A Simplified Mathematical Model for Formation Caprock Integrity Incorporating Creep Deformation: Implications for Hydrogen Underground Storage

Abstract

This research effort aims at addressing the Geo-mechanical aspect of hydrogen underground storage, specifically caprock integrity tests using creep deformation modelling. This study also concentrates on time and injection rate dependent processes which could lead to permanent deformation of reservoir rocks during injection and production cycles due to the cyclical pore-pressure changes. The newly developed model includes a new term that accounts for pore expansion and compaction, and was coupled to the simplified power law. The model was then verified against uniaxial laboratory data and validated by comparing it to the power law model. The idea is to simulate several injection and production cycles of vast amounts of hydrogen into a reservoir that is saturated primarily by saline formation water (aquifer) under certain conditions to assess caprock integrity. The model has been validated using the uniaxial test data provided by Wu et al.2020 and achieved good accuracy. Furthermore, the model was compared to the simplified power law with no apparent advantages. This is attributed to the low-pressure differential and hence it is expected that the model will yield better estimations when applied to high pressure differential cases.