A type of rock failure where small flakes or chips of rock break off from the wellbore wall due to rapid temperature changes caused by extreme thermal cracking. In geothermal drilling, this happens when the relatively cool drilling fluid encounters the extremely hot formation rock. The surface of the rock cools and contracts much faster than the rock deeper in the formation. This difference in contraction creates internal stress that exceeds the rock’s tensile strength, causing pieces to break away.
Thermal Spalling
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