Modelling Viscosity and Mass Fraction of Bitumen-Diluent Mixtures

Abstract

In the recovery of bitumen, viscosity reduction becomes important, both below and above the ground. The addition of a liquid diluent is thought to break down or weaken the intermolecular forces which create high viscosity in bitumen (1) . The effect is so dramatic that the addition of even 5% diluent can cause a viscosity reduction in excess of 80%; thus, facilitating the in situ recovery and pipe line transportation of bitumen.The knowledge of the bitumen-diluent viscosity is highly important, since without it, calculations in upgrading process, in situ recovery, well simulation, heat transfer, fluid flow, and a variety of other engineering problems would be difficult or impossible to solve. This paper presents the development of a simple correlation to predict the viscosity of binary mixtures of bitumen-diluent in any proportion. AbstractThe viscosity model is an important component in enhanced oil recovery packages and, for pure bitumen, several accurate models are available. In this study, a simple correlation presented in an earlier publication is extended to predict the viscosity of bitumen-diluent mixtures, as well as the mass fraction required to reduce bitumen viscosity to pumping viscosity.In developing the viscosity model, viscosities of pure bitumen and diluent were used as the endpoints, and the diluent mass fraction was raised to a power of "n" (a viscosity reduction parameter) to account for the sharp drop in bitumen viscosity with increase in diluent mass fraction. The model was developed with 99 data points from three different bitumens and five diluents; spanning a viscosity range of 10 -1 to 10 6 mm 2 /s. The model was used to recalculate the viscosity and mass fraction values, and results compared with similar correlations by Cragoe and Chirinos. The best match was obtained with our correlation, with overall average absolute deviations of 12% and 5% for viscosity and mass fraction predictions, respectively. Predictions on data not used in developing the model showed an excellent match between experimental and predicted values, with an overall average absolute deviation of below 10% for viscosities of mixtures at 25˚ C, 60.3˚ C, and 82.6˚ C.

Hydrothermal liquefaction of biomass for the production of diluents for bitumen transport

“…Diluent reduces the viscosity of bitumen by weakening the intermolecular forces . Several studies have been done on the commercial use of liquid solvents as diluents to reduce the viscosity of bitumen .…”

Post-Production Heavy Oil Operations: A Case For Partial Upgrading

“…Once we have compositional volumes of each fraction, the next step is to embark on the all-important mission of determining the viscosity of the visbroken product. Several viscosity correlations exist that determine viscosity as a function of specific gravity for heavy oils (Egbogah & Ng 1990, Bennison 1998& Miadonye et al 2001. However, upon testing these models all provided wildly differing results, as shown in Table 9.…”

On modeling of bitumen/n‐tetradecane mixture viscosity: Application in solvent‐assisted recovery method

“…Generally, world's known tar sands, which are a blend of bitumens and sands, have the total bitumen in place larger than 2,000 billion barrels. In most organic deposits, owing to the lack of reservoir energy, low reservoir temperatures, shallow burial depth, extremely high bitumen viscosity, and asphaltene content due to biodegradation, conventional oil production approaches will be inefficient for bitumen recovery …”

“…Solvent‐assisted methods, which consist of vapor extraction process and solvent flooding, are of the most efficient processes for unconventional enhanced hydrocarbon recovery, stimulation, wellbore cleaning and pipeline transportation . Basically, the major mechanism of the bitumen viscosity reduction with a solvent is weakening or breaking down the intermolecular forces leading to sufficient solvent dissolution and possible asphaltene precipitation . Solvent‐assisted methods are potentially implemented remedy to the delineated constraints of thermal‐assisted processes such as formation heat loss, produced water treatment, and water supply requirement .…”