Abstract

The synergy between various enhanced oil recovery (EOR) processes has always been raised as a potential optimization route for achieving a more economic and effective EOR application. In this study, we investigate the possible synergy between polymer and SmartWater flooding. While the potential for such synergy has been suggested and researched in the literature, we investigate this possibility in a more realistic framework—part of the development of an EOR portfolio for a slightly viscous Arabian Heavy reservoir. In this work, we study the possible synergy between SmartWater and polymer flooding by performing rheological, electrokinetic (Zeta) potential, contact angle and displacement experiments.

Rheological tests as expected demonstrated the possibility of achieving the same target viscosity at lower polymer concentrations. With SmartWater, the polymer concentration required to achieve a target viscosity of 11 mPa.s was found to be one-third lower than that with normal high salinity injection water. Electrokinetic potential and contact angle results demonstrated that polymer presence has a negligible to slight yet favorable impact on wettability alteration induced by SmartWater. On synthetic calcite surfaces, polymer showed negligible impact while on rock surfaces polymer resulted in a further reduction in contact angle beyond that obtained with SmartWater.

Coreflooding experiments conducted at reservoir conditions with finite SmartWater/polymer slugs demonstrated the enhanced performance of SmartWater/polymer compared to either of these individual processes besides yielding comparable performance to surfactant/polymer flooding. A combined SmartWater/polymer process was able to recover substantial additional oil (6.5 to 9.9% OOIC) above that obtained with either of the two processes when applied independently. Ultimate recoveries from the application of SmartWater/polymer (70% OOIC) were quite comparable to – actually slightly higher than – that of surfactant/polymer (67% OOIC). However, in terms of the remaining oil in core (ROIC) post polymer flooding, both processes (SmartWater/polymer and surfactant/polymer) exhibited quite similar incremental recoveries of 20.6 and 20.5% OOIC, respectively.

The results of this work clearly demonstrated the potential synergy between SmartWater and polymer flooding – beyond that of the well-established polymer viscosity enhancement – for a realistic scenario. The additive effect of SmartWater was successfully shown to combine with polymer to increase oil recovery, in addition to lowering the polymer concentration. Therefore, this favorable synergy will reduce chemical consumption and costs and improve recovery and returns to enhance EOR project economics for the slightly viscous Arabian heavy oil reservoir considered in this study.

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