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Improved Vertical Stress Profiling for Unconventional Reservoirs
Tom Bratton and Mike Soroka demonstrate a workflow to illuminate the mechanical behavior of each layer and then use an appropriate geomechanical model to profile and understand the stress of the targeted interval.
A critical input in a hydraulic fracture stimulation design is the vertical stress profile. From it, designers can determine the variation in the minimum horizontal stress as a function of depth. The depth profile of the minimum horizontal stress (i.e., the vertical stress profile) is a major factor in controlling the geometry of a hydraulic fracture or fracture network development (e.g., Economides and Nolte, 2000). For example, an optimum stimulation design would define the pumping variables and schedule so as to limit height growth to the productive interval while promoting optimum horizontal growth. Height growth into non-productive layers above or below the pay interval reduces the horizontal length in the productive interval. In addition, gravity can concentrate the proppant in the fractures below the producing interval, diminishing fracture conductivity in the producing interval. Both mechanisms decrease production. Therefore, to design an optimal stimulation, an accurate vertical stress profile is required. This requires appropriate and accurate stress models