Scott R. Reeves1
(1) Advanced Resources International, Houston, TX
ABSTRACT: Geologic Sequestration of CO2 in Deep, Unmineable Coalbeds: An Integrated Research and Commercial-Scale Field Demonstration Project
Coalseams represent an attractive opportunity for near-term sequestration of large volumes of anthropogenic CO2 at low net costs. There are several reasons for this:
They have the ability to physically adsorb large volumes of gas.
They are frequently located near large point sources of CO2 emissions, specifically power generation plants (e.g., coal-fired plants).
The injection of CO2 into coalseams actually enhances the commercial methane recovery process.
The recovery of CBM is enhanced when the injected gas contains nitrogen, the major constituent of power plant flue gas.
A joint U.S. Department of Energy and industry project to study the reservoir mechanisms, field performance and economics of CO2 sequestration in coalseams has been initiated. The project involves laboratory and field-testing to define critical reservoir mechanisms, such as coal matrix expansion and permeability reduction with CO2 injection, multi-component (CO2-CH4-N2 ternary) sorption behavior, and geochemical reactions that could lead to permeability reduction. Two existing fields in the San Juan Basin, the most prolific CBM basin in the world, are currently under CO2 and/or N2 injection. These two fields, the Tiffany Unit - now under N2 injection but with mixed CO2/ N2 injection planned, and the Allison Unit - under CO2 injection since 1995, will be thoroughly studied as to CO2 sequestration and enhanced CBM recovery performance, using both pure CO2 and CO2/ N2 mixtures. This paper presents the fundamental reservoir mechanisms of CO2 sequestration in coalseams, the field performances to date of the Tiffany and Allison Units, the advantages of mixed CO2/N2 injection, and some economic considerations for CO2 sequestration in coalseams. It also summarizes the objectives and work plan for the recently-awarded DOE project.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado