Which signs indicate a permeable formation during drilling?

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Multiple Choice

Which signs indicate a permeable formation during drilling?

Explanation:
When the formation is permeable, drilling mud can invade the rock, causing loss circulation. This shows up as more mud leaving the wellbore into the formation (increased fluid loss) and less mud coming back to the surface (reduced mud returns) because a portion of the mud is seeping into the pore spaces and fractures. The drilling rate may appear faster because the mud is leaking off, which lowers the hydrostatic pressure downhole and reduces the counterpressure against the bit, allowing the bit to advance more readily. These signs together indicate a permeable formation.

When the formation is permeable, drilling mud can invade the rock, causing loss circulation. This shows up as more mud leaving the wellbore into the formation (increased fluid loss) and less mud coming back to the surface (reduced mud returns) because a portion of the mud is seeping into the pore spaces and fractures. The drilling rate may appear faster because the mud is leaking off, which lowers the hydrostatic pressure downhole and reduces the counterpressure against the bit, allowing the bit to advance more readily. These signs together indicate a permeable formation.

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