Modeling of a hydraulic fracture initiation and propagation on an injection well for non-fractured terrigenous rocks on the Priobskoye field

The paper considers a semi-analytical model for the water-injection well critical pressure estimation at which the fracture will initiate. The model is based on the Biot`s theory of poroelasticity and the algorithm based on the Fourier transforms and the finite difference method was used to solve the problem. The solution involves a sequential calculation of changes in the reservoir pressure distribution and changes in rock stresses using plane-stress approach for a periodic development element. For the cases when the assumption of the homogeneity of the elastic, strength and formation reservoir properties is unacceptable three-dimensional geomechanical modeling algorithm is used, taking into account the actual geological parameters of the formations and the results of hydrodynamic modeling using historical data. In addition, a semi-analytical model for the water-induced fracture breakthrough interval (in height) estimation is proposed. The model includes the following parameters: formation pressure, injection speed, fluid viscosity and injection time. The model is based on the net pressure calculation for a rectangular hydraulic fracture in the leakage dominant regime (Perkins–Kern–Nordgren model). The model uses a 1D geomechanical model and reservoir properties as an input data. The breakthrough interval is calculated iteratively with the assumption of the fracture height at each step. The additional net pressure is calculated using the distribution of permeability and formation elastic properties. If this pressure exceeds the compressive rock stresses in the neighboring layers, then the water-induced fracture will grow vertically into the neighboring layers. The iteration continues until the vertical growth stops. The resulting techniques can be used for waterflooding process control and development system optimization.

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