The Sedimentary Characteristics And Distribution Of Favorable Reservoir Facies Of Lower Cretaceous In Guaizihu Depression,Yin-e Basin

The Guaizihu depression is affiliated to the Yin-E Basin and structurally located in the structural joints of the four major plates of Tarim,Kazakhstan,Siberia,and North China.It has undergone multistage tectonic movements and is a faulted-depressed basin.Based on the full use of seismic data and well logging data,this paper makes a detailed study on the characteristics of the sedimentary facies and favorable reservoir facies of the Lower Cretaceous.Based on high-resolution sequence stratigraphy and sedimentology theory,this paper analyzed the strata of the Lower Cretaceous in the Guaizihu depression.(1)Identifying sedimentary microfacies by core observation and logging data analysis(2)Focus on analysis of paleogeomorphology,seismic facies,and seismic attributes to determine the provenance direction of the work area;(3)Study the characteristics and evolution of sedimentary facies in different layers of the Lower Cretaceous in an isochronal stratigraphic frame;(4)Through physical properties and oiliness analysis,combined with features such as sedimentary microfacies and tectonic structures,predicts the distribution of favorable reservoir facies.According to the identification of the unconformity of the Lower Cretaceous in the Guaizihu depression,the Lower Cretaceous can be divided into seven third-order sequences: including Ba-1 member(SQ1),Ba-2 member(SQ2),lower-Su-1 member(SQ3),mid-Su-1 member(SQ4),upper-Su-1 member(SQ5),Su-2 member(SQ6),and Yingen formation(SQ7).The boundary faults in the faulted period(SQ1?SQ5)and the early stage of fault-depressed diversionary period(SQ6)have important controlling effects on the tectono-geomorphology and sedimentary filling of the depression.The faulting activity in the late stage of fault-depressed diversionary period(SQ7)is significantly weakened,the scope of the stratum has been significantly expanded.Several sedimentary facies have been identified in the target layer,including alluvial fans,fan deltas,slump turbidite fans,and lacustrine.In the Bayingebi formation,there is adequate supply of provenance.Coarse-grained deposits are relatively developed,and the sedimentary systems dominated by alluvial fans,fan deltas,slump turbidite fans,and lacustrine sediments.During the sedimentary period of Suhongtu formation,a large set of purple-red mudstones are generally developed in the whole area.Fan delta and lacustrine sediments is mainly developed in the study area.In the period of Yingeng formation,shore-shallow lacustrine developed in the most area and the lithology is characterized by fine grain deposits which mainly consist of gray and purple-red mudstones and siltstones.The analysis of paleogeomorphology,seismic facies and seismic attributes shows that the Ba-1 member provenance comes from multiple directions,including the west edge,the eastern edge and the central uplift.The uplifted area in Ba-2 member is denuded.The provenance is mainly from the west slope of the depression,the hanging wall of the boundary fault in the east,and the direction of the long axis of the depression.During the period of Suhongtu formation,the source system inherited the distribution pattern of provenance of the late Bayingebi formation.This study analyzed the petrophysical properties,oil-bearing properties,based on the characteristics of sedimentary microfacies and tectonic structures.The favorable reservoir facies belts mainly including of alluvial facies,fan delta front,and slump turbidite fans,and the favorable reservoirs are mainly located in Ba-1 member,Ba-2member and mid-Su-1 member vertically.