The purpose of this study is to perform simulation studies for a specific coal bed methane reservoir. First, the theory and reservoir engineering aspects of coal bed methane reservoirs, such as dual porosity concept, permeability characteristics of CBM reservoirs and mechanism of gas storage and gas transportation in CBM reservoir have been discussed. Next, simulation results for the CBM reservoir presented. Simulation studies were carried out by using the CBM reservoir simulator, SIMED II. Injection/fall-off test pressure data were interpreted based on the pressure history matching method. The interpretation results include the determination of reservoir permeability and identification of the reservoir altered zone. Also available production histories were used to simulate the reservoir production behavior. Then the production model was used to predict the reservoir future production and to carry out sensitivity analysis on reservoir performance. For natural pressure depletion, methane recovery was increased significantly as reservoir permeability was increased. Well-bore fracturing creates a fractured zone with higher permeability. This increases methane production rate during early time of reservoir life. Reservoir matrix porosity has a significant effect on the reservoir performance. Higher production peak rate and also higher methane recovery was obtained for the reservoir with lower porosity values. Any increase in the reservoir compressibility causes greater reduction in reservoir absolute permeability as well as relative permeability to gas throughout the reservoir. Therefore, methane recovery decreased as the reservoir compressibility increased. The reservoir production behavior was strongly affected by changes in reservoir size. The production peak rate was significantly postponed and lowered as reservoir size was increased. The effect of reservoir initial pressure was investigated and the results show that higher initial reservoir pressure leads to higher production rate during early years of production. However, for the later years of reservoir life, the production profile is almost identical for different initial pressures. Coal desorption time constant affects the methane production by its own scale. In this study, the range of desorption time did not exceed longer than three days and therefore the difference in production rate was observed only in the first few days of production.
| Identifer | oai:union.ndltd.org:ADTP/279661 |
| Date | January 2005 |
| Creators | Karimi, Kaveh, Petroleum Engineering, Faculty of Engineering, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Petroleum Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Kaveh Karimi, http://unsworks.unsw.edu.au/copyright |
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