An Investigation of Different Borehole Layouts for Carbon Sequestration in Coalbeds
Lee Hosking  1, *@  , Hywel Thomas  1@  
1 : Geoenvironmental Research Centre
School of Engineering, Cardiff University Queen's Buildings, The Parade, Cardiff CF24 3AA -  United Kingdom
* : Corresponding author

This paper investigates how the layout of injection boreholes can influence the effectiveness of carbon sequestration and enhanced methane recovery in a coalbed. A numerical model for high pressure gas transport with kinetically-controlled adsorption and desorption is used to predict the carbon dioxide storage and methane displacement behaviour in two simulation scenarios. In the first scenario, carbon dioxide is injected using a single borehole located at the centre of the domain, whereas the second scenario considers a four-spot layout for the injection boreholes. Both simulations consider the same arrangement of boreholes for the recovery of the displaced methane. It is demonstrated that the four-spot layout increases the amounts of carbon dioxide stored and methane recovered in the simulation period, although the increase in carbon dioxide storage is somewhat offset by interference between the injection boreholes. Based on the observations made, it can be concluded that the layout of the injection boreholes is a key engineering factor influencing the performance of carbon sequestration in coal with enhanced methane recovery. Some of the main physical and chemical phenomena responsible for the observed gas storage and displacement behaviour are also discussed.

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