Changes

==Traps leak==

==Traps leak==

The underlying assumption of all near-surface geochemical exploration techniques is that hydrocarbons are generated and/or trapped at depth and leak in varying but detectable quantities to the surface. This has long been established as fact, and the close association of surface geochemical anomalies with faults and fractures is well known.<ref name=ch18r14>Horvitz, L., 1939, On geochemical prospecting: Geophysics, vol. 4, p. 210–228, doi: 10.1190/1.1440497</ref><ref name=ch18r15>Horvitz, L., 1969, Hydrocarbon prospecting after thirty years, in Heroy, W., B., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas: Dallas, Southern Methodist Univ. Press, p. 205–218.</ref><ref name=ch18r17>Jones, V., T., Drozd, R., J., 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0006/0900/0932.htm Predictions of oil or gas potential by near-surface geochemistry]: AAPG Bulletin, vol. 67, p. 932–952.</ref><ref name=ch18r30>Price, L. C., 1986, A critical overview and proposed working model of surface geochemical exploration, in Davidson, M. J., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas IV: Dallas, Texas, Southern Methodist Univ. Press, p. 81–129.</ref> The surface expression of hydrocarbon seeps is best developed in areas with numerous well-developed migration pathways and an active [[petroleum system]].

The underlying assumption of all near-surface geochemical exploration techniques is that [[hydrocarbon]]s are generated and/or trapped at depth and leak in varying but detectable quantities to the surface. This has long been established as fact, and the close association of surface geochemical anomalies with [[Fault control on hydrocarbon distribution|faults]] and [[fracture]]s is well known.<ref name=ch18r14>Horvitz, L., 1939, On geochemical prospecting: Geophysics, vol. 4, p. 210–228, doi: 10.1190/1.1440497</ref><ref name=ch18r15>Horvitz, L., 1969, Hydrocarbon prospecting after thirty years, in Heroy, W., B., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas: Dallas, Southern Methodist Univ. Press, p. 205–218.</ref><ref name=ch18r17>Jones, V., T., Drozd, R., J., 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0006/0900/0932.htm Predictions of oil or gas potential by near-surface geochemistry]: AAPG Bulletin, vol. 67, p. 932–952.</ref><ref name=ch18r30>Price, L. C., 1986, A critical overview and proposed working model of surface geochemical exploration, in Davidson, M. J., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas IV: Dallas, Texas, Southern Methodist Univ. Press, p. 81–129.</ref> The surface expression of hydrocarbon [[Seepage activity and surficial geochemistry|seeps]] is best developed in areas with numerous well-developed [[migration pathway]]s and an active [[petroleum system]].

[[file:surface-geochemical-exploration-for-petroleum_fig18-1.png|300px|thumb|{{figure number|1}}Examples of contrasting seepage styles and migration pathways from the Gulf of Mexico and the North Sea. Modified from Thrasher et al.;<ref name=ch18r46 /> courtesy AAPG.]]

[[file:surface-geochemical-exploration-for-petroleum_fig18-1.png|300px|thumb|{{figure number|1}}Examples of contrasting seepage styles and migration pathways from the Gulf of Mexico and the North Sea. Modified from Thrasher et al.;<ref name=ch18r46 /> courtesy AAPG.]]