A novel oxidizing breaker system has been developed for fracturing fluids at high temperatures. Below 200°F, the system is not active, but above 200°F, the oxidizing system aggressively attacks the polysaccharide backbone of the fracturing fluids, resulting in a complete break of the crosslinked fluids. In the presence of a gel stabilizer, an intermediate, reactive oxidizing species is formed. The result of this formation is a delayed, soluble, high-temperature oxidizing system.
Controlled viscosity reduction at 200°F to 300°F in crosslinked gelled fluids with and without a gel stabilizer will be demonstrated. Testing included Model 50 viscosity profiles, high-temperature static break tests, and conductivity testing. Results from all testing showed the effect of oxidant concentration in producing apredictable, controlled break of the thermally stabilized crosslinked systems. Data were obtained in low-pH and high-pH Zr-crosslinked fluids as well as in borate-crosslinked fluids. The delayed mechanism of the new breaker system provides fluids with excellent crosslinked viscosity properties at early times with predictable, long-term viscosity reductions. Case histories show that the breaker system can be used throughout the treatment in the pad fluid, proppant-laden fluid, and flush.
This paper provides data that allow significant improvements in job design. The operations engineer can obtain predictable, controlled gel degradation by using the data provided for temperature, gel type, gel stabilizers, and breaker concentration. The results are optimized treatment designs with rapid fluid recovery, improved proppant-bed conductivity, and increased well productivity.