Exploration of Water Injection Development Adjustment Methods in the Ultra-High Water Cut Stage

After years of deep waterflooding development, Daqing Oilfield has reached a comprehensive water cut of over 96%, with remaining oil being highly dispersed. Following nearly 60 years of layered water injection adjustments, the disparities in water cut between layers have significantly narrowed. However, issues such as ineffective utilization of small layers affected by shut-in and control measures within layered well sections, increased workload and difficulty in testing and adjustment have become increasingly prominent. There is an urgent need to explore low-cost water injection adjustment methods suitable for the ultra-high water cut stage. This study analyzes the waterflooding development history of Daqing Oilfield and summarizes the core elements of water injection adjustment for large continental multilayered heterogeneous sandstone reservoirs. Taking the SaZhong Development Zone as an example, it examines the macro-scale distribution characteristics of remaining oil in the ultra-high water cut stage and proposes a combined water injection development technique of “full-layer saturated water injection & layered liquid-controlled production.” This approach establishes an optimized development adjustment system tailored for the ultra-high water cut stage, further improving reservoir recovery efficiency and waterflood sweep efficiency. An exploratory field test of this technology was conducted in the SaZhong Development Zone. Under the extreme condition of a water cut reaching 98.07%, the method achieved a reduction in water cut by 0.39 percentage points and a 30% increase in daily oil production. These results demonstrate its critical role in enabling economically viable waterflooding development under ultra-high water cut conditions.