Formation Damage Assessment of High pH and Salinity Completion Fluids in Gas Wells

Abstract

Abstract High pH saturated brine can cause formation damage to sandstone formation following well completion operations. Hence, it becomes vital to evaluate the potential effectiveness of completion fluids prior to the actual cost and risk of implementation. Permeability reduction of 12-31 % was observed after injection of high pH completion fluid on Berea sandstone core plug. The magnitude of damage depended on the fluid/rock properties. Scaling tendency of calcium sulfate and salt self-precipitation occured when it was mixed with formation water. Elemental concentrations of effluent samples indicated that ions exchange process occurred during coreflood testing. High pH completion fluid and the incompatability with formation water were the main cause of core damage. The damage was found to be reversible when the completion fluid's pH value reduced to 7 and at 300°F.