琼东南盆地X型共轭正断裂及其油气勘探意义

X-Type Conjugate Normal Fault in Qiongdongnan Basin and Its Significance in Oil-Gas Exploration

X型共轭断裂是正断裂的一种典型组合样式,琼东南盆地发育2套典型的X型共轭正断裂:主要分布在凹陷内和凸起的边缘。从剖面特征解析和空间组合样式归纳入手,结合前人研究实例及模拟实验结果,对其形成机制、演化模式进行了探讨。该盆地所发育的X型共轭正断裂是在北西向纯剪切作用下形成的,每组共轭断裂体系的形成具有同步性,其组合样式与最大张应力方向、古地貌及其边界条件有关。它们的存在表明了琼东南盆地发生过2次北西向纯剪切作用。X型正断层不仅可以作为油气运移通道,还可以改善岩石的储集条件,通过蚂蚁自动追踪(Anttracking)技术发现,基岩潜山内部发育X共轭断裂,可见琼东南盆地潜山基岩油气藏是重要的油气勘探领域。

X-type conjugate fault is a typical combination style of normal faults. There are two sets of such a fault in Qiongdongnan basin, mainly found in inner sag and marginal swell. This paper discussed its formation mechanism and evolution pattern in view of its section feature and space combination style, combined with.previous case studies and simulated experiment results. It is recognized that this X-type conjugate normal fault in this basin is formed under the NW pure shear process, and the formation of each group of conjugate fault system is of synchronism and the combination styles are related with the maximum tensile stress orientation, the ancient landform and their bound- ary conditions. Their existence suggests that Qiongdongnan basin underwent two times of such a shear process. The X-type normal fault not only serves as hydrocarbon migration pathway, but also improves the quality of reservoir rocks. It is indicated from analysis by ant tracking technique that X-type conjugate normal faults could exist in interior of ancient basal buried hill in this basin, so the buried hill basement reservoir could be the important domain for further petroleum exploitation in this basin.