Characterization of asphaltic oil occurrences from the southeastern margin of the Basque-Cantabrian Basin, Spain
Keywords:
Asphaltic oil occurrences, Basque-Cantabrian Basin, Álava sector, Ayoluengo oil field, BiodegradationAbstract
A geochemical investigation has been undertaken on biodegraded hydrocarbons in outcropping reservoirs of the south-eastern margin of the Basque-Cantabrian Basin (Álava sector). The aims of the study were the characterization of the geochemical features and biodegradation level of these hydrocarbons, and the evaluation of their resemblance to oils from the Ayoluengo onshore oil field by means of isotopic analyses and gas chromatography-mass spectrometry techniques. Most of the samples lack of n-alkanes, isoprenoids, low molecular weight aromatic compounds, steranes, homohopanes, diasteranes and triaromatic steroids whereas hexacyclic and heptacyclic alkanes appear as key compounds although some structures were not totally elucidated. Thermal maturity has been assessed with several parameters and thus a calculated-equivalent vitrinite reflectance value of around 0.8% was estimated. In addition, gammacerane content, diasterane-to-sterane ratio and C35 to C34 hopanes ratio suggested that the Álava oil shows were derived from a carbonate rock deposited in a reducing, water-stratified and possibly hypersaline environment. Isotopic signature and other data confirmed that these hydrocarbons are not genetically related to the oils from Ayoluengo and, consequently, their origin has to be associated with a yet unknown source rock in the basin.
Downloads
Published
Issue
Section
License
Copyright
The commercial rights of the printed and online versions of Geologica Acta are property of the UB, ICTJA, IDAEA and UAB, and Geologica Acta must be cited for any partial or full reproduction.
The opinions and conclusions stated in each article are the exclusive responsability of the authors and do not necessarily coincide with those of the above mentioned institutions UB, ICTJA, IDAEA and UAB.
Author Rights
Authors retain the copyright on their papers (accepted manuscript, uncorrected proof and published paper) and are authorized to post them on their own Web page or their institutional repositories. In all cases, the complete citation and a link to the Digital Object Identifier (DOI) of the article must be included.
The authors can use excerpts or reproduce illustrations of their papers in other works without prior permission of Geologica Acta provided the source of the paper including the complete citation is fully acknowledged.
Papers are distributed under the Attribution-Share Alike Creative Commons License. This license allows others to alter, remix or build upon a paper and the resulting work may be distributed under the same or similar license to this one.