AAPG Annual Convention and Exhibition

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Correlation of Highly-Mature Hydrocarbon Liquids Using Higher Diamondoids

Abstract

Higher diamondoids are composed of four or more face-fused diamond cages. Unlike the lower diamondoids, adamantane, diamantane and triamantane, higher diamondoids have a variety of structural isomers. There are four different tetramantane isomers found in petroleum, two of which are enantiomeric. There are nine pentamantane isomers of molecular weight 344, six of which are enantiomeric pairs. There are 39 hexamantanes, but only one of which has a molecular weight of 342, the highly condensed cyclohexamantane. Here we show it is possible to use the relative concentrations and distributions of higher diamondoids to determine source in much the way biomarker sterane and terpane-concentrations and distributions are used. Unlike biomarkers which are among the most thermally labile compounds in petroleum, diamondoids are for their molecular weight, the most thermally stable. As a result, unlike biomarker distributions, higher diamondoid distributions can be used to correlate hydrocarbon liquids of any thermal maturity. We will show 1) oil to oil, 2) oil to condensate and 3) oil and condensate to source-rock correlations for a variety of samples, including condensates from liquids collected from highly-mature dry gas wells. Several examples representing various sources in both the US and Mexican GOM will be used to illustrate the application.