Shear Rate Effects on Water in Oil Emulsions
The UMD research team is combining definitive experiments with mechanistic model building to provide an improved quantitative understanding of water in oil dispersions that occur during pipeline transport of petroleum from deep sea wells. Conventional understanding of oil in water dispersions is based on custody transfer issues, where a small amount of water in present as fine droplets in tanker to shore pipelines, and a representative sample is required to determine the cost based on the precise oil fraction.
Current offshore oil reserves contain a substantial amount of water and are located in deep wells at 1,000 to 3,000 feet below sea level. Ultra-deepwater fields are being planned in 8,000 to 12,000 feet water depths. Due to economic considerations, the distance from the well head to the offshore platform can be 10 miles or more. As a result, high pressures and low temperatures exist at the well head in a range that promotes the formation of gas hydrates. Gas-hydrates are ice-like solids that form when water and natural gas chemically combine at high pressure and low temperature. Under uncontrolled conditions, gas hydrates can form extensive networks that can potentially plug the pipeline. However, if the water is present in the form of fine drops that are somewhat uniformly dispersed in the oil, they will yield small solid gas hydrate particles that can be transported as a slurry without pipeline blockages.
It is unlikely that the level of fluid mixing found in conventional pipelines will produce uniform water in oil dispersions. However, it may be possible to emulsify the water by installing high intensity mixing units in the lines that produce small water droplets and prevent agglomeration of the resulting gas hydrate slurry. From a practical perspective, our research program has the following objectives:
- To conduct experiments in laboratory style high shear mixers with surrogate fluids that mimic the range of physicochemical properties and water fractions for petroleum under transport, including the role of surfactant phenomena. Water drop size distribution will be measured over a broad range of agitation rates.
- To analyze the resulting data set in order to understand the drop breakup mechanism and to develop and validate mechanistic correlations that can be used to design pipeline mixers that will lead to slurry transport of gas hydrates.