271-8 The Study of the Characteristics and Controlling Mechanisms of Continental Saline Lake Carbonate Reservoirs: A Case Study of the Qianjiang Formation in the Qianjiang Depression, Jianghan Basin

Session: Geologic Energy Resources and Storage for Now and the Future (Posters)

Presenting Author:

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Abstract:

The lacustrine carbonate reservoirs of the Qianjiang Formation in the Qianjiang Depression, Jianghan Basin, are characterized by strong heterogeneity and represent a new frontier in hydrocarbon exploration within continental saline lake basins. However, studies focusing on reservoir characterization and controlling mechanisms remain limited. This study integrates multiple analytical techniques—including X-ray diffraction (XRD), X-ray fluorescence (XRF) elemental scanning, thin-section petrography, scanning electron microscopy (SEM), high-pressure mercury intrusion (HPMI), nitrogen adsorption, and nuclear magnetic resonance (NMR)—to investigate the lithofacies development, reservoir physical properties, pore types, and controlling factors. The results indicate that the paleoclimate during the deposition of the Qianjiang Formation experienced multiple cyclic fluctuations. The undulating terrain of the rift basin and the variable monsoonal climate led to the interbedded deposition of multiple lithologies such as evaporites, mudstones, and others, resulting in the development of diverse lithofacies. Overall, the reservoirs display favorable physical properties, with storage space dominated by pores—primarily intercrystalline, intergranular, and dissolution pores. Among them, intercrystalline pores are extensively developed; although their pore sizes are relatively small, they exhibit high surface porosity (area porosity), which makes a significant contribution to the reservoir quality of fine-grained lithofacies. Variations in the depositional environment throughout multi-cycle sedimentation are key factors controlling reservoir development. Favorable sedimentary facies such as grain shoals, which develop lithofacies types and assemblages characterized by relatively coarse grain sizes and low degrees of mixing, serve as the foundation for high-quality reservoir formation. Additionally, diagenetic processes also play an important role in modifying reservoir properties. While compaction and cementation tend to reduce pore space, dissolution diagenesis such as early meteoric freshwater dissolution and late-stage organic acid dissolution play crucial roles in enhancing reservoir quality. The findings of this study provide theoretical guidance for hydrocarbon exploration in carbonate reservoirs within continental saline lake basins.

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

doi: 10.1130/abs/2025AM-6046

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