西湖凹陷X气田断层精细分析及其控藏作用

Refined Analysis of Faults and the Influence on Hydrocarbon Accumulation in X Gas Field in Xihu Sag

东海西湖凹陷X气田花港组上段油气藏为典型的下生上储成藏体系,早期研究认为主力H5层为简单的背斜构造,油气经背斜东侧沟源断层垂向运移后,再向高部位聚集。勘探开发实践证实H5层为多期次沉积的大型辫状复合河道,不同河道砂体具有不同的气水系统和含气丰度。为明确“一砂一藏”油气富集影响因素,该文利用宽频宽方位地震数据,结合最大似然属性,分析研究区断裂的分布、活动性及断裂组合样式,指出断层与H5层油气富集状况的关系,建立了H5层新的成藏模式。研究结果显示H5层存在两类优势的成藏模式,即油气经直接沟源断层与层内断层组成的阶梯状输导体系进行运移,以及通过直接沟源断层沟通源、储,向上聚集至高势区的模式。该研究成果指导了本区南部构造高区井位部署工作并取得显著效果,对同类型油气藏的油气勘探与滚动潜力评价具有借鉴作用。

The oil and gas reservoir in the upper section of Huagang Formation in X gas field is a typical lower-source and upper-reservoir accumulation system.The early research suggested that the H5 layer located in a simple anticline structure and the oil and gas vertically migrated through the source fault on the east side of the anticline and accumulated in the high area of traps.It turned out that the H5 layer was a large-scale braided channel with multistage deposition according to exploration and development.Different sand channel bodies developed independent petroleum systems and different gas abundance.In order to clarify the influencing factors of each reservoir's oil and gas accumulation model,this paper analyzed the distributions,activities and combination patterns of the faults based on the broadband and wide-azimuth seismic data and the maximum likelihood attribute,and pointed out the relationship between faults and hydrocarbon abundance,then established a new accumulation model of the H5 layer.The results show that there are two kinds of advantageous accumulation models in the H5 layer,one of which is the oil and gas migration through the stepped transport system composed of direct source faults and intra-layer faults,and the other is communicating source and reservoir through direct source faults and accumulating upwards to the traps height.The research results guide the well placement in the southern tectonic area and achieve remarkable effects,and have reference significance for the oil and gas exploration and potential evaluation of the same type of oil and gas reservoir.