Application of Polymer Specific Enzymes To Clean Up Drill-In Fluids

Abstract

Abstract The industry recognizes that drilling muds can damage a well's producing zone, especially in highly deviated and openhole completions. So-called "drill-in" fluids have been developed and used to reduce mud damage in vertical, horizontal, and multi-lateral completions. Although "cleaner" than conventional muds, drill-in fluids include polymers to build the required viscosity to transport cuttings and deposit a filter cake around the wellbore to reduce fluid loss. Most drill-in fluids are composed of starch, cellulose or xanthan polymers, plus bridging agents such as calcium carbonate or salt particles. Some of the polymer in drill-in fluids invades the near wellbore formation and creates skin damage. This is most noticeable in expensive horizontal and multi-lateral wells. A break-through technology offers environmentally friendly enzymes that are tailored to remove most of these types of polymer damage. These polymer linkage-specific enzymes offer a safe, effective alternative to conventional clean-up methods that usually consist primarily of oxidizers like bleach and acid. This product has none of the "side effects" associated with non-specific reactants such as premature reaction, corrosive damage to down hole tools and tubular goods, and disposal problems. This paper will detail the candidate selection process, applications methods, and the enzyme reaction mechanism. A number of selected application case histories in the South and Northeast U.S. production and gas storage fields will also be described. P. 343