Experimental studies and modeling of solvent migration in paraffin deposits

Paraffin deposition, the precipitation of high molecular weight components from the bulk solution of the crude oil in low-temperature environments, has detrimental effects on crude oil production by decreasing the flow rate and increasing the pumping cost. Effective and economical management of the pipeline operation requires accurate prediction of both thickness and solvent content of the deposit.; Paraffin deposition is a complex phenomenon involving the interactions of three major processes occurring in the pipelines: convective mass transfer of heavy components from the flowing crude oil toward the deposit interface, diffusion of the heavy components from the interface toward the pipeline walls, and shear removal of the deposit by the flowing crude oil.; In this research, we focused on the process of solvent migration in the deposit. A static cell was used to study solvent migration in the deposit in order to remove the effects of convective mass transfer and shear removal on the deposit. Solvent migration is an important process that affects both the thickness and solvent content of the deposits. In addition, it is a process that has applications in separation processes such as melt crystallization.; Experimental data such as interface movement, temperature profiles in the deposit, and concentration profiles in the deposits were obtained from the solvent migration cell. Models of solvent migration were developed based on mass balance, energy balance, equilibrium solubility of heavy components in the liquid phase, and different assumptions of the diffusion mechanism (molecular diffusion or hindered diffusion). Comparison of the experimental data obtained from the solvent migration cell and the model predicted results showed that molecular diffusion is the mechanism responsible for solvent migration in the deposit.