The importance of tuning injection water chemistry for upstream is getting beyond formation damage control/water incompatibility to increase oil recovery from waterflooding and different improved oil recovery (IOR)/enhanced oil recovery (EOR) processes. The water chemistry requirements for IOR/EOR have been relatively addressed in the recent literature, but the key challenge for field implementation is to find an easy, practical, and optimum technology to tune water chemistry. The currently available technologies for tuning water chemistry are limited, and most of the existing ones are adopted from the desalination industry, which relies on membrane based separation. Even though these technologies yield a doable solution, they are not the optimum choice to alter injection water chemistry in terms of incorporating selective ions and providing effective water management for large scale applications. In this study, several of the current, emerging, and future desalination technologies are reviewed with an objective to develop potential water treatment solutions that can most efficiently alter injection water chemistry for SmartWater flooding in carbonate reservoirs.

Standard chemical precipitation technologies, such as lime/soda ash, alkali, and lime/aluminum based reagent, are only applicable for removing certain ions from seawater. The lime/aluminum based reagent process looks interesting, as it can remove both sulfates and hardness ions to provide some tuning flexibility for key ions included in the SmartWater. There are some new technologies under development that use chemical solvents to extract salt ions from seawater, but their capabilities to selectively remove specific ions need further investigation.

Forward osmosis and membrane distillation are the two emerging technologies, and these can provide good alternatives to reverse osmosis seawater desalination for the near-term. These technologies can offer a better cost-effective solution where there is availability of low grade waste heat or steam. The two new desalination technologies, based on dynamic vapor recovery and carrier gas extraction, are well suited to treat high salinity produced water for zero liquid discharge (ZLD). These technologies may not be able to provide an economical solution for seawater desalination. Carbon nanotube desalination, graphene sheet-based desalination, and capacitive deionization are the three potential future seawater desalination technologies identified for the long term. Among these, carbon nanotube based desalination is much attractive, although the technology is still largely under research and development.

This review study results show that there is no commercial technology yet available to selectively remove specific ions from seawater in one step and optimally meet desired water chemistry requirements of SmartWater flooding. As a result, different novel schemes involving selected combinations of chemical precipitation, conventional/emerging desalination, and produced water treatment technologies are proposed. These schemes represent both approximate and improved solutions to selectively incorporate specific key ions in the SmartWater, besides presenting the key opportunities to treat produced water/membrane rejects and provide ZLD capabilities in SmartWater flooding applications. The developed novel schemes can provide an attractive solution to capitalize on existing huge produced water resources in Saudi reservoirs to generate SmartWater and minimize wastewater disposal during field-wide implementation.

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