Exploiting the geochemical attributes of migrated oils for an improved understanding of their sourcing facies : Lessons learned from the southeastern Caribbean and the Norwegian Barents and North Seas

• Published in: Marine and Petroleum Geology
• Main Author: Cedeño Motta, Felipe Andres
• Other Authors: Escalona, Alejandro, Ohm, Sverre
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stavanger, Norway 2023
• Subjects: petroleumsgeologi; petroleum geology; VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Petroleumsgeologi og -geofysikk: 464; VDP::Teknologi: 500::Berg‑ og petroleumsfag: 510::Geoteknikk: 513; Barents Sea; Hekkingen
• Online Access: https://hdl.handle.net/11250/3046134

Assessing the geochemistry of oils and the source rock facies from which they originated is crucial in petroleum systems analysis. Crude oils are usually available for geochemical characterization, but pertinent source rock data is often scarce or absent because exploratory drilling mostly targets reservoirs in structurally elevated areas and fails to sample the deeply buried, prolific basinal source facies. Explorationists, unable to perform direct oil-to-source correlations, must rely on source rock inferences drawn from oil geochemistry, a practice named geochemical inversion. This work focuses on organic geochemical investigations in the southeastern Caribbean-Atlantic margin and selected areas of the Norwegian Continental Shelf. These geologically distinct regions were selected as natural laboratories because their different data sets and geochemical commonalities offer a unique arena to explore the successes and pitfalls of selected geochemical proxies in geochemical inversion. A variety of techniques are employed to: (1) Review the accuracy of stable carbon isotopes in assessing organofacies in source rocks and oils; (2) Explore the utility of inverting oil biomarker composition to source rock organofacies and associated kinetic; and (3) Appraise the validity of selected biomarker ratios employed in age and lithofacies determination. Paper I combines maceral descriptions, TOC and Rock-Eval, carbon isotopes, and palaeogeographical considerations. Integration of this data resulted in a subregional to regional characterization of organofacies and sedimentary environment changes through the Upper Jurassic to Lower Cretaceous Hekkingen Formation in the Norwegian Barents Sea. Importantly, this paper documents a poor correlation between maceral compositions and stable carbon isotopes of source rock extracts. It is tentatively explained as the result of varying degrees of diagenetic alteration of the organic matter. Paper II builds on Paper I and evaluates the petroleum generation potential of the Hekkingen ...