Diagenesis and reservoir quality in continental fault-block reservoirs: Evidence from the Second Member of Shahejie Formation, Dongying Sag, Eastern China

Continental fault-block reservoirs in the Second Member of Shahejie Formation in Dongying Sag of Eastern China are difficult to achieve efficient exploration and development due to the complex geological conditions. This study relates to the in-depth analysis on diagenesis and reservoir quality in such deposits. These deposited sandstones have a wide range of porosity and permeability, which indicate both depositional facies and diagenesis control. Diagenetic processes that influenced the reservoir quality of the study area mainly insist of the formation of carbonate cements, and clay minerals, mechanical compaction, quartz cementation, and dissolution of framework grains. The distribution patterns and mineralogy of cements vary spatially, being relevant to reservoir evaluation. Among the diagenetic menerals, carbonate cements occur as the predominant components in the Shahejie sandstones of the study area. In such settings, the quality-destruction processes include mechanical compaction and carbonate cementation, whereas the quality-generation process is dissolution of detrital grains and calcite cements. The major sequence is eodiagenesis with the types and extent of eogenetic alterations related to the near-surface geological conditions. This study demonstrates diagenesis and related reservoir quality evolution can be linked to fine reservoir characterization, and thereby has an important role on hydrocarbon exploration and exploitation in the continental fault-block reservoirs.