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

摘要

This paper discusses the planning, results, problems, andlessons learned during the first use of the Extended-RangeElectromagnetic (EM) MWD system for underbalanceddrilling in an offshore well. The use of EM MWD in offshoreapplications has historically been limited due primarily to thedifficulty of seabed deployment of the receiving antenna. Inunderbalanced drilling, however, EM is the MWD system ofchoice because mud-pulse telemetry has great difficultyoperating in two-phase flow conditions commonly used. Ifunderbalanced drilling is to become more frequently usedoffshore, then one limitation that must be overcome is thedifficulty for MWD systems to provide real-time annularpressure, directional, and formation evaluation information.Repsol-YPF-Maxus successfully used underbalanced drillingon Krisna Well D12 in offshore Indonesia to prevent massivelost circulation and stuck pipe in the reservoir. Although thetotal vertical depth of the well was relatively shallow(approximately 4,200 ft subsea), the very low resistivity of theformations above the reservoir precluded use of standard EMMWD services. The Extended-Range EM MWD system wasused to extend the depth capability.