The customer had shut in a high-asphaltenic, offshore gas well in early 2010 and wished to clean the well in preparation for temporary abandonment in 2015. The water depth was 3853-ft and the gas sand was located at 18,225 to 18,338-ft MD. The production tubing was:
4.5-in (3.826-in ID) to 17,412
3.5-in (2.992-in ID) to 18,031
a 60 ft inverted telescopic joint with a minimum ID profile of 2.75″
3.5-in sand screen across the reservoir, 18,225-18,338-ft
A plan to clean the completion with 29,000 ft of 1-1/2″ coiled tubing deployed on the Helix Q4000 was prepared. A 2.12-in SC-HydroPull™ equipped with a carbide-tipped bullhead and 6×0.106-in diameter forward facing cleaning jets was specified. The HydroPull® job planning software showed that a pumping 1.25 bpm of xylene would generate 850 psid pulsed jets and 327 psid water hammer suction pulses in the annulus and would require pumping pressure at 10,491 psi with 4200 psi wellhead pressure.
An OSES toolhand arrived at the rig with the SC-HydroPull™ tools via helicopter. A slick line run tagged bottom at 17557-ft, 668 ft above the top of the sand. Xylene was pumped at 1 bpm/ 9200 psi at 17400-ft and the fill was tagged at 17597-ft. Pumping continued for an hour with slow progress, the pumps were stopped for an hour to allow the xylene to soak. Pumping resumed for an hour at 1 bpm and another for another hour at 1.25 bpm/10,200 psi until 18,250-ft, which was 25-ft below the top of the completion screen. The WHP was 4200 psi, but climbed to 4750 psi as the tools entered the screens. The customer then confirmed the ability to bullhead fluid into the completion in preparation for cement placement. Total pumping time was 3 hours with 3.25 bbl of xylene placed. This job illustrates the ability to clean heavy asphaltene that was obstructing access to a small diameter completion. The job was completed quickly despite high well pressure and the small diameter of coiled tubing available for offshore well intervention.