An Integrated Experimental and Numerical Study on Water-Cut Control and Production Enhancement Strategies for Low-Permeability Reservoirs Under Edge-Water Encroachment

Block 116 has an annual oil production of 10.2 × 10 4 t, yet the increasing edge-water encroachment has raised the natural decline rate from 7.8% to 11.4%, significantly deteriorating production performance. The field data shows an edge-water rise rate of 0.4 m/a. Since 2023, 11 flank wells have experienced water breakthrough, resulting in a daily loss of 12.6 t and contributing 4.6% to the overall decline. To address these challenges, this study systematically evaluates development characteristics, identifies key influencing factors, and establishes optimal injection–production parameters through an integrated experimental and numerical approach. The research results show that a novel combined flooding formulation—water + foaming agent + polymer (viscoelastic) + N 2 —is proposed and validated, achieving the highest recovery efficiency of 63.09%, which is 22.99% higher than conventional waterflooding. This confirms that switching to a multimedium injection strategy at mid- to high-water-cut stages can substantially improve ultimate recovery. Numerical simulation quantitatively delineates the remaining oil distribution across individual sublayers, revealing that residual recoverable reserves (76.6 × 10 4 t) are predominantly concentrated in five specific sand bodies, providing precise targets for infill drilling. A comprehensive field-scale adjustment strategy is formulated—integrating optimized technical policies, planar and vertical injection–production improvements, and coordinated end-to-end management—which, over the 15-year forecast period, is projected to increase cumulative oil output from 149.4 × 10 4 t to 168.1 × 10 4 t, raising the recovery factor by 3.3%. These findings offer both theoretical insights and practical guidance for sidetracking and effective reserve utilization in analogous low-permeability reservoirs within the Changqing Oilfield and beyond.