(677c) Remediation of Polyacrylamide-Induced Permeability Damage from Fracturing Using H2O2 Catalyzed By Free and Immobilized Peroxidase Enzyme

Polyacrylamide (PAM) polymers are often employed in hydraulic fracturing fluids, especially in slickwater applications. However, they result in accumulation of “filter cake” on the surface of the formation which is known to lower oil or gas production efficiency. Existing chemical “breakers” may not fully degrade the filter cake or not work at the appropriate times or conditions. Here, we illustrate a novel and environmentally-benign approach for degrading partially hydrolyzed polyacrylamide (HPAM) with hydrogen peroxide catalyzed by the enzyme, horseradish peroxidase (HRP). The system was applied to both HPAM solutions and on HPAM filtercake on low permeability rock. This approach was found to significantly reduce the viscosity of HPAM solutions in pure water and brine. Molecular weight measurements indicated that the viscosity reduction was due to a significant degradation of the carbon-carbon backbone of the polymer and not due to amide hydrolysis or polymer rearrangement, etc. Preliminary results with HPAM-plugged nylon filters illustrate some flowrate recovery. Core flooding studies were conducted on low-permeability (~1 md) Indiana limestone as a model, and damage was partially remediated using free enzyme. The recovery was further improved using a novel approach by immobilizing the enzyme on a common fracturing proppant, Ottawa sand.