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We report apparent permeabilities (k a ) of coal samples from Bansgara, Jharia, and Bokaro collieries from Gondwana coalfield (India) to assess the Klinkenberg coefficients (b) and intrinsic permeabilities (k ∞ ) owing to their characteristic pore-size distributions. All k a values were measured with N 2 at room temperature, constant 6.2 MPa effective stress, and up to 7.6 MPa pore pressures (P p ), except for the Bokaro samples (maximum 3.5 MPa P p ). The permeabilities of the Bansgara samples were also measured with CO 2 up to P p 3.5 MPa. The poresize distributions were measured using low-pressure N 2 adsorption−desorption. We determined the b and k ∞ from the plots of k a versus (1/P p ). The linear and nonlinear sections of k a versus (1/ P p ) plots are modeled using the Klinkenberg and Ashrafi equations, respectively. The Ashrafi model yields lower k ∞ over the Klinkenberg model. The k ∞ and b of the Bansgara sample determined from the Klinkenberg model are nonidentical for N 2 (0.073 md and 0.33 MPa) and CO 2 (0.0052 md and 7.27 MPa). Our data show that b decreases with the total pore volume and interconnected porosity, whereas k ∞ increases with the total pore volume and interconnected porosity. The Bansgara sample with open-ended and well-connected micropores has the lowest b. The Jharia and Bokaro samples have volumetrically higher mesopores; although the pores are semiopen-ended with poor connectivity, they result in higher b compared to the Bansgara sample. The results of this study suggest that gas permeability evolution due to slippage effect is a strong function of the pore characteristics of the concerned reservoir.

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Phase relations of braunitc, hausmannite, jacobsite, bixbyite, hematite, pyrolusite, quartz, and rhodochrosite in the system Mn-Fe-Si-C-O and the subsystem Mn-Fe-Si-O are evaluated using petrographic and thermodynamic data. The results are applicable to metamorphosed Mn oxide-rich rocks occurring in various parts of the world. Petrogenetic grids are constructed •/•fiuid iS in isobaric log fo• -T space and the dependence of the mineral reactions on evaluated.

Heterogeneous nanopore structure and distribution regulate the gas trapping, desorption kinetics, and diffusion in shale matrices. In shale, pores range from continuous micro- and mesopore size distributions, varying with organic (total organic matter-TOC) and inorganic constituents (clay content, Fe-bearing minerals, quartz, etc.). Previous research only showed a linear relationship of pore parameters with these intrinsic properties of shale, which limits our understanding of the concurrent influence of multiple intrinsic rock properties. As a result, in this work, we established multivariate dependency of nanopore structure, distribution, and complexity (from low-pressure N2 and CO2 sorption and small-angle scattering; SAXS/MSANS) in the previously little-studied Cambay shales and provided a better tool (partial least square regression) for analyzing the simultaneous effect of intrinsic shale properties on multiply connected pore-parameters. Furthermore, we discretized continuous pore-size distribution into individual pore families using deconvolution to understand the pore space better. Additionally, predicted shale formation environment in terms of deposition probability (P+) and dissolution probability (P−) using a dynamic model of the fractal interface by precipitation and dissolution. Our findings indicate that the Cambay shales have a high potential for future hydrocarbon exploration (S2: 2.42–12.04 mg HC/g rock), “very good” (2-4 wt.%) to “excellent” (>4 wt.%) TOC content, and thermally mature type II–III admixed and type III kerogen. Deconvolution of the micro- and mesopore size distributions reveals that pore width (w) ranges ∼15.30–35 nm occupies greater than 50% of the total pore volume, and its pore volume increases with the presence of quartz, Fe-bearing minerals, and clay content. However, pores with w∼ 3.60–15.30 nm increase exclusively with TOC. In the micro- and early mesopore region, pore volume decreases with TOC from w∼ 0.30–0.75 nm and increases with TOC from w∼ 0.75–3.60 nm. Furthermore, TOC in shale increases the specific surface area and pore volume (micro-, meso-, and total pores), enhancing both sorption and free gas storage capacities. Cambay shales were likely deposited in three distinct environments, with precipitation probability (P+) values of 1, 0.7–0.8, and 0.5, as revealed by a fractal dimension (Ds) analysis of multiple samples.