鄂尔多斯盆地柴窑区延长组油气二次运移动力

Dynamical of the secondary migration of the petroleum in Yanchang Formation in Chaiyao block,Ordos Basin

计算了浮力要克服毛细管压力所需的连续油柱的高度和长度,发现计算的克服毛细管压力所需油相连续长度远大于目前延长组已发现油藏含油带宽度.因此,浮力无法克服毛细管压力,不能成为研究区长3—长6油层组油气进行二次运移的主要动力.根据平衡深度法,计算了各个层位的孔隙剩余压力.发现自长3油层组之下,各套地层均存在孔隙剩余压力,且在长7油层组达到最大值.源储压力远大于毛细管压力,可以克服毛细管压力而使油气运移.因此孔隙剩余压力是研究区长3—长6油层组油气进行二次运移的主要动力.

The height and the length of the continuous oil column required to overcome capillary pressure are calculated.The results show that the width of the discovered oil-bearing belt in Yanchang Formation is far less than the length of the continuous oil column required to overcome capillary pressure.Therefore buoyancy cannot overcome the capillary pressure,and it should not be the major driving force for the secondary migration of hydrocarbon in Chang 3-Chang 6 strata.The remaining pore pressure of each stratum is calculated according to balancing depth method,it is found that the remaining pore pressure exists in every strata below Chang 3 stratum,and it reaches to the maximum in Chang 7 stratum.The pressure difference between source rock and reservoir is far greater than the capillary pressure,and it can overcome the capillary pressure to make the hydrocarbon migrate.Therefore the remaining pore pressure is the major driving force for the secondary migration of hydrocarbon in the studied area.