Received: 16 March 2017 Revised: 15 December 2017 Accepted: 12 January 2018
Numerical prediction of gas migration properties in
Callovo-Oxfordian (COx) argillite using
Yunnan University, Kunming, China
University of Lille, CNRS, Centrale Lille,
LaMcube FRE 2016, Lille, France
Jean-Baptiste Colliat, University of Lille,
The feasibility study of long-term radioactive waste storage in low-permeable
rocks has been performed by considering various damage and failure scenarios.
This study aims at the numerical investigation of gas (mainly produced by corro-
sion of metallic parts) migration properties through the low-permeable forma-
tion of Callovo-Oxfordian argillite. Traditional methods, based on macroscopic
approaches or homogeneous transport properties, are inappropriate to analyze
this issue at the mesoscopic/microscopic scale. In this study, realistic porous
space morphologies are constructed through union of excursions of random
fields considering different experimental pore size distributions. Afterwards,
purely geometric analysis of pore space is conducted by morpho-mathematical
operations for the purpose of the extraction of preferential gas transport path-
ways and the prediction of the gas entry pressure, the gas breakthrough pressure,
and the following imbibition process.
Callovo-Oxfordian argillite, excursion set of random field, gas breakthrough, morphological mod-
elling, morpho-mathematical operations
Low-permeable argillite is a potential host rock candidate in the context of long-term radioactive waste repository. In
France, Callovo-Oxfordian (COx) argillites are in large quantities in departments of Haute-Marne and Meuse.
(French National Radioactive Waste Management Agency) built a deeply seated underground research laboratory on the
site of Bure to investigate the properties of COx argillite for performance and safety assessments. During the long-term
storage, due to the humid corrosion of metallic structures, the degassing process in clay formation, the radioactive waste
decomposition, and the water radiolysis, a significant amount of hydrogen gas may generate.
Since the amount of dis-
solved gas in interstitial water is limited by the low solubility, the continuously producing hydrogen may accumulate and
form a gas phase. If gas migration is restricted by the low fluid conductivity of rock, the gradually increasing gas pres-
sure may exceed the fracture threshold and damage the repository formation. Considering this, the investigation of gas
transport through COx argillite is of high relevance.
Gas migration in low-permeable media principally follows 4 modes
: advective and diffusive transport of dissolved
gas in porewater; capillary two-phase flow
; gas penetration into micro-cracks
; and gas migration along macroscopic
For COx argillite, the micro-crack threshold is about 9 MPa and the fracture threshold is about 12 MPa.
lowing the capillary two-phase flow mechanism, gas migration involves the creation and the propagation of preferential
Int J Numer Anal Methods Geomech. 2018;42:1125–1143. wileyonlinelibrary.com/journal/nag Copyright © 2018 John Wiley & Sons, Ltd. 1125