic metamorphism in addition to deep-seated metamorphism.

[0039] Furthermore, the S4 is specifically:

[0040] Establish a structural feature classification table, i.e. Table 2, with the header including structural feature classification and structural feature details;

[0041] The structural characteristics of the first structural feature include: no compression faults or folds, gentle stratum dip, i.e. dip angle ≤ 15°, original coal seam structure, stable coal seam occurrence, no shear slip failure inside the coal seam or between the coal seam and the rock layer, good coal seam permeability, permeability coefficient ≥ 3m 2 MPa -2 ·d -1 ;

[0042] The structural features of the second structural feature include: the development of wide and gentle folds or interlayer compression faults, and their scale is relatively small, the formation dip is relatively gentle, that is, 15°<stratum dip ≤30, the coal seam structure is the original structure - fragmentation structure, the coal seam occurrence is relatively stable, small-scale shear slip failure occurs within the coal seam and between the coal seam and the rock layer, the coal seam has good permeability, 1m 2 MPa -2 ·d -1 ≤Air permeability coefficient<3m 2 MPa -2 ·d -1 ;

[0043] The structural characteristics of the third structural feature include: the development of tight, inverted folds or compression faults, and their scale is relatively large; the coal seam structure is a granular structure - mylonitic structure; the coal seam is unstable; the formation dip angle is large, i.e. >30°; there is a large range of shear slip failure inside the coal seam and between the coal seam and the rock layer; the coal seam has poor permeability, and the permeability coefficient is <1m 2 MPa -2 ·d -1 ;

[0044] For units with regional magmatic metamorphism, contact metamorphism, hydrothermal metamorphism, regional magmatic metamorphism + contact metamorphism, regional magmatic metamorphism + hydrothermal metamorphism, contact metamorphism + hydrothermal metamorphism, and regional magmatic metamorphism + contact metamorphism + hydrothermal metamorphism, the structural characteristics of each unit were investigated and analyzed:

[0045] When the unit structural characteristics meet the first structural characteristics or the second structural characteristics in Table 2, the external conditions for dynamic metamorphism are not met, and the unit does not experience dynamic metamorphism;

[0046] When the unit structural characteristics meet the third structural characteristics in Table 2, the unit has the external conditions for dynamic metamorphism, and further determination is made whether it has dynamic metamorphism;

[0047] ① For units with regional magmatic metamorphism, collect hydrothermal quartz veins or calcite vein samples developed in the metamorphic area where the unit is located, and then make inclusion slices to measure the homogenization temperature T of the brine inclusions inside them. 均一 Distribution characteristics, and select its maximum uniform temperature T 均一max The maximum deterioration temperature of the unit T max Conduct comparative analysis:

[0048] When T 均一max Greater than the unit T max When 0℃≤T max -T 均一max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit;

[0049] When T max -T 均一max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism;

[0050] ② For units with contact metamorphism, collect rock samples that have undergone alteration in the metamorphic area where the unit is located and measure their alteration temperature T 蚀变 Distribution range, and select its maximum alteration temperature T 蚀变max The maximum deterioration temperature of the unit T max Conduct comparative analysis:

[0051] When T 蚀变max Greater than the unit T max When 0℃≤T max -T 蚀变max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit;

[0052] When T max -T 蚀变max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism;

[0053] ③ For units with hydrothermal metamorphism, measure the underground fluid temperature T in or near the deep fault zone in the metamorphic area where the unit is located. 流体 distribution range, and select its maximum fluid temperature T 流体max The maximum deterioration temperature of the unit T max Conduct comparative analysis:

[0054] When T 流体max Greater than the unit T max When 0℃≤T max -T 流体max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit;

[0055] When T max -T 流体max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism;

[0056] ④ For units with regional magmatic metamorphism and contact metamorphism, hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit and altered rock samples were collected, and the homogenization temperature T of the brine inclusions inside the vein bodies was measured. 均一 Distribution characteristics and rock alteration temperature T 蚀变 Distribution range, comparative analysis of its maximum uniform temperature T 均 -max and maximum alteration temperature T 蚀变max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis:

[0057] When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit;

[0058] When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism;

[0059] ⑤ For units with regional magmatic metamorphism and hydrothermal metamorphism, collect hydrothermal quartz vein or calcite vein samples developed in the metamorphic area where the unit is located, and measure the homogenization temperature T of the brine inclusions inside the vein body. 均一 distribution characteristics, and at the same time determine the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, comparative analysis of its maximum uniform temperature T 均一max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis:

[0060] When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit;

[0061] When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism;

[0062] ⑥ For units with contact metamorphism + hydrothermal metamorphism, collect rock samples that have undergone alteration in the metamorphic area where the unit is located and measure their alteration temperature T 蚀变 distribution range, and at the same time measure the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, comparative analysis of its maximum alteration temperature T 蚀变max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis:

[0063] When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit;

[0064] When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism;

[0065] ⑦ For units with regional magmatic metamorphism, contact metamorphism, and hydrothermal metamorphism, collect hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit, as well as altered rock samples, and measure the homogenization temperature T of the brine inclusions inside the veins. 均一 Distribution characteristics and rock alteration temperature T 蚀变 distribution range, and at the same time measure the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, and then compare and analyze its maximum uniform temperature T均一max , maximum alteration temperature T 蚀变max and maximum fluid temperature T 流体max , select the largest of the three and the maximum metamorphic temperature T of the unit max Conduct comparative analysis:

[0066] When the largest of the three is greater than the unit T max When 0℃≤T max -When the maximum of the three is ≤20℃, there is no dynamic metamorphism in the unit;

[0067] When T max -When the maximum of the three is greater than 20°C, the unit is subject to dynamic metamorphism.

[0068] The beneficial effects of the present invention are: clarifying the types and combination patterns of coal seam metamorphism in coal mining areas or mines, achieving comprehensive and effective prediction of coal and gas outburst hazards in coal mining areas or mines, comprehensive and effective assessment of the degree of outburst hazard, comprehensive and effective division of outburst hazard areas, and effective implementation of outburst prevention measures based on the main controlling factors of outburst hazard. This avoids the blindness, localization, lag, and inefficiency of coal and gas outburst hazard prevention and control work in coal mining areas or mines.

[0069] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0071] Figure 1 This is a schematic diagram of the present invention;

[0072] Figure 2 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0073] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0074] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0075] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0076] Figure 1 This is a schematic diagram of the present invention. Figure 2 It is a flow chart of the present invention.

[0077] Phase 1: Sorting out the coal rank distribution characteristics of coal mining areas or mines

[0078] Based on the angles of different mines, different geological units or different parts of the mine, different horizontal coal rank areas are horizontally sorted and divided, and numbered A, B, C, etc. in sequence. The number of horizontal coal rank division units is consistent with the number of horizontal coal ranks.

[0079] Based on the perspectives of different coal seams or coal seam groups, the horizontal coal rank division units are again longitudinally sorted and divided one by one, and numbered a, b, c... from top to bottom according to the burial depth. Among them, the number of vertical coal rank division units divided in each horizontal coal rank division unit is consistent with the number of vertical coal ranks, and the number of vertical coal rank division units divided in each horizontal coal rank division unit is ≥1, and the number of vertical coal rank division units divided in each horizontal coal rank division unit is not necessarily the same.

[0080] Phase II: Preliminary determination of the type of deep-seated metamorphism and the existence of other metamorphic types besides deep-seated metamorphism

[0081] 3. Take coal samples of each coal rank unit according to industry standards and measure the maximum vitrinite reflectance (Ro max ).

[0082] 4. Based on the maximum vitrinite reflectance (Ro max ) According to the existing Barker formula T max =(lnRo max +1.2) / 0.0078 to calculate the maximum metamorphic temperature (T max ).

[0083] 5. Obtain the thickness and age of the strata in the area where each coal rank unit is located, the time and number of structural subsidence-uplift, and the amount of uplift erosion, and then use basin simulation software to simulate and obtain the historical maximum burial depth (H) of the coal seam where each coal rank unit is located. max ).

[0084] 6. Obtain the maximum historical depth of the coal seam where each coal rank unit is located (H max ) and then based on the historical maximum burial depth (H max ) and regional geothermal gradient to calculate the formation temperature (t max ).

[0085] 7. Compare and analyze the maximum metamorphic temperature (T) of each coal rank unit one by one max ) and the formation temperature at the historical maximum burial depth of the coal seam (t max ), for the maximum metamorphic temperature (T max ) and the formation temperature at the historical maximum burial depth of the coal seam (t max ) units, the coal seam metamorphism type is deep metamorphism; for the maximum metamorphic temperature (T max ) is significantly greater than the formation temperature at the historical maximum burial depth of the coal seam (t max) units, then in addition to deep-seated metamorphism, the coal seam metamorphism types also include dynamic metamorphism, magmatic metamorphism (regional magmatic metamorphism + contact metamorphism), and hydrothermal metamorphism.

[0086] The third stage: For the maximum metamorphic temperature (T max ) is significantly greater than the formation temperature at the historical maximum burial depth of the coal seam (t max ) units, determine whether there is magmatic metamorphism (regional magmatic metamorphism + contact metamorphism), hydrothermal metamorphism, and dynamic metamorphism based on the type of deep-seated metamorphism.

[0087] 8. Establish a combined characteristic table of comprehensive discrimination conditions for magmatic metamorphism (regional magmatic metamorphism + contact metamorphism) and hydrothermal metamorphism as shown in Table 1.

[0088] Table 1

[0089]

[0090] 9. For the maximum deterioration temperature (T max ) is much greater than the formation temperature at the historical maximum burial depth of the coal seam (t max) coal rank units, a comprehensive geological survey and analysis is conducted on the detailed characteristics of magmatic metamorphism (regional magmatic metamorphism + contact metamorphism) and hydrothermal metamorphism listed in Table 1. When a coal rank unit meets the first condition combination, then the coal rank unit has regional magmatic metamorphism superimposed on the basis of plutonic metamorphism; when a coal rank unit meets the second condition combination, then the coal rank unit has contact metamorphism superimposed on the basis of plutonic metamorphism; when a coal rank unit meets the third condition combination, then the coal rank unit has hydrothermal metamorphism superimposed on the basis of plutonic metamorphism; when a coal rank unit meets both the first and second condition combinations, then the coal rank unit has both regional magmatic metamorphism and contact metamorphism superimposed on the basis of plutonic metamorphism; When the first and third condition combinations are met, the coal rank unit is superimposed with both regional magmatic metamorphism of magmatic metamorphism and hydrothermal hot water metamorphism on the basis of deep-seated metamorphism; when a coal rank unit simultaneously meets the second and third condition combinations, the coal rank unit is superimposed with both contact metamorphism of magmatic metamorphism and hydrothermal hot water metamorphism on the basis of deep-seated metamorphism; when a coal rank unit simultaneously meets the first, second and third condition combinations, the coal rank unit is superimposed with both regional magmatic metamorphism and contact metamorphism of magmatic metamorphism and hydrothermal hot water metamorphism on the basis of deep-seated metamorphism; when a coal rank unit does not meet any one of the first, second and third condition combinations, the coal rank unit is superimposed with dynamic metamorphism on the basis of deep-seated metamorphism.

[0091] The fourth stage: On the basis of the deep metamorphism of each unit, for the units with regional magmatic metamorphism, contact metamorphism, hydrothermal metamorphism, regional magmatic metamorphism + contact metamorphism, regional magmatic metamorphism + hydrothermal metamorphism, contact metamorphism + hydrothermal metamorphism, and regional magmatic metamorphism + contact metamorphism + hydrothermal metamorphism, further determine whether they also have dynamic metamorphism.

[0092] 10. Establish a structural feature classification table as shown in Table 2.

[0093] 11. For units with regional magmatic metamorphism, contact metamorphism, hydrothermal metamorphism, regional magmatic metamorphism plus contact metamorphism, regional magmatic metamorphism plus hydrothermal metamorphism, contact metamorphism plus hydrothermal metamorphism, and regional magmatic metamorphism plus contact metamorphism plus hydrothermal metamorphism, a comprehensive investigation and analysis of the structural characteristics of each unit is conducted. If the structural characteristics of a unit meet the first or second structural characteristics listed in Table 2, the external conditions for dynamic metamorphism are not met, and therefore these units do not experience dynamic metamorphism. If the structural characteristics of a unit meet the third structural characteristic listed in Table 2, the external conditions for dynamic metamorphism are met, and the following steps are required to further determine whether dynamic metamorphism exists.

[0094] 12. For units with regional magmatic metamorphism, collect samples of hydrothermal quartz veins or calcite veins developed in the metamorphic area where the unit is located, and then make inclusion slices to measure the homogenization temperature of the brine inclusions inside them (T 均一 ) distribution characteristics, and select its maximum uniform temperature T 均一max The maximum deterioration temperature of the unit (T max ) for comparative analysis, when its maximum uniform temperature T 均一max Greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) are close, then there is no dynamic metamorphism in the unit; when its maximum uniform temperature T 均一max Significantly lower than the maximum metamorphic temperature of the unit (T max ), the unit is subject to dynamic metamorphism.

[0095] 13. For units with contact metamorphism, collect rock samples that have undergone alteration in the metamorphic area where the unit is located and measure their alteration temperature (T 蚀变 ) distribution range, and select its maximum alteration temperature T 蚀变max The maximum deterioration temperature of the unit (T max ) for comparative analysis, when the maximum alteration temperature T 蚀变max Greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) are close to each other, then there is no dynamic metamorphism in the unit; when its maximum alteration temperature T 蚀变max Significantly lower than the maximum metamorphic temperature of the unit (T max ), the unit is subject to dynamic metamorphism.

[0096] 14. For units with hydrothermal metamorphism, measure the underground fluid temperature (T 流体) distribution range, and select its maximum fluid temperature T 流体max The maximum deterioration temperature of the unit (T max ) for comparative analysis, when the maximum fluid temperature T 流体max Greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) are close, then there is no dynamic metamorphism in the unit; when its maximum fluid temperature T 流体max Significantly lower than the maximum metamorphic temperature of the unit (T max ), the unit is subject to dynamic metamorphism.

[0097] 15. For units with regional magmatic metamorphism and contact metamorphism, hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit and altered rock samples were collected, and the homogenization temperature (T 均一 ) distribution characteristics and rock alteration temperature (T 蚀变 ) distribution range, and compare and analyze its maximum uniform temperature T 均一 max and maximum alteration temperature T 蚀变max , select the larger of the two and the maximum metamorphic temperature of the unit (T max ) for comparative analysis. When it is greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) is close to the maximum metamorphic temperature (T max ), the unit is subject to dynamic metamorphism.

[0098] 16. For units with regional magmatic metamorphism and hydrothermal metamorphism, collect samples of hydrothermal quartz veins or calcite veins developed in the metamorphic area where the unit is located, and measure the homogenization temperature (T 均一 ) distribution characteristics, and at the same time, the underground fluid temperature (T 流体 ) distribution range, and compare and analyze its maximum uniform temperature T 均一max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature of the unit (T max ) for comparative analysis. When it is greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) is close to the maximum metamorphic temperature (T max ), the unit is subject to dynamic metamorphism.

[0099] 17. For units with contact metamorphism and hydrothermal metamorphism, collect rock samples that have undergone alteration in the metamorphic area of ​​the unit and measure their alteration temperature (T 蚀变 ) distribution range, and at the same time measure the underground fluid temperature (T 流体 ) distribution range, and compare and analyze its maximum alteration temperature T 蚀变max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature of the unit (T max ) for comparative analysis. When it is greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) is close to the maximum metamorphic temperature (T max ), the unit is subject to dynamic metamorphism.

[0100] 18. For units with regional magmatic metamorphism, contact metamorphism, and hydrothermal metamorphism, hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit and altered rock samples were collected, and the homogenization temperature (T 均一 ) distribution characteristics and rock alteration temperature (T 蚀变 ) distribution range, and at the same time measure the underground fluid temperature (T 流体 ) distribution range, and then compare and analyze its maximum uniform temperature T 均一max , maximum alteration temperature T 蚀变max and maximum fluid temperature T 流体max , select the largest of the three and the maximum metamorphic temperature of the unit (T max ) for comparative analysis. When it is greater than the maximum metamorphic temperature of the unit (T max ) or the maximum deterioration temperature of the unit (T max ) is close to the maximum metamorphic temperature (T max ), the unit is subject to dynamic metamorphism.

[0101] Table 2

[0102]

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for analyzing the types and combinations of coal seam metamorphism in coal mining areas, characterized by: The method comprises the following steps: S1: Combing the coal rank distribution characteristics of coal mining areas or mines; S2: Determine the type of deep-seated metamorphism and clarify whether other types of metamorphism exist besides the deep-seated metamorphism type; specifically: Take coal samples of each coal rank unit according to industry standards and measure the maximum vitrinite reflectance Ro of each coal rank unit max ; According to Barker's formula: T max =(lnRo max +1.2) / 0.0078, calculate the maximum metamorphic temperature T of each coal rank unit max ; Obtain the development thickness of the regional strata, the age of the regional strata, the time of tectonic subsidence-uplift, the number of tectonic subsidence-uplift, and the amount of tectonic uplift erosion of each coal rank unit, and use basin simulation software to simulate and obtain the historical maximum burial depth H of the coal seam where each coal rank unit is located. max ; Obtain the coal seam settlement of each coal rank unit to H max The regional geothermal gradient at the time of H max Regional geothermal gradient, calculate the formation temperature t at the historical maximum burial depth of each coal rank unit max ; Successive comparative analysis of the maximum metamorphic temperature T of each coal rank unit max The ground temperature t at the maximum historical depth of the coal seam max : For T max -t max For units with a temperature of ≤20°C, the coal seam metamorphism type is plutonic metamorphism; For T max -t max For units with a temperature greater than 20℃, the coal seam metamorphism types include, in addition to deep-seated metamorphism, dynamic metamorphism, magmatic metamorphism, and hydrothermal metamorphism. S3: For the maximum metamorphic temperature T max Significantly greater than the formation temperature t at the historical maximum burial depth of the coal seam max The unit is judged based on the type of deep-seated metamorphism to determine whether it has magmatic metamorphism, hydrothermal metamorphism and dynamic metamorphism; among them, magmatic metamorphism includes regional magmatic metamorphism and contact metamorphism; S4: On the basis of the deep metamorphism of each unit, for units with regional magmatic metamorphism, units with contact metamorphism, units with hydrothermal metamorphism, units with regional magmatic metamorphism + contact metamorphism, units with regional magmatic metamorphism + hydrothermal metamorphism, units with contact metamorphism + hydrothermal metamorphism, and units with regional magmatic metamorphism + contact metamorphism + hydrothermal metamorphism, further determine whether they also have dynamic metamorphism.

2. The method for analyzing coal seam metamorphism types and combinations thereof in a coal mining area according to claim 1, characterized in that: The S1 is specifically: Based on the perspectives of different mines, different geological units or different parts of the mine, different horizontal coal rank areas are horizontally sorted and divided, and numbered A, B, C, etc. in sequence, which are the horizontal coal rank area numbers; the number of horizontal coal rank division units is consistent with the number of horizontal coal ranks; Based on the perspectives of different coal seams or coal seam groups, the horizontal coal rank division units are again longitudinally sorted and divided one by one, and numbered a, b, c... from top to bottom according to the burial depth, which is the vertical coal rank area number, among which the number of vertical coal rank division units divided in each horizontal coal rank division unit is consistent with the number of vertical coal ranks, the number of vertical coal rank division units divided in each horizontal coal rank division unit is ≥1, and the number of vertical coal rank division units divided in each horizontal coal rank division unit is not necessarily the same.

3. The method for analyzing coal seam metamorphism types and combinations thereof in a coal mining area according to claim 1, characterized in that: The S3 is specifically: Establish a comprehensive discrimination condition combination characteristic table for magmatic metamorphism and hydrothermal metamorphism, namely Table 1; The table header includes condition combination classification, feature details and corresponding qualitative action type; The combination classification includes the first condition combination, the second condition combination and the third condition combination; The characteristics of the first condition combination include: the metamorphic area where the unit is located has hydrothermal quartz veins and calcite veins; the area of ​​the metamorphic area where the unit is located is greater than a certain value, has regional characteristics, and the coal rank zoning in the metamorphic area is generally ring-shaped; the rocks in the metamorphic area where the unit is located are altered; the coal rank in the metamorphic area where the unit is located is high, and there are graphite belts, high metamorphic anthracite belts, medium metamorphic anthracite belts, and low metamorphic anthracite belts; the unit has a high metamorphic gradient, and its Ro max The gradient of change is greater than 0.1% / hm; the corresponding metamorphism type is regional magmatic metamorphism; The characteristics of the second conditional combination include: the unit develops intrusive igneous rocks; the metamorphic area where the unit is located is centered on intrusive igneous rocks and is localized or narrow; the metamorphic area where the unit is located has a coke rock mixed zone, a natural coke zone, a coke coal mixed zone, and a thermally altered coal zone, with the intrusive igneous rocks as the center. The rocks in the metamorphic area where the unit is located are altered, and high-medium-low temperature alteration zones are developed from the inside to the outside, with the intrusive igneous rocks as the center. The corresponding metamorphic type is contact metamorphism. The characteristics of the third condition combination include: the metamorphic area where the unit is located has regional and boundary deep fault zones; hot springs are developed around the metamorphic area where the unit is located; the area of ​​the metamorphic area where the unit is located is less than a certain value, showing local characteristics; The corresponding metamorphism types include magmatic metamorphism, hydrothermal metamorphism and dynamic metamorphism; the corresponding metamorphism type is hydrothermal metamorphism; For T max -t max For units with a temperature greater than 20°C, geological survey and analysis are conducted on Table 1: When a coal rank unit meets the first combination of conditions, then the coal rank unit has regional magmatic metamorphism superimposed on plutonic metamorphism; When a coal rank unit meets the second combination of conditions, the coal rank unit has contact metamorphism superimposed on magmatic metamorphism on the basis of deep-seated metamorphism; When a coal rank unit meets the third combination of conditions, the coal rank unit has hydrothermal metamorphism superimposed on deep-seated metamorphism; When a coal rank unit meets both the first and second condition combinations, then the coal rank unit has both regional magmatic metamorphism and contact metamorphism superimposed on the plutonic metamorphism. When a coal rank unit meets both the first and third condition combinations, then the coal rank unit has both regional magmatic metamorphism and hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism. When a coal rank unit meets both the second and third condition combinations, then the coal rank unit has both contact metamorphism of magmatic metamorphism and hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism. When a coal rank unit meets the first, second and third condition combinations at the same time, then the coal rank unit has not only regional magmatic metamorphism and contact metamorphism of magmatic metamorphism, but also hydrothermal metamorphism superimposed on the basis of deep-seated metamorphism; When a coal rank unit does not meet any of the first, second, and third condition combinations, the coal rank unit is subjected to dynamic metamorphism in addition to deep-seated metamorphism.

4. The method for analyzing coal seam metamorphism types and combinations thereof in a coal mining area according to claim 1, characterized in that: The S4 is specifically: Establish a structural feature classification table, i.e. Table 2, with the header including structural feature classification and structural feature details; The structural characteristics of the first structural feature include: no compression faults or folds, gentle stratum dip, i.e. dip angle ≤ 15°, original coal seam structure, stable coal seam occurrence, no shear slip failure inside the coal seam or between the coal seam and the rock layer, good coal seam permeability, permeability coefficient ≥ 3m 2 MPa -2 ·d -1 ; The structural features of the second structural feature include: the development of wide and gentle folds or interlayer compression faults, and their scale is relatively small, the formation dip is relatively gentle, that is, 15°<stratum dip ≤30, the coal seam structure is the original structure - fragmentation structure, the coal seam occurrence is relatively stable, small-scale shear slip failure occurs within the coal seam and between the coal seam and the rock layer, the coal seam has good permeability, 1m 2 MPa -2 ·d -1 ≤Air permeability coefficient<3m 2 MPa -2 ·d -1 ; The structural characteristics of the third structural feature include: the development of tight, inverted folds or compression faults, and their scale is relatively large; the coal seam structure is a granular structure - mylonitic structure; the coal seam is unstable; the formation dip angle is large, i.e. >30°; there is a large range of shear slip failure inside the coal seam and between the coal seam and the rock layer; the coal seam has poor permeability, and the permeability coefficient is <1m 2 MPa -2 ·d -1 ; For units with regional magmatic metamorphism, contact metamorphism, hydrothermal metamorphism, regional magmatic metamorphism + contact metamorphism, regional magmatic metamorphism + hydrothermal metamorphism, contact metamorphism + hydrothermal metamorphism, and regional magmatic metamorphism + contact metamorphism + hydrothermal metamorphism, the structural characteristics of each unit were investigated and analyzed: When the unit structural characteristics meet the first structural characteristics or the second structural characteristics in Table 2, the external conditions for dynamic metamorphism are not met, and the unit does not experience dynamic metamorphism; When the unit structural characteristics meet the third structural characteristics in Table 2, the unit has the external conditions for dynamic metamorphism, and further determination is made whether it has dynamic metamorphism; ① For units with regional magmatic metamorphism, collect hydrothermal quartz veins or calcite vein samples developed in the metamorphic area where the unit is located, and then make inclusion slices to measure the homogenization temperature T of the brine inclusions inside them. 均一 Distribution characteristics, and select its maximum uniform temperature T 均一max The maximum deterioration temperature of the unit T max Conduct comparative analysis: When T 均一max Greater than the unit T max When 0℃≤T max -T 均一max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit; When T max -T 均一max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism; ② For units with contact metamorphism, collect rock samples that have undergone alteration in the metamorphic area where the unit is located and measure their alteration temperature T 蚀变 Distribution range, and select its maximum alteration temperature T 蚀变max The maximum deterioration temperature of the unit T max Conduct comparative analysis: When T 蚀变max Greater than the unit T max When 0℃≤T max -T 蚀变max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit; When T max -T 蚀变max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism; ③ For units with hydrothermal metamorphism, measure the underground fluid temperature T in or near the deep fault zone in the metamorphic area where the unit is located. 流体 distribution range, and select its maximum fluid temperature T 流体max The maximum deterioration temperature of the unit T max Conduct comparative analysis: When T 流体max Greater than the unit T max When 0℃≤T max -T 流体max When the temperature is ≤20℃, there is no dynamic metamorphism in the unit; When T max -T 流体max When the temperature is greater than 20℃, the unit will experience dynamic metamorphism; ④ For units with regional magmatic metamorphism and contact metamorphism, hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit and altered rock samples were collected, and the homogenization temperature T of the brine inclusions inside the vein bodies was measured. 均一 Distribution characteristics and rock alteration temperature T 蚀变 Distribution range, comparative analysis of its maximum uniform temperature T 均 -max and maximum alteration temperature T 蚀变max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis: When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit; When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism; ⑤ For units with regional magmatic metamorphism and hydrothermal metamorphism, collect hydrothermal quartz vein or calcite vein samples developed in the metamorphic area where the unit is located, and measure the homogenization temperature T of the brine inclusions inside the vein body. 均一 distribution characteristics, and at the same time determine the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, comparative analysis of its maximum uniform temperature T 均一max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis: When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit; When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism; ⑥ For units with contact metamorphism + hydrothermal metamorphism, collect rock samples that have undergone alteration in the metamorphic area where the unit is located and measure their alteration temperature T 蚀变 distribution range, and at the same time measure the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, comparative analysis of its maximum alteration temperature T 蚀变max and the maximum fluid temperature T 流体max , select the larger of the two and the maximum metamorphic temperature T of the unit max Conduct comparative analysis: When the larger of the two is greater than the unit T max When 0℃≤T max -When the larger of the two is ≤20℃, there is no dynamic metamorphism in the unit; When T max -When the larger of the two is greater than 20°C, the unit is subject to dynamic metamorphism; ⑦ For units with regional magmatic metamorphism, contact metamorphism, and hydrothermal metamorphism, collect hydrothermal quartz vein or calcite vein samples developed in the metamorphic area of ​​the unit, as well as altered rock samples, and measure the homogenization temperature T of the brine inclusions inside the veins. 均一 Distribution characteristics and rock alteration temperature T 蚀变 distribution range, and at the same time measure the underground fluid temperature T in or near the deep fault zone of the metamorphic area where the unit is located 流体 Distribution range, and then compare and analyze its maximum uniform temperature T 均一max , maximum alteration temperature T 蚀变max and maximum fluid temperature T 流体max , select the largest of the three and the maximum metamorphic temperature T of the unit max Conduct comparative analysis: When the largest of the three is greater than the unit T max When 0℃≤T max -When the maximum of the three is ≤20℃, there is no dynamic metamorphism in the unit; When T max -When the maximum of the three is greater than 20°C, the unit is subject to dynamic metamorphism.

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