skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications

Abstract

This report documents the accomplishments achieved during the project titled “Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications” funded by the US Department of Energy, Office of Fossil Energy. The objectives of the project were to develop modeling capabilities for predicting CO2 and brine migration in fractured reservoirs during geologic carbon storage and to investigate the feasibility of carbon storage in fractured reservoirs using the newly developed modeling capabilities. To achieve these objectives new mass transfer functions were developed to adapt existing dual-continuum approaches – a commonly used approach in hydrocarbon reservoir modeling – to the CO2-brine system. In the dual-continuum approach the undisturbed rock matrix and the fractures are modeled as two separate continua, which are coupled through mass exchange of CO2 and brine between the two continua. Mass transfer functions represent the mass exchange between fractures and the rock matrix, without requiring highly resolved numerical grids of individual fractures, thus allowing large modeling domains relevant to geologic carbon storage questions (tens of meters to hundreds of kilometers). Mass transfer functions for the exchange of both free-phase CO2 and brine between fractures and rock matrix were developed for bothmore » the injection phase and the post-injection phase. During the injection phase the fractures are filled with CO2, while the rock matrix is initially filled with brine. Therefore, a mass transfer function was developed that is based on vertical displacement of brine by CO2 in the rock matrix due to gravitational forces. Once CO2 injection ceases and CO2 migrates away from the direct vicinity of the injection site, the fractures will begin to re-fill with brine, while the rock matrix will have high CO2 saturations. For these conditions a mass transfer functions was developed that is based on spontaneous imbibition, as the pore spaces in the rock matrix are much smaller than in the fractures. For formations with low permeability or high capillary entry pressure of the rock matrix, free-phase CO2 may not be able to enter the rock matrix. However, free-phase CO2 at the interface between fractures and rock matrix can dissolve into brine resident in the rock matrix. Therefore, additional mass transfer functions were developed based on aqueous-phase diffusion of CO2 through the rock matrix. These mass transfer functions are based on existing solutions for diffusion and were expanded to be applicable to a variety of block shapes relevant to dual-continuum modeling. Implementations of the newly developed mass transfer functions showed that they give accurate results when compared to highly resolved models. In addition to developing new transfer functions, a new vertically-integrated dual-continuum modeling framework was developed. This development takes advantage of fast vertical segregation of CO2 and brine in the fractures due to the density difference between CO2 and brine and the high permeability of the fractures. Therefore, a vertically-integrated vertical equilibrium model for the fractures is coupled with a vertically-distributed model for the rock matrix. The newly developed approach significantly reduces the computational effort, but is only accurate for fracture permeabilities of 100 mD or higher. Finally, the newly developed models were applied to real and hypothetical geologic carbon storage sites to investigate the feasibility of using fractured reservoirs for carbon storage. The general results were, that storage of CO2 – both as free-phase and dissolved – is feasible, but that storage capacities are likely lower than in unfractured systems. While the high permeability of the fractures reduces the injection pressure (or permits higher injection rates), fast migration of CO2 may limit the overall storage volume, because CO2 may escape laterally with not enough of the rock matrix being swept for effective storage.« less

Authors:
; ; ;
Publication Date:
Research Org.:
The Trustees of Princeton University, Princeton, NJ 08544-2020
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1496797
Report Number(s):
Final report: DOE-Princeton-0023323
DOE Contract Number:  
FE0023323
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 97 MATHEMATICS AND COMPUTING; 20 FOSSIL-FUELED POWER PLANTS

Citation Formats

Bandilla, Karl, Celia, Michael, Doster, Florian, and Zhou, Quanlin. Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications. United States: N. p., 2019. Web. doi:10.2172/1496797.
Bandilla, Karl, Celia, Michael, Doster, Florian, & Zhou, Quanlin. Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications. United States. doi:10.2172/1496797.
Bandilla, Karl, Celia, Michael, Doster, Florian, and Zhou, Quanlin. Fri . "Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications". United States. doi:10.2172/1496797. https://www.osti.gov/servlets/purl/1496797.
@article{osti_1496797,
title = {Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications},
author = {Bandilla, Karl and Celia, Michael and Doster, Florian and Zhou, Quanlin},
abstractNote = {This report documents the accomplishments achieved during the project titled “Multiscale Modeling of CO2 Migration and Trapping in Fractured Reservoirs with Validation by Model Comparison and Real-Site Applications” funded by the US Department of Energy, Office of Fossil Energy. The objectives of the project were to develop modeling capabilities for predicting CO2 and brine migration in fractured reservoirs during geologic carbon storage and to investigate the feasibility of carbon storage in fractured reservoirs using the newly developed modeling capabilities. To achieve these objectives new mass transfer functions were developed to adapt existing dual-continuum approaches – a commonly used approach in hydrocarbon reservoir modeling – to the CO2-brine system. In the dual-continuum approach the undisturbed rock matrix and the fractures are modeled as two separate continua, which are coupled through mass exchange of CO2 and brine between the two continua. Mass transfer functions represent the mass exchange between fractures and the rock matrix, without requiring highly resolved numerical grids of individual fractures, thus allowing large modeling domains relevant to geologic carbon storage questions (tens of meters to hundreds of kilometers). Mass transfer functions for the exchange of both free-phase CO2 and brine between fractures and rock matrix were developed for both the injection phase and the post-injection phase. During the injection phase the fractures are filled with CO2, while the rock matrix is initially filled with brine. Therefore, a mass transfer function was developed that is based on vertical displacement of brine by CO2 in the rock matrix due to gravitational forces. Once CO2 injection ceases and CO2 migrates away from the direct vicinity of the injection site, the fractures will begin to re-fill with brine, while the rock matrix will have high CO2 saturations. For these conditions a mass transfer functions was developed that is based on spontaneous imbibition, as the pore spaces in the rock matrix are much smaller than in the fractures. For formations with low permeability or high capillary entry pressure of the rock matrix, free-phase CO2 may not be able to enter the rock matrix. However, free-phase CO2 at the interface between fractures and rock matrix can dissolve into brine resident in the rock matrix. Therefore, additional mass transfer functions were developed based on aqueous-phase diffusion of CO2 through the rock matrix. These mass transfer functions are based on existing solutions for diffusion and were expanded to be applicable to a variety of block shapes relevant to dual-continuum modeling. Implementations of the newly developed mass transfer functions showed that they give accurate results when compared to highly resolved models. In addition to developing new transfer functions, a new vertically-integrated dual-continuum modeling framework was developed. This development takes advantage of fast vertical segregation of CO2 and brine in the fractures due to the density difference between CO2 and brine and the high permeability of the fractures. Therefore, a vertically-integrated vertical equilibrium model for the fractures is coupled with a vertically-distributed model for the rock matrix. The newly developed approach significantly reduces the computational effort, but is only accurate for fracture permeabilities of 100 mD or higher. Finally, the newly developed models were applied to real and hypothetical geologic carbon storage sites to investigate the feasibility of using fractured reservoirs for carbon storage. The general results were, that storage of CO2 – both as free-phase and dissolved – is feasible, but that storage capacities are likely lower than in unfractured systems. While the high permeability of the fractures reduces the injection pressure (or permits higher injection rates), fast migration of CO2 may limit the overall storage volume, because CO2 may escape laterally with not enough of the rock matrix being swept for effective storage.},
doi = {10.2172/1496797},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {1}
}