Long-Term Production Results of High-Rate Water Packs: Case Histories From NanHai West Bay, South China Sea

摘要

High-rate water-pack (HRWP) completions frequently perform poorly in both hydrocarbon productivity and production endurance. This poor performance has been linked to pack-permeability damage caused by the fines invading the pack and migrating toward the wellbore. The NanHai West Bay reservoir is a sandstone formation with high CO2 content. It exhibits moderate to high permeability and a high sanding tendency caused by weakly consolidated formation and high watercut. To access this reservoir, multiple wells from two separated platforms were completed in 2002 with HRWPs and extension packs (EPs). The EP completions used proppant that was coated with a surface-modification agent (SMA). This completion method was selected to bypass the near-wellbore damaged formation by creating wide and short propped fractures without fracturing into the nearby water zone. Completion tools consisted of 13Cr material because of high CO2 concentrations. A short and compact weight down-tool system was chosen so that the wells could be completed efficiently with limited rig space on unmanned platforms. This paper presents the long-term evaluation results of these wells and provides detailed descriptions of the completion procedures, challenges, and the difficulties during the course of these treatments. Field results of these HRWP- and EP-treated wells show that their productivity continues to hold up at levels better than expected, even after more than seven years of production. These wells continue to produce at low drawdowns without causing mechanical damage to the proppant packs and sand-control screens, despite the high sanding tendency, high watercut in the formations, and frequent exposure to stress cycling as the wells undergo production and shut-in.