Alternative methods for reduction of operational downtime related to dis-/reconnection of the marine drilling riser

Abstract

The global energy demand is increasing. The oil companies are going into harsher climates and deeper waters to replace their reserves. Much of the undiscovered hydrocarbon reservoirs are believed to be located in the Arctic region. The seasonable ice free waters surrounding the Arctic can be drilled utilizing conventional drilling vessels designed for open water conditions. The region introduces several new operational challenges leading to an increased possibility of the drilling vessel moving off location.

This Master Thesis looks at the challenges related to operating a conventional drilling vessel in the seasonable open waters in the Arctic, using today’s methods for disconnecting and reconnecting the marine drilling riser from the BOP.

The need for a reduction in the operational downtime related to planned and unplanned disconnections is identified and several alternative methods for reducing the dis-/reconnect time are presented and rated.

A concept is chosen based on a wide range of design requirements thus leading to an 89-97 % reduction in costs related to planned and unplanned disconnections, depending on water depth and well type.

The operational subsea control system needs are mapped and several possible control options are presented and evaluated. Based on a Preliminary Hazard Analysis, cost and system complexity, a control system is chosen.