Use of Jack-up Drilling Units in Arctic Seas with Potential Ice Incursions during Open Water Season

摘要

Jack-up drilling units have been used in Arctic open water seasons and areas with very limited icebergs. They have not been used in areas where significant sea ice can move in with high concentrations. These areas have typically been drilled using a floating mobile offshore drilling unit (MODU) although the water depths are typically less than 50 meters. Floating MODU?s in shallow water depths can have significant downtime due to the limited offset in shallow water and typically require placing the well control equipment in a seabed cellar. In these areas, jack-ups can improve both operational safety and efficiency as they have limited weather related downtime. Several studies were carried out to determine the feasibility of using a modern high capacity jack-up MODU?s for exploratory drilling in these areas. This paper will review the studies including structural analysis, ice management approaches, and well control considerations. It will also review the further potential of jack-ups in the Arctic. Studies showed that using a jack-up drilling unit is feasible in shallow Arctic seas such as the Chukchi Sea when coupled with an effective ice management system. The jack-up unit has sufficient ice resistance to withstand interaction with thin early winter ice. Specific designs of jack-ups are capable of taking impact forces from thicker ice floes that may occur during an ice incursion event during the open water season. The maximum floe size during an ice incursion is limited and controlled by the associated ice management system. An ice management system was developed using a combination of satellite imagery, ice management vessels, and ice alert procedures. This system was determined as effective in managing ice to allow the jack-up to operate in the Chukchi Sea area. Environmental and personnel safety is enhanced by the use of a Pre-positioned Capping Device, an in place source control device. The device is independent from the rig?s well control system and provides another level of protection in additional to the jack-up?s BOP. The conclusion, based on structural and ice management studies, is that modern high capacity jack-up drilling units can be an effective way to drill wells during the open water season in shallow waters of Arctic seas including areas in to which sea ice can move. The studies also show that there is potential for use in other areas.