Modeling of Water-Induced Fracture Growth Pressure Using Poroelastic Approach

One of the main factors affecting the efficiency of hydrocarbon production during the field development is waterflooding pattern used for the formation pressure maintenance. It is common practice when production wells that have been worked for depletion are converted to the injection. However, since hydraulic fracturing was previously performed on the majority of production wells, the injection under high pressure can cause risks associated with spontaneous fracture growth. This can lead to the water breakthrough and decreasing of production efficiency. The purpose of this work is modeling of fracture growth pressure on the injection well using poroelasticity approach.

Thus, a physico-mathematical model of the problem for determining the pressure at which the fracture will grow on the injection well is built. Solving a problem involves sequential finding of the pressure field in a development element using Laplace equation, and then the stress field using an equilibrium equation. The solutions were obtained by usage of analytical and numerical approaches including Fourier transform and finite-difference scheme. Verification of the obtained solution was carried out by validating the model on a finite element solution. The criterion of fracture growth was also derived, according to which the fracture propagation occurs when the minimum horizontal stress at the tip of the fracture is exceeded.

The influence of the parameters of the reservoir and the development on the value of the critical pressure was evaluated, namely, it was shown that an increase of Biot coefficient leads to an increase of fracture growth pressure and an increase of Poisson’s ratio decreases the critical pressure.

It was found that an increase of the distance between the wells in the line leads to the decrease of the pressure at which water-induced fracture starts to grow, while an increase in the distance in a row along the vertical increases this pressure.

It should be pointed out that the most common way to control the growth of water-induced fractures is combined hydrodynamic and geomechanical modeling, but this method is very time consuming and computationally expensive. In this connection, a quick method for estimating the fracture initiation pressure was proposed. The presented model can be used to control the growth of water-induced fracture, namely, to determine the regimes of fracture growth, to regulate the waterflood regimes (pressure and flow control), and to optimize the field development system without using combined hydrodynamic and full geomechanical modeling.