柴北缘西部油气藏分布与成藏特征

The Distribution of Petroleum Reservoirs and the Hydrocarbon Accumulation in West Part of Northern Margin of Qaidam Basin

由于地质条件和环境的不同,柴达木盆地北缘西部不同构造带及凹陷区油气分布及其运聚成藏具有不同的特征,断裂、不整合、生储盖组合及埋深是导致这些差异的主要地质因素,不整合和断层控制油气纵横向运移;生储盖组合制约油气分布的层位;埋深决定油气相态;断裂还导致大多数圈闭的形成并影响油气藏的保存。它们决定了柴北缘西部油气分布具有平面上南北成带、西油东气,纵向上油气主要分布于浅层滑脱断层下盘和深层断裂上盘的断展背斜圈闭中的特点,并控制了不同地区和构造单元油气藏类型,形成多种各具特征的运聚成藏模式。

Different features of petroleum distribution, migration and accumulation in different structural belts and sag areas occur in the west part of northern margin of Qaidam basin, due to the differences in geologic condition and enviromnent. The main geologic factors for these differences include the fault and unconformity that control the lateral and vertical migration of oil and gas, the source rock-reservoir- cap rock assemblage that controls the oil-gas distribution horizons and the burial depth that dete^nines the phase of oil or gas. In addition, the fault could result in the formation of most. traps, thus affecting the preservation of oil-gas reservoirs. It is these that are determine the petroleum dis^bution characteristics in the west part of northern margin of Qaidam basin, namely, being belts from north to south, with oil in the south and gas in the east in lateral direction; in the vertical the petroleum is mainly accumulated in anticline traps of footwall of shallow slip fault and upper wall of deep basement fault. These geologic factors still control the types of petroleum reservoirs and the oil-gas migration and accumulation patterns in different areas and tectonic units.