Paper: Liquid Polymers For Improved Friction Properties Of Complexed And Non-Complexed Fracturing Fluids

The use of polymer additives to obtain lower friction pressures in tubular goods has long been an accepted practice which has focused attention on friction-pressure drop as a major factor in job design," Pressure limits set by pipe strength, as well as economic limits on horsepower, often determine the maximum obtainable rate. This rate may not be sufficient to give the most efficient stimulation treatment. The effective use of these polymer friction reducers has allowed higher rates within pipe pressure limits, leading to more successful stimulation treatments without increases in horsepower costs. Many treatments being performed today would be impossible without the use of friction reducers. The most widely used friction reducers are guar gum and cellulose derivatives, i.e., HEC, and polyacrylamides. The polyacrylamides are superior as friction reducers.2"3"4"5 However, guar gum and cellulose derivatives offer the added advantage of viscosity control of fracture leak-off at moderate concentrations. Leak-off control and proppant placement techniques6 led to the use of highly viscous gels and eventually to the development of the high viscosity complexed gels. The increase in viscosity, however, was generally observed to be accompanied by an increase in friction pressure. Although these fluids offered high viscosity, fluid loss control, perfect proppant support, thermal stability, etc., an improvement in friction properties was desired." Even with 50-60 percent friction reduction, desired injection rates are difficult to achieve within pressure limits of tubular goods or at acceptable horsepower costs, especially in small diameter tubing. Earlier attempts to improve the friction properties of these viscous fracturing fluids were directed toward the addition of the more efficient polyacrylamides to these fluids. Such attempts were unsuccessful. This lack of success was attributed to materials-handling problems and hydration problems. Recent advances in polymer technology have offered the polyacrylamides in liquid form. Unlike the traditional powdered polymers, the liquid polymers are prehydrated. They do not form lumps when added to water; thus handling and mixing are facilitated. Furthermore, the addition of liquids can be more uniformly controlled. With the advent of these new polymers, experimentation was resumed. Recent field trials have shown that these liquid polymers can significantly alter the friction properties of both complexed and non-complexed fracturing fluids.