| Abstract: | At least three hydrocarbon seepage mechanisms are interpreted to operate over oil and gas fields. These are: (1) effusion ofh ydrocarbons through inadequate caprocks and along faults and fractures, (2) low-molecular-weight hydrocarbons dissolved in water moving vertically through capping shales as a result of a hydrodynamic or chemical potential drive, and (3) diffusion of gases dissolved in water. Combinations of these mechanisms may also occur.
Seeping hydrocarbons are oxidized near the earth‘s surface, and the resulting carbon dioxide reacts with water producing bicarbonate ions, which combine with calcium and magnesium dissolved in ground waters to yield isotopically distinctive pore-filling carbonate cements and surface rocks. The passage of hydrocarbons and associated compounds such as hydrogen sulfide through surface rocks causes a reducing environment and consequent reduction, mobilization, and loss of iron from iron-bearing minerals commonly resulting in a discoloration. Other metals such as manganese are also mobilized and redistributed. These changes in the physical and chemical properties of surface rocks correlate with the subsurface distribution of petroleum, and potentially can be detected from both airborne and spaceborne platforms. |
| Genre: | USGS Numbered Series |
| ProdID: | 8601 |
| Citation Author: | Donovan, Terrence J.; Dalziel, Mary C. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 44 leaves :ill., map ;28 cm.; (79 p. - PGS) |
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| Citation Publisher: | U.S. Geological Survey, |
| Citation Series: | Open-File Report |
| Citation Series Code: | OFR |
| Citation Series Number: | 77-817 |
| Citation Search Results Text: | Late diagenetic indicators of buried oil and gas; 1977; OFR; 77-817; Donovan, Terrence J.; Dalziel, Mary C. |
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| Citation Year: | 1977 |
| Type: | citation/reference |
| Text: | Late diagenetic indicators of buried oil and gas; 1977; OFR; 77-817; Donovan, Terrence J.; Dalziel, Mary C. |
| URL (THUMBNAIL): | http://pubs.usgs.gov/of/1977/0817/report-thumb.jpg |
| URL (DOCUMENT): | http://pubs.usgs.gov/of/1977/0817/report.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Geological Survey, |
