New Technology Improves Performance of Viscoelastic Surfactant Fluids

Abstract

Summary: For a number of years, viscoelastic surfactant (VES) fluids have been used for a variety of stimulation treatment applications, including hydraulic fracturing, acid diverting, and gravelpacking. VES fluid systems typically offer higher-retained permeability and conductivity of the formation sand and proppant pack than polymeric systems. However, preliminary cost, a 200°F temperature limit, excessive leakoff, and no internal breaker mechanism for dry gas applications have limited VES use. New VES fluid technology has been developed that substantially improves product performance and cost effectiveness. The temperature range has been extended to 300°F by using newly developed VES stabilizer technology. The system works with high-density brines up to 14.4 ppg. Internal breakers have been developed that permit a controlled viscosity break from ambient to 300°F. Laboratory tests have determined that an internally broken fluid rapidly achieves >90% returned permeability and conductivity of the formation sand and proppant pack without the presence or need for contacting hydrocarbons. Fluid loss-control technology has been developed that reduces VES fluid leakoff similar to wall-building fluids, but without filtercake damage. This paper discusses the development of the new VES system chemistry and its properties. The paper also addresses the merits of a viscous fluid that can work in a variety of base fluids for high-pressure applications, such as managing surface-treating pressure or for gas-hydrate inhibition in deep gas or deepwater environments. Breaker technology discussion addresses the ability to ensure and enhance VES fluid-viscosity breaking. Fluid loss-control technology effective to at least 2,000 millidarcies (mD) is presented. This paper also presents rheological, return permeability and conductivity, fluid loss control, treating pressure, and financial results.