Uppermost Permian reefs from the Wubaiti structure eastern Sichuan, China: Implications for exploration of natural gas reservoirs

摘要

Changhsingian (latest Permian) reefs are reported from the Wubaiti structure, northern Sichuan Basof southwest China. Here, reefs grew along the platform margins and their tempo-spatial distribution and growth stages were determined based on the integration of detailed seismic profiles, well logs and core data. The Wubaiti reefs experienced two distinct development stages. The first episode of reef development was characterized by the growth of coral and sponge patch reefs during early-middle Changhsingian time. The second episode, the magrowth phase of the Wubaiti reefs, occurred late Changhsingian time when both sponges and algae acted as major reef-builders. These reef-building organisms disappeared the Permian-Triassic mass extinction. Reef growth coincided with a local transgression event, but ceased due to a fall local sea-level the latest Changhsingian time. Dolostones of various parts of the Wubaiti reefs provide considerably high-quality reservoirs for natural gas the Sichuan Basin.