This occurs when a potential source rock, rich in organic matter, is buried and heated at considerable depth usually thousands of metres below the surface. The hydrocarbons migrate upwards where they may find their way into porous reservoir rocks, typically a sandstone or a porous limestone. If the reservoir rock is overlain by an impermeable cap or seal rock, such as one rich in clay, the hydrocarbons become trapped in the reservoir rock.
Conventional hydrocarbons can be extracted by drilling directly into the reservoir rock. Shale gas is a form of unconventional hydrocarbons because the rock it is extracted from acts as the source, reservoir and cap rock. The gas is produced, stored and sealed within impermeable shale and can be released only after the shale is drilled and artificially fractured during an extraction process. We research all aspects relevant to shale gas in the UK and internationally.
The development of shale formations has been correlated with a rise in employment, with the oil and gas industry adding , jobs between and Energy Information Administration.
The United States is now a leading oil and gas producer, as global supply has diversified away from the Middle East. Reduced imports of hydrocarbons improve the U. However, as oil is priced in a global market, as long as the United States remains connected to global markets, it will always be vulnerable to price shocks. Even if the United States continues to cut its imports of petroleum to nearly zero, a supply interruption in the Middle East would force global oil prices upward, hurting U.
Tight oil production in the United States. However, there are some potential environmental issues that are also associated with the production of shale gas. Shale gas drilling has significant water supply issues. The drilling and fracturing of wells requires large amounts of water. In some areas of the country, significant use of water for shale gas production may affect the availability of water for other uses, and can affect aquatic habitats.
Drilling and fracturing also produce large amounts of wastewater, which may contain dissolved chemicals and other contaminants that require treatment before disposal or reuse. Because of the quantities of water used, and the complexities inherent in treating some of the chemicals used, wastewater treatment and disposal is an important and challenging issue.
If mismanaged, the hydraulic fracturing fluid can be released by spills, leaks, or various other exposure pathways. The use of potentially hazardous chemicals in the fracturing fluid means that any release of this fluid can result in the contamination of surrounding areas, including sources of drinking water, and can negatively impact natural habitats.
What is Shale Gas? Map of Shale Gas Plays in the Lower 48 States Map of the major shale gas plays in the lower 48 states, including the sedimentary basins which contain them. United States Shale Gas Presentation This video provides an overview of shale gas, starting with the first gas well near Fredonia, New York in up through January and the major shale gas plays.
Did You Know? Sedimentary rocks are rocks formed by the accumulation of sediments at the Earth's surface and within bodies of water. Common sedimentary rocks include sandstone, limestone, and shale. Schematic Geology of Natural Gas Resources Diagram showing the geometry of conventional and unconventional natural gas resources.
Hydraulic Fracturing Diagram showing the concept of a horizontal well with hydraulic fracturing zone. In order to increase the flow of gas to boreholes, high water pressure is used in the borehole to fracture up the shale and create cracks around the borehole to which the gas can flow.
This method is called hydraulic fracturing and is used only at depths greater than metres. It is also known as fracking. In connection with fracturing, silica sand is injected to hold the cracks open. Fracturing also requires large volumes of water. The holes drilled for shale gas extraction are often more or less horizontal in the gas-bearing shale. The number of boreholes varies depending on gas content, bedrock density and depth. From each drilling site, several boreholes can be drilled and angled out horizontally in the shale.
Many more boreholes are typically required than in traditional gas extraction. In many cases, biogenic shale gas can be extracted without fracturing or stimulation of the borehole because superficial shales contain more naturally open cracks.
In Sweden, examinations pursuant to the Minerals Act and the Environmental Code are required both for the exploration and the extraction of shale gas.
The Minerals Act imposes specific requirements on access to technical expertise and financial resources for those wishing to explore and extract gas occurrences. Applications for permits under the Minerals Act are made to the Mining Inspectorate of Sweden, whose website contains further information on permit processes. As of December , there are seventeen exploration permits in Sweden under the Minerals Act that expressly relate to gas in alum shale areas.
There are also additional permits authorising the exploration of alum shale as a whole. In one case, an exploitation concession right of extraction has been issued. Extraction in the area is not being considered at present. The Mining Inspectorate of Sweden website new window. The largest estimated supplies of shale gas in Europe are in Poland.
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