The lithofacies superposition patterns of oil-bearing reservoir of different productivity levels of the Lower Fourth Member of Eocene Shahejie Formation in Dongying Sag, Bohai Bay Basin

Abstract

Based on core observation and well logs, the paper reveals the lithofacies superposition patterns of oil-bearing reservoir of different productivity levels of the Lower Fourth Member of Eocene Shahejie Formation in Dongying Sag, Shengli Oilfield. The reservoir is divided to three types according to its productivity levels. Type A: natural productivity > 10 tons per day; Type B: 5 tons per day <natural productivity ≤10 tons per day and Type C: natural productivity ≤5 tons per day. Their corresponding lithofacies superposition patters are “thin bedded sandstone + mudstone superposition model”, “multi-stage superposition of thick-bedded conglomerate and pebbled sandstone” and “superposition of medium thick pebbled sandstone, coarse-grained sandstone and medium-grained sandstone”.