A parametric study to investigate the effect of injection and production well operation on the CO_2 sequestration process in deep unmineable coal seams

摘要

Injection of CO_2 into a coal seam can cause changes to both the chemical and physical structures of the coal. It has been shown that CO_2 adsorption can cause swelling of the coal (Ates and Barron, 1988) and this may lead to reductions in permeability which will cause difficulties in injection of the CO_2 into the coal. This swelling phenomenon introduces complexity to the design of injection systems for CO_2 sequestration in deep coal seams. Drilling an injection well into a deep coal seam (at depths on the order of 1000 m) is an expensive and time consuming process. Therefore a good understanding of the influence of design parameters on the effectiveness of CO_2 sequestration in deep coal seams prior to drilling is imperative. Based on existing knowledge and current understanding of the major processes, numerical modeling, which takes into account the interaction of the various processes, can be used to conduct parametric studies in order to determine the operational parameters to achieve optimal response from the coal seam in the sequestration process. In this study the COMET3 numerical simulator (Sawyer et al., 1990) has been used to develop a model to study the flow behavior inside a coal seam following CO_2 injection.