Characterization of Gas Transport in Low-Permeability Media: Two-Phase Flow Analysis of an In-Situ Experiment

Abstract

This paper describes a field-scale experiment on gas transport mechanisms performed at the Andra Underground Research Laboratory in a clay rock. The experimental layout consists of two parallel boreholes that are equipped with multiple packer completions delimiting three intervals each and which monitor continuously the pore pressure evolution of the clay rock. Nitrogen gas is injected in the middle test interval of one of the boreholes at increasing constant rates. The experimental data collected so far are presented along with their interpretation by means of 1D and 3D numerical modeling of the boundary value problem. The numerical results show that a predictive model as two-phase flow approach is able to reproduce experimental observations in large scale system, as far as the injection flow rate and the gas pressures remain moderate. Moreover permeability is not modified by gas injection, which indicates that the rock mass is not damaged by the gas pressure increase during the test.