Application of Polymer-Surfactant Flooding in Ultra-Low Permeability Reservoir in Jiyuan Area

The ultra-low permeability reservoir in the Jiyuan Oil field exhibits intricate injection-production relationships following multiple cycles of water flooding, limited efficacy of conventional water flooding treatment, uncertain water control, accumulation of residual oil between wells, and suboptimal efficiency of water flooding recovery. In order to achieve the goal of enhancing water flooding treatment effect and improving reservoir recovery, a polymer surfactant composite system displacement test and on-site practical effect evaluation were carried out. The comprehensive indoor experimental results and on-site practical dynamic response research indicate that: ① Surface active agents exhibit significant interfacial activity and emulsifying properties within oil displacement systems, leading to pronounced oil washing effects. Polymer micro-spheres primarily serve the purpose of deep profile control and flooding, thereby extending the scope of water flooding and augmenting the sealing efficacy; ② Polymer microspheres and surfactants are introduced in alternating cycles through the utilization of slugs, leading to a heightened stability in the treatment effect of water flooding; ③ The high water content well group primarily serves to diminish water content and enhance oil production in the primary direction of water drive, albeit with a relatively short validity period of less than six months. Conversely, the medium water content well group predominantly focuses on augmenting oil production in the lateral direction of water drive, with a duration exceeding six months; ④ The main types of wells in the well pattern are water cut reduction and effective reduction (56.5%), while the lateral wells in the well pattern are mainly effective in increasing oil production (43.5%). This study presents the inaugural polymer surfactant composite flooding experiment conducted in the G271 ultra-low permeability reservoir. Through rigorous experimental analysis, it has been elucidated that the interfacial activity and emulsification performance of the composite flooding system significantly enhance oil recovery. These findings shed light on the synergistic mechanism underlying the interfacial activity and emulsification performance in improving oil recovery, thus elucidating the mechanism of composite flooding in ultra-low permeability reservoirs and assessing its practical applicability and effectiveness.