A sudden increase in the drill bit’s rate of penetration. It
sometimes indicates that the bit has penetrated a high-pressure
zone and thus warns of the possibility of a kick. A sudden
increase in the rate of penetration during drilling. When this
increase is significant (two or more times the normal speed,
depending on local conditions), it may indicate a formation
change, a change in the pore pressure of the formation fluids,
or both. It is commonly interpreted as an indication of the bit
drilling sand (high-speed drilling) rather than shale (low-speed
drilling). The fast-drilling formation may or may not contain
high-pressure fluids. Therefore, the driller commonly stops
drilling and performs a flow check to determine if the formation
is flowing. If the well is flowing, or if the results are
uncertain, the driller may close the blowout preventers or
circulate bottoms-up. Depending on the bit being used and the
formations being drilled, a formation, even if sand, may
sometimes drill slower rather than faster