Abundant oil potential has been confirmed in the Eocene Shahejie Formation (Es) in the Chezhen Sag, but the genetic mechanism of its reservoir has not been fully understood. Based on core observation, thin-section identification, scanning electron microscopy (SEM), X-ray diffraction, and formation pressure measurement, the factors controlling the quality of glutenite reservoirs in the Shahejie Formation in the Chezhen Sag were revealed. The petrophysical structure, depositional facies, diagenesis, and formation overpressure jointly control the development and evolution of glutenite reservoirs. Reservoirs with high composition maturity exhibit better physical properties. Depositional facies control the development of high- and poor-quality reservoirs but have little influence on the physical properties of medium-quality reservoirs. Compaction is the main factor for reducing reservoir porosity during burial, and the cementation of carbonate and clay minerals affects the reservoir quality to some extent. Each secondary structural zone shows different dissolution models. The reservoirs in the steep slope zone are in a closed system with weak dissolution, hardly contributing to improving the reservoir porosity. The dissolution of reservoirs in the depression zone has been enhanced; however, the migration of dissolution products is restricted because of the closed reservoirs, causing the redistribution of pore space and limited contribution to improving the physical properties. The reservoir in the gentle slope zone is in an open system with a shallow buried depth, and severe dissolution can effectively improve the reservoir's physical properties. A grading assessment scheme is proposed based on the depositional facies, diagenesis, and formation overpressure, and favorable exploration zones are predicted. The western part of the gentle slope zone in the upper part of the Es4 member and the eastern part of the steep slope zone in the lower part of the Es3 member of the Chezhen Sag are the principal target areas for exploration.