Present status and remaining problems of HDR/HWR system design

The Japanese government!funded geothermal exploration well WD! 0A reached a depth of 2618m in a Quaternary granite\ where the bottom!hole static temperature is more than 499>C[ This is the highest!temperature formation ever drilled at this depth in the world[ A newly developed method was used to cool the sophisticated drilling tools while running them into the hole[ A detailed borehole dynamic temperature experiment produced data useful for practical drilling operations[ Drill!bit seal conditions were also inspected after use[ A total of 03 cores\ as well as a ~uid sample from the bottom of the well\ were taken for scienti_c investigations[ 0887 CNR[ Published by Elsevier Science Ltd[ All ri`hts reserved