Petroleum Industry has enjoyed a huge success since its inception in mid 18^th century. The dwindling oil supplies have posed greater challenges, however. Hence the oil industry has already started to look for the alternate supplies and the abundantly available Heavy oil reserves (North Slope of Alaska, US) present a viable and promising solution. At present, a lot of research is being directed towards the understanding of the behavior of these oils. Viscosity is a one of the crucial properties that defines the behavior. The present work makes a fresh attempt, with thorough literature survey, to compare and suitably adjust the compositional models for Medium-heavy oils.

The viscosity can be modeled in a number of ways. In the broader perspective, the models can be classified in following ways: 1. Fundamental models, 2. Semi-fundamental models, and 3. Correlative models. The fundamental models are very accurate. But, at present, these are applicable only for simple fluid systems, viz. ideal gas-mixtures. On the other hand, since its inception, oil industry has been hugely dependent on the correlative models. These models are generally simple-to-use and require field-measured variables. Over the years these models have served the oil industry very well. The correlative nature of these models, however, doesn’t help the careful extrapolation. Considering above scenario, the Semi-fundamental models, with an optimum blend of previous two classes, would provide an ideal choice to model the viscosities. The proposed work will concentrate on the Compositional modeling of the Medium-Heavy oil viscosities.

Most of the compositional models are mainly based on the principle of the corresponding states. The most famous ones are the Lohrenz-Bray-Clark (LBC) model and that of the Pedersen et.al. These models feature in almost all commercial modeling softwares and accurately predict the viscosities of the light oil systems. Because of their tremendous potential, in the past few years numerous attempts have been made to extend these models as far as Heavy oils are concerned. In the present work, these models will be analyzed and compared against the experimentally available viscosity data. Based on the analysis, their drawbacks and potentials will be highlighted. Recently proposed Lindeloff et al. (2004) model has shown a great potential. However, this model has very low predictive capability. An attempt has been made to upgrade this model to be applied with great degree of confidence. Considering the present need, the proposed work should provide a great insight of current compositional viscosity models. The work will also benefit the user to model the Medium-Heavy oil viscosities.