Reservoir quality, gas accumulation and completion quality assessment of Silurian Longmaxi marine shale gas play in the Sichuan Basin, China

Abstract

The Sichuan Basin in Southwest China holds the most potential for shale gas exploration and development in China. The assessment of reservoir quality, gas accumulation and completion quality of Silurian Longmaxi marine shale gas is conducted based on detailed mapping of depositional systems and shale properties, analyses of geochemical, mineralgical and petrophysical data, investigation on interactions between tectonics, reservoir quality, shale gas accumulation, completion quality, and production. The results show that the Lower Section of the Lower Silurian Longmaxi marine shale in the southern, southeastern, and eastern parts of the Sichuan Basin is good shale reservoir in terms of high TOC, high maturity, high brittle mineral content, and development of inter-particle and intra-organic matter pores and natural fractures. Petroleum system modeling calibrated by production data reveals shale gas tends to accumulate in broad syncline and anticline in tectonically stable area. Tectonic setting and stress field analyses and hydraulic fracturing simulation and practice imply that the siliceous Longmaxi shale interval in the areas with small far-field horizontal stress are more favorable for hydraulic fracturing to form complex fracture network. The best prospects are likely located in broad syncline and anticline in tectonically stable areas with good reservoir quality, shale gas accumulation and completion quality in the southern and southeastern areas inside the Sichuan Basin.