柴达木盆地东部地区不整合与油气成藏的关系

Relationship between Unconformity and Hydrocarbon Accumulation in the Eastern Qaidam Basin

本文论述了柴达木盆地东部地区不整合类型与控油特征、不整合结构与油气运聚特征以及不整合运聚油气的成藏模式。柴达木盆地东部地区经历了多次构造运动的改造,形成了多个不整合。根据不整合在油气运聚中的作用,以不整合的成因机制及地震反射特征为基础将柴达木盆地东部地区不整合划分为褶皱、断褶、削截、超覆和平行5种类型。风化剥蚀程度的不均一性使不整合具有典型的层状结构,即不整合面之上的岩石、风化粘土层和半风化岩石。不整合纵向分层结构构成油气运移的双重通道,同时为油气聚集提供良好的储集空间和圈闭条件。不整合发育部位及剖面形态的差异,导致不同类型的不整合形成不同的油气成藏模式。

This study discussed the relationship between structural type and oil-gas migration-accumulation, unconformity type and oil trap, and unconformity and the hydrocarbon-forming pattern of unconformity migration-accumulation in eastern Qaidam Basin. The Qaidam Basin has undergone multistage tectonic movements and formed several unconformities. The unconformities of the eastern Qaidam Basin can be divided into drape unconformity, fault-fold unconformity, truncation unconformity, onlap unconformity and parallel unconformity in terms of the function of unconformity migration-accumulation and their forming mechanisms as well as reflection characters in seismic sections. They are of typical stratiform structure due to uneven weathering and eroding processes, including overlying rocks above the unconformity interface, such as weathered clay and semi-weathered leached zone. Vertical stratiform structure of unconformities provides not only dual pathways for oil and gas migration, but also accommodation space for oil and gas accumulation. It was the position and diversity of unconformity developed that resulted in different models of oil and gas reservoir formation under various settings of unconformity.