鄂尔多斯盆地镇泾地区中生界油气二次运移动力研究

Dynamic of Mesozoic Hydrocarbon Secondary Migration in Zhenjing Oilfield,Southwestern Ordos Basin

鄂尔多斯盆地西南缘镇泾地区中生界油藏具有储层致密、丰度低、储量大的特点,已钻遇的多口高产井显示出中生界具有良好的油气勘探潜力。西南缘中生界具有多个油气成藏动力系统,不同的油气成藏动力系统具有不同的二次运移动力和通道。通过埋藏史、泥岩压实曲线及物性特征等研究,认为长8段超低渗透油藏的二次运移动力为上覆烃源岩的异常压力,通道主要为渗透层;长6段特低渗透油藏的二次运移动力主要为下伏烃源岩的异常压力,局部为浮力,通道主要为裂缝,其次为渗透层;而延安组油藏的二次运移动力为浮力,通道为裂缝、不整合面和渗透层。对油气二次运移动力和通道的研究,可以更加精细追踪油气运移指向,为鄂尔多斯盆地西南缘下一步的油气勘探提供理论依据。

The Mesozoic reservoirs in Zhenjing oilfield is characterized by tight reservoirs,low permeability,low abundance and large reserves.It has favorable exploration potential which is shown by the drilled high-yielding wells.Previous studies indicate that there are multiple dynamic systems for hydrocarbon migration and accumulation in the southwestern Ordos basin.And different systems have different dynamic and carrier path for secondary migration.Through the research on buried history,mudstone compaction curve and physical property of reservoirs,it is concluded that the dynamic of secondary migration in Chang8 Member with ultra-low permeable reservoir is overlying abnormal pressure but Yan＇an reservoir is buoyancy.Besides,hydrocarbon in Chang6 Member reservoir which is characterized by low permeability accumulated through underlying abnormal pressure mainly and buoyancy locally.Furthermore,permeable bed is the chief carried path in Chang8 Member,while fracture becomes the primary path in Chang6 Member.Permeable bed is the subordinate way for Chang6 Member reserviors.As for Yan＇an Formation,various channels including fracture,unconformity and permeable bed could carry hydrocarbon.From the study on dynamic and carrier path of secondary migration,tracking the hydrocarbon movement can become more accurate and exploratory theories for further exploration.