柴达木盆地第四系层序地层特征与油气评价

依据起源于被动大陆边缘海相盆地的层序地层学基本原理,对缺乏地形坡折的柴达木盆地第四系进行了层序地层研究。通过对野外露头、岩心、测井和地震资料的综合研究,将柴达木盆地第四系划分为5个沉积层序,并总结了层序边界和最大湖泛面的识别标志。指出没有地形坡折的陆相盆地沉积层序仅由下部的湖侵体系域和上部的湖退体系域组成。湖侵体系域多由几个退积式准层序组构成,向上砂泥比减小;湖退体系域多由几个井积式和加积式准层序组构成,向上砂泥比值加大。湖侵体域常在气候湿润、物源供给较多时形成,易形成广泛分布的烃源岩和三角洲,准坝成因的储集体;湖退体系域常在气候干旱、物源供给较少时形成,易形成广泛分布的泥岩和青盐岩盖层。

Quaternary sequence stratigraphy and hydrocarbon evaluation in Qaidam basin

The Quaternary of Qaidam basin, being lack of topographic break, was studied based on the theory of sequence stratigraphy, which originated from marine basins in passive continental margin. Through comprehensive researches on outcrops, cores, well logging and seismic data, the Quaternary of Qaidam basin was divided into five sequences. The distinct characteristics of sequence boundary and maximum flooding surface have been identified. The sedimentary sequence in a continental basin, which is lack of topographic break, only consists of lower trangressive system tract and upper regressive system tract. Trangressive system tract is composed of several retrogradation parasequence sets, its sand shale ratio is decreasing upward; regressive system tract mostly consists of prograded parasequence sets, its sand shale ratio is increa sing downward. The former was formed during moist climate with much material feeding and developed good source rock and reservoirs of delta and beach bar. The latter was formed during arid season with less material feeding and constituted good caps of mudstone and salt.