鄂尔多斯盆地长9油层组石油运聚规律研究

Oil Migration and Accumulation Rules of Chang-9 Oil-Bearing Formation in the Ordos Basin

鄂尔多斯盆地长9油层组是一个新发现的含油层。迄今为止,有关长9油层组石油运聚成藏机理尚不清楚,特别是对石油运聚规律缺乏认识。该问题的解决会进一步完善鄂尔多斯盆地中生界延长组石油成藏理论;同时,对长9油层组石油勘探开发具有重要的指导作用。我们对长9油层组石油来源、油气输导体系、油气运移路径和油气运移动力等油气运聚条件特征及其不同地区差异进行了研究,结果表明,长9油层组原油主要来自长7烃源岩,只有在志丹局部地区来自长7和长9烃源岩;长9油层组石油的纵向运移路径是由上向下运移;孔隙型输导体和断层、构造裂隙输导体是长9油层组石油运移的主要输导体;盆地长7油层组普遍存在高过剩压力带,长7与长9油层组之间存在较大的流体压力差,因此长7油层组生成的油气在高过剩压力驱动下可以向下运移,进入储层物性相对好的长9砂体聚集成藏。同时,建立了3种长9油层组油气运聚模式,讨论了长9油层组油气运聚机理。

Chang-9 subsection of the Yanchang Formation is a new oil-bearing formation discovered in the Ordos basin. So far, the mechanism of oil migration and accumulation in the Chang-9 oil-bearing formation, especially oil migration, is still unknown. Resolving of this problem can perfect the theory of oil poolforming in the Mesozoic Yanchang Formation in the Ordos Basin, and will play an important role in guiding oil exploitation and development. This paper focused on characters of source, transport system, migration pathway and power （so on） of oil in Chang-9 oil-bearing formation, and their differences in different areas. The results show that crude oil of the Chang-9 oil-bearing formation originated mostly from the Chang-7 subsection of the Yanehang Formation, with oil in the Zhidan region partially from Chang-7 and Chang-9 subsections. The Chang-9 erude oil migrates from upper to down. Pores in sandstone, structural fissures, and faults are dominant channels to transport crude oil. Overpressure zone commonly exists in the Chang-7 subsection of the Yanchang Formation and an apparent difference of fluid pressures between Chang-7 and Chang-9 subsections was also observed. Therefore, oil generated in the Chang-7 subsection can migrate downward driven by residual pressure in the overpressure zone, and charge in the Chang-9 sandstone reservoir with better physical property. This paper proposed three models of oil transport and accumulation for the Chang-9 oil formation and also discussed their mechnisams.