Abstract: The studies were systematically made on well- developed major reservoir member, Shahejie fornation depositional system in central uplift belt of Dongying sag (Shandong Province). It is shown that in Shahejie formation there mainly exist three types of depositional systems(delta deposit, underwater fan deposit and coastal lake deposit) and eight sorts of reservoir deposits with different features for each one. Based on these and followed by proper reservoir classification and characteristics analysis,this paper established the methods for reservoir description of subtle pool with complex fault blocks, by which the main trap within the belt could be divided into fault block trap, structural trap and subtle trap which includes sand lens trap,lithologic updip thinning out trap,structural-lithologic trap and fault lithologic trap. For self- confined fault controlling oil flow,its height of oil column can be estimated by utilizing R.R.Rerg's principle. These would be of significance for reference to study of similar reservoirs and their characteristics.

Key words: Dongying sag, Middle, Uplifted zone, Sedimentary system, Reservoir description