ABSTRACT
Historically, the application of breakers in fracturing fluids at elevated temperatures has been a compromise between maintaining proppant transport and achieving the desired fracture conductivity. Conventional oxidative breakers react rapidly at elevated temperatures, potentially leading to catastrophic loss of proppant transport. Encapsulated oxidative breakers have experienced limited utility at elevated temperatures due to a tendency to release prematurely or to have been rendered ineffective through payload self-degradation prior to release.
Enzymes, from a theoretical perspective, are known to provide superior performance relative to oxidative breakers. This is due to the inherent specificity and the "infinite" polymer-degrading activity of enzymes. However, the application of enzymes has historically been limited to low-temperature fracturing treatments due to the perceived pH and temperature constraints. Recent developments in biotechnology have resulted in the isolation of hyper-thermophilic organisms, which led to the separation and purification of extreme temperature-stable, polymer-specific enzymes. Laboratory evaluations utilizing these enzymes as gel breakers have demonstrated exceptional performance capabilities over a pH range of 3-11 and temperatures exceeding 300°F.
Performance properties of systems incorporating the new breakers are provided, including rheology, proppant transport, and retained permeability. Case histories of fractured wells in several moderate to high-temperature reservoirs are provided to validate the utility of this technological breakthrough. The data illustrate that the enzyme breakers can be successfully incorporated without compromising proppant transport capabilities, yielding improved productivity relative to observations in offset cases treated with conventional breakers.