Slickwater fracturing contributes a large portion of current stimulation treatments in tight gas reservoirs. The fluids typically contain only friction reducer and biocide. They are considered incredibly simple with little attention paid to their composition beyond the effects of water quality. In many cases, the biocides are sold and added to the fluid stream by production chemical companies while the friction reducers are added by the service company performing the fracture treatment.
The paper reviews the chemical interactions between the typical anionic friction reducers and the cationic biocides, such as quaternary ammonium compounds. The impact of these biocide-friction reducer interactions is that both materials are consumed, and, therefore, prevented from performing their desired functions. During a treatment this is not obvious, but additional friction reducer eventually must be added to control pumping pressure. Further, the biocide is expected to be unavailable to control bacteria. The goal of any stimulation fluid should be that all components are compatible. As expected, some biocides complex with the oppositely charged friction reducers. This results in the formation of flocks of insoluble polymers in the fluid. Laboratory testing and a field example indicate that the quaternary ammonium biocides reduce the drag reduction seen with the common friction reducer. In comparison, nonionic biocides such as gluteraldehyde do not interact with the friction reducer. The paper also reviews studies with compatible scale inhibitors.