Publications

The cleanup of drilling fluid filter cake in long horizontal open-hole completions is a challenging task. The obstacles encountered are the difficulty to ensure contact of the treating fluid with the filter-cake throughout the whole interval, as well as controlling the reaction rate between the breaker and the filtercake to assure uniform dissolution.The filter cake built by water-based fluids is composed of polymer, starch and CaCO3. Today several chemical systems are available that use either oxidizers or enzymes to attack the polymer and starch components, and an acid to dissolve the CaCO3. The limitations of these fluids are fast reaction rates and corrosiveness provided by the acid. This results in uneven cake dissolution, limited dissolution power due to PH compatibility for those fluids utilizing enzymes and acids, and the need for multiple staged treatments for systems combining oxidizers and acid.This paper shows the results of the testing carried out to determine the effectiveness and feasibility of implementation of a novel cleanup fluid that overcomes the limitations of currently available systems. This fluid attacks CaCO3 with a Chelating Agent Solution (CAS) and polymer and starch with Alpha Amylase Enzyme (AAE) in a single stage treatment. It is much less corrosive and offers an order of magnitude lower cake removal rates compared to those with conventional acid systems.The low reaction rates promote a more uniform cake cleanup and should result in higher production rates. It is also possible to visocosify this new fluid formulation with Visco Elastic Surfactant (VES) to be used as either a single-step carrier/cleanup fluid in open-hole gravel packing or cleanup fluid after gravel packing or in standalone screen completions.