Geomechanical Investigation of Mechanisms Involved in Carbon (CO2) Storage and Caprock System Integrity

Project: FDCRGP

Project Details

Grant Program

Faculty-development competitive research grants program for 2023-2025

Project Description

Carbone dioxide (CO2) Capture and Storage (CCS) is the process of collecting CO2 produced by mankind's daily and industrial activities and injecting it into subsurface geologic storage sites to isolate CO2 from the atmosphere. The major steps involved in CCS are CO2 capture, transport, and storage. The focus of this project is on key aspects of the storage stage. With an increase in demand for CCS and the number of CO2 storage sites, there is a need for a better understanding of mechanisms involved in CO2 storage, to enable the assessment of the risks associated with various storage site breach mechanisms and possible CO2 leakage to the environment. CO2 can be stored in saline aquifers, depleted oil and gas reservoirs, for Enhanced Oil Recovery (EOR) projects, unminable coal seams, or other porous formations.
The idea of carbon dioxide storage in geological formations was first investigated by Koide et al. (1992) and has been a hot topic ever since. The Weyburn-Midale CO2 storage project in Southeast Saskatchewan, the Sleipner CO2 storage project in the North Sea, and the In Salah CO2 storage project in Algeria are good examples of full-scale CO2 storage. The main objective of underground storage is to trap CO2 in geological formations permanently. The general conditions for underground storage are:

• A geologic formation or structure in which CO2 can be stored (e.g., an anticline, a porous rock formation)
• A caprock layer formation with low permeability to seal the storage formation
• Sufficient overburden (depth) to provide enough confining pressure to incarcerate the stored fluid and provide the supercritical state for CO2

The leakage potential of CO2 from the storage site is the most risk-prone element. Major sources of CO2 leakage are wellbore damage (Whittaker et al., 2011), caprock fracturing and breach (Verdon et al., 2013, White et al., 2014), and leakage through faults and major discontinuities (Khiluk et al. 2000; add more Refs....). Despite significant research conducted on various components (e.g. capacity, injectivity, containment) of CO2 storage sites in the past decades, there are still several knowledge gaps related to geomechanics of CO2 storage reservoirs. The reason is the complexity of the process, in particular, the behaviour of the host media which is the rock mass system at large scales. Moreover, the complicated boundary conditions and non-linearities associated with the problem as well as the site and case-specific nature of the subject make it difficult to present a unique solution to the problem. Complex aspects involved in the storage stage of the process are:

• Mechanical in-situ stress field (magnitude, orientation, stress ratio, etc.) and stress field interactions
• CO2 containment mechanisms and aspects including regional and structural geology, host rock fluid flow characteristics and pore pressure field, geometric aspects of storage complex and its structural/stratigraphic traps, and geochemical trapping mechanisms
• Coupled and time-dependent nature of mechanical, hydro, and thermal stress fields associated with CO2 storage
• The storage site 3D stress field change and stress path as a function of injection history and time

The goal of this research is to focus on the geomechanical design aspects of CO2 storage. With regard to the complex nature of the problem, various authors attempted to provide solutions, with varying degrees of success. Jimmens and Chalaturnyk (2002) investigated various geomechanical risks associated with CO2 storage and categorized the sources of risks as storage-induced (various modes of fracturing), tectonic activity-induced (e.g., seismically active zones), and reactivation of major structures after storage. All these mechanisms may lead to CO2 leakage.
The presented solutions for the geomechanical analysis of CCS are in the form of simple analytical solutions, engineered solutions (semi-analytical), and numerical solutions. Examples of analytical solutions are the works of Goulty, 2003; Holt et al., 2004; Hawkes et al., 2005; Bohloli et al., 2017)
In the semi-analytical or engineered solutions, a combination of analytical, numerical integration processes, and validation with some test results are used to present a final solution to the problem (Segall, 1985; Segall et al., 1994; Hickman et al., 1997; Wiprut and Zoback, 2000; Zoback, 2000; Soltanzadeh, 2009). Numerical methods are advanced design tools that provide an approximate solution to complicated problems having non-linear behaviour. CO2 storage problems fall into the class of “data-limited” problems, in which one seldom knows enough about rock mass and storage system to describe them properly analytically. With the ease of access to powerful computers, the ability to include geological information, implementation of advanced constitutive material behaviour and flow models, and 3D visualization capabilities, the focus is shifted toward the use of advanced computational techniques in CCS research. The non-linear thermo-hydro-mechanical behaviour of the CO2 storage system necessitates the use of advanced numerical methods to provide real insights into the problem and as design tools. The single-phase and multi-phase flow in CO2 storage was simulated numerically without consideration of mechanical coupling (Daughty and Pruess, 2004; Gasda et al., 2013). Some authors adapted an iterative and weakly-coupled modelling approach. In these works, geomechanical algorithms are developed independently and then linked to flow simulator algorithms, and the thermal, hydraulic, and mechanical stress fields are solved sequentially (Rutqvist et al., 2010; Pan et al., 2014). In the fully coupled models, the mechanical and hydro stress fields are coupled fully and in a two-way iterative manner. In these models, all mechanical, thermal, and hydro fields are solved simultaneously in each computational step (Gosavi et al., 2006; Xiong et al., 2013; Salimzadeh et al., 2018; Zareidarmiyan et al., 2018).

Geomechanical assessment is a major component in all CCS projects and dominates the safety of CO2 storage operations. Given the complicated nature of CO2 storage, the selection of a realistic storage site characterization scheme and design strategy is of paramount significance. Advanced modelling methods are the only viable alternative for geomechanical design aspects of CO2 storage. They enable consideration of complex material behaviour, in-situ stress, stress interactions, complicated loading, coupling of stress fields, geometric complexities, and scale effects. With regard to uncertainties that exist in rock system characterization and design data prior to storage site development, there are always risks associated with inappropriate design as a function of storage site condition. The main goal of this research is to employ fully coupled numerical methods for geomechanics analysis of CO2 storage problems. Typical CO2 storage scenarios will be simulated at full scale, exploring the governing mechanisms involved in storage site damage mechanisms. 3D numerical methods with interface element/discontinuity modelling capabilities will be used to model active CO2 storage sites with available historical data. The obtained modelling results will be calibrated against field data. A Series of runs will be carried out to assess the role of key design parameters on the storage site stress field and caprock displacement field. Based on sensitivity analysis results design charts will be developed which can be used as an aid in the design of new CCS projects.
Short titleGeomechanical Investigation of CCS
Effective start/end date1/1/2312/31/25


  • CCS, Co2 Storage, Geomechanical Investigation


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