The Small Source To Sink Analysis Of Shahejie Formation In JZ25-1/JZ25-1S Oilfield,Liaodong Bay Basin

The Shahejie Formation of JZ25-1/JZ25-1S Oilfield in Liaodong Bay Basin is a key horizon for oilfield exploration and development.The cause and distribution of sand bodies in the Shahejie Formation restricts the efficient exploration of oil and gas.Based on the “source to sink(S2S)”theory and the latest core,drilling logs,seismic data and related analytical data,this paper carried out research on the coupling of source systems,transport systems,sedimentary systems in the sequential framework and predict the distribution of potential sand bodies.Based on Vail's theory of sequence stratigraphy,the Shahejie Formation is divided into five third-order sequences: SQs3L(SQ1),SQs3M(SQ2),SQs3U(SQ3),SQs2(SQ4)and SQs1(SQ5).Using the seismic progradational direction,changes in thickness of sand bodies,analysis of heavy minerals,and zircon dating,it is believed that there are three major sources,namely,the Mesozoic,Proterozoic,and Archaeocene source from the Yanshan fold belt;the Archaeocene source from the northern part of the middle section of the Liaoxi low uplift;and the Proterozoic and Archaeocene source from the southern part of the middle section of the Liaoxi low uplift.Using layer-leveling and seismic visualization techniques,the relatively paleo-geomorphology of the study area was recovered,and the width-to-depth ratio of the six valleys that developed significantly in the northern part of the middle section of the Liaoxi low uplift was quantified.Through core,logging and seismic analysis,well logging facies and seismic facies were established,and sedimentary facies such as braided river deltas,fan deltas and lakes were identified in the study area.The braided river delta is well developed in the gentle slopes of the western part of the study area,and the fan delta is more developed on the west side of Liaoxi No.1 fault.The lakes are developed on the side edges and front of fan deltas and braided river deltas.By the analysis of the source system,the transport system and the sedimentary system,it is believed that there are two major types of source to sink systems(S2S)in the study area: S2 S of “local provenance-steep slope belt-fan delta” and S2 S of “regional provenance-gentle slope-braided river delta”.Based on the theroy of S2 S,the valleys and fan deltas are matched.And according to the characteristics of small S2 S in northern part of the middle section of the Liaoxi low uplift,two potential fan delta sand bodies of Es3 M in northern part of the study area are predicted.