Unraveling Complex Oil Mixtures in the Williston Basin

Oil mixtures can be encountered in both tight shale and conventional reservoirs. Knowing the components of oil mixtures can improve exploration prospect selection. However, oil mixtures may be difficult to recognize by classical geochemical analysis. Once recognized they may be even more difficult to disentangle and to determine the component sources. We tested new high-resolution geochemical technologies for correlation in the Williston Basin. With its multiple stacked source rocks, the Williston is a prime proving ground for identifying oil sources and mixtures, and if successful, a venue for application with high yield potential for exploration.

The new applied technologies begin with quantitative diamondoid analysis to identify black oil-cracked oil or condensate mixtures. In spite of the occurrence of as many as a dozen possible source rocks in the basin, individual components can be distinguished and correlated by using compound specific isotope analysis of diamondoids (CSIA-D) and biomarkers (CSIA-B), and by the very latest advance in correlation, quantitative extended diamondoid analysis (QEDA). The parallel use of diamondoid and biomarker correlation methods facilitates correlation of both black oil and cracked oil sources and de-convolution of their mixtures.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California