Sedimentary organic facies and hydrocarbon-forming potential of coal in Upper Paleozoic coal measures in Dongpu depression and its peripheral areas

Dongpu depression in the Upper Paleozoic has a superior material basis for hydrocarbon generation, and the potential of oil and gas generation depends on the sedimentary organic facies. Based on the research of coal and its periphery sedimentary organic facies types and distribution characteristics of Dongpu depression, thermal simulation experiment of hydrocarbon source rocks, coal formed hydrocarbon potential of the Upper Paleozoic in Dongpu were discussed. Research shows that the Upper Paleozoic sedimentary organic facies in Dongpu depression can be divided into 6 types, vitrinite humic organic facies is the main research field of organic facies, Taiyuan Formation and lower part of Shanxi Formation have also developed a small containing sapropelic humic organic and chitin humic organic facies and the upper part of Shanxi Formation has a relatively inert organic humic facies, while hydrogen-rich organic facies develops in the northern part of Dongpu depression. In particular, wells Qinggu 2, Mao 4 and Mao 8 have good organic types, while vitreous humus organic facies and inert atmosphere humic organic facies develop the southern part. There are obvious differences in hydrocarbon generation potential between different organic facies. The potential of vitrinite humic organic facies is comparable to that of typical coal -derived oil and gas basins in China, while the hydrogen-riched organic facies has higher hydrocarbon generation potential. Because of differences of the degree of thermal evolution in Dongpu depression, various blocks have differences in oil and gas generation, samples of well Mao 4 have low maturity and low oil and gas production; well Qinggu 2 had Rmax around 1%, was at the liquid hydrocarbon generation peak, had higher coal-derived oil yield, well Wengu 1 was in the mature and high mature area, had higher coal-derived gas yield, but did not yet reach the peak of coal gas yield; southern well Magu 5 was at high mature, had high coal gas potential, because the south suffered magmatism, for the assessment of its coal gas potential it is necessary to take the degree of influence of magma into account.