Naked Science Forum
Non Life Sciences => Technology => Topic started by: Daumic on 08/09/2021 22:47:37
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Perhaps the mining of shale deposits isn’t the enemy of energy transition.
Since 2005, hydraulic fracturing has permit the exploitation of gas and oil confined in shale deposits. These shale deposits produce gas and light liquid hydrocarbons.
Some studies have shown the possibility to extract heavy hydrocarbon molecules like paraffin from shale deposits by using supercritical carbon dioxide (1). This fluid is also ideal for the heat extraction from the deep deposit: its high density facilitates the heat transport and its low viscosity eases the circulation in small cracks of the fractured zone.
The use of supercritical CO2 on depleted shale wells can associate the extraction of heavy hydrocarbons and geothermal heat. The extraction of heavy hydrocarbons can last some years like the classical extraction of gas and light hydrocarbons in shale deposits. By contrast, the heat extraction can last a very long time.
The first test of this heat extraction could be made by the Pittsburgh town in Pennsylvania. This town is surrounded by many wells extracting gas from Marcellus shale deposit (2). This town has also maintained an urban heating network (3). The geothermal heat extracted from the wells located around the town could feed the urban heating network.
The geothermal energy has a good reputation as a stable renewable energy but its development is blocked by its high investment cost. If we can associate geothermal energy and hydrocarbon production, the investment cost can be reduced.
(1) https://www.researchgate.net/publication/283619903_Extraction_of_Hydrocarbons_from_High_Maturity_Marcellus_Shale_Using_Supercritical_Carbon_Dioxide
(2)
https://www.fractracker.org/map/us/pennsylvania/pa-shale-viewer/
(3)
https://apps.pittsburghpa.gov/mayorpeduto/District_Energy_in_Pittsburgh_DOE_Power_Point_AL.pdf
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You could "frack" other rock for geothermal heat.
The problem is that we need to stop extracting hydrocarbons.
I like the idea of supercritical CO2 as a working medium, the low viscosity is good and I suspect that it will be much less likely to dissolve the rock (which is a problem with water because it scales up the pipes.)
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Yes, we can frack other rocks to obtain geothermal heat without gas or oil extraction. But this doesn't happen because geothermal energy needs high investments. Geothermal energy remains blocked.
A possible way to develop geothermal energy is to connect it with shale industry.