Here’s a piece of engineering news to kick off Canada’s National Engineering month:
A team of researchers led by Professor David Sinton of the University of Toronto’s Mechanical and Industrial Engineering Department have developed a process to analyze the behavior of bitumen (an extra heavy oil) using a microfluidic chip, a tool commonly used in the medical diagnostics field. They team believes their new process may reduce the cost and time of analyzing bitumen-gas interaction in heavy oil and bitumen reservoirs . The chip is used to measure the diffusivity of highly pressurized CO2 that’s injected into bitumen and is described in Energy & Fuels.
Natural bitumen is an oil based substance with a viscosity greater than 10,000 centipoises at reservoir temperatures—that’s even more viscous than honey at room temperature. Crude oil is produced from bitumen deposits and bitumen is also used in asphalt. The oil sands in Alberta, Canada contain about 40% of world’s bitumen reserves and are the largest producer of bitumen . However, extraction from reservoirs is challenging because of its high viscosity—it’s nearly immobile at reservoir temperatures . To improve bitumen flow and ultimately bitumen recovery, the viscosity of bitumen can be reduced with the injection of light gases such as carbon dioxide (CO2) .
To determine the rate and amount of a CO2 that should be injected, its diffusion behaviour must be analyzed. Conventional methods involve compositional analysis of liquid samples taken at different times . The analysis may take hours or days and require about half a litre of bitumen .
On the other hand, the team’s microfluidics process only requires about 10 minutes and a one nanolitre sample.
The glass microfluidic chip shaped like a cross is initially filled with CO2 at low pressure (<1.0bar). A small amount of bitumen is then injected into the longer channel of the chip. The shorter channel is kept open to maintain a continuous gas flow. Afterwards, high-pressure CO2 is injected into the both ends of the longer channel. The bitumen swells along the length of the channel in response to the high-pressure CO2. This swelling data is then used in a mathematical model to determine the diffusion behaviour of CO2.
The team believes there is potential for their technique to be used by the oil and gas industry as a rapid and reliable process to understand the bitumen-gas behaviour.
 Fadaei, H., Scarff, B., & Sinton, D. (2011). Rapid Microfluidics-Based Measurement of CO2 Diffusivity in BitumenEnergy & Fuels, 25 (10), 4829-4835 DOI: 10.1021/ef2009265
 Attanasi, E. D. and Meyer, R. F., 2007, Natural bitumen and extra-heavy oil, in 2007 Survey of Energy Resources, eds., J. Trinnaman and A. Clarke: World Energy Council, p.119-143.
 Sheikha, H., Pooladi-Darvish, M., & Mehrotra, A. (2005). Development of Graphical Methods for Estimating the Diffusivity Coefficient of Gases in Bitumen from Pressure-Decay Data Energy & Fuels, 19 (5), 2041-2049 DOI: 10.1021/ef050057c
 Upreti, S., & Mehrotra, A. (2000). Experimental Measurement of Gas Diffusivity in Bitumen: Results for Carbon Dioxide Industrial & Engineering Chemistry Research, 39 (4), 1080-1087 DOI: 10.1021/ie990635a