Abstract Pore structural parameters of organic-rich shales control their gas storage properties and gas transport behaviors. In this work, pore structural parameters of selected organic-rich shale samples belonging to the Lower Permian Barakar Formation from Raniganj basin (India) are studied using low-pressure nitrogen adsorption combined with field emission scanning electron microscopy (FE-SEM), Rock-Eval pyrolysis and energy-dispersive X-ray spectroscopy (EDX). The samples are predominantly mesoporous and in the early to peak range of thermal maturity, with one late mature sample affected by a nearby igneous intrusion. The Brunauer, Emmett, and Teller specific surface area (BET SSA) of the samples display no correlation with total organic carbon (TOC), and a positive correlation with Rock-Eval Tmax. The average pore radii of the shale samples display a negative relationship with the BET SSA and Rock-Eval Tmax values. As thermal maturity advances finer pores are formed, which progressively increases the SSA of shales. A novel fractal-discriminating parameter, ΔS [(slope of the linear segment at P/P0 of 0.5–1.0) – (slope of the linear segment at P/P0 of 0–0.5), where S = D-3] displays a minimum value for a silty-shale sample, and a maximum value for the intrusion-affected shales. The less distinct fractal dimensions for the silty-shale, and the most distinct fractal dimension for the intrusion-affected shales shows influence of both the mineral composition and thermal maturity on fractal dimensions of shales. Among the samples studied, the intrusion-affected shales exhibited the highest BET SSA, pore volume, least average pore radius, larger ΔS and fractal dimensions (D1 and D2), all signifying the impact of high thermal maturity (thermal stress) on pore structural parameters.

中文翻译：

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印度下二叠统 Raniganj 盆地页岩的分形配置和孔隙度表征

摘要 富有机质页岩的孔隙结构参数控制着其储气特性和输气行为。在这项工作中，使用低压氮吸附结合场发射扫描电子显微镜 (FE-SEM)、Rock- Eval 热解和能量色散 X 射线光谱 (EDX)。这些样品主要是中孔的，处于热成熟的早期到峰值范围内，一个晚期成熟的样品受到附近火成岩侵入的影响。样品的 Brunauer、Emmett 和 Teller 比表面积 (BET SSA) 与总有机碳 (TOC) 没有相关性，而与 Rock-Eval Tmax 呈正相关。页岩样品的平均孔隙半径与 BET SSA 和 Rock-Eval Tmax 值呈负相关。随着热成熟度的推进，会形成更细的孔隙，这会逐渐增加页岩的 SSA。一个新的分形判别参数 ΔS [（P/P0 为 0.5–1.0 处的线性段的斜率）-（P/P0 为 0-0.5 处的线性段的斜率），其中 S = D-3]粉质页岩样品的最小值，以及受侵入影响的页岩样品的最大值。粉质页岩较不明显的分形维数和受侵入影响的页岩最明显的分形维数显示了矿物成分和热成熟度对页岩分形维数的影响。在所研究的样品中，受侵入影响的页岩表现出最高的 BET SSA、孔隙体积、最小的平均孔隙半径、