Geochemical significance of tricyclic and tetracyclic terpanes in source rock extracts from the Offshore Niger Delta Basin, Nigeria

Applying biomarkers as paleoenvironmental indicators to reveal the organic matter enrichment of shale during deep energy exploration: a review

“…162 Unusual tri-and tetracyclic terpanes (C 21 tricyclic terpanes, C 25 tricyclic terpanes, C 27 tetracyclic terpanes, C 24 -des-Aoleanane, C 24 -des-A-lupane, and C 24 -des-A-ursane) have recently been reported in crude oils and source rock extracts from the Pearl River Mouth Basin, the Beibuwan Basin, and the Liaohe Basin, China, 169,172 and source rock extracts from Niger Delta Basin, Nigeria. 17 According to Xiao et al (2018), these uncommon compounds contain chemical structures that are comparable to oleanane, ursane, and lupane, and are thought to be derived from alcohols or ketone precursors found in higher plants. 169 The higher abundance of these tri-and tetracyclic terpanes is likely due to the higher plant material input to the OM content of source rocks.…”

“…8,9 The source facies can be distinguished by comparing structurally similar chemicals in sediments and crude oils with their likely biological precursors. 8,9,17,18 The thermal history of the oil can be reconstructed by altering the biomarker structure. 3,17,18 Some biomarkers are biochemical processes or environmental indicators.…”

“…8,9,17,18 The thermal history of the oil can be reconstructed by altering the biomarker structure. 3,17,18 Some biomarkers are biochemical processes or environmental indicators. Triterpenoids and steroids were thoroughly investigated.…”

Organic Geochemistry of Crude Oils from the Kohat Basin, Pakistan

“…The tricyclic terpane ratios C 19 /C 23 and C 20 /C 23 further suggest that the source units have received significant terrestrial input from marine organic matter, as reported in Table 1, because the C 23 tricyclic terpanes are dominant in marine organic materials, while the C 19 and C 20 tricyclic terpanes originate from terrestrial materials [15]. As seen in Figure 4a,b and Table 1 with C 24 Tet/C 23 TCT, the oil samples in both of the examined wells also have a considerable quantity of C 24 tetracyclic, which further indicates a substantial quantity of continental organic matter combined with marine organic materials [60][61][62].…”