Assessing the Impact of Oil Viscosity Mixing Rules in Cyclic Steam Stimulation of Extra-Heavy Oils
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A global steady increase of energy consumption coupled with the decline of conventional oil resources points to a more aggressive exploitation of heavy oil. Heavy oil is a major source of energy in this century with a worldwide base reserve exceeding 2.5 trillion barrels. Management decisions and production strategies from thermal oil recovery processes are frequently based on reservoir simulation. A proper description of the physical properties, particularly oil viscosity, is essential in performing reliable modeling studies of fluid flow in the reservoir. We simulated cyclic steam injections on the highly viscous Hamaca oil, with a viscosity of over 10,000 cp at ambient temperature, and the production was drastically impacted by up to an order of magnitude when using improper mixing rules to describe the oil viscosity. This paper demonstrates the importance of these mixing rules and alerts reservoir engineers the significance of using different options simulators have built in their platforms to describe the viscosity of heavy oils. Log linear and power mixing rules do not provide enough flexibility to describe the viscosity of extra heavy oil with temperature. A recently implemented mixing rule in a commercial simulator has been studied providing satisfactory results. We also suggest more flexible mixing rules that could easily be implemented in commercial simulators. Copyright 2005, Society of Petroleum Engineers.
author list (cited authors)
Mago, A. L., Barrufet, M. A., & Nogueira, M.