NMR-Based Investigation of Pore–Fracture Structure Heterogeneity in Deep Coals of Different Macrolithotypes in the Daning-Jixian Block, Ordos Basin

Energies, Journal Year: 2024, Volume and Issue: 17(23), P. 6081 - 6081

Published: Dec. 3, 2024

Deep coalbed methane (CBM) demonstrates significant production potential, and a fervent exploration development boom is currently underway in China. The permeability of coal reservoirs heavily influenced by pore–fracture structure heterogeneity. Some researches have been conducted on deep coals’ structure; however, these studies mostly consider as homogeneous material, neglecting the heterogeneity macrolithotypes within coal. In this study, 33 coals with burial depths more than 2000 m were obtained from Daning-Jixian block Ordos Basin, covering all macrolithotypes: bright (BC), semi-bright (SBC), semi-dull (SDC), dull (DC). These samples subjected to three sets NMR tests dry, fully saturated, irreducible water conditions, characteristics being analyzed. results demonstrate that sampled highly heterogeneous, transitional pores dominant, followed mesopores, “macropores fractures”, micropores. T2C ranges 0.61 2.44 ms, an average 1.19 ms; higher value indicates developed for producible porosity (φpr) saturation (Spr) are 0.31–7.24% (avg. 2.42%) 6.97–71.47% 31.06%), respectively. Both them exhibit high positive correlation total volumes fractures” mesopores. Compared SDC DC, BC SBC, especially former, overall contain fewer micropores, φpr Spr. findings suggest regions abundant SBC should be prioritized during CBM due inherently superior gas extraction potential likely require less intensive stimulation achieve recovery rates could provide sustainable over time.

Language: Английский

Multiscale Qualitative–Quantitative Characterization of the Pore Structure in Coal-Bearing Reservoirs of the Yan’an Formation in the Longdong Area, Ordos Basin

Processes, Journal Year: 2024, Volume and Issue: 12(12), P. 2787 - 2787

Published: Dec. 6, 2024

Accurate characterization of coal reservoir micro- and nanopores is crucial in evaluating coalbed methane storage gas production capacity. In this work, 12 coal-bearing rock samples from the Jurassic Yan’an Formation, Longdong area, Ordos Basin were taken as research objects, nanopore structures characterized via scanning electron microscopy, high-pressure mercury pressure, low-temperature N2 adsorption low-pressure CO2 experiments. The main factors controlling pore structure development influence on content studied by combining reflectivity specular microscopic composition determined through industrial analyses isothermal absorption results show that strata mine are a very important source, Formation study area exhibit remarkable organic clay mineral accompanied clear microfractures interlayer joints, which together optimize conditions form efficient microseepage pathways for gas. Coalstone, carbonaceous mudstone differential distributions volume specific surface area. general trend best, second weakest. samples’ microporous properties positively correlated with sample group, whereas there no correlation inert group. An increase moisture air-dried matrix promotes development, leading to increases CH4 increasing average maximum approximately 8.13 m3/t. limit amount adsorbed samples, VL, indicating larger is, greater can be samples. PL value, not correlated, direct mathematical relationship between them.

Language: Английский