Coal Reservoir Characterization in a Tectonic Setting and the Effects of Tectonism on the Coalbed Methane (CBM) Content

Abstract

Research on the relationships among tectonics, micropores, microfractures, and coalbed methane (CBM) content is important for the optimal selection of CBM production areas. In this study, micropore-microfracture structural parameters of coal samples from the Guojiahe coalfield are determined through the use of X-ray photography, an image recognition algorithm, and a liquid nitrogen adsorption method. The relationship between the micropore-microfracture characteristics of the reservoir and the gas content is quantitatively assessed using the Grassberger and Procaccia (GP) algorithm to calculate the correlation dimension of the parameters. Micropore-microfracture development varies in different tectonic zones. Additionally, the CBM content varies according to the characteristic parameters of hysteresis loops and the pore diameter. The correlation dimension is an effective indicator of the nonlinear relationship between reservoir micropore-microfracture characteristics and the gas content.

Analysis of Gas Content and Permeability Change Pattern of a Coal Reservoir in the Tectonic Positions Based on a THM Coupled Model

“…The study area is located in the northern part of the Weibei flexure belt first-grade tectonic unit in the southern part of the Ordos Basin and belongs to the Binchang depression thirdgrade tectonic unit. Under the influence of the Indonian-Yanshanian period near north-south tectonic movement, several dip folds have been developed in the Guojiahe wellfield [12]. The axial dip direction generally extends along the north-east-east or near east-west direction, with the dip angle of both limbs ranging from 3 to 10°, showing a gentle dip fold tectonic pattern.…”

“…Therefore, it is of great theoretical significance and engineering application to study the characteristics and changes of coalbed methane (CBM) distribution under geotectonic settings. The published research results show that the "generation, accumulation, and preservation" of CBM is not only closely related to the ground stress, coal seam buried depth, and paleogeothermal and gas generation history under the control of tectonic evolution [1][2][3][4][5][6] but also influenced by the joint effect of formation pressure, lithology of surrounding rock, and microstructural characteristics of a coal reservoir [7][8][9][10][11][12][13], which means that when the environmental conditions such as temperature, stress, and seepage of coal reservoirs change due to tectonism, the gas content and its distribution characteristics in coal seams will change. Therefore, the deposition, generation, and preservation of CBM under the tectonism are the key criteria for CBM enrichment and reservoir formation, which is an important guideline for the efficient development of CBM.…”

Influence of geological structures on the occurrence of coalbed methane in Sima coal mine, China

“…Wang used mathematical statistics, literature analysis, well logging, hydrochemical analysis, and other methods to summarize the research status and development trend of the influence of hydrogeology on CBM . Ye analyzed the relationship among the structure (Pan et al, 2019), micro-pores (Liu X. F. et al, 2022), micro-cracks (Zhang et al, 2021a), and CBM content (Ma Y. K. et al, 2020;Lu et al, 2021), which is of great significance for the optimal selection of CBM production areas (Niu et al, 2019;Ye et al, 2019;Zhou et al, 2021). Sinha took a mine in India as an example to study the geological model of the CBM-enhanced recovery process (Sinha and Gupta, 2021).…”