Natural gas is formed as fossil organic matter, the bodies of ancient organism like algae, plankton, and plants, decompose deep in the earth over millions of years. Find out more about Shale Gas!
Normal or “conventional” gas deposits form in permeable stone reservoirs. These are rock levels that have spaces between their grains or crystals that allow gas to soak into them, and which are covered by impermeable layers that don’t let the gas seep through. It’s relatively easy to collect the gas from these deposits simply by drilling a pipe into them and allowing the gas to rise up it.
Shale gas deposits, however, are more difficult to remove gas from. Shale is a type of sedimentary rock that forms from the mud in deep oceans or at the bottoms of lakes and is compressed into really thin-layered stone. Because this mud often has organic matter in it, gas can form in the cracks between the layers of the shale. However, shale isn’t permeable to gas, so you can just stick in a pipe and suck the gas out of the whole rock level – it’s stuck between all the different, so you would need a separate little straw for each one!
Drilling down and then sideways can help to contact a lot more of the gas in a shale gas deposit. Another way to get to the gas in different layers is to force a liquid under high pressure down into the shale deposit. The high pressure causes fractures, or cracks, to form and that connects the spaces between shale layers and allows the gas to be pulled up more easily. This “hydraulic fracturing” usually uses a lot of fresh water with some chemicals added, and is sometimes considered a pollution issue.
Check out our interesting article about Water Cycle!