Abstract: Based on measured data statistics, thin section analysis and comparative analysis, the genetic mechanism of high-quality glutenite reservoirs at the steep slope in northern Dongying sag was studied from the aspects of sedimentation, diagenesis and hydrocarbon generation. Two pore zones were found vertically at the steep slope in northern Dongying sag, at the buried depth of 1650-2450 m and 2950-3300 m respectively. The study shows that the pore zones are different in genetic mechanism. In the first pore zone (1650-2450 m), the reservoir space is composed of primary pores, which due to the significant control of sedimentation are developed in mid-fan glutenites with low shale content, better sorting degree and moderate grain size. In the second pore zone (2950-3300 m), the reservoir space is composed of secondary pores which were generated by the dissolution of carbonates, felspars and quartz, as the result of alternative dissolution between earlier alkaline fluids and later organic acids formed by hydrocarbon generation of source rocks. The carbonate cementation and hydrocarbon charging at the early stage inhibited the compaction and cementation, contributing to the preservation of pores.

Key words: Dongying sag, glutenite, pore zone, primary pores, secondary pores, organic acid, alkaline fluid, dissolution