Analysis Of The Secondary Hydrocarbon-Generation Mechanism And Potential Of The Carboniferous-Permian Coal-Measure Source Rocks In Jiyang-Linqing Depression

The coal-measure source rocks of Carboniferous-Permian of the eastern Jiyang-Linqing are mainly the coal and the dark mudstone(including carbonaceous mudstone) of Taiyuan formation and Shanxi formation.These coal-measure source rocks experienced the varying degrees of post-uplift,erosion and differential settlement of the later stage,and experienced respectively three main hydrocarbon-generating process including the end of Indo-China,Yanshanian and Himalayan,and a considerable part of them was the second buried in the deep parts of the Tertiary,and hydrocarbon generation occurred again,and the secondary hydrocarbon generation occurred in the Yanshan and Himalayan period, mainly in the Himalayan.It has a lot of progress on the study of"secondary hydrocarbon generation",but there are still many issues to be in-depth study,such as the difference between secondary hydrocarbon generation and continuous hydrocarbon generation?Is it the simple duplication of organic matter evolution,or variation?What are the characteristics of secondary hydrocarbon generation?And what are the impacts on the accumulation and so on,and these issues are still more concerned in the current exploration.This study is aimed at the problems that are in the present research about"secondary hydrocarbon generation",and carry out the simulation experiment of secondary hydrocarbon generation to the coal and the mudstone of the study area.The simulation experimental study indicates that the secondary hydrocarbon generation is a succession of the first hydrocarbon generation,and is also controlled by the characteristics of the source rocks, the temperature and the time, the 3 essential factors of the surrounding rocks, and the thermal degradation, pyrolysis and their associated polycondensation reaction. But even so, the secondarily generated hydrocarbons are different from the first generated hydrocarbons with more diverse and more complicated hydrocarbon generation patterns due to the different reaction environment and the different heating time. The Carboniferous-Permian coal-measure source rocks still have rather high secondary hydrocarbon generation ability when in the low-mature stage, whereas in the high-mature stage and the over-mature stage, their secondary hydrocarbon generation patterns are obviously different.The hydrocarbon generation intensity and the hydrocarbon volume of the Carboniferous-Permian coal-measure source rocks and black mudstones in the Mesozoic period and the Cenozoic period have been calculated respectively according to the study results of the abundance of various kinds of Carboniferous-Permian coal-measure source rocks, the maturity degrees of various evolution stage, and the secondary hydrocarbon generation simulation of various kinds of source rocks. The results show that the Carboniferous coal-measure source rocks contribute most greatly to the secondary hydrocarbon generation, with the Permian coal-measure source rocks being the next. Zizheng-Yangxin area of Jiyang Depression has the greatest cumulative mean hydrocarbon generation intensity, up to 44.09×108m3/km2; whereas the eastern Linqing area has the least hydrocarbon generation intensity, normally below 10×108m3/ km2. The cumulative reserve of the Carboniferous-Permian coal-measure source rocks is 6317.19×108m3 in Jiyang Depression; 1617.69×108m3 in eastern Linqing area; and 0.77×108m3/km2 in Zizheng-Yangxin Area, which has the best reserve abundance.The study of the secondary hydrocarbon generation mechanism and the secondary hydrocarbon generation potential of the Carboniferous-Permian coal-measure source rocks in Jiyang-Linqing Depression have been carried out based on the secondary hydrocarbon simulation experiment and the basin simulation.