The Characteristics Of Enrichment And Hydrocarbon Generation Of Organic Matter In The Saline Lacustrine Basin

There are extensive previous studies which are about the enrichment of organic matter in lacustrine source rocks,but most of the research methods are only the elemental chemical indicators and analysis of the main controlling factors of enrichment of organic matter,ignoring the impact of macroscopic geological events and the internal relations between the controlling factors.The source rocks of different organic carbon content from the third member of Shahejie Formation(Es3)of the Dongpu Sag were used as the samples to systematically discuss the formation of saline racks in the Dongpu sag,tectonic evolution,the climate change in the sedimentary period,the controlling factors of enrichment of organic matter and their inner links,and finally the enrichment patterns of organic matter were established by using the geochemical data,lithology,tectonic evolution profile,the microscopic observation and other methods.The results showed that there were faulting and frequent volcanic activities which existed in the sedimentary period of the Es3 in the Dongpu Sag,and the deep hot brine providesd by paroxysmal volcanic activity enabled the water in the northern lake to evaporate largely,leading to the stratification of water and the sedimentary of saline rocks.When volcanoes were dormant,the salinity decreased to the moderate level duing to the water supply from the runoffs and climate change,providing the suitable environment for the living of Dinoflagellates,and the runoffs could provide nutrients for those creatures.The stratification of water under the higher salinity could provide reductive environment for organic matter.Therefore,the primary productivity and the preservation conditions provided by moderate paleosalinity and adequate nutrients provided by appropriate dilution are the main controlling factors of the enrichment of the lacustrine organic matter.In addition,a sample of low-maturity and high-quality was selected for thermal simulation experiments,and the results showed that the oil and gas yields were high enough to form the oil-gas accumulation with commercial value.