Hydraulic Fracturing
Natural gas is a mixture of four naturally occurring gases that have different molecular structures. Most of this mixture consists of methane (CH4). Natural gas is found where we also find petroleum deposits and is extracted along with oil by conventional methods, as illustrated below:
Oil and natural gas forms within the impermeable shale layers of rock and then migrate upwards. Some of the oil and gas gets trapped in the more permeable yellow sandstone to form an oil and gas reservoir. Although drilling can extract large amounts of oil and natural gas from the reservoir rock, much of it remains trapped within the shale. This oil and gas is very difficult to remove because it is trapped within tiny pore spaces or adsorbed onto clay mineral particles that make-up the shale.
Natural gas is the cleanest burning fossil fuel. Compared to oil and coal, it is the least polluting fuel:
There is a tremendous amount of natural gas that is trapped within black organic shale formations across the United States. This “shale gas” has become a game changer for the US and global energy future. We have shifted coal to the cleaner-burning natural gas and the price of natural gas has decreased.
Extraction of oil and natural gas from these shale formations is difficult because the oil and gas is trapped within tiny pore spaces or adsorbed onto clay mineral particles that make up the shale. In the late 1990s natural gas drilling companies developed new methods for liberating oil and natural gas that is trapped within the tiny pore spaces of shale. This discovery was significant because it unlocked some of the largest natural gas deposits in the world. This new method involves pumping water and other chemicals at very high pressures into the shale layer to break up the shale and liberate the gas from pore spaces. This technique is known as hydraulic fracturing or “fracking.” Drillers also learned how to drill down to the level of the shale and turn the well 90 degrees to drill horizontally through the shale rock unit. This produced a well with a very long "pay zone" through the reservoir rock. This method is known as horizontal drilling. These are considered unconventional methods of energy extraction.
Horizontal drilling and hydraulic fracturing revolutionized drilling technology and paved the way for developing several giant natural gas fields. These include the Marcellus Shale in the Appalachians, the Haynesville Shale in Louisiana and the Fayetteville Shale in Arkansas. These enormous shale reservoirs hold enough natural gas to serve all of the United States' needs for many years and may make the United States energy independent. The Marcellus Shale extends into southern New York and whether to “frack” it is a topic of debate with much disinformation.
The Marcellus Shale, also referred to as the Marcellus Formation was formed about 390 million years ago during the Middle Devonian. It is black, low density, carbonaceous (organic rich) shale that occurs in the subsurface beneath much of Ohio, West Virginia, Pennsylvania and New York.
How are oil and natural gas extracted from these shale deposits?
· Oil companies sign leases with private homeowners (or public lands) that require local DEP (Department of Environmental Protection) review. Guidelines vary state to state.
· Oil companies usually subcontract other private companies to do the actual drilling, hydraulic fracturing and extracting.
· Once approved contractors clear an area to build a drilling pad.
· Drilling begins and methods vary by site. In PA initial drilling involves a drill bit that rotates and “pumps” driving in air at a very high psi. The rock material is broken into very fine dust which is pumped out of the drill and water is added to turn it into a mud and prevent its dispersal
· Typically, steel pipe known as surface casing is cemented into place at the uppermost portion of a well for the explicit purpose of protecting the groundwater. The depth of the surface casing is generally determined based on groundwater protection, among other factors. As the well is drilled deeper, additional casing is installed to isolate the formation(s) from which oil or natural gas is to be produced, which further protects groundwater from the producing formations in the well.
· Once the desired depth is reached, a horizontal drill is put in place,
· Once the horizontal drilling is complete, the drilling rig unit is dismantled and the fracking unit set up. Then “fracturing fluids” consisting primarily of water, sand, and other chemicals (some of which are toxic and carcinogenic) are injected under high pressure to create fissures in the shale. This does not involve “explosions”. This involves a high volume of water (about 7 million gallons).
· About 30% of the water is recovered along with some of the fracking fluid and it must be stored and treated. The rest (but not all) comes out during the extraction process.
· The hydraulic fracturing occurs in stages along the horizontal pipe. Once completed the wells are secured and the extraction process can begin
· Spent or used fracturing fluids are normally recovered at the initial stage of well production and recycled in a closed system for future use or disposed of under regulation, either by surface discharge where authorized under the Clean Water Act or by injection into Class II wells as authorized under the Safe Drinking Water Act. Regulation may also allow recovered fracturing fluids to be disposed of at appropriate commercial facilities. Not all fracturing fluid returns to the surface. Over the life of the well, some is left behind and confined by thousands of feet of rock layers.
- See more at: http://www.energyfromshale.org/hydraulic-fracturing/how-hydraulic-fracturing-works#sthash.mLYE0t0u.dpuf
http://www.youtube.com/watch?feature=player_embedded&v=51wOisfdIPo
http://www.youtube.com/watch?feature=player_embedded&v=VY34PQUiwOQ
http://www.youtube.com/watch?feature=player_embedded&v=YemKzEPugpk
http://www.energyfromshale.org/hydraulic-fracturing/logistics-shale-production
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