油气藏烃类垂向微渗漏的实验模拟

摘要

利用自行研制的物理模拟实验装置,对油气聚集成藏以后其中的烃类穿过上覆盖层运移至地表的过程进行了实验室模拟.实验证实,油气藏中的烃类气体由于与外部地层存在压力、浓度的差异而发生渗透和扩散,即微渗漏作用,方向主要是垂向的.垂向微渗漏致使油气藏中的烃类气体可以穿过上覆盖层直至到达地表,现代测试仪器可以在地表检测到来自深部地层的渗漏烃.同时发现,烃类垂向微渗漏具有间歇性、伴有幕式的特点.基于长期观测和实验模拟的结果,提出"气相压驱裂隙渗透"可能是近地表烃类化探异常的主要成因机制.%A laboratory simulation of the migration process of the hydrocarbons through the overlying cap rock to the surface of the earth has been carried out by means of the self-developed physical simulation device. The results show that the hydrocarbons in the reservoir can permeate and diffuse due to the pressure difference and the concentration difference between the reservoir and its surrounding strata, which is described as micro-seepage, and the direction of this micro-seepage is mainly vertical. It is this vertical micro-seepage that drives the hydrocarbons from the reservoir to migrate through the cap rock and eventually reach the surface of the earth, and the migrated hydrocarbons can be detected by modern apparatus and equipment in the surface. The results also show that the vertical hydrocarbon micro-seepage is characterized by intermittent and episodic migration. A new theory of "gas phase permeation along fracture driven by pressure" has been proposed as the possible main formation mechanism of the near-surface geochemical anomaly based on these simulation results and the long-observed results.