Characterization and Control of Formation Damage During Waterflooding of a High-Clay-Content Reservoir

Abstract

Summary Permeability damage was suspected as a factor contributing to postcompletion production declines observed during waterflooding of a friable to unconsolidated sandstone. A loss in water injectivity also indicated that near-wellbore damage may have been occurring. This paper summarizes the laboratory studies undertaken to evaluate and understand permeability damage in this formation. The experimental program consisted of primarily coreflooding experiments to evaluate the influence of injection fluid composition, temperature, mineralogy, and flow velocity on permeability damage. The significance of damage during brine injection was observed to be a strong function of mineralogy and injection rate. Permeability losses of > 60% were observed in cores from some sand intervals, while little or no damage was apparent in cores from a second zone in identical wells. In the sands that were susceptible to brine damage, a critical velocity below which permeability damage did not occur was repeatedly established. The occurrence of a critical velocity, along with other observations, indicated that the primary damage mechanism was fines migration. Damage could be controlled by maintaining velocities below the critical value or reducing the pH of the injected brine.