WATER-HYDROCARBON EMULSION FLOW IN MICROCHANNELS

摘要

Water-hydrocarbon emulsions are widely used in various oil production processes, for example for blocking drill holes and managing fluid flows. From rheology view point the typical distinctive feature of such emulsions is their higher viscosity and non-Newtonian behavior as compared to that of carrier liquid. However, the flow of emulsions in capillary structures and microchannels reveals a remarkable, quite unexpected phenomenon called "dynamic blocking", whereby the flow of emulsion through microchannel ceases in time despite the presence of the applied constant pressure gradient. The terminology "dynamic blocking" is due to the fact that, despite an apparent macroscopic flow arrest, the flow can nevertheless be observed on a microscopic scale at a much lower (by three to four orders of magnitude) flow rate and with a significantly modified structure of microflows. It should be noted that the size of water microdrops is significantly (by more than an order of magnitude) smaller than the characteristic size of the channel. No clear understanding exists today for the behavior of emulsions as they move through the microstructure. In this paper some experimental results of "dynamic blocking" are presented, and some plausible mechanisms explaining its physical nature are discussed.