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Abstract

2 methane on the coal surfaces that may otherwise stay adsorbed in the coal matrix by decreasing the partial pressure of methane in the gas mixture. In addition, experimental work conducted on enhanced coalbed methane recovery by CO 2 injection [Reznik et al, 1984] shows that CO 2 is more adsorbing on coal than methane thereby giving it the potential to efficiently displace CBM and remain sequestered in the coal-seam. Thus coal-seams are considered to offer a very attractive option for CO 2 sequestration.In this work, focus is on the final part of the sequestration process -storage. The effects of various coal properties as well as operational scenarios on the injection and storage of CO 2 into a given coal-seam are analyzed. The analyses are based on results obtained from PSU-COALCOMP, a compositional coalbed methane numerical reservoir simulator capable of modeling the primary and enhanced recovery of coalbed methane.The operational design parameters considered in this study include the type, length and orientation of the injectors/producers while the coal-seam properties studied include coal porosity, coal permeability, cleat spacing, sorption capacity, and the initial conditions of the coal-seam -the reservoir pressure, adsorbed gas composition, amount of CO 2 initially adsorbed, water saturation and free-gas composition.Based on the data, results and analyses obtained, a CO 2 sequestration performance predictor tool is developed using artificial neural network (ANN) technology. The developed network will be able to predict the values of the performance indicators of the CO 2 sequestration process for a wide range of coal-seams and various production schemes. The developed ANN would also enhance our understanding of CO 2 sequestration process. 3 CHAPTER 2 LITERATURE REVIEW Carbon Dioxide SequestrationThe amount of carbon dioxide (CO 2 ) in the atmosphere has risen from preindustrial levels and most of this increase has been in recent years as shown in the data presented graphically in Figure 2-1. The corresponding increase in temperature as CO 2 levels increase raises environmental concerns such as global warming and its effects.This increase in CO 2 levels is attributed widely to the burning of fossil fuels, and if current trends in resource utilization continue, anthropogenic CO 2 emissions will increase rapidly during the 21 st century. Figure 2-2 shows the sharp increase in global CO 2 emissions over the last 100 years.The term "CO 2 sequestration" refers to the removal of CO 2 from either manmade emissions or the atmosphere and the safe, essentially permanent storage of this CO 2 .There are two main types of sequestration: direct sequestration, where CO 2 is removed from energy systems, and indirect sequestration, where CO 2 is removed from the ambient atmosphe re by enhanced natural processes. Sequestration is one of the three options for stabilizing CO 2 concentrations in the atmosphere and until the late 1990's, was not yet in the scientific lexicon. It is less familiar to the public at large than...