Open AccessOrganic matter heterogeneity and shale oil significance in Triassic Zhangjiatan shale, Ordos Basin, China
Author(s) -
Xiaoyan Li,
Jincai Tuo,
Chenjun Wu,
Xin Hong-gang,
Mingfeng Zhang,
Junwei Zheng,
Xiaofeng Ma
Publication year - 2021
Publication title -
energy exploration and exploitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 30
eISSN - 2048-4054
pISSN - 0144-5987
DOI - 10.1177/01445987211039382
Subject(s) - organic matter , oil shale , terrigenous sediment , geology , total organic carbon , geochemistry , source rock , maturity (psychological) , sedimentary rock , sedimentary organic matter , lithology , structural basin , environmental chemistry , paleontology , chemistry , psychology , developmental psychology , organic chemistry
Organic matter heterogeneity exerts an important impact on the generation, evaluation, and exploitation of shale oil resources. In the past, only a limited number of analytical samples that represented the contribution or influence of high or low organic matter abundance intervals were used to represent an entire set of thick source rocks, and based on this limitation, occasionally researchers have reached incorrect conclusions. Here, the heterogeneity of organic matter and its significance to shale oil in the Triassic Zhangjiatan shale of the Ordos Basin were discussed based on sedimentary and geochemical analyses. Our results indicate that (1) the Chang 7 3 shale within the study area is characterized by high abundance, good quality, strong heterogeneity, and segmented enrichment in the vertical profile. The primary organic matter type was type II 1 , and this was followed by types I, II 2 , and III that exhibited three changing trends in the vertical profile. Organic matter maturity is primarily at the immature stage. (2) Additionally, we observed that the organic matter heterogeneity of Chang 7 3 shale was related to changes in lithology, sedimentary environment, paleoproductivity, terrigenous influence, and event action (such as volcanism and hydrothermal processes). The abundance of organic matter is the result of the coupling control of these processes. In the process of organic matter deposition, if volcano or hydrothermal activities occurred, the organic matter was abnormally enriched, and the total organic carbon content exceeded 20% and could even be as high as 40%. (3) Finally, we observed at least nine enrichment layers that were controlled by the coupling of different geological factors, and there were four potential target resource layers corresponding to the hydrothermal sedimentary area.