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Penetration Rate605040cm/min3020100100 200 300 400 500 600 700 800 900 1000Length (m)Figure 5-6. Penetration rate during core drilling of KFM06C.9000Feed Force800070006000kg500040003000200010000100 200 300 400 500 600 700 800 900 1000Length (m)Figure 5-7. Feed force versus borehole length during drilling of borehole KFM06C.From start at 100 m the feed force is significantly lower than later, which probably reflectsthe more fractured and permeable rock in the upper part of the borehole. Thereafter the feedforce down to 620 m is smoothly undulating, followed by significantly lower values in section620–780 m when the borehole probably is drilled close to more fractured rock connected tofracture zone 60. Finally, from 780 m the feed force shows an increasing trend, probably causedby lager friction as the borehole deviation increases with length.Rotation speedThe rotation speed diagram, Figure 5-8, shows from start an almost constant rotation speedof 850 rpm, which however is raised to c. 1,000 rpm at c. 220 m. After that there is a slowlydecreasing trend, except for a sudden drop at c. 300 m. Finally, from 800 m the rotation speedshows a significantly decreasing trend, probably caused by lager friction as the boreholedeviation increases with length. Also the drill crew felt that the maximum capacity of the rig hadto be used in order to reach the planned borehole length. Sudden drops in the curve representdrilling shut off.35