The huge oil shale resources in China have gradually attracted widespread attention due to the shortage of oil and gas resources in the country and the rapid recovery of world oil prices. A nationwide prospecting survey of oil shale in China was conducted for the first time during a period from 2003 to 2006, reporting on around 719.9 billion tons of oil shale. After that, many large oil shale deposits have been discovered in the country, and the exploration of oil shale is flourishing. Although the total shale oil production from oil shale of China has been fluctuating due to the low world oil prices in recent years, it, in general, has rapidly increased since 2006 and reached the highest annual production of 8.3 × 10⁵ tons in 2015. At present, there are six oil shale production bases in operation in China, and two sets of pilot experiments carried out on oil shale in-situ conversion technology have preliminarily proved to be successful. A green industrial chain including refinery, power generation and building materials production from oil shale in oil shale enterprises has been formed due to the high added value and environmentally friendly impact of oil shale from this chain. Moreover, new insights were gained into the genesis of terrestrial oil shale in China and the characterization of deep lake, shallow lake and limnetic deposited oil shale. These theoretical breakthroughs further enriched the genesis theory of oil shale in continental basins. Although considerable progress has been made in China in the oil shale field both industrially and academically, more work needs to be done to establish a representative oil shale metallogenic model and to accurately evaluate oil shale for its development potential.

Oil shale evaluation is based on oil yield by low-temperature carbonization, which is an extremely complex process. The TOC, semi-coke content, gas loss, bulk density, S₂ and HI correlate well with oil yield. The organic matter in the oil shale from the Songliao Basin, China, is of lacustrine origin, while that in the oil shale from the Huadian Basin, China, stems from different sources. Comparative studies show that the simple organic matter composition of the Songliao oil shale facilitates industrial oil shale grade classification on the basis of TOC content only. Complex mixtures of organic matter found in the Huadian oil shale require, in addi­tion to the TOC content, also the S₂ and HI for grade classification. Knowing organic matter quality and the deduced oil yield conversion factor enables the industrial grade classification of oil shale on the basis of TOC content.

The Songliao Basin contains some of the largest volumes of oil shales in China; however, these energy sources are located in areas covered by arable land, meaning that the best way of exploiting them is likely to be environmentally friendly in situ conversion processing (ICP). Whether the oil shales of the Songliao Basin in the Qingshankou Formation are suitable for ICP remain controversial. In this paper, through sequence stratigraphic correlations, three main thick oil shale layers (N1, N2, and N3) of the Sequence1 (Sq1) unit in the first member of Qingshankou Formation (K₂qn¹) are confirmed as consistently present throughout the Southeastern Uplift region of the basin. The spectral trend attributes reflect that the lake reached a maximum flood surface of the K₂qn¹ in N2 oil shale layer, and the total organic carbon (TOC) and Fischer assay (FA) oil yield are significantly increasing. The N2 and N3 oil shale layers were deposited in a high lake level environment associated with ingressions of ocean water. The oil shale in these layers with the characteristics of high TOC (maximum of 23.9 wt %; average of 7.2 wt %), abundance of aquatic organic matter (OM) (maximum hydrogen index (HI) of 1080.2 mg/g; average of 889.9 mg/g) and carbonate contents (maximum of 29.5%; average of 15.4%). The N2 and N3 oil shale layers have higher brittleness index (BI) values (generally 40–50%), larger cumulative thicknesses (maximum of 13.3 m; average of 12.0 m), and much higher source potential index (SPI) values (0.92 and 0.88 tHC/m², respectively) than the N1 oil shale layer within Sq1 transgressive system tracts (TST), indicating that the N2 and N3 layers are prospective targets for ICP. In addition, oil shales buried to depths of <1000 m have strong hydrocarbon generation capacities that make them suitable for ICP.

In some cases, the oil shale deposited in shallow lakes may be genetically associated with the coal-bearing successions. Although paleovegetation is an important controlling factor for the formation of oil shale- and coal-bearing successions, few studies have focused on their joint characterization. In this study, a total of twenty-one oil shale and coal samples were collected from the upper member of the Lower Cretaceous Muling Formation (K₁ml₂) in the Laoheishan Basin, and investigated for their bulk geochemical, maceral, palynological, and terpenoid biomarker characteristics, in order to reconstruct the paleovegetation and reveal its influence on the formation of oil shale and coal. The K₁ml₂ is subdivided into lower, middle, and upper units. The studied oil shale samples from the lower and upper units display a high ash yield (A_d), low total organic carbon (TOC) and sulfur (S) contents, and limited hydrocarbon generation potential. The studied coal samples from the middle unit are characterized by low A_d, and high TOC and low S values, and show significant hydrocarbon generation potential. The paleovegetation during the formation of the lower unit was dominated by mire vegetation, such as shrubs (e.g., Lygodiaceae, Schizaeaceae), tree ferns (e.g., Dicksoniaceae/Cyatheaceae), and coniferous trees (e.g., Podocarpaceae). In the middle unit interval, the paleovegetation was represented by highland vegetation (Pinaceae and Araucariaceae) and peat-forming coniferous plants (e.g., Podocarpaceae, Cupressaceae/Taxodiaceae). Various vegetation, such as herbs (e.g., Osmundaceae), shrubs (e.g., Schizaeaceae), and coniferous trees (e.g., Podocarpaceae) was prosperous during the upper unit interval. Coniferous trees could provide abundant hydrogen-rich materials (e.g., resins) to the mire/lake, which may elevate the hydrogen content in peat/lake sediments, and finally result in higher hydrocarbon generation potential in the coal than in the oil shale. Therefore, the influence of paleovegetation on the formation of oil shale and coal should be fully considered when studying oil shale- and coal-bearing successions. The results also provide guidance for further exploration studies on oil shale and coal in northeast China.