Sag Shoe Assembly Model RCSSA-130
The Viscometer Sag Shoe Test (VSST) is a well site and laboratory test that
measures the weight material sag tendency of field and lab-prepared drilling
fluids under dynamic conditions. The VSST provides an intrinsic fluid property
without regard to the conditions under which the fluid has been or will be
used. As such, results must be combined with operational factors to correlate
results with sag experienced in the field.
The VSST designation is derived from the rotational viscometer used as
a mixer and the thermoplastic insert (Sag Shoe) designed to concentrate
sagged weight material in the bottom of a viscometer thermocup. Sag
tendency is determined by the density increase of samples extracted from the
collection well over a 30-minute period at a standard temperature and under
a consistent rate of shear.
Weight-material bed pickup can be run as an optional measurement to
characterize bed removal by higher shear levels. Results can be used to
suggest opportunities for bed removal in the field prior to tripping out of the
hole.
Recommended Equipment:
- VSST Sag Shoe
- Direct-indicating API rotational viscometer capable of operating at 100
and 600 RPM
- Viscometer thermocup, with temperature control
The VSST Sag Shoe should fit inside of the thermocup without being too
tight.
- 10 mL Luer Syringe
- Cannula with luer connection
- Timer capable of measuring ± 1 second
- Balance with 0.01 g resolution
- Pycnometer, retort cup, or weigh boat