In many coastal areas maritime depositions (only 20-80 m deep) are covered by clay which provides a water-tight layer. Due to micro-biological activity in these maritime deposition layers gasses are formed (mainly methane) that will rise up and dissolve in the ground water. This methane reaches the surface only through diffusion through the ground and some natural springs where deep ground water flows to the surface through channels.
What if the methane saturated water would be pumped to the surface, where the methane is removed, and pumped back into the ground (at another location)?
Could this be a viable technique to exploit this natural gas?
This methane is now emitted freely in nature through diffusion and it would reduce the green-house effect to win and burn it, as methane has a 20x larger green house effect compared to CO2.
Attached you can find a graph showing the maximal CH4 concentration in water versus pressure (depth).
Dear Erik,
According to the information solubility of CH4 in deep sea (at the depth about 40 m) is below 100 mg·L−1. However, solubility of CH4 in water at atmospheric pressure around 20- 30 degrees of Celsius is about 20 - 23 mg·L−1. If we pump this water from deep see to surface at atmospheric pressure, level of CH4 will decrease to 20 - 23 mg·L−1 at the surface due to loss of pressure. If it is conducted under high pressure (without pressure loss) we can maintain the CH4 level as at the bottom. Anyway, If it is extracted 1 mole of CH4 from water, the energy gained, ΔH, is 891x1.25 kJ/mol (for 20 g of CH4 per 1000 L of water pumped from bottom), However, if we taken in to account the energy requirement for the pumping, this is a mean less process and economically not viable.
for more details about CH4, link given below is important.
Piyal Aravinna
https://www.ess.uci.edu/~reeburgh/cr050362v.pdf
Dear Erik,
That is definitely an interesting subject for scientific research purposes, but I think the CH4 content of these deposits are not in economic levels.
Cheers,
As the water after methane stripping will be repositioned at the same ground-level, the same amount (mass) of water is pumped up as is falling down. So, the energy needed for waterpumping is only due to friction (not increase in potential energy).
Would not this reduce the energy needed for pumping significantly, to make this economically feasable?
Dear Eric,
Yes, That is an important point.
But, If we think about the piratical situation, I feel that establishment of that type of project, may not economically viable (because extraction of that layer from a particular location is not easy like petroleum extraction), when compared to CH4 generation/production by anaerobic digestion at present in the world.
Piyal Aravinna