Water flooding is a secondary recovery strategy which involves the injection of water into the oil reservoir to improve its recovery factor – get more of the oil out! The process begins with a good understanding of the reservoir (the rock) and the fluids (the oil). Some reservoirs are more amenable to water flooding than others, and the oil viscosity is very important to determining the success of the program. Generally one wants the oil viscosity to be less that 1,000 cP or centipoise (similar to motor oil) to have a successful flood.
To implement a water flood we start by drilling water injection wells (or converts producing wells) along a defined pattern. Water is then injected into these wells to first replace the oil that has already been produced, and then to pressure the reservoir back up to the bubble point – the pressure where the gas dissolved in the oil bubbles up. Once this pressure is reached we will begin to see a production response at the producing wells (in between the injectors). As we continue to inject water at the injectors, oil will be pushed (swept) to the producers, and larger amount of oil will ultimately be recovered.
At Rock’s Mantario pool we are proceeding to begin water injection by the third quarter of 2014 so that we can ensure maintenance of the reservoir pressure above the bubble point. By being pro-active, we will avoid the production of significant gas which would occur as the gas bubbles out, prevent the increase in viscosity due to the release of the gas, and avoid any pre mature production decline. This strategy will provide the highest possible recovery factor, and a stable production profile.