Determination of mass transfer parameters in solvent-based oil recovery techniques using a non-equilibrium boundary condition at the interface

•Dilute dissolution of gases into heavy oil was modeled accounting for 3 parameters.•The unknown parameters were diffusion and mass transfer coefficients, and solubility.•3 Mass transfer parameters were measured through running one diffusion experiment.•Sensitivity coefficients were applied to find the sensitivity of P to each unknown.•Closer to onset of asphaltene precipitation, the interface resistance becomes larger.

Having a reliable estimate of gaseous-solvents molecular diffusion coefficients in heavy oil and bitumen is a requisite for analysis and design of gas injection and solvent-based recovery techniques. Nevertheless, diffusion coefficient is not measured accurately unless all other contributing mass transfer parameters are considered, included in the modeling, and estimated correctly. These other parameters are gas solubility and interface resistance, of which the latter is represented by mass transfer coefficient term. In this work, an analytical model is introduced in conjunction with an inverse technique to obtain these three abovementioned parameters using a single pressure decay data set. Sensitivity coefficient analysis is applied as an additional practical evaluation tool to display the sensitivity of the measured pressure to each of the unknown parameters. Characterization of the interface resistance as a physical phenomenon which hinders the molecular diffusion of gas through the interface and complicates the modeling is further investigated in this work. Incipient asphaltene precipitation in heptane–toluene–asphaltene mixture was chosen as a potential phenomenon which alters the interfacial resistance. It is shown that our proposed inverse analysis locates the unknown parameters correctly when history matching per se is not disclosing all the sufficient information for accurate parameter estimation.