摘要:
根据钻井岩心、铸体薄片、扫描电镜、测录井资料及分析化验资料,对柴达木盆地北缘西段平台地区古近系路乐河组地层岩心的沉积构造、粒度特征、沉积序列等进行详细研究,分析平台地区古近系路乐河组的沉积相类型及演化过程。研究表明,平台地区路乐河组主要受近源沉积控制,沉积了一套以砾岩、含砾粗砂岩、泥质粉砂岩和泥岩为主的粗粒碎屑岩,发育槽状交错层理和板状交错层理,成分成熟度和结构成熟度较差。粒度概率累积曲线显示碎屑颗粒沉积物主要由悬浮组分和跳跃组分组成,表明水动力条件较强,以河流相沉积为主。沉积微相类型以河床亚相的河床滞留和心滩沉积为主,其次为河漫亚相的河漫滩沉积和泛滥平原沉积。沉积相的研究清楚展示出平台地区古近纪早期路乐河组的沉积特征和演化规律,为该地区下一步油气勘探工作提供可靠的地质依据。
Abstract:
The Qaidam Basin is a giant Mesozoic-Cenozoic petroleum basin in northwestern China. The present paper deals, on the basis of core examination, SEM, well logs and laboratory data, with sedimentary structure, grain size, sedimentary sequence and sedimentary facies types in the Lulehe Formation, Pingtai area, Qaidam Basin, Qinghai. The Lulehe Formation constrained by the proximal sediments is primarily built up of conglomerates, gravelly coarse-grained sandstones, muddy siltstones and mudstones with trough and tabular cross-beddings, and poor compositional and textural maturity. The grain size probability accumulation curves for the coarse-grained clastic rocks cited above are characteristic of the fluvial deposits composed of suspension and saltation populations, and indicate relatively strong hydrodynamic conditions during the deposition of the Lulehe Formation. The sedimentary microfacies consist mainly of channel lag deposits and channel bar deposits in the channel subfacies, and overbank deposits and flood plain deposits in the flood subfacies. This study will provide reliable geological data for the future petroleum exploration in the study area.
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