Keywords: enzyme breakers, enzyme activity, shear rate, hydraulic fracture cleanup, tight unconventional reservoirs, guar–based fracturing fluids, enzymes, hydraulic fracturing, fracking, polymeric fluids, oil and gas industry
Effect of shear rate on the activity of enzymes used in hydraulic fracture cleanup of tight unconventional reservoirs
Injection of polymeric solutions in order to propagate a fracture and carry proppants to keep the fracture open is a common practice in hydraulic fracturing of ultra–tight formations. Polymeric fluids open and extend the already existing network of fractures. Considering the low permeability of the formation, small width of the micro–fractures, and the importance of fracture cleanup during the production phase, using breakers is recommended to degrade the more concentrated polymeric fluid and increase the conductivity of the fractures. Enzymes are typically used successfully as breakers for fracturing fluids. In this study, the effect of high shear rates on the activity of enzymes was studied. Enzyme activity decreased at increasing shear rates. However, this activity reduction is reversible. This proves insignificant damage to the enzyme structure due to shear effects. This will assure the activity of the enzymes after reaching the fracture and the more efficient cleanup of the fracture(s). [Received: 31 July 2013; Accepted: 26 January 2014].