Dimonddoids and biomarkers in oil from San Joaquin basin and Santa Barbara basin, Southern California

Abstract

This research focused on analyzing diamondoids and biomarkers in oils from the San Joaquin* and Santa Barbara** Basins. These archived samples provide an opportunity to identify mixed petroleum sources in these well-explored basins allowing for the discovery of possible previously unrecognized cracked oil inputs from deeper sources. Standard solutions and Gas Chromatography-Mass Spectrometry (GCMS) were used to identify compounds (diamondoids and biomarkers) and calculate their concentrations. Diamondoid analyses from 89 samples indicate that 42 (18*+24**) samples are uncracked oils with low diamondoid concentrations. Higher diamondoid concentrations indicate that 38 (24*+14**) samples are mixed oils with dominant slightly cracked sources and 9 (5*+4**) samples are mixed oils with dominant intensely cracked sources. Biomarker analyses suggest that the San Joaquin and Santa Barbara Basins source rocks were likely deposited in hypersaline continental shelf and continental slope with significant plankton inputs, respectively. In conclusion, both basins oils are of relatively moderate to high maturity, varied in biodegradation ranks and generated by multiple source rocks (Cretaceous, Paleogene and Neogene).