Many layered no-crossflow gas reservoirs when initially completed did not benefit from the use of selective stimulation. Without aid of an effective diversion technique, the stimulation treatment only acts on the high permeability layers. This generally leaves the lower permeability layers in a poorly stimulated condition. Significant upside potential may exist in mature areas through restimulation of the lower permeability intervals.

We present the results of a study of the depletion performance of a two-layer gas reservoir suffering from a poor initial stimulation. We assume that only the higher permeability interval has been successfully stimulated. A 2-D radial simulator is used to investigate the subsequent depletion performance after the low permeability layer is restimulated. Using a graphical presentation of rate versus time and pressure-cumulative production, we illustrate the restimulation effects on the depletion performance of these reservoirs. The graphical presentations clearly illustrate the advantages of re-stimulation as a function of volume ratio, layer skin, and abandonment rate. In addition, a 3-D Cartesian model is used to investigate the restimulation impact in competitive reservoirs. We discuss the magnitude of potential reserve increases and present several field case histories illustrating the restimulation effect. Guidelines for selecting potential restimulation candidates are presented.

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