Faced with a civil society that is increasingly skeptical and opposed to the exploitation of shale gas using hydraulic fracturing, propane gas billing seems to be a real alternative. This “waterless” fracturing technology was ranked among the “25 best inventions of 2013” by the magazine “TIME”.
For the exploitation of bedrock gas (shale gas), it is necessary to fracture the rock with a fluid to release the gas or oil contained in it.
More and more North American companies (Canadian and American) are developing this technology for GasFrac and eCorpStim. Propane fracturing has many advantages over hydraulic fracturing; the concept is simple – simply replace the water – generally used to fracture the so-called “mother rock” – with a reusable gas, which happens to be PROPANE. So how do you use this gas to fracture a rock?
For this operation, propane is used in its liquid form (at atmospheric pressure, it only becomes liquid below -42°C) mixed with a gelling agent. Liquefied this gas has the advantage of being very low viscous, it is therefore used without the many additives essential for hydraulic fracturing; only a supporting agent is added (frequently sand or ceramic beads) to keep the cracks in the rock open. As for the gel, it keeps this retaining agent in suspension, transporting it to the furthest cracks and keeping it there.
Another big advantage is that, under the double effect of rising temperature and falling pressure, propane rises to a gaseous state after fracturing the rock, making it recoverable and reusable in the order of 95%, as opposed to 30% to 80% in the case of water, which prevents any contamination of the subsoil.
However, this technique involves some risks due to the highly flammable nature of propane, the consequences of a leak could, therefore, be very disastrous, and its storage in large quantities would require very strict safety measures. But, there may be a solution, in 2012 a subsidiary of the American company eCorp called eCorpStim, developed a pure propane stimulation (PPS) technology instead of propane gel, and in 2013 it will improve on its invention by developing non-flammable propane (NFP), heptafluoropropane (CH3F7), a fluorinated form of propane that excludes any risk. The technology has been successfully tested in Texas. The U.S. oil giant has also stated that the cost of this fluid would make propane stimulation competitive with hydraulic fracturing.
Thanks to propane fracturing, millions of cubic meters of water are saved and no chemical additives threaten the water tables, which could solve the problem of shale gas exploitation in Algeria, for example, which has the 3rd largest exploitable reserve in the world, with 22,500 billion cubic meters according to the American Department of Energy. The exploitation that is now blocked, due to the great risk of contamination of the water table of the Albian, the largest freshwater reserve in the world hidden in the subsoil of the Algerian Sahara. However, no statement from the Algerian authorities has been made on the subject.
In conclusion, this new technique brings many advantages to the exploitation of shale gas. Although it is very little used compared to hydraulic fracturing, more and more companies are now interested in it.
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