三肇凹陷青一段油气向扶杨油层“倒灌”运移的最小超压及其研究意义

Fuyang oil layer in Sanzhao depression minimum overpressure value required for oil-gas migration downward

分析三肇凹陷青一段源岩生成排出的油气向扶杨油层"倒灌"运移条件,表明青一段源岩因具超压和油源断裂发育,其生成排出的油气可以向扶杨油层"倒灌"运移.分析油向下"倒灌"运移所受压力,表明油向下"倒灌"运移所需的最小压力应为断裂带毛细管阻力.统计三肇凹陷扶杨油层目前油底深度与青一段源岩在明水组沉积末期古超压之间的关系,表明三肇凹陷断裂带毛细管阻力约为5MPa,即青一段源岩生成排出的油气向扶杨油层"倒灌"运移最小古超压约为5MPa.利用最小古超压可以预测青一段源岩生成排出的油气向扶杨油层"倒灌"运移深度、层位和范围,以及扶扬油层油成藏与分布的有利区域.

By the analysis of geological conditions of migration downward of oil from K1qn1 source rock in Sanzhao depression,it was considered that there was overpressure and T2 source faults developed.Oil generated from K1qn1 source rock could migrate downward.According to pressure analysis of oil migration downward,minimum pressure required in oil migration downward should be capillary force of fault zone.Because the value can not be obtained directly,by the statistical relation between current depths of oil bottom in F,Y oil layers and ancient overpressure value of K1Q1n source rock in the end of K2m deposition period in Sanzhao depression,capillary force of fault zone in Sanzhao depression is about 5 MPa,or the minimum ancient overpressure value for migration downward of oil form K1Q1n source rock in Sanzhao depression was about 5 MPa.Obtaining of minimum ancient overpressure value for migration downward of oil from K1Q1n source rock has two significances for oil accumulation and distribution of Fuyang oil layer in Sanzhao depression:it can forecast area,depth and horizons of migration downward of oil from K1Q1n source rock and forecast favorable areas for oil accumulation and distribution of Fuyang oil layer in Sanzhao depression.