Journal of Canadian Petroleum Technology
Volume 49, Number 4, April 2010, pp. 44-50

Abstract

The Japanese consortium to enhance CO₂-ECBM carried out a pilot project on CO₂ injection from 2002 to 2007 in the city of Yubari, Hokkaido, Japan. However, supercritical CO₂ could not be obtained because of low CO₂ injectivity and heat loss along the deep injection tubing. The absolute pressure and CO₂ temperature at the bottomhole was approximately 15.5 MPa and 28°C, respectively. Therefore, it can be assumed that CO₂ was injected into the coal seam in its liquid phase. Liquid CO₂ is less permeable in the coal seam because of its high viscosity and the resultant swelling of the coal matrix to decrease permeability.

This study provides a numerical system to predict CO₂ flow characteristics of pressure, temperature, supercritical or liquid by considering heat transfer from the injector into surrounding casings and strata. This study focused on keeping supercritical CO₂ in the tubing because the viscosity of supercritical CO₂ is 40% less than that of liquid CO₂. The CO₂ temperature required to keep CO₂ in its supercritical condition from the surface to the bottom was successfully predicted for various CO₂ injection rates and electric heating powers.

Finally, injected CO₂ is expected to be supercritical at an injection rate of over 12 ton/d without any heating.

© 2010. Society of Petroleum Engineers

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History

• Original manuscript received: 23 June 2009
• Meeting paper published: 18 June 2008
• Revised manuscript received: 18 February 2010
• Manuscript approved: 2 March 2010