1. n. [Drilling Fluids]

The instantaneous volume (spurt) of liquid that passes through a filter medium prior to deposition of a competent and controlling filter cake. In static filtration, the spurt volume can be a disproportionately large percentage of the total 30-minute filtrate in an API-type test. This indicates that filter cake is slow in being deposited compared to a similar mud with lower spurt loss. To avoid uncertainties of spurt-loss volume, relative filtrate volume is used in static tests.

See related terms: filtrate,  filtrate volume,  fluid-loss control,  low-pressure, low-temperature filtration test,  relative filtrate volume,  static filtration