Successful Optimization of Viscoelastic Foamed Fracturing Fluids With Ultralightweight Proppants for Ultralow-Permeability Reservoirs

Abstract

Summary Successful fracturing treatments in ultralow-permeability reservoirs require combining the most recent innovations in fracturing technologies. Viscoelastic surfactants, foams, and ultralightweight proppants (ULWPs) have specific properties that when combined offer the unique performance required in fracturing these reservoirs. Viscoelastic-surfactant foams are particularly suited for treating ultralow-permeability reservoirs because they minimize the interfacial tension and minimize the amount of water used in the fracturing fluid. This significantly reduces the permanent retention of water and the amount of water trapped in the near-wellbore region that would impair the ability of gas to flow (Gupta 2009). Inexpensive, logistically simple, polymer-free viscoelastic surfactants provide exceptionally high viscosity under low-shear conditions required for proppant transport. They also provide excellent cleanup characteristics. Foamed viscoelastic surfactants provide increased viscosity for frac width, provide better leakoff control, and further improve fluid cleanup characteristics, particularly in low-pressure reservoirs. ULWPs provide excellent transport properties in conventional fracturing fluids with minimal viscosity, which ensures desired effective propped-fracture conductivity. Use of these ULWPs in foamed viscoelastic fluids provides fracturing treatments with optimum proppant placement and excellent cleanup. As with all successfully applied fracturing fluids, the fluid systems must be optimized. These combined systems require significant laboratory testing to characterize and optimize the fluid system successfully for the demands of ultralow-permeability reservoirs. This paper focuses on small- and large-scale laboratory testing performed to optimize these viscoelastic foamed systems in an effort to test the technical limit of this new technology for future field developments.