Occurrence of natural gas

In 400 B.C., Ktesias of Knidos mentioned the occurrence of natural gas in Karamania, Asia Minor. It provided perpetual flame for the fire-worshippers and fuel for their homes (23). 

There are four requirements for generation of natural gas hydrates (1) low temperature, (2) high pressure, (3) the availability of methane or other small nonpolar molecules, and (4) the availability of water. Without any one of these four criteria, hydrates will not be stable. As indicated in both the previous section and in Section 7.4.3, the third criteria for hydrate stability—namely methane availability—is the most critical issue controlling the occurrence of natural gas hydrates. Water is ubiquitous in nature so it seldom limits hydrate formation. However, the first two criteria are considered here as an initial means of determining the extent of a hydrated reservoir. 

Kvenvolden K. K. and Lorenson T. D. (2001) The global occurrence of natural gas hydrate. In Natural Gas Hydra-tes.Occurrence, Distribution and Detection, Geophysical Monograph 124 (eds. C. K. Pauli and W. D. Dillon). American Geophysical Union, Washington, DC. 

Uchida T., Lu H., Tomaru T., Dallimore S. R. and Nankai Trough Scientific Party (2004) Subsurface occurrence of natural gas hydrate in the Nankai Trough area implication for gas hydrate concentration. Resource Geol. 54,35-44. 

To represent the range of estimates of the EUR of natural gas, a very pessimistic estimate of 283 Tm3 by Laherrere (2004a) and a very optimistic estimate of 558 Tm3 by Chabrelie (2002) have been selected. For comparison, the USGS (2000) estimates the P95 EUR of natural gas at 301 Tm3, theP5 EUR at 604 Tm3 and the mean at 436 Tm3. The estimate of the Federal Institute for Geosciences and Natural Resources (BGR, 2007) of 466 Tm3 is in the middle. As for unconventional gas, only reserves have been taken into account, owing to the large uncertainties related to unconventional gas occurrences. As of today, 81 Tm3 of natural gas have already been produced. 

Kvenvolden and McMenamin Hydrates of Natural Gas A Review of Their Geologic Occurrence... 

OCCURRENCE OF DILUTE GAS-IN-LIQUID EMULSIONS IN NATURAL WATERS... 

Commodity Pipeline Occurrence Report - Natural Gas Pipeline Rupture. Transportation Safety Board of Canada Report Number P94H0003, 1995-08-23. 

Methane. (Marsh Gas, Fire Damp), Methan, Sumpfgas, or Grubengas (Ger) Methane or Grisou (Fr) Metan (Russ) CH4 mw 16.04 a colorl, odorless, and tasteless gas mp —182.5°, bp —161.5°, crit temp —82.1°, crit p 672 psi (Ref 1) CA Registry No 74-82-8 Occurrence. It is the chief constituent of natural gas, which is from 60—98% methane. It occurs to some extent in all coal mines where mixts with air are called by the miners fire damp as it is the cause of almost all coal mine fires and explns (Ref 3). It also occurs in the gases evolved when organic matter decomposes anaerobically as in the bottoms of swamps and marshes, hence the name marsh gas ... 

K. A. Kvenvolden and M. A. McMenamin, Hydrates of Natural Gas A Review of Their Geologic Occurrence, Geol Surv. Circ (US) 825, Washington, DC, 1980. 

A common feature associated with cold seeps is the presence of gas hydrates, which are naturally occurring solids comprised essentially of natural gas, mainly methane, trapped in frozen, crystalline water (see reviews by Kvenvolden, 1993 and Buffet, 2000). The occurrence of gas hydrates is controlled by an interrelation among temperature, pressure and composition, and they are stable in solid form only in a narrow range of these conditions (Kvenvolden, 1993). Because of these restrictions, gas hydrates are common mainly in polar and deep... 

Kvenvolden, K.A. and McMenamin, 1980. Hydrate of natural gas. A review of their geological occurrence. 

Matsumoto R., Uchida T., Waseda A., Uchida T., Takeya S., Hirano T., Yamada K., Maeda Y. and Okui T. (2000) Occurrence, structure and composition of natural gas hydrates recovered from the Blake Ridge, Northwest Atlantic. In Proc. ODP, Sci. Results 164 (eds. C. K. Paull, R. Matsumoto, P. J. Wallace and W. P. Dillon), pp. 13-28. Ocean DriUing Program, College Station, TX. 

The occurrence and consumption of energy in what are called pit coal units (CU) are given in Table 24-1. The CU is an energy unit and one CU corresponds to the energy content of 1 kg of medium quality pit coal, that is 1 CU is about 29300 kJ. The CU unit was introduced many years ago when pit coal was the main source of energy and it was used as a standard for all other sources of energy. The energy content of one ton of pit coal corresponds to that of about 700 kg of petroleum, 1000 m of natural gas, or 7 kg of uranium. 

The occurrence of some of the important petrochemical reactions, such as the water gas shift reaction, methane steam reforming, partial oxidation of natural gas to syngas, dry reforming of methane, etc., has been mentioned in detail in previous chapters in this book, but the application of membrane reactors in other industrial important reactions is briefly mentioned. 

Han and Weng (2011) consider that accidents caused by gas pipelines rupturing bring about major threats to public safety. Due to the physical and chemical characteristics of natural gas and the complexity of the topology of pipeline networks, the occurrence of accidents in pipelines are completely different from any other kind of industrial accident. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Occurrence. Magnesium bromide [7789-48-2] MgBr2, is found in seawater, some mineral springs, natural brines, inland seas and lakes such as the Dead Sea and the Great Salt Lake, and salt deposits such as the Stassfurt deposits. In seawater, it is the primary source of bromine (qv). By the action of chlorine gas upon seawater or seawater bitterns, bromine is formed (see Chemicals frombrine). 

Occurrence. Iodine [7553-56-2] is widely distributed in the Hthosphere at low concentrations (about 0.3 ppm) (32). It is present in seawater at a concentration of 0.05 ppm (33). Certain marine plants concentrate iodine to higher levels than occur in the sea brine these plants have been used for their iodine content. A significant source of iodine is caUche deposits of the Atacama Desert, Chile. About 40% of the free world s iodine was produced in Japan from natural gas wells (34), but production from Atacama Desert caUche deposits is relatively inexpensive and on the increase. By 1992, Chile was the primary world producer. In the United States, underground brine is the sole commercial source of iodine (35). Such brine can be found in the northern Oklahoma oil fields originating in the Mississippian geological system (see Iodine and iodine compounds). 

Corrosion protection using bitumen coatings reaches back into antiquity. The most ancient occurrence of bitumen deposits was in Mesopotamia. Many writers of antiquity, such as Dido, Strabo, and Vitruvius, mention that asphalt was obtained for many years near Babylon. About 5000 yeare ago, the streets of Ur, capital of the Sumerians (north of present-day Kuwait), were lit at night with mineral oil. Natural gas was reported to be used for lighting in the Middle East and China. 

Non-conventional gas is natural gas found in unusual underground conditions, such as very impermeable reservoirs which require massive stimulation in order to be recovered, or in underground occurrences of gas hydrates, or dissolved in formation water, or coal-bed methane, or gas from in-situ gasification of coal. 

Because of NGC s co-occurrence with coal, the targeted coal seam locations and their geographical distribution are typically well known from coal assessments. Natural gas from coal is produced by reducing the natural pressure within the coal seam by creating fracture systems (so-called fracs ) to allow the gas to release from the coal and then flow through a well to the surface. 

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