Geological Conditions and Entrapment Models of Outcrop Trap Reservoirs

Outcrop oil reservoir is a special reservoir controlled by water table. Theoretical analyses and detailed studies of the Qiketai oilfield in the Tuha basin showed that the outcrop oil reservoirs were formed in basins with deeply-buried water table, rich source of oil and outcrop traps. There were two entrapment models for the outcrop reservoirs. One model was that outcrop reservoirs developed in the wing of an outcrop anticline. The other model was that the outcrop reservoir occurred in the monocline that was laterally sealed by lithology. The outcrop reservoirs were usually characterized by small burial depth (tens to hundreds of meters), late accumulation and usually good reservoir porosity and permeability (the porosity was usually higher than 15%).