This research effort discusses the effects of a comprehensive range of fluid, rock-fluid and operational properties on the efficiency of steam injection in naturally fractured reservoirs with heavy oil. For this purpose, a fully implicit dual-porosity/dual-permeability simulator is developed, and the model is applied to an inverted nine-spot pattern in a naturally fractured reservoir with heavy oil. The effects of the reservoir and operational properties on the steam displacement of heavy oil are studied comparatively in naturally fractured reservoirs with and without interacting matrix blocks and in approximate single porosity realizations of these naturally fractured reservoirs.

The field scale numerical model is three-dimensional and three phase accounting for capillary, gravitational and viscous forces. The model solves for (nHC+5) primary variables simultaneously, where nHC is the number of hydrocarbon components. The fully implicit model formulates all reservoir and operational parameters as functions of all the primary variables. The model is linearized using the Newton-Raphson method. A direct and an iterative solver is used in the solution of the system of linear equations.

The simulations of steam injection in naturally fractured systems are carried out for long periods of time in order to test the features of the model under strained conditions. The model is verified against the Fourth and Sixth SPE Comparative Solution Projects.

This study should help in screening naturally fractured reservoirs for steam injection, and in designing steam injection operations in these reservoirs. The comparative analysis of the effects of reservoir and the operational parameters in naturally fractured reservoirs should provide insight into the range of confidence of heavy oil recovery from naturally fractured reservoirs by steam injection.

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