GEOLOGICAL SURVEY OF ALABAMA

CARBON SEQUESTRATION RESEARCH

Discrete Fracture Network Models for Risk Assessment of Carbon Sequestration in Coal

A study sponsored by the

U.S. Department of Energy

National Energy Technology Laboratory

Project start date: 5/1/05

Completion: 10/27/08

Overview

Coal is an important sink for the sequestration of carbon dioxide, and software technology is being developed to assess the potential risks associated with carbon sequestration in coal. Natural fractures provide important conduits for fluid flow in coal-bearing strata, and these fractures present the most tangible risks for the leakage of injected carbon dioxide. Discrete fracture network (DFN) models have been used successfully to assess leakage risks associated with hydraulic fracturing and coalbed methane production, and these models show promise for assessing risks associated with carbon sequestration in coal. The objectives of this project were to develop a software package called DFNModeler for risk assessment and to use this software to assess risks in the Black Warrior basin of Alabama, where coal-bearing strata have high potential for carbon sequestration and enhanced coalbed methane recovery.

This project was sponsored primarily by the National Energy Technology Laboratory of the U.S. Department of Energy and was conducted by the Geological Survey of Alabama in partnership with the University of Alabama and Jim Walter Resources, Incorporated. Major activities included developing software for constructing DFN models, developing OpenGL tools for the visualization and analysis of DFN models, and developing software to facilitate flow modeling of carbon dioxide and water. Data sets from outcrops and cores in the Black Warrior basin were used to develop DFN models, to develop flow models, and to assess potential risks associated with carbon sequestration. Geologic and hydrologic data sets were also used to test and validate the models and to aid in risk assessment.

Capabilities

Development of DFNModeler software was originally sponsored by the U.S. Environmental Protection Agency as an OpenGL front end to FracMan software, which is available from Golder Associates. Under the NETL-sponsored program, DFNModeler has been expanded into a stand-alone software package that is tailored specifically toward understanding fracture networks and the flow of water and gas in coal-bearing formations.

Capabilities include the realization and visualization of discrete fracture networks in coal-bearing strata. Fractures and beds can be color-contoured according to aperture, transmissivity, and storativity. The software also enables compartmentalization analysis, and export of DFN models to multi-phase flow modeling packages that are commonly used in carbon sequestration studies, such as TOUGH2.

Technology Transfer

This project included a vigorous technology transfer program that is designed to support the demonstration and commercialization of carbon sequestration technology. An advisory group consisting of the project team, coalbed methane producers, a utility representative, and researchers involved in reservoir simulation helped guide the project and provided a forum for communication among stakeholders two can implement carbon sequestration technology. Results are being presented at technical meetings and workshops and are being published in technical journals and meeting proceedings. This website is also central to technology transfer activities, and links to relevant reports and materials are given below. At the close of this project, DFNModeler software will be made available for download as freeware from this website.

Guohai Jin, Pashin, J. C., and Payton, J. W., 2003, Application of discrete fracture network models to coalbed methane reservoirs of the Black Warrior basin: Tuscaloosa ,Alabama, University of Alabama College of Continuing Studies, 2003 International Coalbed Methane Symposium Proceedings, Paper 0321, 13 p. (PDF; 31.7 Mb).

Pashin, J. C., Guohai Jin, and Payton, J. W., 2004, Three-dimensional computer models of natural and induced fractures in coalbed methane reservoirs of the Black Warrior basin: Alabama Geological Survey Bulletin 174, 62 p. Available for purchase from the Geological Survey of Alabama Publications Sales Office.

Guohai Jin and Pashin, J. C., 2007, DFNModeler: an efficient discrete fracture network modeler: Tuscaloosa, Alabama, University of Alabama College of Continuing Studies, 2007 International Coalbed Methane Symposium Proceedings, Paper 0709, 16 p (PDF; 0.7 Mb).

Guohai Jin and Pashin, J. C., 2008, Discrete fracture network models of the SECARB carbon sequestration test site, Deerlick Creek Field, Black Warrior Basin, Alabama: Tuscaloosa, Alabama, University of Alabama, College of Continuing Studies, 2008 International Coalbed & Shale Gas Symposium Proceedings, paper 0821, 8 p (PDF; 1.9 Mb).

Final Report

Pashin, J. C., Guohai Jin, Chunmiao Zheng, Song Chen, and McIntyre, M. R., 2008, Discrete fracture networks for Risk Assessment of Carbon Sequestration in Coal: Final Technical Report, U.S. Department of Energy, National Energy Technology Laboratory, Award DE-FC26-05NT42435, 118 p (PDF; 12.8 Mb).

Software Download

DFNModeler software (ZIP archive; 1.3 Mb). Software documentation is provided in the final report, which can be downloaded here (PDF; 12.8 Mb).

Project Team

Jack C. Pashin, Geological Survey of Alabama (Principal investigator; coal and petroleum geology)

Chunmiao Zheng, University of Alabama (Co-principal investigator; hydrogeology, software development)

Guohai Jin, Geological Survey of Alabama (Structural geology, software development)

Marcella McIntyre, Geological Survey of Alabama (Structural geology)

Song Chen, University of Alabama (Hydrogeology, software development)

Marty G. Gates, Geological Survey of Alabama (Structural geology)

Richard E. Carroll, Geological Survey of Alabama (Coal geology)

DOE Contracting Officer Representative

Karen Cohen, National Energy Technology Laboratory

Project Advisory Group

Terry Burns, Geomet Operating Company

Richard Esposito, Southern Company

Richard H. Groshong, Jr., 3D Structure Research

Larry Knox, Dominion Exploration and Production

Scott Reeves, Advanced Resources International

Duane Smith, National Energy Technology Laboratory

Yu-Shu Wu, Lawrence Berkeley National Laboratory

Acknowledgment

This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-FC26-05NT42435.

The Geological Survey of Alabama (GSA) makes every effort to collect, provide, and maintain accurate and complete information. However, data acquisition and research are ongoing activities of GSA, and interpretations may be revised as new data are acquired. Therefore, all information made available to the public by GSA should be viewed in that context. Neither the GSA nor any employee thereof makes any warranty, expressed or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, software, or process disclosed in this report. Conclusions drawn or actions taken on the basis of these data and information are the sole responsibility of the user.

Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government or any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe on privately owned rights. Reference to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.