Where does this shale gas?
This gas is produced from the decomposition of plants that have remained buried in the earth's crust and trapped in the shale rather than simply remained "in situ" in the layers. Because there are millions of years, the climate was tropical Quebec (yes!) And lush vegetation. That is why our basement is full of this gas coveted today. The gas is captured, trapped in microscopic pores of rock layers. The shale is a sedimentary rock deposited at its origin as clay and silt. But this gas is one source called "unconventional" natural gas, which include coal bed methane and tight gas.
You'll notice that many items appoints shale gas of his real name geology.
How do you extract this shale gas?
Conventional gas is easier and cheaper to produce. In this case, to make a simple picture, there often enough to plant a "straw" in the rock underground to the pond and inhaling the bubbles, as in a glass of soda. However, gas production from these deposits is declining in the world (because we have burned). To avoid this future shortage, the oil and gas industry turned to fossil fuels whose production was previously difficult and too costly. Here is the shale gas becomes buoy Relief ...
Because the presence of shale gas in the St Lawrence is attested since the 1960s. In the 1970s, surveys conducted by the Société québécoise d'initiatives oil (SOQUIP), near Saint-Hyacinthe, confirmed the existence of these gas fields ... remained to enter the shale to extract the gas. An operation that has long seemed to take on the impossible.
This was the case until a certain George Mitchell, a petroleum engineer from the United States, enters the scene. Literally overwhelmed by the huge deposits that contain shale of North Texas, he experimented in 1981, a new technique: the hydraulic fracturing. But his tests proved inconclusive, because the volume of gas produced is too low for profitable operation.
It was not until a few years later, when Bill Penhall, now vice president of Devon Energy Group, had the idea to run a horizontal drilling to fracture the geological layer along its length. It is this technological innovation that can extract more gas and at least costs.
To make a simple picture, imagine a layer cake in the form of a glass filled with soda: to bring out the bubbles, not only are planted "straw" to the "rock" but then you have to deflect horizontally into the shale layer (or cake here) and promising to inject pressurized water and chemicals to break the layers "of cake" that traps the bubbles, then aspirated. Here, following cons, an illustration of the process.
more detail, the first cement is poured inside the steel cylinder, then rises on the periphery of the tube to the surface. reforce is all for injecting a slurry consisting of water and gel that lines the walls and solidifies. It also helps remove the debris created by drilling. This internal formwork can channel the gas while being ... supposed to prevent leaks to the groundwater (water in the pure basement). Once done, the drilling is deflected horizontally. The layer of shale is then traversed over a length of 1 km. After installation, a final cement sheath, horizontal this time, is introduced. It will be perforated to allow passage water jets during fracturing ahead. then installed an anti-rash above the sink: single plate of steel that prevents gas from escaping in case of sudden pressure change in- field.
Once the "straw" is installed to extract the gas, it requires lots and lots of water under pressure! This fracturing is caused by the injection of about 12 million liters of water, 1.2 million liters of sand and 72,000 gallons of hydrochloric acid to dissolve the rock. The shock wave from the fracture affects the cracking up of 100 meters up the rock layers. After this injection, 35% to 50% of the liquid gush to the surface to be followed by 10 to 20 years of gas supply.
... Poof, the bubbles sort of like a bottle of Champagne ...
Do you come more ... Next episode: how the operation of the gas damages the environment?
References:
Quebec Science
ABC Shale Gas in Canada - Energy Brief
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