Quiz Ch5 - Quiz Ch. 5 Geologic facts: must be explained by...

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Quiz Ch. 5 Geologic facts: must be explained by any petroleum genesis theory 1. Major accumulations of hydrocarbons characteristically occur in sedimentary rocks. 2. Numerous cases of hydrocarbon accumulations in sandstone and limestone reservoirs are totally enclosed by impermeable rocks 3. Other geologic occurrences to consider are: a. Commercial accumulations of hydrocarbons have been found in basement rocks. i. Commercial accumulations in basement rocks are always in lateral fluid continuity with sedimentary rocks. b. Traces of indigenous hydrocarbons have been found in igneous and metamorphic rocks. c. Traces of hydrocarbons occur in stony chondritic meteorites Chemical facts: must be explained by any petroleum genesis theory 1. Crude oil differs from recent shallow hydrocarbons. a. They show a preference of even numbered carbon chains, while modern hydrocarbons tend to occur in odd numbered chains. b. They contain more than 50% light hydrocarbons, which are rare or absent in modern sediments. 2. Crude oil show affinities with modern organic hydrocarbons; a. Young oils show levorotation (the counterclockwise rotation of the plane of polarization of light caused by a particular arrangement of the atoms in the substance). This optical property is characteristic of hydrocarbons produced biosynthetically. b. They contain certain complex molecules that occur either in modern organic matter or as a product of their degradation. c. It is possible to use biomarkers to fingerprint the depositional environment within which a particular petroleum originated 3. Correlation between source rock and reservoir oil can be carried out by fingerprinting using gas chromatography. Biogenic theory:
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Quiz Ch5 - Quiz Ch. 5 Geologic facts: must be explained by...

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