Experimental and molecular dynamics simulation investigations of adhesion in heavy oil/water/pipeline wall systems during cold transportation

Abstract

With the increased water content in heavy oil gathering pipelines and application of cold transportation methods, understanding adhesion behavior in heavy oil/water/pipeline wall systems has greatly gained in importance. Here, a combined experimental and molecular dynamics (MD) simulation was used to investigate the effect of the heavy oil composition and molecular structures on adhesion. The capacity of heavy oil adhesion and the effect of adding asphaltene molecules to the heavy oil were studied experimentally. MD simulation systems with different asphaltene concentrations were established based on the NPT and NVT ensembles. The results showed that the addition of asphaltene increases the adhesion of heavy oil by as much as 16.60–83.35%. The center of mass, mean square displacement, and radial distribution function of heavy oil droplets were also analyzed, which indicated that the viscosity and thickness of the heavy oil adhesion layer were also affected by the asphaltene content. The functional groups in asphaltene molecules promote the adhesion of oil droplets and inhibit the adhesion of the water phase. Further, asphaltene aggregates are formed by face-to-face stacking, which severely impedes heavy oil flow assurance. The results from this study greatly contribute to understanding the mechanisms of heavy oil adhesion during cold transportation.