The Capillary Suction Time TestTubing measures the relative flow capacity of a slurry of ground formation rock used to form an artificial core and it is an indication of clay swelling.
A rock sample with dispersible or swelling clays would have a lower pseudo permeability and will have a longer CST time while the one without clay or other fine particles would have a shorter retention time.
Capillary Suction Time Testing Results
The CST analyse is used as preliminary screening tools to study the relative sensitivity of a rock sample to various fluids:
Guidance for drilling & completion fluids
Analysis of various Production Water/Fresh Water Ratios