Purpose: Drilling fluids (often referred to as "muds") must perform under a range of temperature conditions. In deep well drilling, temperatures can rise significantly. HTFL testing helps assess how much water or other base liquids a fluid will lose when exposed to high temperatures, which affects its ability to lubricate and cool the drilling bit, carry cuttings to the surface, and maintain well stability.
Why Important: Excessive fluid loss can lead to wellbore instability, formation damage, and loss of control over the drilling process.