Modeling of a Hydraulic Fracture Initiation and Propagation on an Injection Well for Non-Fractured Terrigenous Rocks on the Priobskoye Field

Abstract

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.

Injection of Gelling Systems to a Layered Reservoir for Conformance Improvement

“…Examples of such irregularities are “super-reservoirs” with permeabilities that differ from the average field values by tens or hundreds of times, regional or induced fracturing of formations. Examples include the local occurrence of a super-reservoir at the Talinskoye Field [ 18 ] or the development of induced or so-called auto-fractures at the Priobskoye Field, where the water breaks through into fractured producers due to the convergence of two types of fractures [ 19 ]. Manipulating these causes of reduced reservoir sweep is called flow-diverting technologies, although the agent bases of conformance control and injected water diverting technologies are very close, as a rule, only the content and injection volumes differ.…”