Customizable Synergistic Dual Breaker Technology Improves Fracture Fluid Cleanup

Abstract

Natural and synthetic polymers are commonly used within the oil and gas industry as viscosifying agents in hydraulic fracturing applications. Hydraulic fracturing involves pumping of a highly crosslinked fluid into a formation to create fractures. The viscoelastic fluids are used to provide sufficient viscosity for proppant suspension, transport, and enhanced fracture width. Breaking the crosslinked polymers after the fracturing operation is a crucial step that can greatly impact hydrocarbon production. Conventional breakers, such as oxidizers, are most commonly used for breaking fracturing fluids; however, these breaker packages sometimes show inferior regained permeability at lower temperatures (100 to 160°F). Regained permeability studies with fracturing fluid compositions tested in low-perm cores show that persulfate-type oxidizing breakers do not always adequately degrade the polymer; furthermore, higher concentrations do not always show improved breaking. This paper presents an alternative breaker solution that is superior to conventional breakers in terms of improving regained permeability.Recently it was shown that in situ acid-generating hydrolytically degradable polymers, in combination with oxidizing breakers, dramatically improved the regained conductivity of the proppant pack without the detrimental effects associated with the use of higher breaker concentrations at lower temperatures. For example, test results show that, even at temperatures as low as 150°F, the synergistic phenomenon of this dual breaker system provided multiple and beneficial functions. The hydrolysis rate of degradable polymers to generate acid in situ is dependent on several factors. The wide variety of degradable polymers containing ester-linkages that are available permits one to select a polymer that will result in a desired break profile for the given conditions, making this chemistry customizable.In addition, these acid-generating self-degradable polymers are biodegradable, potentially minimizing health, safety, and environmental (HSE) concerns.Conductivity improvement as compared to using a breaker system based on individual components are attributed to the improved cleanup provided by the synergy between the degradable polymer and the oxidizing breaker (even at lower temperatures). This represents a significant improvement to current technology.