Behavior of Re and Os during contact between an aqueous solution and oil: Consequences for the application of the Re–Os geochronometer to petroleum

Rhenium–osmium geochronology and oil–source correlation of the Duvernay petroleum system, Western Canada sedimentary basin: Implications for the application of the rhenium–osmium geochronometer to petroleum systems

“…Although we propose that the Re and Os in oil are inherited from a source rock, based on the similarity of the Os i values of the asphaltene fractions and the Os g values of the Duvernay Formation shales, an experimental study has suggested that Re and Os in oil can also be derived from contact with formation water (Mahdaoui et al, 2015). The outcome of this experimental work has recently been questioned (Wu et al, 2016) (Table 3).…”

“…Here, oils are suggested to have been contaminated by fault-charged mantle-fluids that contain Os with a non-radiogenic generation age, but instead trace the crustal-scale fluid dynamics and migration. Such processes have also been demonstrated in the laboratory, where experiments have shown that Re and Os in aqueous phase can transfer into oil during oil-water contact under various conditions (Mahdaoui et al, 2015). Thermal cracking may also reset the Re-Os isotope systematics in petroleum and result in only the timing of thermal cracking and generation of dry gas and pyrobitumen being recorded (Lillis and Selby, 2013;Ge et al, 2016).…”

Remotely constraining the temporal evolution of offshore oil systems

“…Studies of weakly to heavily biodegraded crude oils have repeatedly shown that their Re-Os system is not significantly affected by microbial alteration 10,11,13,14 . However, laboratory experiments have demonstrated rapid transfer of Re and Os to liquid oils from an enriched aqueous solution 30 . The authors of this study note that the concentrations of Re and Os used in their experiments were not intended to accurately mimic the natural environment, and that experiments attempting to do so are unlikely to yield meaningful results due to current technical limitations associated with extremely low Re and Os abundances 31 .…”

“…3), the mechanism behind this variation is not fully understood. As discussed above, variation may be driven by interaction with formation waters 30 , or because the asphaltites analysed in this study were collected over the course of three years, and likely represent products of continuous, low intensity seepage. Therefore, the variation could also be attributable to the prolonged duration (>1 Myr) of bitumen generation and expulsion when the chronometer is initially reset 12 .…”

A second type of highly asphaltic crude oil seepage stranded on the South Australian coastline

“…A second potential explanation for resetting Re-Os systematics is oil-water interaction without TSR. Laboratory experiments have also shown Re and Os may be rapidly transferred to liquid oil when in contact with a solution enriched in Re and Os (Mahdaoui et al, 2015;Hurtig et al, 2019). Though these studies cannot fully mimic natural oil-water interactions in a geologic setting, their results suggest that interaction of oil with formation waters, which contain much lower abundances of Re and Os, may be capable of altering and resetting the Re-Os composition of an oil, given sufficiently high water/oil ratios (ca.…”