Comparison of the RamRig versus conventional drilling systems

Abstract

Abstract The market for mobile offshore drilling units has changed over the two last years. In general the activity level is higher, with utilisation of floating drilling units close to 100 %. The reason for this increased activity level is mainly due to the following elements :Increased number of production wells to be drilled by floating rigs, for sub-sea field developments.New deep water areas opened for exploration. The drilling rig technology has basically been more or less identical over the last twenty or thirty years, except for the implementation of the top drive system in the early eighties. Challenging technical requirements for exploring and exploiting harsh environments areas have motivated the industry to search for new solutions. New technology and ideas are implemented both for the type of vessel and for the drilling rig. The RamRig as presented at OTC 96 (1) is one of the contributors to the new technology. This paper outlines differences between the RamRig (RR) and the conventional drawworks based rig (DWBR). Improvements are specifically for the following topics:Hoisting and compensating systemWeight and center of gravityTubular handlingBOP handlingSafety and working environment The coming year four units based on the RR technology will be operative, and MH have defined further development programmes that will complete the RR and further improve its performance compared to conventional rigs. Two of these products are :Power slip joint, PSJ (2), for making the conventional riser tensioning system obsolete.TOPIN coiled tubing system (3), to reduce rig-up time and Improve system performance from floating rigs. Introduction The DWBR was developed early this century and as technical requirements have increased, all new developments have been added to the existing concept. The basic rig was also used when the industry went offshore and initial compensation was executed by means of bumper subs. Later on in-line drill string compensator, top mounted compensator and active heave compensator have been developed and added to the DWBR. (ref. fig. 1 Draw works based rig main functions). Further requirements for top-drive and mechanized pipe handling have also been adopted without any changes to the base concept. For control of the equipment and the entire rig, advancedcomputer control systems have been implemented. In addition, for controlling components related to each other regarding working envelope, zone management systems are required. All these systems built into the existing rig has made it more costly to maintain and less optimized for safety and working environment. Another problem area for operations is handling and stacking of the BOP and X-mas trees. On many rigs the layout is not suitable for the size and number of modules to be handled.