Reservior characteristics and main controlling factors of the third member of Paleogene Shahejie Formation in Fulin sag, Bohai Bay Basin

This paper is the result of oil and gas exploration engineering.

Objective The third member of Shahejie Formation of the Paleogene is the most important oil and gas horizon in Fulin sag, Zhanhua sag, jiyang sag, Bohai Bay Basin, and it has the essential scientific and guiding significance of strengthening the reservoir characteristics of Shahejie Formation, analyzing the main controlling factors of the reservoir, and guiding the reservoir prediction and oil and gas exploration engineering and resources of Shahejie Formation in the area.

Methods Based on the petrography and reservoir physical property data, this paper is aiming to dicipher the origin of the sandstone reservoirs of Paleogene Shahejie Formation the Zhanhua sag, Bohai Bay basin.

Results The thin sections observation and sem analysis show that the lithofacies of the reservoirs are consist of feldspathic lithic sandstone and lithic feldspar sandstone, with low compositional and structural maturities, indicating that they rapidly deposited in the environment proximal to provenance. The reservoir space type of the reservoir is mainly residual primary intergranular pores, intergranular solution pores and intragranular solution pores, mainly low medium porosity and ultra-low permeability pore type reservoirs. The development of high-quality reservoirs is controlled by sedimentary microfacies and diagenesis. The sedimentary microfacies are the basis for the development of high-quality reservoirs, and cementation and dissolution are the key factors for the development of high-quality reservoirs.

Conclusions (1) The rock types in the study area were mainly feldspathic lithic sandstone and lithic feldspar sandstone. (2) It is generally a low-to-mesoporous and ultra-low permeability reservoir; (3) High-quality reservoirs in the study area are mainly distributed in braided river delta distributary channels and estuarine bars; (4) Compaction and cementation are the main destructive diagenesis in the study, while dissolution has constructive diagenesis on reservoir physical properties.