Abstract

A new hole-cleaning process applied in a PDVSA Servicios Drilling Project, in the Heavy Oil Orinoco Belt, Bolivarian Republik of Venezuela saved 3 rig days and reduced the stuck-pipe risk and avoided damage to the MWD/LWD BHA and PDC bit. A long sought solution for effective wellbore cleaning was validated. Applied the first time, this concept provides a novel integrated solution for hole-cleaning, is transferrable to other well construction projects, is reducing project costs, lessens lost-in-hole BHAs and significantly reduces flat drilling time & invisible lost time.

Effective hole-cleaning is the main challenge of any deviated drilling operation, with problems in cuttings and cuttings beds removal. Even optimized mud flow rates, with reciprocal and rotational pipe movements physically cannot completely remove cutting beds. The herewith presented solution constitutes to incorporate a non-rotational scraper assembly into the drill string, applied together with an engineered and optimized hole-cleaning process.

With no access to dedicated casing cleaning tools, the 9 5/8” casing was cleaned from cuttings by back-reaming inside the casing with the BHA drill string, requiring minimum 2-3 runs and 2 days, and causing excessive wear on casing, BHA and PDC bit. After drilling the 8 ½” section, the new concept was to place a non-rotational scraper assembly into the drill string, allowing only minimum POOH of DP stands as part of the scheduled final openhole wiper trip activity, followed by RIH back to TD – and as such completing the openhole wiper trip without the need of tripping the drill string to surface. The tested solution eliminated all back-reaming inside casing and ensured a full 360° casing contact cleaning prior to RIH the liner, guaranteeing the casing is free of cuttings and also eliminating any additional round nose mill trips. The scraper never moved outside the 9 5/8” casing. This first application of RIH a scraper as part of the drill string gave outstanding results with 3 rig days been saved and a smooth RIH of the liner.

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