Geochemical Characteristics and Oil Generation Potential Evaluation of Lower Cretaceous Xiahuapidianzi Formation Shale in the Southeastern Sankeyushu Depression, Tonghua Basin: Evidence from Shale Pyrolysis Experiments and Biomarkers

Abstract

Oil and gas exploration in the Tonghua Basin, a potential petroleumbearing basin in Northeast China, is still in the early stages. In this article, the organic geochemistry and kerogen petrology of a Xiahuapidianzi formation shale core from a geological survey well in the southeastern Sankeyushu depression of the tonghua basin are studied. The mean vitrinite reflectance (Ro) values (0.85−2.36%), pyrolysis T max values (438−485 °C), and biomarker parameters of the studied samples indicate that the Xiahuapidianzi formation shale have entered the oil generation window and that its maturity may be at its peak. The depositional environment of the Xiahuapidianzi formation featured high-salinity reducing conditions, and the source material was mainly plankton and higher plants but may have also included some marine biological components. Volcanic activities and sea water were conducive to the accumulation of organic matter because they brought nutrients to the organic organisms in the lake basin, increased the productivity of organic matter, and led to the formation of a reduction environment conducive to the preservation of organic matter at the bottom of the lake. According to the analysis of the geochemical data, the Xiahuapidianzi formation shale can be divided into six units. The first, third, and fifth units have good to very good source rocks and good shale oil production potential, and these units may be important contributors to the southeastern oilfield of the Sankeyushu depression in the Tonghua Basin.

Organic Matter Accumulation in the Youganwo Formation (Middle Eocene), Maoming Basin, South China: Constraints from Multiple Geochemical Proxies and Organic Petrology

“…As an important part of the primary productivity of lakes, the biomasses of algae and microbes affect the accumulation of OM. , The morphology of lamalginite transitions from dispersed to enriched with increasing TOC content in the YJOS (Figure a–c). Figure a indicates that the lamalginite contents and HI have a reasonable positive correlation in the YJOS ( R 2 = 0.47) and a negative correlation in the JTOS ( R 2 = 0.07).…”

Paleoenvironment, Provenance, and Hydrocarbon Potential of Lower Permian Coal-Bearing Source Rocks in the Southern North China Basin: A Case Study of the Pingdingshan Coalfield

“…However, the accumulation of organic matter always depends on the paleoenvironment and paleoclimate in the sedimentary period . The anoxic water environment and stable provenance are favorable for the preservation of organic matter. , Compared with the marine shale, the organic matter in transitional source rocks is possibly derived from both marine and terrestrial inputs. , This difference in source inputs also indirectly leads to the uniqueness of transitional gas generation, accumulation, and storage. Meanwhile, the difference of carbon and nitrogen stable isotopes between natural gas and organic matter is an important symbol to distinguish marine source rocks from transitional source rocks. , On the other hand, transitional strata are usually the assemblage of coal, mudstone, shale, and sandstone and form a cyclical distribution of lithology vertically. , This also leads to the special diagenetic background of transitional facies, making the mineral and maceral composition of coal-bearing rocks influenced by the terrigenous clastic material compared with marine shale. − Moreover, burial thermal metamorphism experienced by transitional source rocks in North China is weaker than that of marine shale, which leads to the lower maturity of organic matter. − Accordingly, the thermal evolution and hydrocarbon generation potential of transitional shale are very different from those of marine shale.…”

“…20 The anoxic water environment and stable provenance are favorable for the preservation of organic matter. 12,21 Compared with the marine shale, the organic matter in transitional source rocks is possibly derived from both marine and terrestrial inputs. 22,23 This difference in source inputs also indirectly leads to the uniqueness of transitional gas generation, accumulation, and storage.…”