This work introduces a new model for production decline analysis of hydraulically fractured wells based on the concept of induced permeability field. We consider the case when the hydraulic fracturing operation – in addition to establishing the fundamental linear flow geometry in the drainage volume – alters the permeability throughout, but with varying degree depending on the distance from the main fracture plane. We show that, under these circumstances, the reservoir response departs from the uniform-permeability approach significantly.

The new model differs from the once promising group of models that are inherently related to power-law type variation of the permeability-area product and hence are burdened by a mathematical singularity inside the fracture. Analysis of field cases reveals that the induced permeability field can be properly represented by a linear or exponential function characterized by the induced "threshold permeability" and the "stimulation ratio". The threshold permeability is the minimum value of the permeability within the stimulated reservoir volume and the stimulation ratio is the contrast between its maximum and minimum values. Knowledge of these parameters is crucial in evaluating the effectiveness of today’s intensively stimulated well completions, especially multi-fractured horizontal wells in shale- gas. The approach describes, in a straightforward manner, the production performance of such wells exhibiting skin factor effect, transient linear flow, and late time boundary effects.

This work provides a new approach to modeling hydraulic fractured reservoirs, together with its analytical solution in the Laplace space. Furthermore, we provide type curves for decline curve analysis, approximate solutions in the time domain, field examples, and practical guidelines for the analysis of commonly occurring production characteristics of highly stimulated reservoirs.

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