CN-121994668-A - Multi-scale quantitative characterization method for coal pore structure

CN121994668ACN 121994668 ACN121994668 ACN 121994668ACN-121994668-A

Abstract

The application provides a multi-scale quantitative characterization method of a coal pore structure, which belongs to the field of gas extraction and coal engineering and comprises the steps of scanning a pretreated coal sample by a scanning electron microscope to obtain a coal sample macroscopic image, scanning the pretreated coal sample by a computer tomography scanner to obtain a coal sample micrometer-scale image, scanning the pretreated coal sample by an X-ray scattering instrument to obtain a coal sample nanometer-scale image, extracting macroscopic features of the coal sample pore structure from the coal sample macroscopic image, extracting micrometer-scale features of the coal sample pore structure according to the coal sample macroscopic image and the coal sample micrometer-scale image, and extracting nanometer-scale features of the coal sample pore structure from the coal sample nanometer-scale image. The application combines three different technologies to complement and verify each other, quantitatively characterizes the coal pore structure from multiple scales such as macroscopic scale, micron scale and nanometer scale, and can comprehensively and accurately acquire the characteristic information of the coal pore structure under different scales.

Inventors

JIA PENG
LI YAQI
HUANG XIAOQI
JIA JINZHANG

Assignees

辽宁工程技术大学鄂尔多斯研究院

Dates

Publication Date: 20260508
Application Date: 20241106

Claims (7)

1. A method for multi-scale quantitative characterization of a coal pore structure, comprising: Collecting a coal sample and preprocessing the coal sample; scanning the pretreated coal sample by adopting a scanning electron microscope to obtain a macroscopic picture of the coal sample; scanning the pretreated coal sample by adopting a computer tomography scanner to obtain a micron-sized picture of the coal sample; scanning the pretreated coal sample by adopting an X-ray scatterometer to obtain a nano-scale picture of the coal sample; extracting macro features of a pore structure of the coal sample from the macro pictures of the coal sample; Extracting micron-sized features of a pore structure of the coal sample according to the coal sample macroscopic picture and the coal sample micron-sized picture; and extracting nanoscale features of the pore structure of the coal sample from the nanoscale picture of the coal sample, and taking macroscopic features of the pore structure of the coal sample, micron-sized features of the pore structure of the coal sample and nanoscale features of the pore structure of the coal sample as multiscale quantitative characterization results of the pore structure of the coal sample.
2. The method for multi-scale quantitative characterization of a pore structure of coal according to claim 1, wherein the extracting the micron-scale features of the pore structure of the coal according to the macro-scale picture of the coal and the micron-scale picture of the coal comprises: Carrying out three-dimensional reconstruction on the coal sample macroscopic picture and the coal sample micron-sized picture by adopting a reconstruction algorithm to obtain a three-dimensional reconstructed picture; performing filtering noise reduction treatment on the three-dimensional reconstruction slice by adopting median filtering to obtain a filtered three-dimensional picture; And carrying out image segmentation on the filtered three-dimensional picture to obtain micron-sized features of the pore structure of the coal sample.
3. The method for quantitatively characterizing a coal pore structure according to claim 2, wherein the three-dimensional reconstruction of the macroscopic picture of the coal sample and the micron-sized picture of the coal sample by using a reconstruction algorithm to obtain a three-dimensional reconstruction slice comprises: respectively calculating projection parameters in a coal sample macroscopic picture and a coal sample micron-sized picture to obtain a first projection parameter and a second projection parameter; Carrying out weighted summation on the first projection parameters and the second projection parameters to obtain final projection parameters; and carrying out back projection reconstruction on the final projection parameters to obtain a three-dimensional reconstruction picture.
4. The method for multi-scale quantitative characterization of a coal pore structure according to claim 2, wherein the image segmentation of the filtered three-dimensional image is performed to obtain micron-sized features of the coal sample pore structure, and the method comprises the steps of: Image segmentation is carried out on the three-dimensional picture after filtering to obtain a pore distinguishing result, a coal matrix distinguishing result and a mineral distinguishing result; Performing pore space characteristic analysis on the pore space distinguishing result, the coal matrix distinguishing result and the mineral distinguishing result to obtain a representative volume unit, a pore volume fraction, pore size distribution and porosity; And aiming at the pore distinguishing result, the coal matrix distinguishing result and the mineral distinguishing result, adopting a maximum sphere algorithm, and representing the pore structure by using an interconnected equivalent pore network model, wherein in the interconnected equivalent pore network model, the pore structure with the pores larger than a preset threshold value is equivalent to a sphere, and the pore structure with the pores smaller than or equal to the preset threshold value is equivalent to a throat, so as to obtain pore-throat characteristics and coordination numbers.
5. The method of claim 1, wherein the micron-scale features of the pore structure of the coal sample comprise representative volume units, pore volume fractions, pore size distribution, porosity, pore throat characteristics, and coordination numbers.
6. The method of multi-scale quantitative characterization of a coal pore structure of claim 1, wherein the macroscopic features of the coal sample pore structure include pore connectivity and crack expansion.
7. The method of claim 1, wherein the nanoscale features of the pore structure of the coal sample comprise scattering intensity, radius of gyration, pore distribution, and fractal dimension.

Description

Multi-scale quantitative characterization method for coal pore structure Technical Field The invention belongs to the field of gas extraction and coal engineering, and particularly relates to a multi-scale quantitative characterization method of a coal pore structure. Background Coal is used as a composite porous medium, and the formation, distribution and structural characteristics of pores are critical to the gas storage and gas transmission performances. Some conventional characterization methods, such as mercury intrusion, nuclear magnetic resonance and gas adsorption analysis, have been widely used, but each has certain limitations, and it is difficult to fully demonstrate the multi-scale characteristics of the coal pores. Mercury intrusion is based on the principle of mercury intrusion into the pores of coal under pressure to measure pore structure. However, this method assumes that mercury intrusion into pores is an ideal capillary phenomenon, but in practice, the physicochemical properties of the pore surfaces of coal are complex, and there are cases such as surface roughness and uneven wettability, which make the mercury intrusion process not completely conform to the ideal assumption, and thus the microstructure information such as connectivity between pores is difficult to accurately obtain, so that the measurement result is deviated, fluids (such as water, gas, etc.) in different pores and coal substrates in nuclear magnetic resonance can affect the nuclear magnetic resonance signals, and the movement states of fluid molecules in pores of different sizes are greatly different, so that accurate interpretation of nuclear magnetic resonance signals becomes very difficult, thus resulting in large errors in quantitative analysis of pore structures, and the conventional adsorption models of gas adsorption methods are ideal assumptions and have great differences from the coal structures, so that there are also great errors in analysis. Therefore, there is a strong need for a method that integrates multiple advanced analytical techniques to fully understand the pore structure and characteristics of coal. Disclosure of Invention Aiming at the defects of the prior art, the application provides a multi-scale quantitative characterization method for a coal pore structure, which quantitatively characterizes the pore characteristics of the coal structure in detail from multiple scales such as macroscopic scale, micron scale, nano scale and the like, thereby realizing the efficient exploitation of gas and the reasonable utilization of coal energy. The application provides a multi-scale quantitative characterization method of a coal pore structure, which comprises the following steps: Collecting a coal sample and preprocessing the coal sample; scanning the pretreated coal sample by adopting a scanning electron microscope to obtain a macroscopic picture of the coal sample; scanning the pretreated coal sample by adopting a computer tomography scanner to obtain a micron-sized picture of the coal sample; scanning the pretreated coal sample by adopting an X-ray scatterometer to obtain a nano-scale picture of the coal sample; extracting macro features of a pore structure of the coal sample from the macro pictures of the coal sample; Extracting micron-sized features of a pore structure of the coal sample according to the coal sample macroscopic picture and the coal sample micron-sized picture; and extracting nanoscale features of the pore structure of the coal sample from the nanoscale picture of the coal sample, and taking macroscopic features of the pore structure of the coal sample, micron-sized features of the pore structure of the coal sample and nanoscale features of the pore structure of the coal sample as multiscale quantitative characterization results of the pore structure of the coal sample. Extracting micron-sized features of a pore structure of the coal sample according to the coal sample macroscopic picture and the coal sample micron-sized picture, comprising: Carrying out three-dimensional reconstruction on the coal sample macroscopic picture and the coal sample micron-sized picture by adopting a reconstruction algorithm to obtain a three-dimensional reconstructed picture; performing filtering noise reduction treatment on the three-dimensional reconstruction slice by adopting median filtering to obtain a filtered three-dimensional picture; And carrying out image segmentation on the filtered three-dimensional picture to obtain micron-sized features of the pore structure of the coal sample. The method for carrying out three-dimensional reconstruction on the coal sample macroscopic picture and the coal sample micron-sized picture by adopting a reconstruction algorithm to obtain a three-dimensional reconstruction picture comprises the following steps: respectively calculating projection parameters in a coal sample macroscopic picture and a coal sample micron-sized picture to obtain a first projection parame