Fill Cleanout Operations in Offshore Saudi Arabian Fields: Case Histories toward Improving Economics and Operational Logistics

Coiled tubing (CT) fill cleanouts have been in existence for over four decades and today account for approximately 30% of the services performed. Both CT and conventional jointed pipe offer a forward or reverse circulation mode to remove solids; however, using conventional water-based fluids, a sand cleanout method may apply excess hydrostatic pressure to the formation, resulting in some lost circulation to a sub-hydrostatic reservoir. Nitrogen (N2) can be used to reduce hydrostatics, but this requires a very precise job design and execution. Moreover, N2 use can have adverse logistical and economic implications – large amounts of N2 may be needed, especially in larger diameter wellbores and in horizontal wells. Several cleanout methods have been utilized in the past, employing a variety of different approaches. CT historically has incorporated limited circulation rates, exotic/costly fluids and reversing circulation to remove solids. The use of CT to remove sand from wellbores was one of its earliest applications and continues to be an important service today. This paper will discuss cost-effective solutions in Saudi Arabia, highlighting field cases and job optimization. The selection of the most appropriate sand cleanout method has to be based on both logistical and technical issues. This paper shows how to select the most cost-effective fills cleanout method for these wells. A few field cases are discussed to demonstrate the proper operational procedure, challenges and lessons learned. The combination of how to utilize the sophisticated solids transport software, downhole switchable nozzle, and proper operational procedure with the frequent evaluation of downhole conditions on site is essential to insure the fills cleanout is executed 100% successfully.