Abstract
An extensive big bore gas well drilling and completions program is in progress to develop the giant North Field, offshore Qatar. Benefits of the big-bore concept, compared to the prior 7-in. monobore design, include reduced development costs by requiring fewer wells, and deferred installation of compression by providing higher flowing wellhead pressures.
This is the widest known application of a big bore design in one single field and involves a large number of wells. Many of these wells are drilled and completed to date and believed to be among the world's most prolific gas producers. These are also the first offshore wells to incorporate big bore well design for large-scale field development and feature industry advances in equipment design and manufacture. An extensive system of detailed design review, equipment performance testing, and quality programs has been implemented to meet challenging project requirements for well reliability.
The wells feature a tapered tubing design known as the "Optimized Big Bore" (OBB). This paper discusses the challenges of planning and executing these OBB wells. It reviews the initial OBB well design, anticipated North Field drilling challenges, critical equipment specifications, and design revisions resulting from optimisation efforts over the past four years.
