Improvement of Well Productivity Using Smart Water Techniques: Case of Rio Del Rey Reservoirs

Abstract

The Rio Del Rey Basin in southwestern Cameroon hosts some of Central Africa's most significant offshore and shallow-water oil reservoirs. Despite decades of primary and secondary recovery operations, a considerable fraction of the original oil in place (OOIP) remains unrecovered due to suboptimal displacement efficiency, wettability alteration challenges, and high residual oil saturation. This study investigates the potential for improving well productivity in the Rio Del Rey reservoirs through the systematic application of smart water (low-salinity water flooding and seawater ion-tuning) techniques. By combining core-scale laboratory experiments, compositional reservoir simulation, and field-analogue benchmarking from comparable West African and North Sea formations, the research evaluates the displacement efficiency, wettability modification effects, and incremental oil recovery achievable under optimized smart water injection strategies.
Results indicate that reducing injected water salinity from formation brine levels (~45,000 mg/L TDS) to a designed ionic composition of approximately 1,500–5,000 mg/L TDS, with controlled sulfate and magnesium concentrations, shifts the reservoir rock wettability from oil-wet to mixed/water-wet conditions. Core flood experiments on Rio Del Rey sandstone plugs demonstrated incremental oil recovery of 8–15% OOIP above conventional seawater flooding. Compositional simulations project a field-scale incremental recovery of 6–12% OOIP across key producing blocks (Kole, Moudi, and Lokele fields) over a 15-year injection period. Economic analysis confirms that smart water injection is technically and economically viable when integrated with existing offshore water-handling infrastructure, yielding an estimated net present value (NPV) uplift of USD 120–340 million per field depending on oil price scenarios. The study further identifies critical operational parameters — ionic ratios (SO4²⁻/Mg²⁺ and Ca²⁺/SO4²⁻), injection water salinity, injection rate, and reservoir temperature — that govern the efficiency of smart water flooding in Rio Del Rey conditions. Recommendations for pilot design and phased field implementation are provided.