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Carbon isotope signals for chemical stratigraphy and hydrocarbon exploration in northern Gulf of Mexico

Conference · · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)
OSTI ID:5753417
Stable carbon (C/sub 13//C/sub 12/) isotope records derived from the carbonate contained in the fine-grained (< 63 ..mu..m) sediment of well cuttings exhibit coherent stratigraphic patterns. These patterns have potential importance for chemical stratigraphy and hydrocarbon exploration in Pliocene-Pleistocene deep-water tracts of the northern Gulf of Mexico. Preliminary x-ray diffraction results suggest that calcite is the dominant carbonate phase in the fine fraction. The fine fraction C/sub 13/ record in any given exploration well is characterized by a combination of events (or anomalies), shifts, and long-term trends with time. Wells from some offshore areas show definable negative shifts of nearly 7 per mil from the baseline C/sub 13/ signal for a given stratigraphic interval. In addition to shifts, large negative /sub 13/ events, or anomalies, of > 10 per thousand occur in some sections. Absolute isotope values of some parts of the C/sub 13/ record suggest that a portion of the fine-fraction calcite precipitated in the presence of isotopically light (negative) hydrocarbons. The observed isotopic anomalies may be due to the presence of (1) a particular facies with hydrocarbons, (2) lithostratigraphic units through which hydrocarbons migrated, and/or (3) facies from which hydrocarbons were expelled.
Research Organization:
Univ. of South Carolina, Columbia
OSTI ID:
5753417
Report Number(s):
CONF-8710198-
Conference Information:
Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 71:9
Country of Publication:
United States
Language:
English