Deposition and Diagenesis of Steep-Slope Glutenite Reservoirs: Shengtuo Field, Eastern China

Abstract

This study deals with the diagenesis of steep-slope glutenites in the view of relationship between depositional facies and diagenetic alterations. The Lower Member of Shahejie glutenites sit along steep slopes of an intracontinental lacustrine basin, which is an important area of hydrocarbon exploration in eastern China. This kind of reservoir rocks can be divided into three major depositional environments: transgressive fan deltas, channelized sediment flows and fluxoturbidite fans. The glutenites are lithic arkose and feldspathic litharenite having an average composition of Q35F36R29, rich in metamorphic rock fragments. Diagenetic processes that have affected the glutenites include mechanical and chemical compaction, dissolution of detrital grains, and cementation by quartz overgrowths, calcite, ankerite, kaolin, illite, chlorite, and mixed-layer illite-smectite clays, as well as formation of minor zeolite, epsomite, halite, and glauberite. Considering glutenites in different depositional environments experiencing different diagenetic evolution pathways along the lacustrine basin margin, a schematic model was constructed to predict diagenetic conditions within the defined depositional facies. This study reveals that the spatial and temporal distribution of diagenetic alterations within depositional facies, and provides important insights to the controls on reservoir quality evolution. In addition, findings of the study are applicable to other continental steep-slope glutenite reservoirs of lacustrine basins.