Model 415C & 415SGS Instruction Manual
D01669102
April 2019, Revision A
6
1.2 Model 415SGS
Model 415SGS combines thickening time and static gel strength testing into one
compact, easy to use, simple to maintain unit. Model 415SGS represents the easiest
to operate and most reliable static gel strength tester in the industry. This additional
gel static gel strength determination software package is designed to perform static
gel strength tests in accordance with API specifications.
The static gel strength of cement slurry is measured using a standard paddle and
with the same configuration as a thickening time test. This makes transitioning
from thickening time to static gel strength testing instantaneous, simulating real-
world downhole conditions. The paddle is held in a virtually stationary position
allowing for extremely precise direct measurement of static gel strength
development in real time.
Model 415SGS represents the new standard for static gel strength measurement and
is backed by over 20 years of proven research and results. The portable
combination of API thickening time tester and static gel strength determination
make his an economical and powerful tool for any laboratory.
Critical static gel strength (CSGS) is the specific static gel strength of a cement in
which hydrostatic-pressure equilibrium is reached between the decayed hydrostatic
pressure transmission of the cement column (and other fluids in the annulus) and
the pore pressure of the formation. CSGS is measured in pascals or newtons per
square meter (pounds force per 100 square feet).
Critical static gel strength period is the time interval required for the cement to
progress from the CSGS to a static gel strength of 250 Pa (500 lbf/100 ft
2
). Static
gel strength (SGS) is the shear strength (stress) measurement derived from force
required to initiate flow of a fluid. Also measured in pascals or newtons per square
meter (pounds force per 100 square feet).
The apparatus contains a pressure chamber that can be heated and pressurized
according to a simulated cement job schedule. The SGS is calculated from the
torque required to rotate a paddle of known geometry at very low speed. The
rotation speed of the paddle during the SGS measurement portion of the test is
normally a continuous
0.0000092 r/s (0.2°/min). The initial stirring to simulate placement in the well is
typically conducted at 2.5 r/s ± 0.25 r/s (150 r/min ± 15 r/min). The permissible
range of rotational speed for the apparatus is 0.0000069 r/s to 0.0000231 r/s.