Diagenetic Characteristics and Controlling Factors of the Paleogene Sandy Conglomerate Reservoirs in the North Chezhen Sag, Bohai Bay Basin, China

Abstract

Abstract The Paleogene sandy conglomerate reservoirs in the North Chezhen Sag, Bohai Bay basin have undergone significant diagenesis, resulting in complex reservoir characteristics. This study investigates the diagenetic characteristics and controlling factors of these reservoirs using petrographic analysis, scanning electron microscopy, X-ray diffraction, and fluid inclusion analysis. The diagenetic processes include compaction, cementation, dissolution, and replacement. Compaction is the dominant diagenetic process, leading to a reduction in porosity and permeability. Cementation is mainly due to quartz overgrowth and carbonate cements, which further reduce the reservoir quality. Dissolution and replacement, on the other hand, have a positive impact on reservoir quality, creating secondary porosity and enhancing permeability. The controlling factors of diagenesis include sedimentary environment, lithology, burial depth, and fluid flow. The sedimentary environment and lithology control the original texture and mineral composition of the reservoirs. Burial depth affects the degree and timing of diagenesis, with deeper burial leading to more significant diagenesis. Fluid flow influences the type and timing of cementation and dissolution, which further impact reservoir quality. Understanding the diagenetic characteristics and controlling factors of the Paleogene sandy conglomerate reservoirs in the North Chezhen Sag, Bohai Bay Basin is essential for reservoir evaluation and exploration. The results of this study can be used to guide future reservoir development strategies and optimize production.