1. n. []

The leakage of the liquid phase of drilling fluid, slurry or treatment fluid containing solid particles into the formation matrix. The resulting buildup of solid material or filter cake may be undesirable, as may the penetration of filtrate through the formation. Fluid-loss additives are used to control the process and avoid potential reservoir damage.

See: acrylamido-methyl-propane sulfonate polymer,  API fluid-loss test,  drilling fluid,  filtercake,  fluid-loss control,  fluid-loss-control material,  treatment fluid,  water loss