グリーンタフにおけるフィックスドカッタービットの適用

Abstract

INPEX is considering Reentry-drilling and completion campaign with 6″ hole in Minami-Nagaoka Green-Tuff reservoir. It is challenging to drill such a slim hole with tri-corn bit. In order to evaluate the applicability of fixed cutter bit, the first trial to drill 8-1/2″ hole in the Green-Tuff with fixed cutter bit and down hole motor was performed in Minami-Nagaoka well A. Two types of fixed cutter bit, PDC bit and Impregnated bit, were evaluated. The bit performances of these two bits were lower than tri-corn bit.Therefore, it can be concluded that tri-corn bit is suitable rather than these fixed cutter bits. However, when 6″ slim hole was drilled with tri-corn bit, severe bit damage and lower bit performance were found due to its low structural strength. From these points of view, it was concluded that especially with impregnated bit is better to be applied for drilling the slim hole in the field.To improve the performance of impregnated bit, it is essential to achieve higher rate of penetration and further extend the bit life. In this report, the applicability of high speed down hole motor with impregnated bit which has a small total flow area is studied and its hydraulics is calculated.As a result, it can be suggested that impregnated bit with high speed motor is suitable for drilling in the slim hole if limitations of rig capacity exists and both drilling and hole problems can be overcome.