柴达木盆地北缘冷湖-南八仙构造带异常高压特征

Abnormal High Pressure Feature in Lenghu-Nanbaxian Structural Belt in Northern Margin of Qaidam Basin

柴北缘冷湖-南八仙构造带从新近系到侏罗系普遍存在异常高压,且通常发育在欠压实泥岩中。柴北缘异常高压主要由欠压实作用、生烃作用及构造挤压作用形成。侏罗系原生油气藏和古近系、新近系次生油气藏的泥质岩盖层不仅是异常高压层,同时又具有较好的压力封闭,控制着油气在纵向上的分布,异常高压层下方是油气富集的有利部位,异常高压层是柴北缘地区一种良好的封盖层。研究柴北缘地区异常高压的特征、成因以及对油气的封闭作用,对该区油气勘探与开发具有重要的意义。

Abnormal high pressure is found from Neogene to Jurassic in Lenghu-Nanbaxian structural belt in the northern margin of Qaidam basin, and mostly occurs in undercompaction shale. It was primarily formed by undercompaction, hydrocarbon generation and tectonic compression. The shale caprocks in Jurassic primary hydrocarbon reservoir and Tertiary secondary reservoirs are both abnormal high pressure zones and good pressure-sealed ones, which control the vertical distribution of hydrocarbons. The study shows that the under the abnormal high pressure zone which can be as a good sealing or cap rock is favorable for hydrocarbon enrichment and for exploration and development in the northern margin of Qaidam basin.