Sequence-lithofacies paleogeographic characteristics of Feixianguan Formation in southern sector of Kaijiang-Liangping ocean trough

Abstract：There are many important oil-gas resources in Feixianguan Formation of northeast Sichuan. The south sector of Liangping-Kaijiang ocean trough is very extensive and has many important potential oil-gas resources. Based on an analysis of rock core, field cross section, logging, well logging and thin-section observation data, the authors studied the sequence-lithofacies paleogeographic characteristics of Feixianguan Formation in south sector of Liangping-Kaijiang ocean trough. The result indicates that the sedimentary model of the study area belongs to the attached land platform which includes the platform, sloping ground, and residual ocean trough facies. Based on the sequence interface identification, the authors divided the Feixianguan Formation into three third-level sequences, namely SQ1, SQ2, and SQ3. Each of the sequence is divided into three system tracts, i.e., TST, EHST, and LHST. With the system tract as the unit of the sequence-lithofacies paleogeographic map, this paper discusses in detail the lithofacies paleogeographic characteristics and evolution of various sequence system tracts. With the reduction of the ocean trough, the attached land platform expanded gradually, the platform edge beach and intra-platform beach gradually advanced to the ocean trough, which controlled the reservoir distribution.