Flow Contact Efficiency for Barriers
As I described on the last slide, we ran a series of simulations where we varied the amount of oil and water injected.
For each simulation, we determined the flow contact efficiency through a barrier consisting of a line of injection wells, and the volume contact efficiency for the region between injection wells.
Simulations were run for aquifers with low, medium and high levels of heterogeneity.
As expected, the average contact efficiencies were some what better for the more homogeneous aquifers and somewhat poorer for the high heterogeneity simulations.
However, the results were reasonably similar for all permeability distributions, so we have only presented results for the medium heterogeneity distributions.
Shown on this slide is a three dimensional surface relating flow contact efficiency through a barrier to the mass and volume scaling factors.
Injection of more oil is represented by an increase in the mass scaling factor.
Injection of more water is represented by an increase in the volume scaling factor.
When we first developed this process, we recommended that people inject 1 pore volume of water and enough oil to fill the maximum oil retention for the treatment zone.
This is equivalent to using mass and volume scaling factors of 1
Based on the curve show above, this should result in a flow contact efficiency of about 80%.
Increasing the amount of oil and water injected by 50% increases the mass and volume scaling factors to 1.5.
This should increase the flow contact efficiency to over 90%.
However, this will also significantly increase the cost for oil and labor to implement the injection.
The flow contact efficiencies shown in this figure are pretty high because most groundwater flows through the high permeability zones and the high permeability zones are most effectively treated by the emulsified oil.
When using this relationship to estimate contact efficiency, please be aware that this curve was generated for a ‘medium' heterogeneity aquifer.
The actual contact efficiency at your site will undoubtedly be somewhat higher or lower.
However, the general trends shown here will probably hold for most sites.
Injecting more water and more oil will generally lead to higher contact efficiencies.
This figure is repeated in the design tool along an equation that allows users to calculate the range of expected contact efficiencies for specified values of the mass and volume scaling factors.