Facing the challenges of extremely high water cut,developed preferential channels,highly dispersed remaining oil,and strong heterogeneity in nearly abandoned reservoirs,the study focuses on the 4-5 layer series of the North Block Ⅱ(Oil Group No.2)in the Shuanghe Oilfield.By employing detailed reservoir geological modeling,numerical simulation methods,and microscopic displacement experiments,the distribution characteristics of remaining oil after polymer flooding were characterized.Post-polymer flooding,the remaining oil saturation is higher in areas away from the main streamlines on the macro scale,including non-mainstream areas,weak zones along main streamlines,and peripheral areas with larger injector-producer distances.Vertically,remaining oil tends to accumulate at the top of positive rhythm sequences.Microscopically,the remaining oil is primarily in the form of semi-bound state.Based on the characteristics of remaining oil distribution,a technical concept of heterogeneous composite driving and streamline well pattern densification adjustment was proposed.By adjusting the well pattern to alter streamlines,creating a staggered row and column well pattern with a change in streamline direction of over 30 and a streamline deflection rate of 80％,the effective mobilization of remaining oil is promoted.Numerical simulation predicts that this technique could increase the recovery factor by 10.96％,add 706.1 thousand tons of recoverable reserves,and extend the life cycle by 15 years.This offers a new technical approach for significantly enhancing the recovery factor of reservoirs after polymer flooding.
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