异常压力与油气藏的同生关系——以库车坳陷为例

Syngenesis relationship between abnormal overpressure and gas pool formation—With Kuqa Depression as an example

以库车坳陷克拉2气田为例,研究挤压背景异常压力与油气成藏的关系。大规模抬升早期阶段是天然气注入的主要时期,同时也是气藏压力急剧增加的时期。克拉2气藏的成藏模式总体为深大断裂沟通储集层和烃源岩层,在深部超压的驱动下油气运移至储集层成藏。储集层在成藏早期不是强超压,并且不完全封闭,可以存在流体排出过程。随着天然气替换构造圈闭中的地层水和成岩作用逐渐进行,储集层封闭性加强,气藏压力不断升高,最后形成超压气藏,气藏强超压形成于距今2Ma以来。异常高压与气藏的形成均是构造作用和保存条件演化的结果,二者本身不具备因果关系。气源断层与盖层完整的匹配是控制天然气成藏的关键因素。

The paper analyzes the relationship between abnormal overpressure and gas pool formation in the tectonic compression environment, taking the Kela 2 gas field of Kuqa Depression as an example. In the earlier cosmic elevating, most gas is injected into pool and the pressure of gas accumulation rises rapidly. The hydrocarbon accumulation model of Kela 2 is that the reservoir and source rocks are communicated by faults, and oil and gas driven by superpressure migrate into reservoir and accumulate. In the earlier accumulation, the reservoir has no strong superpressure and is not closed. The fluids can outflow from it. With the natural gas replacing water in the structural trap and the diagenesis, the liquid pressure of gas accumulation rises and the overpressure pool is formed no more than 2 Ma ago. Abnormal overpressure and gas accumulation are the results of structural event and conservation condition; there is not a cause-effect connection between them. The perfect match between gas source and seal is the key factor of gas accumulation.