Development features and controlling factors of deep-water turbidite fans in north slope of Chezhen sag-A case study of the block Che66 in the lower third member of Shahejie Formation
On the basis of cores observation and samples analysis,the development features of deep-water turbidite fans in the block Che66 of Chezhen sag were analyzed and then the factors controlling development of deep-water turbidite fans were determined by using logging data and seismic data. The results show that deep-water turbidite fans in the block Che66 slumped and were buried deeply,and their lithology are cobble and pebble-conglomerates composed of micrite gravel,interbedded with thin or thick dark mudstone or shale. They graded poorly. Sand bodies of single stage are characterized by normal graded sequence,and they overlay each other in different stages in the whole with characters of reverse cycle changing coarse and thick upward. Four sets of sand body developed from the bottom in the lower third member of Shahejie Formation in the area with two provenances in northwest and northeast respectively,which overlay vertically. The sedimentary period of deep-water turbidite fans in Che66 area is corresponding to low stand system tract or lacustrine transgressive system tract of the 3rd grade sequences in the intensively faulting period. Their distributions are controlled by basin edge boundary fault activity,the occurrence and the development of the wide slope deep area in scraper structural fault resulted from the secondary fault and fracture development. There are typical turbidite rocks developed in such area under the configuration of source-slope-sag(source-faulted slope-sag)in the north of steep slope of Chezhen sag,and their distribution of fans are controlled by the double-source supply of different directions.