INJECTION WATER-QUALITY - A KEY FACTOR TO SUCCESSFUL WATERFLOODING

Poor injection water quality is a prime factor in the reduction in inj ectivity in many water injection and disposal wells. These reductions in injectivity often result in costly workovers, stimulation jobs and recompletions, or, in many cases, the uncontrolled fracturing of wells by high bottomhole pressures resulting in poor water injection confor mance and reduced overall sweep efficiency and recovery. This paper di scusses many commonly occurring water quality issues and how they impa ct injectivity, including damage due to injection of suspended solids, fines migration, clay swelling and deflocculation, formation dissolut ion, chemical adsorption and wettability alterations, relative permeab ility effects associated with the injection of skim oil or grease and the injection of entrained free gas, biologically and bacterially indu ced damage, formation of insoluble scales and precipitates, emulsifica tion, wax and asphaltene deposition. Screening criteria are presented to allow for a rigorous evaluation of a particular injection water sou rce to investigate potential areas of sensitivity and to attempt to mi nimize problems associated with impaired injectivity.