Petroleum source rock identification
First Claim
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1. A method for determining the source rock type of a crude oil sample comprising:
- (a) determining the relative amounts of benzothiophenes and dibenzothiophenes in the sample of crude oil;
(b) determining the relative amounts of the isomeric methyldibenzothiophenes present in the sample of crude oil;
(c) determining the relative amounts of dimethyl- and trimethyldibenzothiophenes present in the sample of crude oil; and
(d) identifying, on the basis of the results of steps a, b, and c, the source rock type of the crude oil sample.
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Abstract
The geochemical oil prospecting method is disclosed in which a crude oil sample is analyzed for the presence of distinctive patterns of aromatic sulfur compounds which are indicative of the petroleum source rock type. Using relative proportions of benzothiophenes, dibenzothiophene, isomeric methyl dibenzothiophenes, dimethyl- and trimethydibenzothiophenes a crude oil can be identified as having a carbonate or siliciclastic source. The information obtained can be used in combination with geological and seismic studies to determine potential oil locations.
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Citations
16 Claims
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1. A method for determining the source rock type of a crude oil sample comprising:
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(a) determining the relative amounts of benzothiophenes and dibenzothiophenes in the sample of crude oil; (b) determining the relative amounts of the isomeric methyldibenzothiophenes present in the sample of crude oil; (c) determining the relative amounts of dimethyl- and trimethyldibenzothiophenes present in the sample of crude oil; and (d) identifying, on the basis of the results of steps a, b, and c, the source rock type of the crude oil sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of geochemical oil prospecting which involves identifying a crude oil sample as having a carbonate source, the method comprising:
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(a) extracting an organosulfur-containing aromatic fraction from the crude oil; (b) injecting the aromatic fraction into a gas chromatograph column and separating on the column constituents comprising benzothiophenes, dibenzothiophenes, three major isomers of methyldibenzothiophenes, dimethyldibenzothiophenes and trimethyldibenzothiophenes; (c) detecting each constituent as it elutes from the column and producing an output signal for each which is proportional to the amount of each constituent present; (d) obtaining an output signal for benzothiophenes which is at least approximately equal to the output signal for dibenzothiophenes; (e) obtaining an output signal for the first major isomer which is greater than or equal to the output signal for the third major isomer of methyldibenzothiophene which in turn is greater than the output signal for the second major isomer of methyldibenzothiophene the first, second and third major isomer being numbered in terms of their order of elution from the column; and (f) obtaining output signals for methyl-, dimethyl- and trimethyldibenzothiophenes, none of which is more than twice the magnitude of any other of the three. - View Dependent Claims (11, 12)
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13. A method of geochemical oil prospecting which involves identifying a crude oil sample as having a siliciclastic source, the method comprising:
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(a) extracting an organosulfur-containing aromatic fraction from the crude oil; (b) injecting the aromatic fraction into a gas chromatograph column and separating on the column constituents comprising benzothiophenes, dibenzothiophenes, three major isomers of methyldibenzothiophene, dimethyldibenzothiophenes and trimethyldibenzothiophenes; (c) detecting each constituent as it elutes from the column and producing an output signal for each which is representative of the amount of each constituent present; (d) obtaining an output signal for benzothiophenes which is small in comparison with the output signal for dibenzothiophenes; (e) obtaining an output signal for the first isomer of methyldibenzothiophene which is greater than or equal to the output signal for the second isomer, which in turn is greater than the output signal for the third isomer, the first, second and third isomers being numbered according to their order of elution from the column; (f) obtaining combined output signals for dibenzothiophenes and methyldibenzothiophenes which are greater than the combined output signals for dimethyl- and trimethyldibenzothiophenes. - View Dependent Claims (14, 15)
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16. A method of geochemical oil prospecting which involves identifying a mature crude oil sample as having a carbonate source, the method comprising:
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(a) extracting an aromatic fraction from the crude oil; (b) injecting the aromatic fraction into a gas chromatograph column and separating on the column constituents comprising benzothiophenes, dibenzothiophenes, three major isomers of methyldibenzothiophene, dimethyldibenzothiophenes and trimethyldibenzothiophenes; (c) detecting each constituent as it elutes from the column and producing an output signal for each which is proportional to the amount of each constituent present; (d) obtaining an output signal for benzothiophenes which is no greater than the output signal for dibenzothiophenes; (e) obtaining an output signal for the first isomer of methyldibenzothiophene which is greater than the output signal for the second isomer which in turn is greater than or equal to the output signal for the third isomer, the first, second and third isomers being numbered according to their order of elution from the column; and (f) obtaining combined output signals for dibenzothiophene and methyldibenzothiophenes which are no greater than the combined output signals for dimethylbenzothiophenes and trimethyldibenzothiophenes.
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Specification