Downhole Coiled Tubing Telemetry Reduced Time and Uncertainty During a Challenging Deepwater Milling Operation

Abstract

Fishing, cleanouts, and milling constitute the most common coiled tubing (CT) operations on the coast of Louisiana. The objective of the operations is to remove obstructions from a wellbore and to promote an unobstructed flow path for fluid, either for injection or production. Sometimes, due to the nature, weight, or length of the fish, a straight fishing operation cannot be performed. In these cases, dressing and baiting the fish with CT before a fishing attempt is necessary. Considering previous experiences in the area, the operator wanted to remove common uncertainties that exist during CT operations including whether the correct force is transmitted from the surface, if the bottomhole assembly (BHA) is functioning correctly, and if the downhole motor is applying the correct amount of weight on bit for successful milling. This study describes how a real-time CT downhole measurement system optimized an intervention that required dressing and baiting the top of the fish (a stuck CT string) to enable the subsequent fishing operation. The risks involved with milling a fish inside an injector well with CT in deepwater conditions motivated the use of CT telemetry capable of providing real-time downhole parameters to operate the mill both safely and efficiently. The combination of conventional milling techniques and real-time downhole measurement capabilities enabled rapid response and adjustments to the actual downhole conditions throughout the operation, as the combination system developed and confirmed the tubing force module simulation.