Hydraulic fracturing in the upper crust

Abstract

The coupled problem of the slow motions of a viscous fluid in a crack and the deformations and percolation induced by them in the external poroelastic medium is examined. The motions are produced by injection of a liquid into a borehole. The flow in the crack is described by the equations of the Stokes hydrodynamics in the lubricating layer approximation. The outer problem is described by the equations of poroelasticity. The plane motion is studied analytically in more detail. The problem for numerical calculation in the 3-D case is formulated. The goal of the work is to gain an insight into the essence of geomechanical processes associated with hydraulic and magmatic fracturing in upper (cold and brittle) parts of the Earth’s crust and to find optimal methods for the numerical description of these processes. They are based on reducing the coupled problem to successive solution of the uncoupled problems. The main hydrodynamic effect of the fluid flow in a crack is connected with the presence of crack tip singularities that can lead to crack disintegration or a change in the conditions of the equilibrium state of the crack.