鄂尔多斯盆地延长组致密油成藏控制因素

Controlling Factors of Tight Oil Reservior in Triassic Yanchang Formation in Ordos Basin

鄂尔多斯盆地延长组发育我国典型的低渗透和特低渗透油气资源,其油藏呈现出储层致密、储集砂体预测难度大、成藏机理复杂等特征。目前,根据勘探开发实践,长庆油田成功实现对渗透率大于0.3×10-3μm2油藏的开发,目前正在开展渗透率为（0.1~0.3）×10-3μm2致密砂岩储层的技术攻关。笔者结合国外最新致密油气资源研究成果和鄂尔多斯盆地延长组低渗透油藏的特征,从延长组致密油分布、致密油流体特征、赋存状态、储集体和致密油形成的控制因素入手,对鄂尔多斯盆地延长组致密油形成与分布规律进行了探讨。确定了延长组致密油形成的控制因素：1长7优质烃源岩分布范围广,生烃强度大,为致密油形成提供了充足的油源供给和资源基础;2大面积广泛展布的复合叠加的碎屑岩储集体,为致密油藏形成提供了储集空间;3油页岩与致密砂岩互层共生,形成了近源成藏的有利配置关系;4成藏期生烃增压,致密储层石油充注程度高,为致密油形成提供了运移动力。

Ordos basin is a typical area of distribution of low permeability and ultra-low permeability oil reservoirs.Triassic Yanchang Formation is rich in low permeability oil reservoirs.They are characterized by many sets of thin sand layers containing oil with large reserve,low reserve abundance,and low single well production.Based on exploration and development practices,greater than 0.3×10-3μm2 permeability reservoirs have been well exploited in Changqing oilfield,while（0.1-0.3）× 10-3μm2tight sandstone reservoir is currently the focus for exploration and development.The controlling factors of tight oil reservoirs in Triassic Yanchang Formation were investigated.The tight oil in Yanchang Formation is featured as large-sized sand body complex,tight reservoir,complicated pore throat structure,high content of rigid components,abundant fracture and saturation,low fluid pressure,et al.The forming of the large-scaled superimposed tight oil reservoir is controlled by the combination of the interbed lithology of wide-ranging source rock and reservoirs with strong hydrocarbon generation and expulsion during the geological history.