鄂尔多斯盆地延长组长7和长8油层组流体过剩压力特征与油气运移研究

为了揭示鄂尔多斯盆地中生界延长组岩性油藏的成藏动力特征及油气运移规律，利用测井声波资料计算延长组各油层组的过剩压力值，分析延长组泥岩压实特征与流体过剩压力的分布特征，并以长8油藏为例探讨长7油层组和长8油层组之间的油气运移聚集规律。结果表明:延长组下部广泛发育稳定的欠压实带，长7油层组过剩压力值普遍较高，主要分布在8～14MPa之间，最高可达到18MPa；长8油层组过剩压力相对较低，只在局部地区达10MPa以上。泥岩厚度和性质是影响过剩压力分布的重要原因，高泥岩厚度分布区与过剩压力的高值区相吻合。长7油层组与长8油层组之间存在着较大的过剩压力差，该过剩压力差是油气纵向运移的主要驱动力；在横向上过剩压力低值区为油气运聚成藏的有利区。

Fluid Overpressure and Oil Migration in Chang 7 and Chang 8 Subsections of Yanchang Formation in Ordos Basin,China

In order to investigate the dynamic characteristics of reservoir formation and hydrocarbon migration in Yanchang Formation of Ordos Basin,this paper established a suitable normal mudstone compaction equation,studied the compaction characteristics of Yanchang Formation,analyzed the distribution of the fluid overpressure and discussed oil migration rule in Chang 7 and Chang 8 subsections.The results showed that the lower part of Yanchang Formation widely develops into uncompacted belt.The fluid overpressure of Chang 7 subsection is high compared to other subsections,ranging from 8MPa to 18MPa.The fluid overpressure of Chang 8 subsection ranges mainly from 2MPa to 12MPa.It was observed that the differences in thickness and property of mudstones affect the formation of overpressure.The region of high overpressure distribution is consistent with mudstone distribution.There is obvious difference in fluid overpressure between Chang 7 and Chang 8 subsections,which offers energy for vertical hydrocarbon migration.The distribution area of low overpressure is favorable area for lateral hydrocarbon migration accumulation.