Heavy , biodegraded crude oils are often high in viscosity , sulfur, metals, Conradson carbon residue, and naphthenic acids. As a result, they are diffi- cult to produce, transport, and refine. Their major advantage is their vast abundance. Heavy crudes not only are priced much below conventional crude oils, their market is limited to refineries with vacuum resid conversion and with the ability to cope with additional problems: fouling, corrosion, water emulsions, sulfur removal, and catalyst poisoning. It is, therefore, not surprising that anew trend is to partially upgrade heavy crudes near the production site to reduce the viscosity and density for easier transport and to remove catalyst poisons and corrosion agents for increased refinery mar- kets. The challenges and opportunities of partial upgrading from the well to the refinery are reviewed, including the potential problems in refining partially upgraded crude oils.
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