Research paperEvaluation of the shale gas potential of the lower Silurian Longmaxi Formation in northwest Hunan Province, China

- A comprehensive analysis on geological setting and reservoir property of Longmaxi shale in Hunan.
- An integrated methodology for comparison between Longmaxi shale in Hunan and Sichuan.
- Combination of spatial and timing factors is critical in evaluation of shale reservoir quality.

Commercial gas production has been achieved in China's marine shale of the Silurian Longmaxi formation in the eastern Sichuan area, and experience for developing shale gas in complex structural areas has been gathered. A set of Longmaxi Formation shales deposited in the northwestern Hunan area has close relationship with the eastern Sichuan Longmaxi shale on both depositional environment and tectonic evolution. Therefore, it is important to undertake an integrated evaluation of the Longmaxi formation shale in the northwestern Hunan area. This work combined field investigations and the laboratory measurements using outcrop samples to study the petrology, geochemistry, reservoir and adsorption characteristics of the Longmaxi shale in the northwestern Hunan area. The geological settings and reservoir properties were compared with those of the eastern Sichuan Longmaxi shale using publically available data. The results show that the hydrocarbon generation ability, organic matter maturity, sealing capacity and reservoir stimulation effectiveness of the Longmaxi Formation shale in the northwestern Hunan area are comparable to those in the eastern Sichuan area. The Longmaxi shale in the northwestern Hunan area therefore shows early signs of development potential, and the drilling of exploration wells is thus warranted to further evaluate its gas content and other in-situ reservoir properties for possible shale gas development in the near future.