More than 20 years ago, the first e-line coiled tubing drilling (CTD) systems were introduced. Since then, the technology has evolved and proven to be an efficient, economic means of enabling additional production from aging oil and gas fields. These systems are now established as a standard, viable solution for re-entry drilling in a variety of maturing fields and applications. Corresponding technologies and procedures were developed, and continuously improved.

Utilizing project data from more than 20 years of operational experience, this paper describes the progression from the first e-line CTD bottom hole assembly (BHA) applications in Europe through to today's continuous operations in several areas worldwide. It presents the technology changes and procedural adjustments that were necessary to address new challenges related to extending the economic life and improving the production of mature fields by economically accessing stranded reserves, and includes:

  • Wellbore design changes from single re-entry to multilateral wells, along with the envelope extension from pure geometric wellbore placement according to plan, to real-time reservoir navigation utilizing geo and bio-steering services.

  • Introduction of special applications such as precise kick-off from vertical, dual casing exits and extended reach drilling (ERD) with CT technology.

  • Progression from overbalanced drilling operations to full underbalanced (UB) applications, with nitrogen injection through the CT string and the requirement to manage production while drilling.

  • Equipment development to enable safe pressure deployment of the drilling BHA, enabling a move from conventional tower set-ups to dedicated highly mobile coiled tubing rigs.

Continual improvements of technology and steady implementation of new developments in many aspects of CTD technology were the result of innovative re-entry projects executed worldwide. To achieve the necessary efficiency and economic goals, improvements and new technology developments occurred in the downhole BHA technology, casing exit equipment, surface equipment, rig and other associated systems. Simultaneously, processes and procedures were also optimized with new ones introduced to adapt for changing environments and observed challenges.

Based on worldwide CTD experience, the trend of technology developments and continuous improvement will continue. The goal is to further drive project efficiencies and economics, enabling the life of maturing fields to be extended, deferring abandonment and improving ultimate recovery.

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