Carbon Dioxide Sequestration in Unmineable Coal Seams:A Numerical Simulation Study

摘要

Fossil fuels are a major source of the world's energy production and this is expected to be the case well into the 21st century.Consequently,the extensive utilization of fossil fuels has measurably increased the total load of carbon dioxide in the atmosphere and concern about the effects on global warming has prompted the inception of various methods and policies geared at reducing the concentration of this green-house gas in the atmosphere.One of the more promising technologies is carbon dioxide sequestration which involves the capture,separation and secure storage of carbon dioxide.Production of coalbed methane is a well-developed mature technology,but enhanced recovery by the carbon dioxide injection has so far undergone relatively limited study.Recent research suggests that carbon dioxide preferentially sorbs to coal,replacing methane which can be produced and sold to offset the costs of sequestering carbon dioxide thereby providing a dual role for unmineable coal seams;a source of coalbed methane and a repository for the sequestration of carbon dioxide.We use PSU-COALCOMP,a compositional coalbed methane reservoir simulator,to model the primary and enhanced recovery of coalbed methane by carbon dioxide injection for a variety of coal properties and operational scenarios.The simulations are based on a hypothetical pilot project which is terminated as soon as the breakthrough of carbon dioxide at the production wells occurs.The results obtained and analyzed from the simulations performed at the end of the process include the cumulative amount of CO_2 injected and retained in the coal seam,the cumulative amount of coalbed methane produced as well as the duration of the project.