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added Category:Treatise Handbook 3 using HotCat
==Gasification==
==Gasification==
Gasification is the conversion of oil to gas resulting from thermal [[cracking]]. It primarily takes place during burial. If oil is spilled from a trap by gas displacement during gasification, the oil may occur in economic [[accumulation]]s updip along the migration pathway.<ref name=ch11r12>Gussow, W. C., 1954, [http://archives.datapages.com/data/bulletns/1953-56/data/pg/0038/0005/0800/0816.htm Differential entrapment of oil and gas: a fundamental principle]: AAPG Bulletin, vol. 38, p. 816–853.</ref>
Gasification is the conversion of oil to gas resulting from thermal [[cracking]]. It primarily takes place during burial. If oil is spilled from a trap by gas displacement during gasification, the oil may occur in economic [[accumulation]]s updip along the [[migration pathway]].<ref name=ch11r12>Gussow, W. C., 1954, [http://archives.datapages.com/data/bulletns/1953-56/data/pg/0038/0005/0800/0816.htm Differential entrapment of oil and gas: a fundamental principle]: AAPG Bulletin, vol. 38, p. 816–853.</ref>
==Predicting and recognizing gasification==
==Predicting and recognizing gasification==
* Geohistory analysis with proper gasification [[kinetics]] can usually predict at what depth [[accumulation]]s have been gasified.
* Geohistory analysis with proper gasification [[kinetics]] can usually predict at what depth [[accumulation]]s have been gasified.
* As a rule of thumb, oil should not be expected at subsurface temperatures > [[temperature::150°C]] or a maturation level much above 1.3% R<sub>o</sub>. Dry gas accumulations can occur at shallower depths, but oil is not likely at greater depths.
* As a rule of thumb, oil should not be expected at subsurface temperatures > [[temperature::150°C]] or a [[maturation]] level much above 1.3% R<sub>o</sub>. Dry gas accumulations can occur at shallower depths, but oil is not likely at greater depths.
* Gasification of oil in reservoirs is associated with the formation of pyrobitumen.<ref name=ch11r34>Tissot, B. P., D. H. Welte, 1984, Petroleum Formation and Occurrence, 2 ed.: New York, Springer-Verlag, 699 p. 460–461</ref>
* Gasification of oil in reservoirs is associated with the formation of pyrobitumen.<ref name=ch11r34>Tissot, B. P., D. H. Welte, 1984, Petroleum Formation and Occurrence, 2 ed.: New York, Springer-Verlag, 699 p. 460–461</ref>
* Displacement of oil from a trap by gas is associated with asphaltene precipitates and/or relatively unaltered oil stain.
* Displacement of oil from a trap by gas is associated with asphaltene precipitates and/or relatively unaltered oil stain.
==Predicting gas destruction==
==Predicting gas destruction==
It is not the destruction of methane as much as the lack of economic [[accumulation]]s which occurs at higher maturation levels. Methane occurs in fluid inclusions from lower crustal depths, and shows of methane are not unusual where drilling through low-grade metamorphic rocks—even those at a grade high enough to contain graphite instead of kerogen (R<sub>0</sub> > 8%). For example the Shell Barret #1 well in Hill County, Texas, had a 30-minute methane flare at over [[depth::13,000 ft]] depth in rock described as [[dolomite]] and calcite marble with graphitic inclusions.<ref name=ch11r30>Rozendal, R. A., and W. S. Erskine, 1971, [http://archives.datapages.com/data/bulletns/1971-73/data/pg/0055/0011/2000/2008.htm Deep test in Ouachita structural belt of Central Texas]: AAPG Bulletin, vol. 56, p. 2008–2017.</ref>
It is not the destruction of methane as much as the lack of economic [[accumulation]]s which occurs at higher maturation levels. Methane occurs in fluid inclusions from lower crustal depths, and shows of methane are not unusual where drilling through low-grade metamorphic rocks—even those at a grade high enough to contain graphite instead of [[kerogen]] (R<sub>0</sub> > 8%). For example the Shell Barret #1 well in Hill County, Texas, had a 30-minute methane flare at over [[depth::13,000 ft]] depth in rock described as [[dolomite]] and calcite marble with graphitic inclusions.<ref name=ch11r30>Rozendal, R. A., and W. S. Erskine, 1971, [http://archives.datapages.com/data/bulletns/1971-73/data/pg/0055/0011/2000/2008.htm Deep test in Ouachita structural belt of Central Texas]: AAPG Bulletin, vol. 56, p. 2008–2017.</ref>
The following characteristics can help us predict and recognize gas destruction:
The following characteristics can help us predict and recognize gas destruction:
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting preservation and destruction of accumulations]]
[[Category:Predicting preservation and destruction of accumulations]]
[[Category:Treatise Handbook 3]]