Recent research published in the journal “Minerals” has unveiled significant insights into the characteristics and control factors of high-quality deeply buried calcareous sandstone reservoirs in the Western Sichuan Basin, China. Led by Dong Wu from the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development in Beijing, this study highlights the potential of calcareous sandstones, particularly from the Upper Triassic Xujiahe Formation, as a promising target for natural gas exploration.
Calcareous sandstones are a unique type of rock primarily composed of carbonate rock fragments, which dominate the framework grain composition. The study found that these sandstones, classified as litharenite, exhibit an average composition of 30% quartz, 1% feldspar, and a striking 69% rock fragments. Despite their potential, the quality of these reservoirs is generally poor, with an average porosity of just 3.63% and a median permeability of 0.026 millidarcies, making it challenging for hydrocarbons to accumulate.
The research emphasizes that high-energy depositional conditions, low late cement content, and the development of fractures are crucial for the formation of high-quality reservoirs. Wu stated, “Compaction is one of the most significant diagenetic alterations in the calcareous sandstone,” underscoring the geological processes that influence reservoir quality. The study also highlights the role of dissolution processes, which can enhance reservoir quality by creating secondary pore spaces, although these were found to be rare in the calcareous sandstones examined.
For the energy sector, these findings present both challenges and opportunities. The unique composition and characteristics of calcareous sandstones suggest that targeted exploration strategies could yield better results in locating and developing natural gas resources. The study’s insights into the differences between calcareous sandstones and traditional Xu4 sandstones indicate that understanding local geological variations is essential for successful drilling operations.
As industrial gas flow has already been confirmed in several calcareous sandstone wells, the commercial implications are significant. Companies focused on tight gas exploration in the Sichuan Basin may look to adapt their strategies based on these findings, potentially leading to more efficient resource extraction and increased production rates.
Overall, Dong Wu’s research not only enhances the understanding of deeply buried calcareous sandstone reservoirs but also paves the way for more effective gas exploration and development in one of China’s key energy-producing regions. The study serves as a valuable guide for future endeavors in this evolving sector, highlighting the importance of geological factors in determining reservoir quality and hydrocarbon potential.
