The water used for this process is usually brine but can also be produced water from the well. Filtration is often necessary to ensure that no materials clog the well pores and needs to be treated to reduce any bacteria growth
Primary production usually only recovers 30-35% of the oil. Water injection can recover 5-50% of the oil remaining in the reservoir, greatly enhancing the productivity and economics of the development. This form of EOR is typically more productive when there are relatively small amounts of primary production.