10 research outputs found
Sulphur stable isotope systematics in diagenetic pyrite from the North Sea hydrocarbon reservoirs revealed by laser combustion analysis
Our study focuses on pyrite nodules developed in the Brent Group sandstones, which host the Brent Oilfield, one of the North Sea's greatest oil and gas producers. Timing of nodule formation is equivocal, but due to the forceful, penetrative textures that abound, it is considered late. This pyrite offers a research opportunity because it records the development of the supply of H<sub>2</sub>S in a hydrocarbon reservoir and its sulphur isotopic composition. Laser-based analysis of ÎŽ<sup>34</sup>S reveals an extraordinary diversity in values and patterns. The values range fromâ27 to+72â°, covering half the terrestrial range, with large variations at the submillimetre scale. Isotopically heavy (ÎŽ<sup>34</sup>S +30â° or higher) sulphide is endemic, but low ÎŽ<sup>34</sup>S pyrite is also present and appears to represent a temporally though not spatially (on the cm scale) distinct pyritisation event. The distribution of ÎŽ<sup>34</sup>S values within individual concretions can be normal (Gaussian), but in some cases may reflect progressive isotope fractionation process(es), conceivably of Rayleigh type. The source of the sulphur and the identity of the isotope fractionation process(es) remai