Characteristics and Distribution Patterns of Mixed Reservoirs in the Upper Subsea of Liangjialou Sand Formation During Purification
Abstract
The upper member of sha 4 in the study area belongs to beach bar deposits in underwater uplift, which is relatively far away from terrigenous clastic supply area and is mainly affected by lake waves and shore currents. The sediments have the characteristics of terrigenous clastic and carbonate mixed facies deposits, forming a special lithofacies system. The upper part of Es4（Shahejie Formation 4th Member） in the study area is a shore-shallow lake subfacies deposit, developed with shore-shallow lake sand bar, shore-shallow lake sand beach and shore-shallow lake mud bay three microfacies, lithology is divided into sandstone and carbonate rock, both can form a single type of reservoir, but also can form a complex mixed reservoir. The shallow lake beach bar sedimentary reservoir body of the upper submember of Shahejie Formation can be divided into 6 lithofacies types, which are sandstone bar body, calcareous sandstone bar side edge, argillaceous beach sand, calcareous beach sand and mudstone bay.Through the analysis of oil and gas logging and comprehensive oil testing results of the target layer in the research area, it is believed that the favorable lithofacies are the main body of the sandstone dam and the lateral edge of the calcareous sandstone dam.