Study On Structure And Sedimentary Facies Of Oil Group Ⅳ In Yangqian-1 Fault Block

Located in Yanglou structural belt of Wangji Delta,Yangqian-1 fault block is an oil-bearing block of Yanglou oilfield with an area of 9km2.The oil-bearing target interval is the 4th oil group of the 3rd member of Hetaoyuan Formation.In view of the unclear understanding of the structure of the study area,the unclear block sealing conditions,the unclear distribution law of sedimentary microfacies and sand bodies,and the unclear law of oil and gas accumulation,these problems not only affect the exploitation and production of drilling completion,but also make it difficult to carry out further exploration work.In this study,Yangqian-1 fault block is taken as the research object,based on 3D seismic,well logging,core observation and description of core well,core analysis and other data,and referring to previous geological research results,the formation marker ofⅣ oil group is identified,and the formation division and correlation are carried out.The three dimensional seismic structure interpretation was carried out,and the top structure maps of the two main sub-strata were compiled.The petrological characteristics are studied to determine the types of rock facies and sedimentary microfacies.The petrological research is combined with logging phase analysis,and the petrological research is calibrated to the logging curve to provide a basis for the comprehensive and systematic study of sedimentary microfacies and providing technical support for increasing storage and production in the study area.The results show that:(1)The oil group Ⅳ lacks a large set of stable mudstone segments and typical marker beds,but the sedimentary cycles and associations of the oil group Ⅳ are clear.Based on the control of sedimentary cycles and the combination of well and earthquake,the oil group Ⅳ is divided into 9 small beds.(2)Compared with the previously compiled structural map,F3 fault changes from the original northeast direction to nearly east-west direction,F4 fault changes from the original northeast direction to "S" type fault,and the western part of the fault is connected with F3 fault.After the two faults are connected,a north-south sealing condition is formed.(3)The color of oil group Ⅳ is mainly gray,light gray and light gray green.The lithology is mainly siltstone,fine sandstone and pebbled sandstone,sandstone contains a small amount of conglomerate;The sedimentary structures such as scour surface,massive bedding,cross bedding,parallel bedding,horizontal bedding and deformation can be seen in the rocks.(4)The depositional system is braided river delta,the provenance direction is from the north,and the delta phyllosomes extend nearly north-south in the Yangqian-1 fault block.(5)The oil group Ⅳ mainly develops delta front and foredelta subfacies.The depositional microfacies include 6 kinds of depositional microfacies,such as estuarine bar,underwater distributary channel,sheet sand,far sand bar,interdistributary bay and foredelta mud.