Characterization of the Formation, Flowability, and Resolution of Brazilian Crude Oil Emulsions

Abstract

The stability and flow properties of w/o emulsions are investigated using two Brazilian crude oils: a heavy crude oil and a waxy crude oil. Stable emulsions are shown to form with the heavy crude oil at water cuts up to 50 vol %, while the waxy oil forms stable emulsions with water cuts as high as 70 vol %. Rheological flow curves show shear thinning behavior for the crude oils as well as emulsions at low-temperature conditions. The presence of emulsified water is shown to significantly increase the yield strength of waxy crude oil gels formed by quiescent cooling. The waxy gels exhibit third-order degradation kinetics with respect to absolute imposed strain. Nuclear magnetic resonance (NMR) analysis confirms tight emulsions with average droplet sizes of 1.7 μm at 30 vol % water cut. Electro-coalescence measurements indicate decreasing critical electric field values with increasing temperature, resulting from a lower viscosity of the continuous phase as well as dissolution of paraffin wax. From a fluid processing perspective, high emulsion stability and shear thinning behavior are promising characteristics for using emulsion transport of hydrate particles at low-temperature and elevated pressure conditions. To prevent hydrate plugging, low water cuts should be maintained and emulsification should be completed before the fluid enters the hydrate formation envelope. Mixing of dissimilar formation fluids should be avoided subsequent to hydrate formation. In addition, pipeline startup risks associated with paraffin wax gelling should be considered during the design phase of the production system.