Summary

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 #90928©1999 AAPG Annual Convention, San Antonio, Texas