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The objective of this research program is to continue research and development on the use of chemical dispersants. One task will be addressed: Heavy Oil Dispersion Research.
The chemical dispersion of heavy or viscous oils and the upper limit of viscosity for the successful dispersion of viscous oils have been studied by a number of researchers including past work at Ohmsett (SL Ross 2005, 2008). Most of this work has focused on determining what the limiting viscosity is for chemical dispersion not what the primary reason is for the inability to chemically disperse the oil. Two dispersion processes may be affected by the oil’s viscosity. One is the ability to get the applied dispersant to penetrate into the viscous oil in sufficient quantity to be effective before it is washed away in the dominant water phase (we will call this “mixing one”). The other is internal visco-elasticity of the oil that may prevent the oil from being broken into small droplets under the prevailing energy conditions even if a significant quantity of dispersant has penetrated into the oil (we will call this “mixing two”).
This proposed research project will investigate which of these processes is the limiting factor for a number of viscous oils. Preliminary laboratory scale work using the SL Ross wave tank will be conducted using pre-mixed viscous oil and dispersant samples to determine when the internal oil viscosity is the controlling factor. A range of dispersant doses will be pre-mixed with a number of viscous oils and oil-dispersant mix viscosities will be monitored to separate the surfactant and viscosity influences on the dispersion process. The viscous oils that disperse when pre-mixed with dispersant will be tested using a spray application of dispersant at similar (and possibly higher) doses to determine if “mixing one” is the limiting factor in the chemical dispersion of the oil.
Results from a recent study on low-dose repeat application of dispersants (SL Ross 2009) indicate that multiple low-dose applications of dispersant to viscous oil slicks may in fact result in a better dispersion outcome than one single dose. Multiple low-dose applications on the viscous oils where dispersion is not limited by the “mixing two” process will also be proposed in this project to study the merits of this strategy in improving the “mixing one” process. Initial small scale testing in the SL Ross wave tank will be proposed to be followed by full scale testing at Ohmsett where more realistic dispersant application and mixing regimes can be studied. |
