Changes

==Determining age of accumulations==

==Determining age of accumulations==

[[Accumulation]]s should be dated to evaluate the potential importance of accumulation destruction in an area of interest. Leakage, spillage, petroleum destruction, and cementation are more likely to alter the size and quality of old accumulations than young accumulations. Young accumulations with active [[Calculating charge volume|petroleum charge]] are more likely to be affected by displacement of oil by later gas charge. Accumulation preservation is a function of tectonic setting, trap type, depth of burial, and seal type.<ref name=ch11r24>Mcgregor, D., S., 1996, Factors controlling the destruction or preservation of giant light oilfields: Petroleum Geoscience, vol. 2, p. 197–217., 10., 1144/petgeo., 2., 3., 197</ref>

[[Accumulation]]s should be dated to evaluate the potential importance of accumulation destruction in an area of interest. Leakage, spillage, petroleum destruction, and cementation are more likely to alter the size and quality of old accumulations than young accumulations. Young accumulations with active [[Calculating charge volume|petroleum charge]] are more likely to be affected by displacement of oil by later gas charge. Accumulation preservation is a function of tectonic setting, trap type, depth of burial, and seal type.<ref name=ch11r24>Mcgregor, D. S., 1996, Factors controlling the destruction or preservation of giant light oilfields: Petroleum Geoscience, vol. 2, p. 197–217., 10., 1144/petgeo., 2., 3., 197</ref>

Three methods help us determine the age of accumulations.

Three methods help us determine the age of accumulations.

In '''dating the formation of the reservoir, seal, and trap''', the age of an accumulation can be no older than the age of the reservoir, seal, or trapping geometry. For example, offshore Gulf of Mexico accumulations in Pleistocene reservoirs can be no older than the Pleistocene.

In '''dating the formation of the reservoir, seal, and trap''', the age of an accumulation can be no older than the age of the reservoir, seal, or trapping geometry. For example, offshore Gulf of Mexico accumulations in Pleistocene reservoirs can be no older than the Pleistocene.

'''Direct radiometric measurements''' are difficult to perform because most reservoirs do not have datable material that formed during charging. The Groningen gas field (Permian, the Netherlands) has been dated as pre-Late Jurassic by the retardation effect of gas on radiometrically datable illite cements in the reservoir.<ref name=ch11r22>Lee, M., Aronson, J., L., Savin, S., M., 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0009/1350/1381.htm K/Ar dating of time of gas emplacement in Rotliegendes sandstone, Netherlands]: AAPG Bulletin, vol. 69, p. 1381–1385.</ref>

'''Direct radiometric measurements''' are difficult to perform because most reservoirs do not have datable material that formed during charging. The Groningen gas field (Permian, the Netherlands) has been dated as pre-Late Jurassic by the retardation effect of gas on radiometrically datable illite cements in the reservoir.<ref name=ch11r22>Lee, M., J. L. Aronson, and S. M. Savin, 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0009/1350/1381.htm K/Ar dating of time of gas emplacement in Rotliegendes sandstone, Netherlands]: AAPG Bulletin, vol. 69, p. 1381–1385.</ref>

==References==

==References==