Energy Mining
Because the mining of coal differs significantly from other forms of types of industrial resource mining, it is discussed in the last section. Other forms of energy mined in Indiana include oil, natural gas, and methane. Oil and natural gas formation is described in your textbook.
Can You Find Oil and Natural Gas in Indiana?
The amount of oil and natural gas mined in Indiana is incredibly small compared to the amount used in Indiana. Most oil and natural gas is trapped in former oceanic reefs that once encircled northeast and southwest Indiana during the Paleozoic. These reefs were buried under mud, which later turned into the rock shale. The reefs turned into the rock limestone. Decaying organic material trapped within the reefs slowly turned into petroleum. Normally, petroleum wants to rise to Earth's surface because it is less dense than rock. However, shale acts as an aquitard, and does not allow liquids to travel through it. So, the oil is trapped.
Most of this trapped oil was squandered away during the early petroleum industry of the 1800s, but some oil still exists in small quantities. Oil is still removed every year in Indiana, enough for small companies to make a profit, but an amount that equals to less than 1% of what Indiana residents use every year. Typically, small companies (known as wildcats) extract the oil and sell it off to the major oil companies who then process it.
Natural gas forms by the same processes and is found in association with oil. If enough natural gas exists, it can be recovered separately. Otherwise, it is burnt off as a waste product during the recovery of oil.
Natural Gas Storage
A surface well for an underground gas storage facility in Indiana. These facilities are spread throughout Indiana. These small wells inject or pump natural gas out of deep bedrock aquifers or former oil fields. While considered safe, in Hutchinson, KS the Yaggy storage field leaked, causing several explosions in the city in 2001 that killed several, and required evacuation of parts of town for months. (Indiana Geological Survey)
Natural gas is extremely volatile--it explodes easily, and it takes up a lot of space (gasses take up more space than liquids or solids). Basically, its too expensive and dangerous to store it above ground. But, natural gas has to be stored, because it is mostly used during the winter months when demand far exceeds winter production. So, during the summer months natural gas is pumped into large underground storage facilities. Each winter about one-fifth of the natural gas Americans consume comes from gas storage sites. Some of these facilities are abandoned salt mines, but many of them are abandoned oil fields and former groundwater aquifers. Why old oil fields? Because geologists know if conditions existed to trap oil, they can easily pump gas back into the rock and know it will be trapped. The gas is trapped in tiny pore spaces in the rock that used to hold the oil. Any old well holes are plugged, and companies can measure pressure to make sure no gas is leaking out.
There are several major storage fields in Indiana (including one in Indianapolis)--few people are aware of them, as they only require a small pump station at the surface. The gas is not dangerous below ground, it cannot explode in the absence of oxygen.
Methane
Methane is essentially natural gas, but "methane" is typically used to refer to natural gas recovered from coal (and as you'll find out later in this course--landfills). Southwest Indiana has significant coal deposits, and deposits that have not been mined yet sometimes contain enough methane gas that it can be sold for profit. The process, known as "coal-bed methane extraction" takes advantage of a resource that up until the mid 1990s was left to escape into the atmosphere during the coal mining process.