Development of Automated Dual Elevator System Enabling Deeper Drilling

The scientific Deep-Sea Drilling Vessel "Chikyu" was designed to have the capability to drill down to a maximum drill string length of 10,000 m and technical equipment developments were needed in order to achieve this drilling depth. During drilling operation a hoop stress is generated by conventional handling equipment slips. The hoop stress can become critical with the increased drill string length if the force is sufficient and can actually damage or in the extreme case crush the pipe. This phenomenon is called slip-crushing. In order to avoid this potential problem and to reach the drilling depth (the length of the drill string) of 10,000 m, the automated Dual Elevator System (patent pending), which is an integrated pipe handling system using two elevators, has been developed for "Chikyu". This paper describes the critical problem such as the slip-crushing due to the hoop stress in ultra deep drilling which will be the intended operations for "Chikyu". It is a problem of this type which determines maximum drilling depth which in turn limits the access to deep formations where core samples recovered. Also, this describes the outline of functions and automation system of the Dual Elevator System.