Abstract

Heavy oil has gained significant attention and importance recently because of a multitude of reasons—growing demand of oil from developing economies, declining availability of easily recoverable or "conventional" oil, and significant advances in required technology. Even though the current estimates of heavy oil in place are three times that of conventional oil, they have only recently become economically viable because of sustained high oil prices. Improved technology has also driven down the recovery risk to minimal levels. The earliest recovery methods for heavy oil were largely cyclic stimulation, with steamflooding gaining acceptance in the 1970s. Despite other thermal and non-thermal recovery methods for heavy oil, steamflooding remains the most widely used technology. Current production by steamfloods alone totals more than 1.1 million BOPD.

Previous studies have established how steamfloods are affected by parameters, such as rock properties, oil composition, degree of steam override, sweep efficiency, steam quality, and steam injection rate. However, the capital-intensive nature and low profit margins of the steamfloods mean that each field development decision is crucial and the oil recovery and margins are much more susceptible to uncertainties in oil price, well performance, facility costs, and subsurface parameters.

While studies have been performed to corroborate the effect of subsurface parameters and economic uncertainties separately, there has been little advancement in terms of coupling all of them together in one unified study. In this paper, the effects of uncertainties on project net present value (NPV) are studied by coupling numerical reservoir simulation; a design- of-experiments based approach to handle uncertainty, an established economic model, and a commercial optimizing tool to determine the optimal field operating variables.

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