Changes In Drilling Techniques Provide New Opportunities For The Deepwater Challenge

Exploration and production of deepwater hydrocarbon reservoirs is a great challenge to the Oil Industry. Environmental constraints and the high costs involved add new risks to deepwater projects. In order to make such projects economically and technically feasible, it is crucial to adopt step-change technical and organisational solutions. The implementation of innovative drilling techniques and the reshaping of an existing offshore rig can provide interesting perspectives with regard to the deepwater challenge. Starting from the reservoir requirements, it is now possible to review the casing profile according to the "cut-to-the-bone" principle. In fact, a technique to reduce the clearance between casing and borehole, permitting "slimmer" well profiles to be achieved, has been developed and field proven. This technique, which has been named "lean profile drilling", has proven to be effective in cutting drilling costs in certain onshore drilling environments. Briefly, the lean profile drilling technique, with respect to the standard technology, allows smaller holes to be drilled while keeping standard production casing or liner sizes. The benefit lies in the possibility to reduce the sizes of all tubulars to case the well and to reduce BOP's and riser sizes. In other words, this technique offers outstanding opportunities for re-thinking and re-shaping the drilling approach in the deepwater environment, by making it possible to replace the conventional drilling rig of an existing semisubmersible, with a light weight hydraulic rig, thereby expanding the capabilities of the drilling unit to deeper water and cutting costs. This paper develops the idea, discussing the main issues and outlining the main technical and economical advantages of the concept.