Study On High-resolution Sequence Stratigraphy And Lithologic Traps Prediction Of Shahejie Formation In Chengdao East Slope

Based on the theory and techniques of high-resolution sequence stratigraphy, thesequence stratigraphic framework and sedimentary facies of Shahejie formation inChengdao east slope are identified. Trough the literature review, analysis andinterpretation of drilling/logging data and three-dimensional seismic data, ahigh-resolution sequence stratigraphic framework in this area is established. The typesof sedimentary facies and the distribution characteristics of the favorable oil-bearingformations are identified. Eventually, the lithologic traps are preidicted.In light of the high-resolution sequence stratigraphic method, Shahejie formationis divided into2third-order sequences, which are named as Shasanxia and Shayiersequence from the bottom to the top. Shayier sequence is also divided into5forth-order sequences. Regarding of this,5sand groups are divided, which are namedas S1-Ⅴ, S1-Ⅳ, S1-Ⅲ, S1-Ⅱ, S1-Ⅰin bottom-up sequence.Through comprehensive analysis of drilling/logging facies and seismic data,there are four sedimentary facies that are identified: fan delta, sand beach-bar,bioclastic beach-bar and lake. By using geological and geophysical methods closely,at the same time combining the controlling effect of paleogeomorphology, thedistribution and evolution characteristics of sedimentary facies under Shahejieformation sequence framework in Chengdao east slope are identified, which aredrawn with the sand groups as the unit. In period S1-Ⅴ, Shayier section developes alarge scale fan delta and sand beach-bar near source; In period S1-Ⅳ, fan delta insouth of the study area retrogrades,and sand beach-bars in northern are still large; Inperiod S1-Ⅲ,water significantly increases, and fan delta and bioclastic beach bars aremainly developed; in period S1-Ⅱ, water intaking range expandes continuously todevelop small beach bars, and bioclastic beach bars isolate in high projection, whilethe distribution scale of sandy beach along the dam becomes smaller; In periodS1-Ⅰ,less sand bodies develop, while small sand beach bars only exist along the fandelta.After comprehensive consideration of the sequence stratigraphic position, structure, paleogeomorphologic features, sedimentary facies, discovered oil and gastraps and trap types factors, the favorable oil-bearing formations are S1-Ⅳ、S1-Ⅲ andS1-Ⅱ, and favorable sedimentary facies are beach bars and fan delta; six favorableexploration areas are determined,in which the most favorable one is the compositesand body parts around CHB328and CHB323.