Study On Sedimentary Characteristics Of Qingshuihe Formation Of Cretaceous In Moxizhuang-Yongjin Area,Junggar Basin

Junggar basin is an important petroliferous basin in China.Moxizhuang-Yongjin area is located in the hinterland of Junggar Basin and.Jurassic-Cretaceous oil and gas reservoir is an important field of high efficiency oil and gas exploration because of its shallow burial,excellent reservoir and fast production.The unconformity surface at the bottom of Cretaceous provides a good channel for oil and gas migration.The glutenite at the bottom of Qingshuihe formation has great exploration potential.Good oil and gas have been obtained in many wells,and it is an important stratum for searching for large-scale reserves.This paper uses field outcrop data,logging data,chemical analysis data,etc to conduct a comprehensive study of the sequence and sedimentary facies of Qingshuihe Formation in Moxizhuang-Yongjin area.We established the sequence division plan of Qingshuihe Formation and the sequence stratigraphic framework of the study area,we also identified the sedimentary facies types and explored the sand body distribution characteristics.In Qingshuihe formation of Moxizhuang Yongjin area,three sequence boundaries are identified and two third-order sequences are divided.SB1 and Sb3 are regional stratigraphic unconformity,SQ2-HST is not developed,and SQ1-LST is not developed locally in Shawodi area in the northwest of the study area.SQ1-LST is mainly composed of thick sandstone,which is well developed in Moxizhuang area in the northeast and Yongjin area in the south of the study area.SQ1-LST in zhengshacun area is composed of mudstone.The whole thickness of sequence stratigraphy is thin in the West and thick in the East in the north of the study area,and there is little difference between the East-West thickness in the middle and south of the study area.According to the rock color,sedimentary structure and logging characteristics of Qingshuihe formation,the sedimentary facies of Qingshuihe formation in the study area is braided river delta-shore shallow lake sedimentary facies.LST mainly develops braided river delta front underwater distributary channel and mouth bar,while TST and HST mainly develop shore-shallow lake muddy and sandy sediments.The delta sandbodies of the early Qingshuihe formation are thick and well connected,which are well developed in Moxizhuang area and Yongjin area.Qingshuihe formation experienced the change of transgression,regression and transgression,and the sedimentary center moved to the South gradually.There are two types of traps in the study area: lithologic trap and lithologic-stratigraphic trap caused by structural inversion.Combined with logging interpretation,sand body distribution characteristics and sedimentary facies characteristics,it is considered that the lithologic stratigraphic trap formed from well Yong 2 to the north of well Yong 1 in Yongjin area is a favorable exploration area.