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.