In Canada’s Alberta, a project is on to convert coal to gas at depths beyond 1000 metres – the deepest ever to generate power from coal--without digging it up.
Working at that depth could lessen the threat of groundwater contamination from the smoldering decomposing coal. If the technology can get at deeper layers of coal, it could allow access to more of the fossil fuel, whether that’s good or bad!
When the project starts up in 2015, Swan Hills hopes to generate 300 megawatts of power from its coal gas while selling over 1.3 million tons of carbon dioxide per year. The CO2 could be used by oil producers and ultimately stored in oil wells. This could result in the storage of 10 to 20 million tons of carbon dioxide per year by 2020.
The pilot produced excellent gas using a pair of adjacent wells spaced 50 to 60 meters apart, installed in the coal seam with the same directional-drilling techniques behind the accelerating production of natural gas from contentious shale deposits.
Oxygen is driven down the feed well and the coal seam is ignited, driving the temperature to 800 to 900 ºC and the pressure to almost 2,000 PSI. Under those pressures, the oxygen, coal, and saline water (present in the coal and also injected via the feed well) react to form a gas that is roughly one-third methane and two-thirds hydrogen, along with some carbon monoxide and carbon dioxide. The gas is drawn to the surface via the adjacent production well, where the carbon monoxide is converted to hydrogen and CO2, and all of the CO2 is removed.
How the company managed to achieve gas flow between its wells, given the low permeability of coal squashed under 1,400 meters of rock, is not known. The standard mechanical method by which shale gas production is stimulated is the fracture of rock with high-pressure water.
Does such deep drilling into the earth cause tremors or tectonic shifts?? Do we know enough? Recently Sweden has dropped one of its geothermal projects after deep drilling caused fractures in neighbouring structures.
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