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Thermal maturity parameters derived from tetra-, penta-substituted naphthalenes and organosulfur compounds in highly mature sediments
Fuel ( IF 6.7 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.fuel.2020.119626 Qianru Wang , Haiping Huang , Lunjun Zheng
Fuel ( IF 6.7 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.fuel.2020.119626 Qianru Wang , Haiping Huang , Lunjun Zheng
Abstract Sediments of a natural thermal evolution sequence from the Upper Carboniferous marine-continental transitional depositional environment in the Qaidam Basin, NW China and an artificially matured series in a semi-open pyrolysis system have been analyzed for bulk and molecular geochemical compositions. Thermal stability of compound pairs of tetramethylnaphthalenes (TeMNs) and dibenzothiophene (DBT), pentamethylnaphthalenes (PMNs) and methyldibenzothiophenes (MDBTs), and tetramethylphenanthrenes (TeMPs) and benzo[b]naphthothiophenes (BNTs) were assessed using their chromatogram appearances and concentrations. Dibenzothiophene, methyldibenzothiophenes and benzo[b]naphthothiophenes are much more thermally stable than highly alkylated naphthalenes and phenanthrenes in high maturity sediments (Ro > 1.0%). Ratios of TeMNs/DBT and PMNs/MDBTs decrease systematically with increasing maturity levels or pyrolysis temperature and can serve as novel maturity parameters. TeMNs, PMNs and TeMPs are in very low concentrations or fully removed in highly mature sediments (Ro > 1.0%). Maturity parameters derived from tetra- or penta-substituted homologues of naphthalene, such as tetramethylnaphthalene ratio (TeMNr) and pentamethylnaphthalene ratio (PMNr), are invalid in mature or overmature sediments. While methylnaphthalene ratio (MNR) and methyldibenzothiophene ratio (MDR) remain valid, the correlation of TeMNs/DBT, PMNs/MDBTs with vitrinite reflectance is better than MNR or MDR by the premise of detectable abundance of TeMNs and PMNs. Moreover, benzo[b]naphthothiophenes with sulfur incorporated and cyclized as fused aromatic structures show quite high thermal stability at high maturity levels as evidenced by their concentrations, especially for benzo[b]naphtho[2,1–d]thiophene (BN21T). Ratios of BN21T/BN12T and BN21T/(BN12T + BN23T) are proposed as another novel parameter type for thermal maturity assessment in highly mature sediments (Ro > 1.0%).
更新日期：2021-03-01
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