Currently, an ‘ultra-deep core bit’, ‘Turbine Driven Coring System (TDCS)’ and more advanced ‘Measurement-while-Coring (MWC)/Logging-while-Coring (LWC) tools’ are under development. In moldingthe ultra-deep core bit, diamond particles are evenly mixed into its body. During drilling, the diamonds attached to the blades wear off, however, with this newly improved bit, new diamond particles continue to appear on the surface, making the bit more durable over extended periods.

　With the TDCS, the turbine is rotated by drilling fluid to cut the cores.When drilling fluid flows into the turbine unit, the rotor blades rotate at a maximum speed of 8000 rotation per minute (rpm) which reduction gear converts into rotational power or torque. A piston is installed further down, rotating and pushing out the small core bit located at the tip of the inner tube. The outer tube is rotated by a top drive system in order to ream down after the core is recovered.

　The deeper the system drills in, the more difficult it becomes to check the positions where cores have been recovered so that highly advanced Measurement-while-Coring (MWC) / Logging-while-Coring (LWC) tools to measure borehole inclination and directional data to be sent in real time to the surface vessel through pressure waves (mud pulse telemetry) are essential. This will also enable accurate measurements of the direction of the cores themselves at the time of recovery, which can only be assumed at present by using paleomagnetism. Moreover, the weight-on-bit, rotary speed of the core bit, temperature and pressure inside the borehole can also be accurately monitored. The development of a system capable of measuring the natural gamma-ray, electrical resistance of layers, even when cores cannot be recovered, is underway and expected to be completed within five years.

Fundamentals and Applications of Drilling the Ocean Floor

‘Fundamentals and Applications of Drilling the Ocean Floor’ Awarded
　Shoichi Sumita Encouragement Award of the Marine Engineering ’Fundamentals and Applications of Drilling the Ocean Floor’ (Seizando Shoten), a book covering all the drilling engineering at the ocean floor, written by a scientist of CDEX at JAMSTEC, in addition to the writing assistance from five staffs at JAMSTEC, was awarded 2010 ‘Shoichi Sumita Encouragement Award of the Marine Engineering’.

Coring System

Coring System