Modelling the rheology of complex fluids : Cases of bitumen and heavy oils at low temperatures.

摘要

As complex fluids such as heavy oil or bitumen pass from the field to process units, structural and compositional changes occur that are intimately linked with pressure (P), temperature (T), and shear histories. In this exploratory work, a modified Structural Kinetics Model is used to calculate the apparent shear viscosity of three complex fluids: Maya Crude Oil (MCO), Athabasca Bitumen (AB) and Safaniya Heavy Oil (SP) and their related nano-filtered fractions (permeates and retentates) at low temperatures. The proposed model involves a structural parameter λ that tracks the mechanical history of these fluids and a temperature shift factor aTP that integrates the thermal history, through the usage of the concept of fictive temperature T eff inside a modified Williams Landel Ferry (WLF) equation. Rheological data for the feedstocks were divided into a training data set, used to fit model parameters, and an extrapolation data set, used to test the asymptotic behaviour of the model with respect to temperature and shear history. Rheological data for the nano-filtered permeates and retentates, with varying mass fractions of structured phase, comprised a prediction data set. Average absolute deviations (AAD) less than 15% and R2 values approaching unity were obtained for the prediction data set. AAD values were less than 4 % for the training and less than 10 % for the extrapolation data sets. The modified Structure-Kinetics Model offers insights, as well as flexibility and accuracy for simulating heavy oil and bitumen rheological properties under conditions where these fluids are structured.