THE PALEOHYDROGEOLOGICAL CONDITION AND THE MIGRATION-ACCUMULATION OF OIL AND GAS IN JIYANG DEPRESSION

The paleohydrogeological condition and its relationship to the migration and accumulation of oil and gas in Jiyang Depression are studied with the cyclic standpoints. Depending on the hydrogeological cycles, the Cenozoic (K₂) in this area can be divided into Eocene (E₂), Oligocene (E₃) and Nogene(N)-Quaternary(Q). Each cycle can be divided into two hydrogeological stages of sedimentation and seeping. The water-exchanges of Shahejie Formation (except E_s⁴) are evaluated. The result shows the activity of deposition water is far exceeded than that of seeping water. This condition is quite favourable for migration, accumulation and preservation of oil/gas. The prospects of oil and gas in this area are evaluated in accordance to the paleohydrodynamic effects, and the time, trend and size of migration and accumulation of oil/gas are discussed as well.