安塞地区上三叠统延长组沉积体系研究

在野外剖面观察、岩心描述及测井、测试资料分析的基础上,对陕北安塞地区上三叠统延长组沉积体系的类型、特征及其时空演化等进行了分析。结果表明:安塞地区延长组主要发育湖泊、三角洲沉积。湖泊沉积体系主要由浅湖亚相和深湖亚相组成;三角洲沉积体系主要由三角洲平原亚相及三角洲前缘亚相组成。研究区长8期主要发育子长-吴旗三角洲和延安-甘泉三角洲。长7期安塞三角洲扩大,长6期安塞三角洲进入发育的鼎盛时期,三角洲前缘连片,面积最大。长4+5期以浅湖亚相为主,三角洲前缘分布范围有限。长3、长2期以三角洲平原沉积为主。沉积体系的演变,在纵向上构成了三套储盖组合,长8、长6及长2成为区内主要勘探目的层。

Sedimentary system of Upper Triassic Yanchang Formation in Ansai district

Based on the outcrop observing,core describing and data analyzing of well logging and testing,as well as labor measurement,the sedimentary systems of Upper Triassic Yanchang Formation in Ansai district is researched involving systems' classification,characteristic and evolution.The result shows that the lake and delta depositions are the main sedimentary systems in study area.The former is made of shallow lake and deep lake while the later are made of delta plain,delta front and mat sands.During Chang8 period,in the study area developed the Zichang-Wuqi delta and Yanan-Ganquan delta.In Chang7 period,Ansai delta began to form,and in Chang6 the delta get to its highest development.The delta fronts connect each other and possess the largest area.In Chang4+5 period shallow lake is the main subfacies.The delta front is limited.During Chang3 and Chang2 periods,the delta plain is dominantly developing.The evolution of the sedimentary systems formed three reservoirs and cap assemblages.As a result the intervals of Chang8,Chang6 and Chang2 are main exploration targets.