Characteristics and Evaluation of the High‐Quality Source Rocks of Cretaceous Continental Shale Oil in Tonghua Basin, China

Abstract

The presence of shale oil in the Cretaceous Hengtongshan Formation in the Tonghua Basin, drilled by the well TD-01, has been discussed in this geological investigation for the first time. To evaluate the high-quality source rocks of Cretaceous continental shale oil, the distribution characteristics and the evolution of the ancient environment, samples of shale were systematically analyzed in terms of sedimentary facies, organic geochemistry, and organic carbon isotopic composition. The results demonstrate that a TOC value of 1.5% represents the lower-limit TOC value of the high-quality source rocks. Source rocks have an aggregate thickness of 211 m and contain abundant organic matter, with TOC values of 2.69% on average and a maximum value over 5.44%. The original hydrocarbon-generative potential value (S 1 +S 2 ) is between 0.18 mg/g and 6.13 mg/g, and the R o is between 0.97% and 1.40%. The thermal maturation of the source rocks is relatively mature to highly mature. The δ 13 C value range is between −34.75‰ and −26.53‰. The ratio of saturated hydrocarbons to aromatic hydrocarbons is 1.55 to 5.24, with an average of 2.85, which is greater than 1.6. The organic types are mainly type II 1 , followed by type I. The organic carbon source was C 3 plants and hydrophytes. The paleoclimate of the Hengtongshan Formation can be characterized as hot and dry to humid, and these conditions were conducive to the development of high-quality source rocks. A favorable paleoenvironment and abundant organic carbon sources provide a solid hydrocarbon generation base for the formation and accumulation of oil and gas in the shale of the Tonghua Basin.

Characteristics of Hydrogen‐rich Coals in Southern China: Implications from Organic Geochemistry and Carbon Isotopic Compositions

“…Thus the carbon isotope fractionations caused by different types of coalforming plants can be ignored. Previous studies have shown that diagenesis, coalification and the rising coal ranks have little or only a negligible impact on carbon isotope fractionation (Holdgate et al, 2007;Chen et al, 2014), the stable carbon isotope composition in coal retaining the characteristics of the coal-forming plants (Sun et al, 2013;Shan et al, 2019).…”

“…Carbon isotope composition (δ 13 C) has a large role in reconstructing paleoclimatic conditions (Guo et al, 2006;Ding et al, 2018;Shan et al, 2019). A large amount of research on carbon isotopes have been focused on different types of modern plant and their relationships with temperature, moisture and rainfall (Kohn et al, 2010).…”

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

“…(B) Location map of the TK-1 well. (C) Thickness contour map of the Xiahuapidianzi formation Adapted with permission from ref , copyright 2019. College of Earth Sciences, Jilin University, Changchun, China; Xuanlong Shan.…”

“…Yu preliminarily identified the structural geology of the Tonghua Basin using geophysical methods in 2011. 3 Han, 4 Wang, 1 and Shan 5 preliminarily analyzed the petroleum geology of the entire Tonghua Basin. Therefore, research on the shale oil in the Tonghua Basin is still in the primary stage; in addition, research on key regional oilfields is also very limited, which is not conducive to the development and utilization of shale oil in the future.…”

Petroleum Origins and Accumulation Patterns in the Weixinan Sag in the Beibu Gulf Basin, Using Subsag B as an Example

“…Different genetic crude oils have different compositions of fractions, carbon isotopes, chain alkanes, steranes and terpanes (Sofer, 1984;Moldowan et al, 1994a;Peters et al, 2005;Shan et al, 2019), which form the basis of crude oil classifications. However, the parameter differences between oil families vary from obvious to weak contrasts.…”