Study On The Sequence Stratigraphy And Sedimentary Systems In The Lower Sha2 Member In Niu9 Aera Wangjiagang Oilfield

Under the guidance of Vail sequence stratigraphic theory and Cross high resolution- sequence stratigraphic theory, and the combination of seismic data, well logging data, drilling cores and other related analyzed data and experimental technique, the sequence stratigraphy framework has been established. The sequence is difined to be a third-order sequence. It is divided into transgressive systems tract and high-stand systems tract. The transgressive systems tract which is divided into cycle one to cycle five is mainly the ascending half cycle. The high-stand systems tract which is divided into cycle six to cycle ten is mainly the descending half cycle.Based on analysis of core, drilling core well facies, single well facies multidisciplinary analysis, profile facies and plane facies, referring to modern sedimentological theory,this paper comprehensively studies sedimentary microfacies in lower Shaer member. Lacustrine facies, delta, beach-bar developed in lower Shaer member. Delta front and beach-bar mainly developed in transgressive systems tract, delta plain, delta front and beach-bar mainly developed in high-stand systems tract. When the lake shrinked and the lake wave weakened, constructive delta developed in the ascending half cycle. When the lake enlarged and the lake wave enhanced, beach-bar developed in the descending half cycle. The beach-bar has a close relationship with the delta which developed in descending half cycle. Different facies models are established in ascending half cycle and descending half cycle.Based on the sedimentary facies, the genesis types of sandbody in lower Shaer formation is divided into channel sand which include delta plain channel sand and delta front channel sand, mouth bar, distal bar and beach-bar. Controlling factors of the formation and distribution of sandbody are researched in this paper. Controlling factors of the formation sandbody has the characteristics of facies controlled by ancient water depth and sandbody controlled by paleocurrent. Distribution of sandbody has the characteristics of weakly zonation in plain and stage display in longitudinal section.