Inversion of heavy crude oil-in-brine emulsions

The inversion of heavy crude oil in brine emulsions stabilized with nonionic surfactants has been studied experimentally. Most of the tests were carried out in beakers and in a cone and plate viscometer with the cone displaced at some distance from the plate. The effects of shear rate, surfactant species and concentration, temperature and oil fraction on emulsion inversion were studied. Rotating toroid tests were carried out to compare the data generated from the cone and plate viscometer to that for a pipeline. found that inversion of oil-in-brine emulsions was always associated with the disappearance of the surfactant from the aqueous phase. The surfactant affinity (i.e., hydrophilic property) for the aqueous phase appeared to be critical in the stabilization of these emulsions. Increasing the number of ethylene oxide units increased the hydrophilic property of the nonionic surfactant and the stability of the emulsion. The emulsion stability also depends on the strength of the interfacial adsorption film. High shear rates not only destroyed the film, but also displaced fragments of the film back to the aqueous phase. The emulsions appeared to remain stable only when the surfactant concentration in the aqueous phase was above the C.M.C. level, providing sufficient surfactant stock to maintain the stability of the interfacial adsorption film. High temperatures reduced the physical strength of the interfacial adsorption film, encouraging inversion. roid tests indicated that the cone and plate viscometer is probably a good simulation of the emulsion flow behavior in pipelines. The cone and plate viscometer can be used to select a suitable surfactant concentration for pipeline transport.