Hydraulic fracturing is a technique used in "unconventional" gas production. This is often because the gas is highly dispersed in the rock, rather than occurring in a concentrated underground location. Extracting unconventional gas is relatively new.
Coalbed methane production began in the s; shale gas extraction is even more recent. The main enabling technologies, hydraulic fracturing and horizontal drilling, have opened up new areas for oil and gas development, with particular focus on natural gas reservoirs such as shale, coalbed and tight sands.
Shale Gas Extraction. Shale rock formations have become an important source of natural gas in the United States. Shale gas is present in many locations in the contiguous United States, including some areas where oil or gas production has never occurred before. Production of Coalbed Methane. Coalbed methane CBM was first extracted from coal mines as a safety measure to reduce the explosion hazard posed by methane gas in the mines.
Today the methane is captured and used as a source of energy. Deeper coal formations might require hydraulic fracturing to release the natural gas. All hydraulic fracturing fluids, including their chemical composition, are assessed by the operator and by government agencies.
Hydraulic fracturing can occur during three stages of the petroleum development cycle — exploration, evaluation and production. Generally, the process is undertaken only once for the life of a well. During exploration, fracturing of a vertical well may occur to test different rock formations for gas. Hydraulic fracturing of unconventional reservoirs has only been undertaken at the exploration stage in Western Australia.
During production, vertical or horizontal wells are drilled and can undergo hydraulic fracturing to enhance commercial flows of hydrocarbons. A shale or tight gas well site typically requires 1. A well pad is generally drilled in the centre of the clearing, using a drill rig. Other equipment such as data monitoring vans, vehicles, sand and chemical storage units, pumping trucks and collection ponds are also located on the site. The number of well sites required when developing a shale or tight gas field depends on the size of the gas field being targeted.
Advances in horizontal drilling techniques now enable several wells to be drilled from one location. These wells extend to a maximum depth of five kilometres, deviating horizontally for one to two kilometres once reaching the gas-bearing rock.
This significantly limits the footprint of surface activity, including the number of access tracks. For example, if a petroleum company drilled six shale gas wells from one well pad and used horizontal drilling, it is estimated one well pad would be required for every hectares 2.
Well pads would be approximately 1. After hydraulic fracturing is completed, most equipment is moved offsite. This reduces the site footprint from around 1. Generally, all that remains visible at the surface is a series of sealed valves Christmas trees about two metres high.
Once the site reaches the production stage, it will also include a gas pipeline pipelines are buried or isolated within a security fenced area which leads to a gas processing plant. Oil and gas companies typically add chemicals to the water used for fracking.
Those chemicals can help decrease friction or prevent corrosion and so forth. They typically make up about 0. Different operations require different chemicals, but all told some 2, different fracking chemicals have been identified. A good list can be found here. Some of the additives used are quite ordinary, including salt and citric acid. Others, like benzene, are toxic. One congressional investigation identified at least toxic additives that have been used.
It can sometimes be difficult to get a full list of chemicals used. Many fracking companies are now listing the compounds they employ on their websites, and some states like Texas have public disclosure laws, but these rules can vary from state to state. Fracking requires a lot of water to crack open the shale rock.
A typical well can use between 2 million to 7 million gallons over the course of its lifetime. How much is that all together?
In , water used for shale wells represented about 0. But the percentages can vary by region — in Texas, it's about 1 percent. That raises the question of whether it can stress local water supplies. In dry regions of Texas or Colorado, fracking operations can put a fair bit of stress on local water sources.
But that's not universal. In the Marcellus region in the East, by contrast, studies have found that there's no danger of a water shortage.
Fracking is currently regulated by the states, who have very different rules on everything from the disclosure of chemicals to wastewater treatment to well casings. You can find a number of useful maps showing the state of play for different fracking regulations at Resources for the Future. This map, for instance, shows how different states regulate the injection of wastewater underground.
Missouri has no regulations, whereas North Carolina has a statewide ban:. One major issue is whether the US federal government should get more involved in fracking regulations. Currently, the Environmental Protection Agency has issued rules requiring oil and gas companies to limit air pollution from fracking operations, and it is currently studying groundwater contamination.
But, for now, the feds have tread lightly. And Congress has exempted fracking from certain provisions of the Clean Water Act. Some states and localities, meanwhile, have proposed blanket bans on fracking. New York state, for instance, has had a moratorium since Here's a longer list of regulations in the United States.
Fracking itself has rarely been linked to earthquakes though Ohio is investigating this. But the disposal of all the wastewater used in fracking has been known to cause tremors.
Once a well is fracked, there are thousands of gallons of wastewater left over. Companies often dispose of that chemical-laced water by pumping it into separate underground "injection wells. If those rocks lie near a geologic fault, that could trigger a tremor. At least, that's the theory.
One study by the U. Geologic Survey found that earthquakes were on the rise in areas where wastewater injection was increasing. A follow-up study found that wastewater injection likely caused a earthquake in Oklahoma. It's worth noting that not all injection wells are associated with earthquakes, and many of these events were minor tremors. Still, there are plenty of questions about whether these earthquakes could get stronger as fracking expands.
As of , the United States had billion barrels of oil and 2, trillion cubic feet of natural gas that was "technically recoverable. This is oil and gas that we currently have the technology to access. But that doesn't mean we'll actually extract all that oil and gas. A lot depends on economic conditions. If prices go higher, then it will become more profitable for companies to drill for more oil and gas.
But if prices fall, it becomes less profitable and they might just leave it in the ground. That's why many analysts focus on a different measure, known as "proved reserves" — the stuff we could recover given existing technology and economic conditions.
By that measure, there are 29 billion barrels of oil and To put that all into perspective, the United States consumed about 7 billion barrels of oil and 26 trillion cubic feet of natural gas in So that means we have anywhere from a 13 years' supply of natural gas to an 84 years' supply. It all depends. Lots of things. About 93 percent of the fuel we use for transportation comes from oil. And natural gas is currently used to provide about one-third of the nation's electricity.
Here's a more precise breakdown:. Oil: The U. Roughly 87 percent is turned into fuel for cars, trucks, and airplanes. Some of the oil is refined into home heating fuel.
The rest is used for a wide array of industrial purposes to make chemicals, paints, plastics, greases, asphalt, and so forth. Natural gas: The United States consumed about 25 trillion cubic feet of natural gas in About 36 percent of that was used to generate electricity at power plants.
Another 28 percent was used to heat homes and buildings. And the rest was used for various industrial purposes generating electricity or heat to help produce everything from steel to paper to food.
For the past few decades, the United States has been a major importer of oil and natural gas. But thanks to the fracking boom, the country is now in a position to sell some of its newfound abundance to other countries. But that would require changing certain laws — and doing so is controversial. Natural gas: If companies want to ship natural gas to other countries, they need to get a permit from the Department of Energy to do so they get one automatically if the United States has a free trade agreement with that country.
More and more companies are applying for export permits these days and building shipping terminals. Opponents of these plans say that increased exports could lead to increases in the price of natural gas for Americans, hurting consumers and domestic manufacturers. See here for more detail.
Oil: Ever since the s, it has been illegal for companies to export crude oil abroad with a few exceptions. In the wake of the fracking boom, many oil companies want to revise these laws, claiming that these restrictions are depressing prices and hurting their business. Opponents of exports argue, among other things, that this could raise gasoline prices for some drivers in the Midwest.
Right now, the United States imports 40 percent of the oil that it consumes. That number is expected to shrink to about 32 percent in the decades ahead, thanks to increased production and the fact that we're driving more efficient vehicles. But it still means plenty of imports :.
Even if we could reduce our imports all the way to zero, however, the United States still wouldn't be totally independent of foreign countries. That's because oil prices are set on the global market. So instability in the Middle East or rapid growth in China would still drive up global oil prices — leading to price spikes here in the United States. Natural gas is a fossil fuel, and when we burn it for electricity, we produce carbon-dioxide emissions that contribute to global warming.
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