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Abstract: Compound Specific Isotopic Analysis of Individual n-Alkanes: A Case Study Showing Their Utility in Oil-to-Oil and Oil-to-Source Rock Correlations in the Noroeste Basin, Argentina

GUTHRIE, JOHN M., Petrobras/Cenpes/Segeq (currently at Mobil Exploration and Producing Technical Center); JOSE R. CERQUEIRA, Petrobras/Cenpes/Segeq; ALBERTO E. SCHULZ, Tecpetrol


In the Noroeste Basin of Argentina, compound specific isotopic analysis (CSIA) of individual n-alkanes proved to be a valuable tool for establishing oil-to-oil and oil-to-source rock correlations that were not made complete using conventional biomarker techniques. The d13C n-alkane profiles for three, oils are similar. Slight differences in d13C are thought to be the result of thermal maturity effects. The d13C of n-alkanes also was measured for several Devonian and Silurian extracts. These d13C data show that 1) the Devonian extracts are derived from at least two organic facies and/or organic intervals, 2) the d13C n-alkane profile for a Silurian extract is unique and does not correlate to the oils, and 3) the d13C n-alkane profiles for the oils correlate more closely to the Devonian extracts.

In one oil the detection of sufficient quantities of biomarkers was made possible by using gas chromatography/ mass spectrometry/mass spectrometry (GC/MS/MS). The high relative abundance of C27-Ca35 17a(H)-diahopanes and predominance of C29 over C27 and C[28] steranes in this oil correlates with Devonian extracts. The lack of C27-Ca35 17a(H) diahopanes and a predominance of C27 over C28 and C29 steranes in the Silurian extract show that it is unrelated to the oils.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah