Detailed Sedimentary Facies of the 8th Member of Shihezi Formation in the Block S47 in Western Sulige Gas Field

Sulige gas field in Ordos basin is the largest terrestrial gas production field in China. As a typical tight sandstone gas pool,distribution of reservoirs of the main gas- producing strata in Sulige gas field—— the 8th member of Shihezi formation in Permian system( P2h8 for short),is mainly controlled by detailed sedimentary facies. But disagreements about detailed sedimentary facies still exist in the Block S47——an important new region in the western part of Sulige gas field. Detailed sedimentary facies of P2h8 in the Block S47 were studied on the basis of drilling core observation,analysis of well logs and samples. It is considered that the strata of P2h8 in the Block S47 was deposited in braided delta front,which can be further sub- divided into subaqueous distributary channel,estuary bar, sand sheet,subaqueous levee and interdistributary bay etc. 5 detailed sedimentary facies. The most favorable reservoir is subaqueous distributary channel overlaid sand bodies and estuary bar sand bodies secondarily. New understandings on detailed sedimentary facies and distribution features provide theoretical foundations for reservoir prediction and integrated exploitation by horizontal wells in the Block S47.