Challenges of Polymer and Surfactant-Polymer Flooding with High-Salinity Effluent Water in a Complex Middle-Eastern Clastic Reservoir

An integrated EOR study was performed to de-risk EOR implementation in a mature clastic reservoir located in West Kuwait with complex sand distribution, faults, poorly connected sand bodies, limited aquifer support, and unfavorable mobility ratio. The details of EOR screening, lab evaluation and pilot design for polymer and surfactant polymer flooding to increase oil production and unlock additional reserves are presented for these unique reservoir conditions.

The reservoir of interest is depleting and the availability of high-quality water for injection is a major challenge. This calls of the utilization of produced/effluent water with a salinity in excess of 200,000 ppm to optimize cost and establish operational ease, thus restricting the potential EOR methods that can be pursued. Pressure depletion and lack of commercially-viable gas sources eliminates miscible gas injection. In view of that, extensive lab evaluation was performed to identify techno-economic chemical formulations that can withstand harsh reservoir conditions using available high salinity water. A pilot scale field implementation plan was thereafter developed using numerical simulation.

The only viable methods of chemical EOR using the available high-salinity water were found to be polymer and surfactant-polymer flooding. The efficiency of these technologies was assessed in the laboratory and potential chemical formulations for surfactant-polymer and polymer flooding were evaluated. Judiciously designed mobility-control polymer-flooding and surfactant-polymer flooding worked well using effluent water in core-flood experiments using reservoir rock and fluids. Surfactant-polymer flooding demonstrated a potential additional 4.8% OOIP oil recovery over polymer flooding with 14.8% OOIP incremental over waterflooding. Numerical simulation of polymer flooding in an inverted pattern pilot showed incremental recovery of 6.9% OOIP. This pilot is aimed at de-risking phased commercial development using a combination of existing and new wells. A long-term polymer injectivity test is planned before pilot implementation.

An integrated EOR study was performed to de-risk chemical EOR implementation for a complex and mature clastic reservoir. This involved EOR screening, extensive lab experiments, numerical simulation and fit-for-purpose pilot design. The implementation of a mobility-control polymer flood followed by surfactant-polymer flooding, using high salinity effluent water, is expected to generate positive results in terms of oil production, reserves growth and cost optimization