1. n. 
A test to measure static filtration behavior of water mud or oil mud at elevated temperature, up to about 380 degF [193 degC], maximum 450 degF [227 degC] if a special cell is used), usually according to the specifications of API. Although the test can simulate downhole temperature conditions, it does not simulate downhole pressure. Total pressure in a cell should not exceed 700 psi [4,900 kPa], and the differential pressure across the filter medium is specified as 500 psi [3,500 kPa]. Because these cells are half the size of the ambient filtration area, HPHT filtrate volumes after 30 minutes are doubled.
Synonyms: static filter press
Alternate Form: HPHT filtration test
See: electrical stability test, filtercake, filter press, filter-cake thickness, filtrate volume, fluid-loss control, fluid-loss-control material, geothermal gradient, high-pressure, high-temperature, jar test, particle-plugging apparatus, sintered