Study and Application of Agents for Increasing Water Injection in Wells Rejecting Sewage Containing H₂S

The quality of sewage water in three reinjection wells of NHX offshore oilfield is poor, resulting in increasing in injection pressure and decreasing in water injection rate. The main reasons for reservoir damage near wellbore area have been analyzed. The compound plugging removal system (ZSJ-Y and ZSJ-W) has been built, which has strong applicability, low corrosion rate, with strong stabilizing capability in ferricion and clay. The results of laboratory evaluation experiment indicated that the core permeability recovery rate after plugging removal was 102.37%. This system has been used successfully in NHX-12b well, with water injection rate increased 656 m³/d, and the apparent water injectivity index was increased from 161.3 m³/d·MPa to 232.6 m³/d·MPa, increased by 44.2%. This system has excellent plugging removal results and injection stimulation effect, and can be used widely. In addition, it provides reference for plugging removal in similar offshore reinjection well.