Natural coke and coal identification method based on pore characteristics

Abstract

The invention relates to the technical field of coal field geology, in particular to a method for identifying natural coke and coal based on pore characteristics, which comprises the following steps: collecting natural coke or coal samples with different distances from a magma invading body, and determining physical characteristics of the natural coke or coal samples with different distances from the magma invading body, calculating the pore linear density and the pore surface density of the natural coke or coal samples with different distances from the magma invading body; and identifying the natural coke or coal sample according to the physical characteristics, the pore linear density and the pore surface density of the natural coke or coal sample to obtain an identification result. According to the method, the natural coke and the coal are identified more efficiently and accurately, so that a theoretical basis is provided for subsequent efficient development and full utilization of natural coke resources.

Description

Technical Field

[0001] The invention relates to the technical field of coalfield geology, and in particular to a method for identifying natural coke and coal based on pore characteristics. Background Art

[0002] The geological phenomenon of magma intrusion into coal seams has been recorded and discovered in coal fields all over the world. The process of magma intrusion into coal seams not only destroys the continuity and integrity of the coal seams, but also the high temperature and high pressure environment it brings often transforms the raw coal into natural coke, changing its original reservoir properties. Natural coke often has a higher ash yield, weaker cohesiveness, and worse coal quality, which has a negative impact on the subsequent utilization of coal resources, especially increasing the difficulty of subsequent coal preparation processes.

[0003] The distribution range of natural coke can be controlled by many factors such as the occurrence of magma intrusion, the type of magma intrusion body, and the time of magma intrusion. Therefore, how to distinguish natural coke from coal is the key to the efficient development and full utilization of natural coke resources. At present, natural coke and coal are often distinguished by measuring the coal rock and coal quality of coal samples at different distances from the magma intrusion body (including industrial analysis, elemental analysis, identification of coal rock microscopic components, and determination of the maximum reflectance of the vitrinite group). However, this identification method often involves numerous and complicated experiments, a long experimental cycle, high experimental costs, and low identification efficiency. Summary of the invention

[0004] The present invention proposes a method for identifying natural coke and coal based on pore characteristics, so as to more efficiently and accurately identify natural coke and coal, thereby providing a theoretical basis for subsequent efficient development and full utilization of natural coke resources.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for identifying natural coke and coal based on pore characteristics, comprising:

[0007] Collecting natural coke or coal samples at different distances from the magma intrusion, determining the physical characteristics of the natural coke or coal samples at different distances from the magma intrusion, and calculating the pore linear density and pore surface density of the natural coke or coal samples at different distances from the magma intrusion;

[0008] The natural coke or coal sample is identified according to the physical characteristics, pore line density and pore surface density of the natural coke or coal sample to obtain an identification result.

[0009] Optionally, collecting the natural coke or coal samples at different distances from the magma intrusion body comprises:

[0010] Preset the number of wells to be drilled, and then sample the wells in the well fields with magma intrusion into coal seams according to the preset number of wells, and adjust the drilling direction according to the occurrence of magma intrusion;

[0011] Among them, each drilling direction is at a different position of the magma intrusion body.

[0012] Optionally, drilling sampling for a well field with magma intrusion into coal seams includes:

[0013] According to the principle of close proximity and far sparseness, drilling sampling is carried out in the well fields with magma intrusion into coal seams:

[0014] If the magmatic intrusion is a thin layer, the number of natural coke or coal samples should not be less than the first preset drilling number; if the magmatic intrusion is a medium-thick layer, the number of natural coke or coal samples should not be less than the second preset drilling number; if the magmatic intrusion is an ultra-thick layer, the number of natural coke or coal samples should not be less than the third preset drilling number.

[0015] Optionally, adjusting the drilling direction according to the occurrence of magma intrusion includes:

[0016] If the occurrence of the magmatic intrusion is a bedrock or a rock cap, the drilling directions are adjusted to be perpendicular to the bedding direction of the coal seam for sampling. If the occurrence of the magmatic intrusion is a dyke or a rock stock, the drilling directions are adjusted to be parallel to the bedding direction of the coal seam for sampling.

[0017] Optionally, the physical characteristics include: color, gloss, fracture, density, hardness and development of endogenous cracks.

[0018] Optionally, the method for calculating the pore linear density is:

[0019] η = L a / L

[0020] L a =

[0021] Where η is the pore linear density, is the length of each pore on the measuring line, L is the length of the measuring line, and L a is the total length of the pores on the measuring line, It is the number of pores observed on the measurement line when observing natural coke or coal samples through an optical microscope or a scanning electron microscope.

[0022] Optionally, the method for calculating the pore surface density is:

[0023] ψ = S a / S

[0024] S a =

[0025] Where ψ is the pore surface density, S is the total area of ​​the field of view when measuring pores during the observation of natural coke or coal samples using an optical microscope or a scanning electron microscope, and S a is the total area of ​​stomata in the field of view when measuring stomata, To measure the pore surface density, the area of ​​each pore in the field of view is: It is a method for measuring the number of pores observed in a surface of a natural coke or coal sample when observed through an optical microscope or a scanning electron microscope.

[0026] Optionally, obtaining the recognition result includes:

[0027] According to the physical characteristics of the natural coke or coal samples, the natural coke or coal samples are preliminarily classified, and according to the pore line density and the pore surface density, the preliminarily classified natural coke or coal samples are identified to obtain the identification results.

[0028] Optionally, the natural coke or coal sample after preliminary classification is identified including:

[0029] The pore line density and pore surface density of the natural coke or coal sample are analyzed by using R-type cluster analysis using SPSS software. According to the cluster analysis results, the collected samples can be subdivided into natural coke and coal.

[0030] The beneficial effects of the present invention are:

[0031] The present invention firstly performs drilling sampling on a well field where magma intrudes into a coal seam, and collects natural coke or coal samples at different distances from the magma intrusion body based on the principle of close proximity and sparseness; then observes the appearance physical characteristics of the natural coke or coal samples collected by the above method, and preliminarily distinguishes natural coke from coal through the difference in their appearance physical characteristics; in the process of magma intruding into the coal seam, the high temperature and high pressure environment brought by the magma causes a large amount of gas production and rapid hydrocarbon generation in the natural coke area, forming numerous pyrolysis pores, therefore, it is reasonable and feasible to identify natural coke and coal in combination with pore characteristics (pore linear density η, pore surface density ψ); compared with the prior art, the present invention can identify natural coke and coal more economically and efficiently, thereby being able to more quickly and accurately divide the distribution range of natural coke and coal; the present invention has a concise experimental process, simple operation, scientific principle, high recognition efficiency and good recognition effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 This is a flow chart of a method for identifying natural coke and coal based on pore characteristics according to an embodiment of the present invention;

[0034] Figure 2 This is a comparison diagram of pore characteristics of natural coke and coal samples under an optical microscope in this embodiment of the invention;

[0035] Figure 3 This is a graph showing the determination of pore line density under a natural focus optical microscope according to an embodiment of the present invention;

[0036] Figure 4 This is a graph showing the determination of pore surface density under a natural focus optical microscope according to an embodiment of the present invention;

[0037] Figure 5 This is a graph showing the determination of pore line density of coal under a scanning electron microscope according to an embodiment of the present invention;

[0038] Figure 6 This is a graph showing the determination of pore surface density of coal under a scanning electron microscope according to an embodiment of the present invention;

[0039] Figure 7 It is a spectrum diagram of pore characteristic parameters of natural coke and coal samples of a certain drilling well according to an embodiment of the present invention;

[0040] Figure 8 This is a columnar classification diagram of the pore characteristic parameters of natural coke and coal samples from a certain drilling well according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 As shown, a method for identifying natural coke and coal based on pore characteristics implemented by the present invention includes: collecting natural coke or coal samples at different distances from a magmatic intrusion, determining the physical characteristics of the natural coke or coal samples at different distances from the magmatic intrusion, and calculating the pore line density and pore surface density of the natural coke or coal samples at different distances from the magmatic intrusion; identifying the natural coke or coal samples according to the physical characteristics, pore line density and pore surface density of the natural coke or coal samples to obtain an identification result.

[0044] The collection of natural coke or coal samples at different distances from the magma intrusion body includes: presetting the number of drillings, and drilling and sampling the well field with magma intrusion into the coal seam according to the preset number of drillings, and adjusting the drilling direction according to the occurrence of the magma intrusion; wherein each drilling direction is at a different position of the magma intrusion body.

[0045] The drilling sampling of the well field with magma intrusion into the coal seam includes: according to the principle of close density and far sparseness, the drilling sampling of the well field with magma intrusion into the coal seam includes: if the magma intrusion body is a thin layer, the number of natural coke or coal samples should not be less than the first preset drilling number; if the magma intrusion body is a medium-thick layer, the number of natural coke or coal samples should not be less than the second preset drilling number; if the magma intrusion body is an extra-thick layer, the number of natural coke or coal samples should not be less than the third preset drilling number.

[0046] Among them, if the thickness of the magmatic intrusion is less than 0.5m, the magmatic intrusion is defined as a thin layer; if the thickness of the magmatic intrusion is between 0.5-5m, the magmatic intrusion is defined as a medium-thick layer; if the thickness of the magmatic intrusion is greater than 5m, the magmatic intrusion is defined as an ultra-thick layer.

[0047] Adjusting the drilling direction according to the occurrence of the magma intrusion includes: if the occurrence of the magma intrusion is a bedrock or a rock cap, adjusting each drilling direction to take samples perpendicular to the bedding direction of the coal seam; if the occurrence of the magma intrusion is a dyke or a rock stock, adjusting each drilling direction to take samples parallel to the bedding direction of the coal seam.

[0048] The physical characteristics include: color, gloss, fracture, density, hardness and the development of endogenous cracks.

[0049] Obtaining the identification result includes: preliminarily classifying the natural coke or coal sample according to the physical characteristics of the natural coke or coal sample, identifying the preliminarily classified natural coke or coal sample according to the pore line density and the pore surface density, and obtaining the identification result.

[0050] Identifying the natural coke or coal samples after preliminary classification includes: analyzing the pore line density and pore surface density of the natural coke or coal samples using R-type cluster analysis through SPSS software, and according to the cluster analysis results, the collected samples can be subdivided into natural coke and coal.

[0051] The specific steps are as follows:

[0052] Step S1, drilling and sampling are carried out in the well field where magma intrusion occurs in the coal seam. The drilling direction is adjusted according to the occurrence of the magma intrusion, and is generally perpendicular to the magma intrusion direction. The number of drilling wells is not less than 4, and each drilling direction should be in a different direction of the magma intrusion body.

[0053] Step S2: Based on the principle of close proximity and sparse distance, natural coke or coal samples are collected at different distances from the magma intrusion body, and no less than 10 coal or natural coke samples are collected from each well.

[0054] Step S3, observing the physical characteristics of the appearance of natural coke or coal samples. Natural coke is black-gray to steel-gray in color, semi-metallic luster, jagged fracture, dense and hard, and its pores and cracks are widely filled with minerals; coal is black to gray-black in color, glassy luster to semi-metallic luster to metallic luster, stepped fracture to shell-like fracture, obvious bedding structure, and widely developed endogenous cracks. The difference in their physical characteristics can be used to preliminarily distinguish natural coke from coal.

[0055] Step S4: observe the pore development of natural coke or coal by optical microscope and scanning electron microscope, and characterize the pore characteristics of natural coke or coal by measuring and calculating the two parameter dimensions of pore linear density η and pore surface density ψ, η=L a / L,ψ=S a / S, where L a = is the total length of the pores on the measuring line, L is the length of the measuring line, S a = is the total area of ​​pores in the measuring surface, and S is the total area of ​​the measuring surface.

[0056] Step S5, repeat the above steps 3 to 4 for the natural coke or coal samples collected from different drillings, finally sort out and summarize the appearance physical characteristics of the natural coke and coal samples collected from all drillings, and summarize the pore characteristic parameters (pore linear density η and pore surface density ψ) of natural coke and coal.

[0057] Step S6: Comprehensively analyze the physical characteristics of the appearance and pore characteristic parameters (pore linear density η and pore surface density ψ) of natural coke and coal to determine whether it is coal or natural coke, thereby realizing the identification of natural coke and coal.

[0058] This embodiment conducts geological background investigation and geological exploration operations on a mining area where magma has been proven to intrude into coal seams. The geological exploration operations include drilling, logging, gravity exploration, seismic exploration and other methods. After preliminary investigation and exploration, it was found that there is a 3.2m wide rock wall intrusion in a coal seam in the mining area, which penetrates the coal seam bedding direction. The coal around the intrusion body undergoes contact metamorphism to form natural coke. The following work is performed to distinguish natural coke from coal:

[0059] The first step is to carry out drilling work from different directions of the magma intrusion body. Since the magma intrusion occurs in the form of rock walls and interspersed with the bedding direction of the coal seams, the drilling construction is carried out along the bedding direction of the coal seams, and the number of drilling is set to 5.

[0060] In the second step, based on the principle of dense near and sparse far, natural coke or coal samples were collected at different distances from the magma intrusion. The samples were all from the cores of the above-mentioned drilling operations. Since the thickness of the rock wall intrusion in the study area was 3.2m and the thickness of the intrusion was between 1-5m, the number of natural coke and coal samples collected was set to 20.

[0061] The third step is to observe the physical characteristics of the appearance of natural coke or coal samples, and observe the natural coke or coal samples from multiple aspects such as color, luster, fracture, density, hardness, bedding, pore and fissure development, and mineral filling to achieve a preliminary classification of natural coke and coal samples. By observing the physical characteristics of the appearance of natural coke or coal samples, it is found that the natural coke in this mining area is steel gray in color, semi-metallic luster, jagged fracture, dense and hard, and extensive mineral filling can be observed in its pores and fissures; the coal color is black-gray black, glassy-semi-metallic luster, stepped and shell-shaped fracture, obvious bedding structure can be seen, and endogenous fissures are widely developed.

[0062] The fourth step is to observe the pore development of natural coke or coal by optical microscope and scanning electron microscope. First, the collected coal samples are pre-observed, such as Figure 2 As shown, Figure 2 This is a comparison chart of the pore characteristics of natural coke and coal samples in the mining area under an optical microscope. It can be seen that there are obvious differences in the pore characteristics of natural coke and coal samples. It is found that when the magnification of the optical microscope is 400× (eyepiece 20×, objective lens 20×), the pores in the coal sample can be observed under the optical microscope. Therefore, the optical microscope magnification of 400× is used as a unified measurement factor in the process of measuring the pore line density η and pore surface density ψ of natural coke or coal samples. Then, a scanning electron microscope is used to observe the nanoscale pores in natural coke or coal samples. It is found that when the magnification of the scanning electron microscope is 5000x, the pores in each sample can be observed under the scanning electron microscope. Therefore, the scanning electron microscope magnification of 5000X is used as a unified measurement factor in the process of measuring the pore line density η and pore surface density ψ of natural coke or coal samples. The pore characteristics of natural coke or coal samples are characterized by measuring and calculating the two parameter dimensions of pore line density η and pore surface density ψ, η=L a / L,ψ=S a / S, where L a = is the total length of the pores on the measuring line, L is the length of the measuring line, S a = is the total area of ​​pores in the measurement surface, and S is the total area of ​​the measurement surface. When measuring the pore linear density η of natural coke or coal samples, the measurement line should be selected as the diagonal line of the measurement field, and the pores blocked or filled with minerals should also be included in the determination of the pore linear density η, such as Figure 3 As shown, Figure 3 It is a measurement diagram of the pore line density in a certain field of view of a natural coke sample in the mining area under an optical microscope; L a = =167.25μm, L=341.81μm, so according to the pore line density η=L a / L calculated that the pore line density of the natural coke sample in this field of view is 48.93%. Figure 4 As shown, Figure 4 This is a measurement diagram of the pore surface density in a certain field of view of a natural coke optical microscope in the mining area. The S a = =1.64×10 5 μm 2 , S=3.62×10 5 μm 2 , so according to the pore surface density ψ=S a / S calculated that the pore surface density of the natural coke sample in this field of view is 45.39%. Figure 5 As shown, Figure 5 This is a measurement diagram of the pore line density in a certain field of view of a coal sample in the mining area under a scanning electron microscope. The L a = =3.6μm, L=28.6μm, so according to the pore line density η=L a / L calculated that the pore line density of the coal sample in this field of view is 12.59%. Figure 6 As shown, Figure 6 This is a measurement diagram of the pore surface density of a coal sample in the mining area under a certain field of view in a scanning electron microscope. The S a = =15.51μm 2 , S=371.24μm 2 , so according to the pore surface density ψ=S a / S calculated that the pore surface density of the natural coke sample in the field of view is 4.18%. Among them, the two parameters of the pore line density η and pore surface density ψ of the natural coke or coal sample are measured and calculated in 20 random fields of view under an optical microscope and a scanning electron microscope. The pore line density η and pore surface density ψ of the sample obtained by the above calculation are the average values ​​of the two measurement methods under the optical microscope and the scanning electron microscope.

[0063] The fifth step is to repeat the above steps 3 to 4 for the natural coke or coal samples collected from different wells, and finally organize and summarize the appearance physical characteristics of the natural coke and coal samples collected from all wells, and summarize the pore characteristic parameters of natural coke and coal (pore linear density η and pore surface density ψ), as shown in Table 1. Table 1 is the statistical situation of the pore linear density and surface density of the natural coke or coal samples collected from Well No. 1 in this mining area.

[0064] Table 1: Statistics of pore linear density and surface density of natural coke or coal samples from Well No. 1 in this area.

[0065]

[0066] The sixth step is to use SPSS software to perform cluster analysis (R-type cluster analysis) on the pore characteristic parameters (pore linear density η and pore surface density ψ) of natural coke and coal samples at different distances from the intrusion to subdivide coal or natural coke and realize the identification of natural coke and coal based on pore characteristics. SPSS software is used to perform R-type cluster analysis on the pore characteristic parameters (pore linear density, pore surface density) of each sample, such as Figure 7 As shown, Figure 7 This is a spectrum diagram of the pore characteristic parameters of natural coke and coal samples from a drilling well in the mining area. The analysis results show that the 20 samples collected from the drilling well can be divided into two major groups: samples 1 to 4 are one group, and samples 5 to 20 are another group. Combined with the physical characteristics of the appearance of each sample, and based on Figure 7 The results of the inversion plot Figure 8 , Figure 8 This is a columnar classification diagram of the pore characteristic parameters of natural coke and coal samples from a certain drilling well, which can more intuitively distinguish the differences in pore line density and surface density between coal or natural coke samples, so that samples 1 to 4 are identified as natural coke, and the remaining samples are identified as coal, ultimately realizing a method for identifying natural coke and coal based on pore characteristics.

[0067] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for identifying natural coke and coal based on pore characteristics, characterized in that: include: Collecting natural coke or coal samples at different distances from the magma intrusion, determining the physical characteristics of the natural coke or coal samples at different distances from the magma intrusion, and calculating the pore linear density and pore surface density of the natural coke or coal samples at different distances from the magma intrusion; The natural coke or coal sample is identified according to the physical characteristics, pore line density and pore surface density of the natural coke or coal sample to obtain an identification result.

2. The method for identifying natural coke and coal based on pore characteristics according to claim 1, characterized in that: Collecting natural coke or coal samples at different distances from the magma intrusion body includes: Preset the number of wells to be drilled, and then sample the wells in the well fields with magma intrusion into coal seams according to the preset number of wells, and adjust the drilling direction according to the occurrence of magma intrusion; Among them, each drilling direction is at a different position of the magma intrusion body.

3. The method for identifying natural coke and coal based on pore characteristics according to claim 2, characterized in that: Drilling sampling for well fields with magma intrusion into coal seams includes: According to the principle of close proximity and far sparseness, drilling sampling is carried out in the well fields with magma intrusion into coal seams: If the magmatic intrusion is a thin layer, the number of natural coke or coal samples should not be less than the first preset drilling number; if the magmatic intrusion is a medium-thick layer, the number of natural coke or coal samples should not be less than the second preset drilling number; if the magmatic intrusion is an ultra-thick layer, the number of natural coke or coal samples should not be less than the third preset drilling number.

4. The method for identifying natural coke and coal based on pore characteristics according to claim 2, characterized in that: Adjusting the drilling direction according to the occurrence of magma intrusion includes: If the occurrence of the magmatic intrusion is a bedrock or a rock cap, the drilling directions are adjusted to be perpendicular to the bedding direction of the coal seam for sampling. If the occurrence of the magmatic intrusion is a dyke or a rock stock, the drilling directions are adjusted to be parallel to the bedding direction of the coal seam for sampling.

5. The method for identifying natural coke and coal based on pore characteristics according to claim 1, characterized in that: The physical characteristics include: color, gloss, fracture, density, hardness and the development of endogenous cracks.

6. The method for identifying natural coke and coal based on pore characteristics according to claim 1, characterized in that: The method for calculating the pore linear density is: n=L a / L L a = Where η is the pore linear density, is the length of each pore on the measuring line, L is the length of the measuring line, and L a is the total length of the pores on the measuring line, It is the number of pores observed on the measurement line when observing natural coke or coal samples through an optical microscope or a scanning electron microscope.

7. The method for identifying natural coke and coal based on pore characteristics according to claim 1, characterized in that: The method for calculating the pore surface density is: ψ=S a / S S a = Where ψ is the pore surface density, S is the total area of ​​the field of view when measuring pores during the observation of natural coke or coal samples using an optical microscope or a scanning electron microscope, and S a is the total area of ​​stomata in the field of view when measuring stomata, To measure the pore surface density, the area of ​​each pore in the field of view is: It is a method for measuring the number of pores observed in a surface of a natural coke or coal sample when observed through an optical microscope or a scanning electron microscope.

8. The method for identifying natural coke and coal based on pore characteristics according to claim 1, characterized in that: Obtaining the recognition result includes: According to the physical characteristics of the natural coke or coal samples, the natural coke or coal samples are preliminarily classified, and according to the pore line density and the pore surface density, the preliminarily classified natural coke or coal samples are identified to obtain the identification results.

9. The method for identifying natural coke and coal based on pore characteristics according to claim 8, characterized in that: Identification of natural coke or coal samples after preliminary classification includes: The pore line density and pore surface density of the natural coke or coal sample are analyzed by using R-type cluster analysis using SPSS software. According to the cluster analysis results, the collected samples can be subdivided into natural coke and coal.

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