With primary oil recovery methods leaving approximately two-thirds of a reservoir’s oil in the ground, secondary recovery methods including waterfloods are common in fields where the geology makes them feasible. Waterfloods alone can extend a reservoir’s life by years, but there are two challenges in the mix.
The first is that injection of the typically hard water in a field can lead to a buildup of scale and corrosion in injectors, flowlines and pumps. Buildups like this narrow cause either a reduction in water injection rates, an increase in line pressure, or both. Reduced flow rates can reduce formation production. Increased line pressure can make pumps work harder with diminished results, wasting energy and shortening pump life if left untreated.
Top corrosion sources include iron sulfide and other iron compounds, calcium carbonate and a range of sulfates. For corrosion, oxygen in the water is a prime mover.
Traditional treatments involve acidizing, hot oiling and other chemical injections. In the harshest environments these workovers may be required weekly—if not continuously—and filters on water systems may require daily changes. This leaves personnel with little time to do their main jobs.
Frequent well treatments can be costly, time consuming and may release substances hazardous to those onsite. Due to limited effectiveness, production may be reduced even with regular or continuous chemical application.