Study On Sedimentary Characteristic And Accumulation Regularity Of The Permian Lower Urho Formation In The Dabasong Bulge Of The Junggar Basin

The Dabasong bulge is located in the north western part of the central sag of the Junggar Basin.adjacent to the two major hydrocarbon-generating sags of Mahu and the west of Well Pen 1.It is a favorable direction for hydrocarbon migration in the two major hydrocarbon-generating sags.This study takes the Permian Lower Urho Formation in the Dabasong bulge of Junggar Basin as the research object,combined with previous research results,and comprehensively applies drilling and well logging,core analysis and laboratory data to finely divide and compare the strata.,Based on the analysis of sedimentary evolution characteristics,summarized the oil and gas accumulation conditions in the study area,analyzed the main controlling factors of oil and gas accumulation,established the oil and gas accumulation model,and finally clarified the law of oil and gas accumulation in this area.Mainly obtain the following knowledge:(1)Selecting typical wells,comprehensive drilling and well logging,and seismic data,the Permian Lower Urho Formation stratigraphic division and comparison plan of the Permian in the Dabasong bulge zone is determined,and the Lower Urho Formation is divided into the Lower Urho Formation from bottom to top.The first member of the Lower Urho Formation(P₂w₁),the second member of the Lower Urho Formation(P₂w₂),the third member of the Lower Urho Formation(P₂w₃),and the fourth member of the Lower Urho Formation(P₂w₄).Make a reasonable comparison between.(2)Through comprehensive analysis of drilling,logging,logging,and core data,a typical sedimentary facies sequence has been established.The study area mainly develops fan delta-lacustrine facies deposits,which can be further divided into distributary channels,interdistributed channels,and underwater distributaries.Mud microfacies between river channels,underwater distributary channels,estuaries,and coastal shallow lakes.The corresponding sedimentary facies model was established on the basis of detailed research on the sedimentary facies characteristics and sedimentary evolution laws of the Urho Formation in the lower Dabasong bulge.From the first member of the Lower Urho Formation to the fourth member of the Lower Urho Formation in the Dabasong bulge,the lake level continues to rise,and the area of coastal shallow lake subfacies continues to expand.During this period,the provenance was sufficient,and the front edge of the fan delta developed sand bodies.(3)The oil and gas of the Permian Lower Urho Formation in the Dabasong bulge mainly comes from the source rocks of the Fengcheng Formation.The deep faults and channel sand bodies provide channels for the vertical and lateral migration of oil and gas.(4)The favorable conditions for oil and gas accumulation in the Lower Urho Formation in the Dabasong bulge are summarized.The source rocks of the Fengcheng Formation have a wide distribution area and strong hydrocarbon generation intensity,which provides a rich source of oil for the Lower Urho Formation.The reservoir type is low porosity-low permeability,and mudstone caprock.With the development of structural traps,the dominant drainage systems are mainly deep faults and channel sand bodies.The reservoir types are mainly fault-lithologic reservoirs and fault block reservoirs.Faults,sedimentary facies belts and nose structures are important factors for hydrocarbon accumulation,and a three-dimensional hydrocarbon accumulation model in the Lower Urho Formation of the Permian in the Dabasong bulge has been established.