A scaled physical model representing one-twelfth of an inverted seven spot flooding pattern was used to study the various mechanisms of the steam driveprocess. The apparatus was designed to operate at pressures close to atmospheric and temperatures from 25.0 to 130.0 °C. A two-dimensional interpolation program was used to generate temperature distribution profiles in horizontal and vertical cuts of the model and the resulting profiles clearly demons traced the gravity override of steam during the experiment. The effects of steam injection rate and steam quality on oil recovery, oil-steam ratio, steam zone volume, temperature distribution, and residual oil saturation in steam, hot water, and cold water zones were examined. Results showed there is an optimum injection rate to efficiently displace the crude oil to a low residual saturation while reducing the heat losses from the reservoir. It also showed that high quality steam reduced the steam zone residual oil saturation more significantly than low quality steam. A simple calculation based on volumetric balances was used to estimate the oil produced from the different zones. Finally, the energy balance and thermal efficiency are presented to verify the validity of the results.
Steam drive is one of the most common and efficient methods to displace heavy oil from reservoirs. This thermal recovery process is complicated, involving simultaneous heat and mass transfer, chemical reactions, and physical changes. The major contributions that affect the displacement are:
reduction of oil viscosity due to increase in temperature,
thermal expansion of the oil,
change of relative permeabilities and residual saturation,
steam distillation of the light components from the residual oil in the steam zone, and
gas drive and solvent extraction.
Both scaled and unsealed physical models have been used in the past to study the steam drive process. Unsealed experiments1,2 conducted in cores and sandpacks indicated that steam drive is a very effective method for recovering heavy oil and waterflood residual oil. These results, however, cannot be used for prediction of field performance since they are not scaled. A number of investigators3,4 have proposed scaling laws for the process, and efforts have been made to develop scaling laws for heat and fluid flow which are the most important parameters in a steam drive. Once these are scaled adequately, physical models should provide much useful information about the process.
In this study, a scaled physical model of one-twelfth of an inverted seven-spot flooding pattern with improved thermal insulation over previous experiments5 was used to examine the technique of steam injection for recovery of a Lloydminster heavy oil.
In order to properly scale a physical model, the following requirements must be considered:
Field model must be geometrically similar.
Field and model must have the same initial and boundary conditions.
Values of several parameters containing fluid and rock properties as well as terms related to heat and mass transport must be equal in the field and the model.