Tight gas is

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon d ...

produced from reservoir rocks with such low permeability that massive

hydraulic fracturing Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "fra ...

is necessary to produce the well at economic rates. This natural gas is trapped within rocks with very low permeability, in other words, they are sealed in very impermeable and hard rocks, making their formation "tight". These impermeable reservoirs which produce dry natural gas are also called "Tight Sand". Tight gas reservoirs are generally defined as having less than 0.1 milli darcy (mD) matrix permeability and less than ten percent matrix porosity. Although shales have low permeability and low effective porosity,

shale gas Shale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and some ...

is usually considered separate from tight gas, which is contained most commonly in sandstone, but sometimes in limestone. Tight gas is considered an unconventional source of natural gas. But they are much older than the Conventional gas. Tight gas was formed 248 million years ago in Paleozoic formations. Cementation and recrystallization changed a conventional gas reserve which reduced the permeability of the rock and natural gas was trapped within these rock formations. Horizontal and directional drilling is used to extract tight gas deposits as they run along the formation which in turn allows more natural gas to enter the well that was dug. Numerous wells can be drilled to access the gas. Hydraulic fracturing is one of the main methods to access the gas which requires breaking apart the rocks in the formation by pumping fracking fluids in to the wells. This increases permeability and allows gas to flow easily, freeing it from the trap. After that deliquifaction is used to help in the extraction. Rock with permeabilities as little as one nanodarcy, reservoir stimulation may be economically productive with optimized spacing and completion of staged fractures to maximize yield concerning cost.

Examples

Some examples of tight gas reservoirs are: * Muddy Sandstone/J Sandstone –

Wattenberg Gas Field The Wattenberg Gas Field is a large producing area of natural gas and condensate in the Denver Basin of central Colorado, USA. Discovered in 1970, the field was one of the first places where massive hydraulic fracturing was performed routinely and ...

Denver Basin The Denver Basin, variously referred to as the Julesburg Basin, Denver-Julesburg Basin (after Julesburg, Colorado), or the D-J Basin, is a geologic structural basin centered in eastern Colorado in the United States, but extending into southeast ...

, Colorado, US * Mesaverde Group – Piceance Basin, Colorado, US *

Rotliegend The Rotliegend, Rotliegend Group or Rotliegendes (german: the underlying red) is a lithostratigraphic unit (a sequence of rock strata) of latest Carboniferous to Guadalupian (middle Permian) age that is found in the subsurface of large areas in wes ...

– Germany and NetherlandsAlan Petzet
"Wintershall starts Dutch North Sea tight gas flow,"
''Oil and Gas Journal'', 6 Mar. 2012. * Utica – Appalachian Basin, US & Canada

References

Unconventional gas {{petroleum-stub

Examples

See also

References