136-3 Anisotropy of nanopore structure and gas permeability in deep Longmaxi Shale: implications for gas preservation and transport

Session: Micro-Nano Scale Pore-Fracture Architecture and Fluid Dynamics in Shale and Coal Reservoirs

Presenting Author:

Jianjiang Wen

Authors:

Wen, Jianjiang¹, Sun, Mengdi², Yu, Bingsong³, Ji, Yeping⁴, Ostadhassan, Mehdi⁵

(1) School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing, 100083, China, Beijing, China, (2) State Key Laboratory of Continental Shale Oil, Northeast Petroleum University, Daqing, 163318, China, Daqing, China, (3) School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing, 100083, China, Beijing, China, (4) CSIRO Energy, Kensington, WA 6151, Australia, Kensington, Australia, (5) State Key Laboratory of Continental Shale Oil, Northeast Petroleum University, Daqing, 163318, China, Daqing, China,

Abstract:

Abstract: The anisotropic pore structure and permeability are crucial for assessing shale gas extraction, as they influence gas preservation, transport mechanisms, and hydraulic fracturing efficiency. This study integrates small-angle neutron scattering (SANS), directional permeability testing, mercury intrusion capillary pressure (MICP), Wood's metal (WM) injection and field-emission scanning electron microscopy (FE-SEM) to systematically analyze four deep Longmaxi Formation shale samples. Our findings demonstrate that total organic carbon (TOC) and mineral composition, particularly quartz and clay, play a key role in controlling nanopore orientation. Shales with high TOC and quartz content exhibit isotropic behavior, whereas those with low TOC and high clay content display pronounced anisotropy. Permeability measurements yield horizontal-to-vertical permeability ratios (K_H/K_V) ranging from 7.58 to 16.43, highlighting pronounced anisotropy. Furthermore, modulus-corrected MICP data shows that nearly 100% of matrix pores (<100 nm) are inaccessible to mercury. FE-SEM observations following WM injection confirm poor fracture-matrix connectivity, as WM fails to penetrate these pore spaces. These results offer significant insights into the preservation and transport of gas within shale formations. Keywords: Permeability anisotropy; Pore compressibility, Neutron scattering; Deep formation; Longmaxi shale

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4768

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