Use of ROV to cut abandoned well casing in shallow water

Abstract

This work aims to present the pioneering service of cutting the external casing of an abandoned well in a shallow waters, in the Rio Grande do Norte region, entirely by ROV. For wells in water depth of less than 100 meters, after permanent abandonment, it is necessary to cut the section of casing that is exposed on the seabed, in order to avoid possible risks to other sea activities. Historically, in the Northeast region of Brazil, this service was performed by divers, which led to considerable exposure to risk. Seeking to avoid this exposure, it was possible to carry out the operation using only ROV, using tools and accessories adapted for handling by the vehicle. The main stages of the service were the initial survey, dredging, tool assembly, cutting of the coating, and collection of the cut section. A diamond wire cutting tool, hydraulically driven by the vehicle, was used which was able to cut the 30-inch casings of two wells in water depth of approximately 45 meters. This operation provided gains in several areas, with emphasis on the elimination of occupational risk for divers, and savings of more than 90% of the cost when compared to the alternative of performing the cut with an intervention drilling rig. This operation also serves as a benchmark for decommissioning activities in shallow waters in Brazil and around the world.