Rare earth elements (REEs) geochemistry of Sinian–Cambrian reservoir solid bitumens in Sichuan Basin, SW China: potential application to petroleum exploration

Abstract

AbstractIn order to evaluate rare earth elements (REEs) as a potential proxy for solid bitumen classification, we employed traditional correlation approaches, such as carbon isotopes and V/(V + Ni) ratios, to infer the source rocks of Sinian–Cambrian reservoir solid bitumens in the Sichuan Basin and analyse solid bitumens for their REE compositions by inductively coupled plasma–mass spectrometry. Our data suggested that Sinian–Cambrian reservoir solid bitumens were primarily sourced from the lower Cambrian shales deposited under anoxic–euxinic conditions. REE and their associated parameters seemed to be more sensitive to classify solid bitumens than traditional correlation approaches. REE concentrations played a dominant role and fractionation degree between light and heavy REE and played a secondary role in solid bitumen classification. REE concentration and pattern in solid bitumens might be controlled by two processes, including inheritance from source rocks and water–rock interaction. The major factor controlling REE concentrations in solid bitumens was the type of organic matter of source rocks. Authigenic minerals in solid bitumens formed by water–rock interaction appeared to have little influence on REE compositions of solid bitumens because of their trace contents. Overall, REE could be used as a novel complementary approach to solid bitumen classification in complicated petroleum systems. Copyright © 2015 John Wiley & Sons, Ltd.