Reservoir characteristics and controlling factors of the Lower paleogene sandstones in the southeast part of Jiyang Sag, BohaiBay Basin, China

Abstract

With the continuous improvement of exploration degree in Bohai Bay Basin, the red beds in Jiyang Sag has become a hot exploration spot in recent years, the red beds is buried deep, and the distribution of favorable reservoirs has become a key factor restricting oil and gas exploration. This paper combines logging, core and seismic data, mainly introduces the sandstone reservoir characteristics of red beds in the southeast of Jiyang depression, and analyzes the influence of sedimentary environment and diagenesis on its reservoir characteristics respectively. The results showed that the red bed sandstone is mainly composed of arkose, quartz-feldspar and feldspar-quartz graywackes, with good porosity and permeability. Under the control of the original sedimentary environment, three types of reservoir sand bodies are mainly developed in the study area: proluvial fan, fan delta and beach bar deposits, among them, fan delta deposits have better storage performance. The diagenetic environment was early alkaline and late acidic, compaction and cementation greatly reduced primary pores and a large number of secondary pores are produced due to minerals dissolution. Under the combined influence of sedimentary environment and diagenesis, the red-bed reservoirs have various types of reservoir spaces, with obvious differences in porosity and permeability.