Development of 4,000 m Class CFRP Drilling Riser

摘要

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is operating a deep sea scientificdrilling vessel “CHIKYU” (Figure 1) to promote research on the earth sciences. 21st Century Mohole isone of the most challenging projects among current science proposals for the next decade. In this projectit is proposed to penetrate oceanic crust, drill into the uppermost mantle across the Mohorovi(c)i©discontinuity and to obtain samples of mantle directly.In order to accomplish this objective, it is required to drill about 7,000m below deep sea floor whichwater depth is over 4,000m. One of the elements which have a great influence on the realization of thistarget is a deep water riser. Generally, the material of a riser is high tensile steel. However, it will be verydifficult to apply the steel riser to a drilling operation in the locations of more than 4,000m water depthdue to the limitation of the strength. Therefore, JAMSTEC started to study a new material riser. CFRP(Carbon Fiber Reinforced Plastic) was selected as the primary candidate for the new material. It isclassified by its raw material to two types, pitch-based carbon fiber (Pitch-CF) and PAN-based carbonfiber (PAN-CF). Pitch-CF has higher modulus of longitudinal elasticity and it will be more favorable forthe dynamics of the riser. In this paper, outline on the developments of pitch-based CFRP riser arepresented.