Review of friction reducers used in slickwater fracturing fluids for shale gas reservoirs

Friction reducers (FRs) play a vital role in large-displacement shale hydraulic fracturing. This paper reviews the drag reduction (DR) mechanism of FRs, its development and application, and its effect on slickwater. Existing problems involving solubility, salt tolerance, reservoir damage and viscosity of slickwater are summarized. From the aspect of molecular structure, it is discussed how to obtain FRs with the characteristics of salt-tolerant, fast dissolving, low reservoir damage, proper viscosity, environmental friendly and low cost by optimizing molecular structure, charge type and distribution, block mode, and synthesis process.