| Mercury is a global pollutant.Oil and gas generally contain mercury,which is significantly harmful to the equipment and the environment.However,there are few studies on mercury in source rocks that can generate oil and gas.And the research on mercury isotope in source rocks has not yet been involved.Whether mercury in oil and gas is derived from the source rock,and whether the mercury can trace the oil and gas are worth studying.This thesis measures the mercury concentration and mercury isotope compositions of terrestrial source rocks in Liaohe Oilfield,and marine and terrestrial sources rocks in Sichuan Puchuang gasfield.This thesis deeply delves into the similarity of mercury isotopes of marine and terrestrial source rocks,the difference between mercury isotopes of terrestrial source rocks and terrestrial non-source rocks,and the similarity of the mercury isotopes of oil and gas and their source rocks.It is helpful to reduce the harm of mercury in oil and gas,and to provide a new proxy for oil-gas exploration and oil-source rock correlation.The thesis measures the mercury concentration of terrestrial source rocks in Liaohe Oilfield,and marine and terrestrial sources in the Puguang Gasfield in Sichuan.The source rocks generally host mercury due to the rich organic matter,but the mercury content varies greatly.This thesis focuses on the measurement and discussion of mercury isotope compositions of these source rocks,that generally show positive mass-independent fractionation（MIF）,the averageΔ199Hg value is 0.12±0.12‰（n=29,1SD）,and the range is-0.04‰～0.48‰.The MIF of marine source rocks and terrestrial source rocks are similar,and both have positive MIF values.The MIF of source rocks are similar to those of lower plankton such as lake algae,but are significantly different from terrestrial higher plants.Therefore,the source rocks may inherit the Hg-MIF characteristics from algae.It is speculated that the main oil-forming organic matter of terrestrial oilfield in China is also lower plankton such as algae.The MIF of the terrestrial source socks in Liaohe field and Sichuan Puguang Gasfield are significantly different from the Cretaceous terrestrial non-source rock in India,which has certain significance for guiding the exploration of terrestrial oil and gas fields.This thesis also compares the mercury isotope characteristics of oil,gas,and their source rocks in Liaohe Oilfield,as well as the mercury isotope characteristics of marine source rocks in Sichuan and marine oil in Tahe Oilfield in Xinjiang.The Hg-MIF characteristics of oil and gas are consistent with their source rocks.This similarity indicates that mercury isotope may become a new proxy of oil-source correlation.It is further speculated that the mercury isotope fractionation model in the marine and terrestrial oil-forming processes.For terrestrial oilfields,only the continental source rocks that show positive MIF can form oil and gas fields. |
