Enhancement of water-annular heavy oil transportation by superhydrophilic surface and its simulation

In view of the high viscosity, poor fluidity and high transportation cost of heavy oil, water-annular transportation is an effective solution to realize the flow drag reduction during heavy oil transportation, but the large density difference between oil and water leads to the instability of water annular. For this reason, a superhydrophilic surface is introduced to improve the stability of the water annular in the pipeline and reduce the transportation resistance of heavy oil. Besides, the enhancement of heavy oil transportation by superhydrophilic surface was verified through numerical simulation and experiments in combination. Meanwhile, the effect of various factors on oil-water flow, oil-water distribution and pressure drop in pipelines during water-annular transportation were analyzed. The research results show that the superhydrophilic surface could improve the stability of water annular in the water-annular transportation system of heavy oil, with the obvious effect of flow drag reduction. Compared with the water-annular white oil transportation by ordinary pipeline, the flow drag reduction of over 17.49% can be realized, the maximum flow drag reduction is up to 50.15%, and the enhancement is within 9.06%-39.09% after the superhydrophilic surface is introduced. Compared with the white oil transportation without water annular, the flow drag reduction can reach 72.02%-78.21%. Generally, the superhydrophilic surface could significantly enhance water-annular heavy oil transportation with promising application prospects, capable of effectively improving the applicability of water-annular heavy oil transportation technology.