Advanced Geochemical Technologies Extend Petroleum Systems to Include Previously Missed Sources Revealing New Exploration Plays
Normal biomarker analysis falls short of giving a full accounting of the petroleum systems in mature petroleum provinces. This is due to the fact that highly mature and severely biodegraded oil often lack unaltered biomarkers to be used in correlations of those altered fluids. Also, possible co-sources of mixed oil are often obscured by the overprinting of fresh biomarker-rich oil from one of the sources. Relative abundances of large diamondoid molecules including triamantane, three tetramantane isomers, four pentamantane isomers and cyclohexamantane, measured by a technique called quantitative extended diamondoid analysis (QEDA) are used to correlate any petroleum liquids including the most mature condensates, extracts from source rocks, severely biodegraded oils and black oils. It is critical to obtain accurate and precise analyses of the diamondoids. Deuterated internal standards consisting of the same diamondoids labeled with deuterium, are added to the oil in precise accurate amounts. A diamondoid fraction is then isolated and analyzed by GCMS with using the internal standard as a quantitative calibration method. Like biomarkers, the fingerprints generated from analysis of these diamondoids relate to the source rock, but unlike biomarkers large diamondoid fingerprints are ubiquitously applicable to all petroleum liquids. Meanwhile, QEDA, when applied in combination with other methods such a compound specific isotope analysis of biomarkers (CSIA-B) and of diamondoids (CSIA-D), becomes part of a powerful tour de force to determine constituents of co-sourced oil mixtures. These advanced tools for geochemical analysis are exemplified by studies that have delineated new features of the petroleum systems of Central and South America pertaining to Mexico, Brazil, Colombia and Eastern Venezuela. The resulting knowledge gleaned from these applications can enhance exploration prospect evaluation while reducing the risks involved with new exploration in mature basins.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017