Study Of Sequence Stratigraphy And Distribution Of Sand-body, The Fourth Section Of Shahejie Formation, Qi-shu Area, Liaohe Basin

Sequence stratigraphy can contribute directly to the exploration of subtle traps. It is effective to increase the precision of stratigraphic correlation, therefor to enhance the reliability of subtle traps prediction, stratigraphic correlation approaches using in this paper based on principle of stratigraphic base-level cycles developed by T. A. Cross, which are well tested in shallow marine and coastal plain strata. Utilizing core, drilling, logging, seismic data and other information, the paper focus on recognizing the stratigraphic cycles formed by multi-order base-level cycles, establishing the stratigraphic correlation framework, researching on the distribution of reservoir and the prediction of the prospecting targets of the Fourth Section of Shahejie Formation in Qi-Shu area, Liaohe basin.The long-term base-level cycle comprises the Third and the Fourth Section of Shahejie Formation, which are successive,and the Fourth Section is rising term of the long-term base-level cycle; the underside of the Fourth Section of Shahejie Formation is the Fangshenpao Formation, and their interface is a unconformity . The Fourth Section in the stage of basin depression is divided into one intermediate-term base-level cycles. In the chronstratigraphic framework, the facies, the depositional system and the principle and range of reservoirs distribution are studied. The main depositional system is braided delta梥ub-lake fan. The coarse lithofacies which form braided delta depositional system is sub-water channel deposits; The coarse lithofacies which form the sub-lake fan depositional system include turbidity channel deposits and bedded turbidity deposits. The paleotopography is the main factor controlling the types, characters and distribution of the depositional system.Considering all factors in trap-forming, the most prospective reservoirs are the sub-water channel sandstones, the front sheet sandstones of braided delta and bedded turbidity sandstones. The petroleum exploration targets are identified further.