Degradation of Water-based Mud Filter Cakes using Environmental Friendly Pullulanase Enzyme

The filter cake removal is of primary concern in a horizontal oil producer. It has been highlighted in many publications that the cleanup process in long horizontal and multilateral wells is a challenging task. Many chemical solutions have been used to remove the polymeric and bridging agents in oil producers. Due to their nonspecific characteristics, the chemical solutions have their limitations and in some cases have affected the well productivity. Thus an enzyme treatment using Pullulanase had been applied to degrade the mud filter cake of drill-in fluids, which comprised starch and xanthan gum. In this research work, static fluid loss and soaking tests were performed at temperatures ranging from 75oF to 250°F. The experimental results revealed that the efficiency of the cleaning solution comprising Pullulanase in degrading starch and xanthan gum was influenced by solution temperature and its concentration. For 6% concentration of Pullulanase, the highest degrading efficiencies experienced were 63%, 74%, 87%, 66% and 59% at temperatures of 75°F, 100°F, 150°F, 200°F, and 250°F respectively. In terms of concentration, it was found that 6% of Pullulanase gave the optimum efficiency as compared to 7% and 8% concentrations at temperature of 150°F. The experimental results also proved that enzyme stabilizer and viscoelastic surfactant could prevent the deactivation of enzyme activity at temperatures above 150°F.