Case History of First Use of Extended-Range EM MWD in Offshore, Underbalanced Drilling

Abstract This paper discusses the planning, results, problems, and lessons learned during the first use of the Extended-Range Electromagnetic (EM) MWD system for underbalanced drilling in an offshore well. The use of EM MWD in offshore applications has historically been limited due primarily to the difficulty of seabed deployment of the receiving antenna. In underbalanced drilling, however, EM is the MWD system of choice because mud-pulse telemetry has great difficulty operating in two-phase flow conditions commonly used. If underbalanced drilling is to become more frequently used offshore, then one limitation that must be overcome is the difficulty for MWD systems to provide real-time annular pressure, directional, and formation evaluation information. Repsol-YPF-Maxus successfully used underbalanced drilling on Krisna Well D12 in offshore Indonesia to prevent massive lost circulation and stuck pipe in the reservoir. Although the total vertical depth of the well was relatively shallow (approximately 4,200 ft subsea), the very low resistivity of the formations above the reservoir precluded use of standard EM MWD services. The Extended-Range EM MWD system was used to extend the depth capability.