Experimental measurement and parametric study of CO2 solubility and molecular diffusivity in heavy crude oil systems

CO2 solubility in two heavy oil samples with 5 and 20 Pa.s viscosities at operating pressures of 1.73, 3.10, and 4.48 MPa and temperatures of 295, 298, 301, and 305 K were determined using pressure decay technique. These measurements were conducted on two different heavy oil states to minimize the associated experimental errors. First, the measurement was conducted under static condition where oil and gas were at stationary condition. Second, a Mini-bench top reactor (PARR-4560) was used to re-determine the solubility of CO2 under dynamic condition. Later, a numerical method was employed to solve the mass transfer equation and compute the diffusion coefficients under each operating condition. It was seen that the effect of pressure on CO2 solubility and diffusivity is more pronounced at higher temperatures for both heavy oil samples. In other words, a better CO2 recovery factor can be achieved if a thermal process can be followed by a CO2 injection to the heavy oil reservoirs. It was also found that increasing CO2 initial pressure yields to higher CO2 solubility and diffusivity in heavy oil. Furthermore, in contrast with the adverse impact of temperature on CO2 solubility in heavy oil, it was seen that CO2 diffusivity benefits from higher temperature. (C) 2014 Elsevier B.V. All rights reserved.