First use of extended-range EM MWD in offshore, underbalanced drilling

The use of EM MWD in offshore applications has been limited, primarily due to the difficulty of seabed deployment of the receiving antenna. In certain underbalanced drilling (UBD) operations, however, EM is the MWD system of choice because mud-pulse telemetry has great difficulty operating in the two-phase flow conditions sometimes used. Repsol-YPF-Maxus successfully used UBD on Krisna Well D12 in offshore Indonesia to prevent massive lost circulation and stuck pipe in the reservoir. Although the vertical depth of the well was relatively shallow (about 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. This article discusses the planning, results, problems and lessons learned during the first use of the Extended-Range Electromagnetic (EM) MWD system for UBD in an offshore well.