Functioning Mechanism of Drag Reducer Used in Shale Reservoir Fracturing

Six types of drag reducers were studied for their solution viscosities and drag reducing effects at different concentrations and in pipeline flow. The study shows that the water solutions of these drag reducers have power law flow patterns, and the drag reducing ratios increases with the increase of the concentrations of these drag reducers, if the concentrations are in certain ranges. Viscosity of the solution and ion characteristics have no obvious effect on the drag reducing ratios of these drag reducers. At the same concentrations, drag reducers having molecular weight (MW) greater than 1000,000 have almost the same drag reducing ratios. The main factor affecting the drag reducing performance is the molecular structures of the reducers. Drag reducers with low MW and long molecular chains, those with branched and long molecular chains, and those with flexible, helical molecular structures have drag reducing performances that are much more stable. Long chain drag reducers with branched chains dissolve quickly in water and have good drag reducing performance in a wide range of Reynolds numbers. Drag reducers with low MW are easy to degrade and hence impose very slight damage to the reservoirs. These drag reducers are suitable for use in large scale shale reservoir fracturing with slippery water fracturing fluids.