SPE October Meeting

Abstract: 

A new method of using existing coiled tubing equipment has resulted in the industry’s first riser-less coiled tubing drilling operation being successfully completed on the Oda (Butch) field in the Norwegian North Sea. A standard coiled tubing surface package was combined with an innovative new subsea coiled tubing injector head to allow riser-less drilling operations to be done from a Light Well Intervention (LWI) vessel. The advantages of such a method are both cost and safety, as the vessel can be moved off location, while maintaining the ability to kill the well, by paying out the coiled tubing as the vessel moves.

The operation was both new and with a range of risks. Intensive planning of both equipment and procedures was required to mitigate these.

In order to reduce the overall project risk of the Oda field development, there was a requirement to drill a pilot hole in advance of any infrastructure being installed on the sea bed.  The purpose of the pilot hole was to check for shallow gas in the near-surface formations that could be a source of risk to personnel and equipment. The drilling of pilot holes is typically done by large mobile drilling units, such as semi-submersible rigs. The capability of these rigs is several times greater than the requirements needed to drill a shallow pilot hole, which are typically drilled with sea water and no pressure control equipment. This leads to high cost drilling units being used for a low complexity operation.

The Oda pilot hole was drilled to a depth of 351m TVD below the sea floor and achieved all of its objectives.  The operation was completed in 4.25 days at the offshore location, within budget and ahead of time. Very few operational problems related to hole conditions or equipment were experienced.  The success of the project has proven the concept of riser-less coiled tubing drilling in the oil and gas industry. This introduces a new drilling method to operators who seek to increase safety and reduce well cost.

About the presenter: 

Olav Log is the drilling manager of Centrica Norway and has been closely involved with the riserless coiled tubing drilling project. Before joining Centrica six years ago Olav held several positions from drilling engineer to drilling superintendent for ConocoPhillips in Norway, USA and China.