松辽盆地徐家围子断陷营四段沉积相研究

RESEARCH OF SEDIMENTARY FACIES OF FORTH MEMBER OF YINGCHENG FORMATION IN XUJIAWEIZI FAULT DEPRESSION IN THE SONGLIAO BASIN

徐家围子断陷是一个构造格局呈西断东超、地层厚度西厚东薄的箕状断陷盆地,在沉积上具有多沉积中心、多物源和近物源的特征,北部安达地区火山是主要物源区。通过对研究区20多口井的岩心观察、以及测井、录井、地震和分析化验资料等的综合研究认为,徐家围子断陷营四段主要发育一套以粗砂岩—粗砾岩为主的河湖相粗碎屑沉积,主要发育7大岩相类型和5大沉积体系;其中,营四段下亚段在研究区北部主要发育扇三角洲沉积体系,南部则主要发育冲积扇和泛滥盆地;营四段上亚段,在宋西断层以东主要发育辫状三角洲体系,而以西主要发育扇三角洲沉积体系,南部则主要发育河流三角洲体系;在各沉积体系前缘则发育滨浅湖沉积。

The Xujiaweizi Fault Depression is a half graben-like fault basin that is fault in the west and transgression in the east in tectonic style,and that is thicker in the west and thinner in the east in formation thickness.There have the characteristic of multi-depocenter,many and near matter source.The volcano is the main matter source in Anda aera.By means of the research of rock core observation more than 20 wells,and well logging,seismic,test data and so on,there has chiefly a set of coarse fragment sedimentation of river and lacustrine facies from gritstone to cobblestone in K1yc4;there are 7 lithofacies types and 5 depositional systems.In it,there are fan delta sedimentary system in the north of research area in the lower member of K1yc4,there are alluvial fan and flood basin in the south.There are mainly braided delta sedimentary system in the east of Songxi Fault and fan delta sedimentary system in the west of Songxi Fault in the upper member of K1yc4;there are mainly delta sedimentary system in the south.But there are shore and mere sediment in the front of every depositional system.