In sedimentary basins, the evolution of hydrocarbon including oil/gas generation, migration, and accumulation, as well as reservoir destruction, is often controlled by regional tectonic activities. Key to understanding the evolution is quantifying the timing of formation of the hydrocarbon and reservoir itself, which is of great value in enriching the theory of hydrocarbon evolution and improving oil and gas exploration efficiency. However, reliable time constraints often require comprehensive data on basin stratigraphy, tectonic characteristics, and reliable geothermal parameters, which have always been a challenge in the oil and gas geology industry.
Recently, Associate Professor ZHANG Yong from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), together with othe researchers from Nanjing University, Imperial College London, and Durham University, used a combination of paleomagnetic remanence and rhenium-osmium isotopes for the first time to provide reliable time constraints on the generation, migration, and accumulation of oil and gas under complex conditions.
The work was recently published in the natural index journal Journal of Geophysical Research Solid Earth.
This study focused on oil/bitumen-bearing Permian carbonate rocks in the northwestern margin of the Sichuan Basin. The reservoir carbonate rocks were selected for the study of remagnetization, which revealed two periods of oil and gas migration into the reservoir carbonate rocks during the late Triassic and Middle Jurassic-Cretaceous.
ZHANG says, "rhenium-osmium isotope studies on corresponding crucial oil and bitumen revealed the times for oil and gas generation, which were during ~264 Ma and ~94 Ma".
The two methods therefore reliably identified two periods of hydrocarbon formation, followed by two extended periods of hydrocarbon migration.
Together with the geology context, we suggest that the main geological structures for migrating and entrapping of hydrocarbon formed during the Indosinian event; the Dongwu magmatism and Yanshan tectonism provided the heat for hydrocarbon maturation, and the latter may also have reactived migration paths.
The study also pointed out that the two methods are completely independent in terms of methods and principles, but they can reveal the same oil and gas process, so the two methods can provide additional tests for each dating technique. Moreover, this combined method is particularly powerful as it is independent of the hydrocarbon source rock and complex geological settings.
This research was supported by the National Natural Science Foundation of China and Chinese Academy of Sciences projects.
Reference: Hu Jing, Zhang Yong*, Dong Jia*, Adrian Muxworthy, David Selby, Li Yongxiang, Matthew J. Brzozowski, Wei Guoqi, Cao Jian, Yin Hongwei, Li Wei, 2023. Combining paleomagnetic and Re–Os isotope data to date hydrocarbon generation and accumulation processes，Journal of Geophysical Research: Solid Earth, e2022JB025955. https://doi.org/10.1029/2022JB025955.
Relationship between hydrocarbon evolution and tectonic events
Contact:
LIU Yun, Propagandist
Email: yunliu@nigpas.ac.cn
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences
Nanjing, Jiangsu 210008, China
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