盖层力学性质及其应力状态对盖层封闭性能的影响——以克拉2气田为例

INFLUENCE OF MECHANICAL PROPERTIES AND STRESS STATE OF CAPROCK ON ITS SEALING PERFORMANCE:TAKING KELA-2 GAS FIELD AS AN EXAMPLE

应力对盖层的封闭性能有着不可忽视的影响作用。根据岩石发生破裂的应力条件和不同岩性盖层力学性质的差异,从理论上探讨了盖层力学性质及其应力状态对盖层封闭性能的影响,指出应力状态直接决定了盖层所能承受最大超压的大小,应力对不同岩性盖层封闭性能的影响程度和影响方式也不一样。并以克拉2气田为例,利用三维应力场数值模拟方法,定量分析了盐膏层的力学性质及应力状态对其封闭性能的影响,指出下第三系盐膏层对克拉2超高压气田形成具有决定性的作用,构造挤压并不是克拉2气藏超高压的主要原因。

Stress is very important to the sealing properties of caprocks.The influences of mechanical properties and stress state of caprock on its sealing properties are studied theoretically according to the stress conditions of fracturing rocks and the differential mechanical properties of caprocks with different lithologies.Taking Kela-2 gas field as an example,the influences of stress state on sealing properties of caprocks are analyzed quantitatively through numerical simulation of 3D stress field.It is believed that the Lower Tertiary evaporate sequence is a determinant to the formation of the large Kela-2 gas field.This is an important complimentary to the conventional comprehensive evaluation method of sealing properties.