Viscoelastic Surfactant Fracturing Fluids: Applications in Low Permeability Reservoirs

Abstract

AbstractThe introduction of viscoelastic surfactant (VES) base fracturing fluids has changed the way industry views fracturing fluids and proppant transport during a fracture treatment.1 Elimination of polymers allows one to achieve highly conductive proppant packs with no polymer damage. Retained permeability and leakoff control are two of the most important requirements for fracturing fluids. Traditional and new generations of cross-linked gels provide good leakoff control, but they often adversely affect the retained permeability of the proppant pack. In addition, minimizing frac-height growth and increasing effective fracture length are a few other advantages of using VES fluids.2In the majority of cases in low permeability formations, a long and conductive fracture is the ultimate aim of hydraulic fracturing. Borate or metal crosslinked guar fluids, because of their inherent high viscosity, typically result in height growth rather than increased fracture length. With VES fluids proppant transport is based on the elasticity and structure rather than the viscosity of fluid. Therefore VES fluids efficiently transport proppants at lower viscosities. At the same time, VES fluids let one achieve a better fracture geometry, that with minimum fracture height and maximum fracture length. Pressure transient analysis and tracer studies have shown that this non-damaging low viscosity fluid can give longer effective frac-length even when using much less fluid and proppant volumes (Figure 1). Reduced friction pressure is another added advantage while using VES fluids. Hence VES fluid is the fluid of choice when fracturing is performed through coiled tubing.3,4 Simplicity and reliability of this two component system are the other features of this fluid that attract the industry globally.5The use of VES technology is now extended to other oilfield applications, such as selective matrix diversion,6 filtercake removal,7 and coiled tubing clean out. VES technology is also defining new engineering practices in hydraulic fracturing that cannot be accomplished with conventional fluid systems, such as fracturing through coiled tubing.