鄂尔多斯盆地西缘古峰庄-红井子地区长9油藏特征及油气富集规律

鄂尔多斯盆地西缘古峰庄-红井子地区地跨西缘逆冲带和天环坳陷两大构造。通过地震资料解释、地层对比和构造对比等识别发现该区存在两种类型的断层,早期的逆断层位于研究区的西部,呈南北向和北西-南东向展布;晚期的正断层分布于区的中部,呈北西-南东向展布。天环坳陷的形成与长7烃源岩分布及生烃高峰期在时空上匹配,促进了油气侧向运移并成藏。古峰庄-红井子地区长9油藏发育3种类型油藏:早期鼻状隆起带成藏、西缘逆冲带逆断层成藏和晚期天环坳陷内正断层成藏。前两种类型同期形成于早白垩世末期,形成时间较早,为原始油藏;后者形成喜山期,时间较晚,属改造型油藏。晚期断层对油藏进行重新调整,造成断层下盘油藏被破坏。建立了古峰庄-红井子地区长9油藏的成藏模式,总结其成藏规律为断层是油气运移的通道、异常压力和底水浮力驱动是油气运移的动力、连通宽广的砂体是油气运移的载体、泥岩和断层阻挡以及构造高点是油气运移的最终落脚点。

The characteristic of oil reservoir and the law of petroleum accumulation in Chang 9 reservoir in Gufengzhuang-Hongjingzi area, western margin of Ordos Basin

Gufengzhuang-Hongjingzi area which local in western margin of Ordos Basin span two tectonics of the thrust belt on the western edge and Tianhuan depression. By seismic interpretation, strata and structure correlations and core observation, two types of faults were found in study area. The early reversed fault is located at the west of the study area, and N-S and NW-SE trending, the late normal fault located at the middle, NW-SE trending. The time and space of Tianhuan depression and hydrocarbon-generating peak of Chang 7 hydrocarbon-generating rocks are matched which promotes the hydrocarbon lateral migration and accumulation. Three types of petroleum accumulation were discovered including early nose-like uplifts accumulation, the thrust belt on the western edge accumulation and late normal fault of Tianhuan depression accumulation. The first two types were formed in Early Cretaceous that forming time is earlier, as the original reservoir; the latter forms the Himalayan period, the forming time is late, is a modified form of reservoir. The formation of fault readjusts the reservoir, and causes the reservoir beneath the fault damaged. The accumulation model of Chang 9 reservoir was built in Gufengzhuang-Hongjingzi area. The law of oil migration can be summarize as following: the fault is the passage, abnormal pressure and driving of bottom-water buoyant are the force, widely connecting sand body is the carrier, mudstone and fault block and structural high are the ultimate goal.