Improved Wellbore Clean Up - Successful Case Histories in Saudi Arabia from Development to Field Implementation

Abstract

Abstract An effective and efficient means to remove the filter cake and remediate the internal near wellbore damage associated with synthetic or oil-based mud (S/OBM) filtrate is required in reservoirs drilled with oil-based mud (OBM) drill-in fluid (DIF). Often traditional chemical methods using inorganic acids, organic solvents, and mutual solvents used to clean-up filter cake deposits and remove skin damage are ineffective, even with multiple treatments. Collaborative laboratory research between the operator and a service company resulted in a treatment for removing much of the damage associated with OBM drill-in fluid. A fluid was developed to fluidize and reverse the wettability of the OBM filter cake solids, acidizing soluble particles and remediating the near wellbore skin damage caused by the drill-in fluid. Invert emulsion drill-in fluids are commonly used to drill the dune sandstone reservoirs in Saudi Arabia because of their performance and the minimized risk of formation damage due to swelling of in-situ clays. The wells were drilled with sized calcium carbonate weighted OBM; and were open-hole completed with stand-alone screens. Well diagnostics indicated that the productivity impairment on these wells was potentially related to near wellbore damage and/or severe screen plugging, either while running the screens to bottom in solids free OBM, or induced by a mixture of formation sand and OBM filter cake adhering to the screen during draw down. After spotting the treatment in the reservoir and soaking, collected fluid samples and well production measurements indicated removal of the plugging solids from the screens and wellbore, yielding significant production improvements. Field results and complimentary traditional laboratory methods, including return permeability data show that the effectual use of this technology will remediate skin damage and plugged screens associated with the OBM DIF, water-wet the solids, acidize the majority of acid soluble particles, and improve well productivity. Introduction A number of damage mechanisms, that are often the direct result of drilling and/or completion fluids affecting the near wellbore region of a formation, can limit reservoir productivity or injectivity.