TITLE:
Characteristics and Main Controlling Factors of Low Permeability Reservoirs in E3s2 of A Oilfield, Bohai Bay Basin
AUTHORS:
Junshou Zhao, Yanan Xu, Qiang Sun, Junliang Zhou, Xin Yang
KEYWORDS:
Sedimentation, Diagenesis, Low Permeability Reservoir, A Oilfield, Bohai Bay Basin
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.12,
December
5,
2025
ABSTRACT: The Second Member of the Shahejie Formation in A oilfield, Bohai Bay Basin, contains typical medium-low porosityand low permeability tight sandstone reservoirs. To study the features (petrology, porosity and physical properties ) and forming mechanism of the target reservoirs, a series of experimental data were used, including cores observation, casting section identification, electron microscope observation and X-ray diffraction, combining with the theory of sedimentary petrology, reservoir sedimentology. The results show that the reservoir is porous reservoir featuring in middle composition and texture maturity, lithic arkoses, secondary dissolution porosity and I type of pore structure. The forming mechanisms of the reservoirs include sedimentation and diagenesis. Sedimentary facies are mainly by braid river deltas front sub-facies, the microfacies of underwater distributary channel have the best reservoir physical property and oiliness, easily forming favorable reservoirs. Particle size and the content of matrix are controlled by sedimentary hydrodynamic in different kinds of microfacies, then the best reservoirs are the coarse grained sandstone which have low matrix content. Primary pores in the reservoirs were almost killed by compaction and the cementation of carbonate cements and clay minerals, paulopost solution created secondary pores which are the mainly reservoir space. But the dissolution is not so strong that reservoirs still have low permeability. Therefore, secondary pores area in underwater distributary channel is the most favorable area for reservoirs to develop.