Smeared Modeling of Hydraulic Fracture Using Partially Coupled Reservoir and Geomechanics Simulators

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  • There are aspects of the hydraulic fracturing process that remain unresolved for weakly
    consolidated sandstones. These issues include fracture modes and geometries for weak
    sandstones, and higher-than-expected fracture pressure in some field projects. The development
    of shear bands and the concomitant shear dilation may result in stress alterations in the reservoir,
    requiring higher injection pressures to induce tensile fractures. Further, pressure redistribution in
    the medium can result in stress increases, hence, create conditions in which a tensile fracture
    may not be induced under operating conditions.
    In this paper, a smeared fracture type hydraulic fracture simulator is developed through
    numerical coupling between an in-house reservoir simulator and a geomechanical commercial
    software (FLAC2D). The new package falls within the category of partially decoupled model
    and is versatile, flexible and efficient. This approach can be used to couple any other advanced
    commercial fluid flow or geomechanical simulators for an accurate description of the initiation
    and propagation of hydraulic fractures.
    The paper contains a discussion of the partial coupling technique to link fluid flow and
    geomechanical calculations in modeling fracture initiation and propagation. The models use a
    common gridblock for the fracture and reservoir and use the deformation calculations to update
    the porosity and permeability. The method captures the interactive effects of the fracture on
    reservoir fluid flow and formation geomechanics through stress dependent permeability and
    The developed smeared fracture model can capture both tensile and shear fractures in the
    formation. Major features of this model include modeling poroelasticity and plasticity, matrix
    flow, shear and tensile fracturing with concomitant permeability enhancement, saturationdependent permeability, stress-dependent stiffness and gradual degradation of oil sands due to
    dilatant shear deformation. The model has been applied to numerically simulate field size
    hydraulic fracturing in oil sands during cold water injection to show the predictive capability of
    the simulator.

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    Article (Draft / Submitted)
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    Attribution-NonCommercial 4.0 International