CIDS: A Mobile Concrete Island Drilling System for Arctic Offshore Operations

Abstract

This paper describes a unique system that can provide an alternative to gravel islands as a means of supporting drilling operations in shallow Arctic waters. The Concrete Island Drilling System (CIDS) is composed of modular concrete "bricks" stacked one on top of the other which, in turn, support a barge-mounted drilling rig. Sequentially stacking these modules provides a great deal of flexibility in siting the modules in water depths of 18 to 52 ft. The modules incorporate an efficient concrete "honeycomb" structural system that offers inherent longitudinal, transverse and torsional strength. The superior strength of the CIDS, coupled with its massive ballasted weight, enables it to withstand the ice pressures prevalent in the landfast ice areas of the Arctic. Several key features of the CIDS make it a unique and economically advantageous exploratory drilling platform. Because it is modular, the CIDS reduces construction and transportation problems and allows the use of various configurations that can be modified to suit the water depth requirement. No dredging or gravel-hauling activity is associated with the CIDS since the gravity load is achieved by merely ballasting the modules with seawater. The entire system, with the drilling rig intact, can be relocated by pumping out the saltwater ballast and towing the CIDS to a new site. No rig demobilization or "under-dredging" of caisson fill is required. The use of concrete insures a long-lived structure that can be reused on many wells.