Shale gas

Shale gas ( shale gas english ) is stored in natural gas shales. Shale gas is considered " unconventional " natural gas as opposed to " conventional " natural gas deposits mentioned comes from natural gas traps. The shale gas production is technically demanding.

Etymology

The term shale gas stems from the colloquial use of the term slate for mudstones ago. In the geological jargon slate but is no longer used for fine-grained, well- fissile sedimentary rocks, but as a collective term for metamorphic rocks. The latter usually contain no more gas. Nevertheless, the term shale gas has also enforced in technical language. Another reason may be the literal translation of the English shale gas.

Formation

The deposited with the clays organic matter is increasingly degraded primarily by microbial processes. After the consumption of the oxygen occurs under anaerobic conditions to form methane. Due to the small particle size of the material and to the high adsorption capacity of clays and the remaining organic matter, the gas does not escape into adjacent stones, but remains in the layer organization. Shale gas is considered one of the natural gas reserves, which need not be investigated by geological prospecting, because the presence of gas in a Tonsteinschicht with organic material is likely.

Occurrence

Tonsteinformationen embodying economic recoverable quantities of gas, have some common characteristics. There usually are old, oil-bearing rocks that are rich in organic matter (0.5 to 25%), and in which heat and pressure have converted oil into gas. Further, such layers are brittle and rigid enough not to close cracks formed again. Sometimes going strong natural gamma radiation associated with high carbon content. Such Tonsteinschichten are particularly productive.

The gas is partially held in natural fractures or porous places, partly it adsorbed onto the organic material. In promoting the program stored in the cracks of gas is directly released while the adsorbed gas is desorbed only delayed by the falling pressure after the hole. The energy stored in mudstones amount of gas per unit volume of host rock is lower than in natural gas traps.

The European populations are insignificant for the global market, which is why only a minor impact on the price of gas can be expected.

In Germany there are, according to estimates by the Federal Institute for Geosciences between 7 to 22 trillion cubic meters of shale gas, of which about 10 % could be promoted.

Extraction

Shale gas is mainly produced by hydraulic fracturing ( fracking short, hydraulic fracturing ).

Mudstone has a low matrix permeability and shale gas production on a commercial scale requires cracks to ensure this permeability. Shale gas is produced from formations with many natural cracks for a long time.

By directional drilling horizontal wells arise that increase the exit area for the stored natural gas in shale rock. A high pressure liquid pressed ( " Fracfluid ": water, sand and chemicals) generated around the drill string gas permeable structures. Some of the chemicals used therein contain carcinogenic compounds such as benzene. Against Fracking, there are huge environmental concerns.