Secondary oil recovery projects, also known as waterfloods, rely on water injection to increase reservoir pressure to improve production rates and sweep incremental oil from the reservoir. In some cases, we work larger mature assets where we use our technical knowledge to modify and optimize existing waterfloods. In other situations, we work on partially developed pools, where waterfloods have not yet been attempted.
A successful waterflood project can increase oil recovery from the 5% to 15% range normally seen under primary recovery, up to typically a 40% recovery of the initial oil-in-place.
To implement a waterflood, producing wells are converted to water injection wells. The location of the injection wells is carefully selected to maximize the oil recoveries. While this injected water will help to maintain the reservoir pressure, it will also help sweep oil to the producing wells. Since extra capital investment is required for a waterflood, projects suit larger oil reservoirs where a larger number of wells can be drilled for both oil production and water injection purposes. Each waterflood requires careful planning and active management through the life of the project to properly control the performance.
Once water injection commences, it may take years for the reservoir to re-pressure and to realize improved production rates. Typically, once water injection has restored reservoir pressures, we accelerate production with the drilling of horizontal or vertical drainage. Waterfloods can have a lengthy start-up period as regulatory approvals are required prior to construction or modification of field facilities for water injection.