Rheologica Acta, Vol.54, No.9-10, 817-829, 2015
Structural breakdown and recovery of waxy crude oil emulsion gels
The structural breakdown and recovery behaviors of waxy crude emulsion gels were investigated. First, the tests of stepwise increase in shear rate and hysteresis loop were carried out, and the structural breakdown process was further analyzed. Then, the structural recovery behaviors were investigated from the recoveries of apparent viscosity, storage modulus, and yield characteristics. It was found that the thixotropy of emulsion gels weakens with increasing water cut and the structural breakdown process gradually changes from solid-like brittle fracture to ductile failure. The broken-down structure of emulsion gels can only recover partially, and both the recovery rate and the recoverability are related to water cut, precipitated wax content, and pre-shear rate. To be specific, the storage modulus recovers faster with increasing water cut and decreasing precipitated wax crystals, or after pre-sheared at a higher rate, while the effects of water cut and precipitated wax on the recovery rate of yield stress are opposite. The recovery degree of both storage modulus and yield stress decreases obviously with increasing amount of wax crystals but is barely influenced by the water cut.