A Model for Tracking Fronts of Stress-Induced Permeability Enhancement

TL;DR

This paper develops a mathematical model for the movement of damage fronts caused by stress-induced permeability changes, using an analogy to the Stefan problem, and applies it to interpret field data from fluid injection experiments.

Contribution

It introduces a novel evolution equation model for stress-induced damage fronts, providing analytical solutions and applying them to real field data interpretation.

Findings

Derived closed-form expressions for damage front position over time.

Provided flow rate estimates during constant pressure fluid injection.

Interpreted field data from Desert Peak, NV using the model.

Abstract

Using an analogy to the classical Stefan problem, we construct evolution equations for the fluid pore pressure on both sides of a propagating stress-induced damage front. Closed form expressions are derived for the position of the damage front as a function of time for the cases of thermally-induced damage as well as damage induced by over-pressure. We derive expressions for the flow rate during constant pressure fluid injection from the surface corresponding to a spherically shaped subsurface damage front. Finally, our model results suggest an interpretation of field data obtained during constant pressure fluid injection over the course of 16 days at an injection site near Desert Peak, NV.