Viscosity
and flow behavior of crude oils are key properties for
the characterization, management, and development of petroleum reservoirs.
To measure the rheological properties of heavy crude oils with a high
accuracy, a capillary rheometer was designed and built at the Ruhr
University in Bochum (RUB), Germany. The capillary rheometer was calibrated
with three Newtonian reference blends of 1000, 10 000, and
50 000 mPa s. For these standards, the viscosity tables have
been extended up to 1000 bar in the temperature range of 20–120
°C. The extended viscosity data were determined with a falling
body viscometer at the Universidad Nacional Autónoma de México
(UNAM), obtaining average deviations better than 2.0% at high pressure.
The capillary rheometer is then calibrated with the same reference
fluids at 40, 60, 80, and 100 °C at pressures from 1 to 260 bar.
The deviation from the reference value was found to be lower than
3% at high pressure. The flow behavior of a heavy oil sample is determined
at 80, 100, and 120 °C at atmospheric pressure. Furthermore,
the viscosity is measured from atmospheric pressure to 180 bar. The
investigated heavy oil shows a Newtonian behavior at high temperatures.
This is consistent with rheological measurement carried out at UNAM.
The viscosity increases with increasing pressure at all temperatures.
For example, at 40 °C, the viscosity increases by about 35% by
increasing the pressure from 1 to 100 bar.