柴西南区古近系层序地层特征及岩性圈闭发育模式

应用层序地层学理论,利用地震、钻井和测井资料,对柴西南地区古近系层序地层框架进行系统分析.古近系处在以中新统内不整合面(T2′)和古新统合新生界之间的不整合面(TR)为顶底界的二级层序中,共发育有3个三级层序:即路乐河层序(SA)、下干柴沟层序(SB)和上干柴沟层序(SC).重点分析了下干柴沟层序及上干柴沟层序,认为下干柴沟层序由3个体系域组成:即低位体系域、湖侵体系域及高位体系域.上干柴沟层序由于低位体系域不发育,故将其划分为湖侵体系域和湖退体系域两个体系域.另外,分析了柴西南地区不同的体系域中岩性圈闭可能发育位置,并且建立了隐蔽圈闭的分布模式.

Sequence stratigraphic feature of the Paleogene strata in the southwestern area of Qaidam Basin and the distribution mode of the subtle traps

Based on seismic,drilling and logging data,the sequence stratigraphic framework of the Paleogene strata in the Southwestern area of Qaidam Basin is analyzed using the theory of sequence stratigraphy.The Paleogene strata can be divided into 3 third-order sequences:the Lulehe Sequence(SA),the Lower Ganchaigou Sequence(SB)and the Upper Ganchaigou Sequence(SC),and all these 3 third-order sequences are in one super-sequence which takes the T2’and TR unconformity surfaces as the top and the bottom interfaces.The SB and SC are emphatically analyzed.It is held that SA is composed of a lowstand system tract (LST),a transgressive system tract (TST) and a highstand system tract (HST),while the SC is just composed of a transgressive system tract and a gressive system tract because the LST isn't developed.On the other hand,the positions where the lithologic traps are possibly in different system tracts are emphatically analyzed,and the distribution mode of the subtle traps in the sequence stratigraphic framework is established.