Estimation of Mass Transfer Parameters of Gaseous Solvents in Heavy Oils Using the Pressure-Decay Technique

摘要

Estimating the mass transfer parameters of gaseous solvents in heavy oils is relevant for many petroleum engineering applications, including the design and modeling of oil recovery processes involving mass transport between gaseous and liquid phases. These parameters are inferred from data obtained through diverse experimental methods, with the pressure-decay technique (PDT) being the most convenient. This technique uses a diffusion cell in which a high pressure gas cap is established on top of a column of heavy oil. The gas phase pressure decays as gas diffuses into heavy oil, hence, the name PDT. The existent difficulty in evaluating these mass-transfer parameters and the need of producing simple procedures to obtain quick, yet acceptable estimates was identified. Therefore, in this research, analytical-graphical, numerical, and experimental approaches were implemented to estimate mass transfer parameters of gaseous solvents in heavy oils from pressure-decay data.;In particular, two analytical-graphical methods based on the Integral-Method were developed to estimate Henry's constant, diffusion coefficient, and interface-mass resistivity in the form of mass-transfer coefficient. The resultant estimated parameters were in agreement with the ones reported in the literature. Additionally, the capability of PDT data to estimate the dependency of the diffusion coefficient on the gas concentration in a bitumen layer was evaluated. Full nonlinear simulations together with a history matching technique were applied to a wide range of experimental pressure-decay tests taken from the literature. The results from these simulations revealed the incapability of PDT data to provide information for such diffusion-coefficient-concentration functionality.;Finally, and in response to very limited data on the gas-heavy oil diffusion process at low temperatures, pressure-decay tests were conducted to determine the solubility and diffusivity of methane and carbon dioxide in dodecane, hexadecane, and bitumen at temperatures lower than 25 °C. The effect of low temperatures in gas diffusion and solubility was analyzed and discussed.;This work builds upon the current state-of-the-art research in gaseous solvent transport in heavy oil. It also provides new insights for using pressure-decay data to estimate the mass transfer parameters of such processes.