298-6 Micropore Systems in High-Organic-Matter Marine Shales of the Permian Wujiaping Formation, Eastern Sichuan Basin: Implications for Shale Gas Storage

Session: Joint SGD-SEPM-IAS Focus on Sedimentary Geology and Energy Transitions (Posters)

Presenting Author:

Authors:

Abstract:

The Second Member of the Permian Wujiaping Formation (Wu-2 Member) in the Eastern Sichuan Basin is a critical target for shale gas exploration, yet its complex pore architecture and controlling mechanisms remain unclear. This study integrates multi-scale analytical techniques—including field-emission - scanning electron microscopy (FE-SEM), low-pressure gas adsorption (CO₂ and N₂), high-pressure mercury intrusion porosimetry (HMIP), and small-angle X-ray scattering (SAXS)—to systematically characterize the pore systems of 24 high-organic-matter shale samples from the Hongxing area.

Results identify four distinct lithofacies-controlled pore systems: (1) High-carbon siliceous (HS) shales feature 3D interconnected microporous networks, facilitating efficient methane adsorption and transport; (2) High-carbon mixed (HM) shales exhibit balanced micro-mesopore development but reduced connectivity due to clay deformation and pore blocking; (3) Medium-carbon mixed (MM) shales act as closed pore traps, with ~70% of pores occluded by clay minerals; (4) Low-carbon calcareous (LC) shales display a seepage-storage paradox, where calcite-cemented macropores provide minimal storage despite low tortuosity.

Total organic carbon (TOC) enhances organic pore formation, while authigenic quartz preserves interparticle pores during compaction. Carbonate cementation reduces porosity, though late-stage dissolution generates secondary microporosity. Compared to other typical marine shales, Wu-2 Member microporosity primarily forms via early carbonate cementation and dissolution, contrasting with the siliceous framework-supported networks of the Silurian Longmaxi Formation in the Sichuan Basin and the Barnett Shale in the Fort Worth Basin.

This study establishes a genetic model for pore evolution, highlighting the roles of organic matter maturation, mineral diagenesis, and compaction, and identifies HS shales as the most favorable reservoir facies—providing key insights for shale gas exploration in analogous settings.

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

doi: 10.1130/abs/2025AM-6407

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.