Interaction between Injection Points during Hydraulic Fracturing

TL;DR

This paper develops a continuum model to study how multiple injection points interact during hydraulic fracturing in heterogeneous rocks, revealing a correlation length that influences fracture behavior and a novel attractive force between fractures.

Contribution

It introduces a new formalism for modeling coupled fluid and rock dynamics and analyzes the interaction effects between injection points in hydraulic fracturing.

Findings

Correlation length of 30-45 m in low-permeability rocks.

Strong interaction causes fractures to be attracted to neighboring injection points.

Fracture behavior depends on rock heterogeneity and injection point separation.

Abstract

We present a model of the hydraulic fracturing of heterogeneous poroelastic media. The formalism is an effective continuum model that captures the coupled dynamics of the fluid pressure and the fractured rock matrix and models both the tensile and shear failure of the rock. As an application of the formalism, we study the geomechanical stress interaction between two injection points during hydraulic fracturing (hydrofracking) and how this interaction influences the fracturing process. For injection points that are separated by less than a critical correlation length, we find that the fracturing process around each point is strongly correlated with the position of the neighboring point. The magnitude of the correlation length depends on the degree of heterogeneity of the rock and is on the order of 30-45 m for rocks with low permeabilities. In the strongly correlated regime, we predict a novel effective fracture-force that attracts the fractures toward the neighboring injection point.