Assessment of oil potentials for humic coals on the basis of flash Py-GC, Rock-Eval and confined pyrolysis experiments. (October 2020)

• Record Type: Journal Article
• Authors: Zeng, Lifei; Huang, Wenkui; Pan, Changchun; Jin, Jun; Ma, Wanyun; Yu, Shuang; Xu, Hao; Liu, Dayong; Liao, Yuhong; Liu, Jinzhong
• Is Part Of: Organic geochemistry. Volume 148(2020)
• Publication Date: 2020-10
• Subjects: Quantitative flash Py-GC -- Confined pyrolysis -- Oil potentials -- Gas to oil ratios -- Humic coals; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2020.104097
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: Confined pyrolysis (CP) and Py-GC were performed on coals. Oil yields from CP on coals correlate well to n -alkane/ene yields from Py-GC. Oil yields from CP on coals correlate poorly to Rock-Eval QI. Liquid yields from Py-GC on coals correlate poorly to Rock-Eval QI. Abstract: Confined pyrolysis experiments (gold capsules), quantitative flash pyrolysis-gas chromatography (Py-GC) and Rock-Eval analysis were performed on ten coals from the Junggar Basin and seven coals from the Kuqa Depression, Tarim Basin, northwestern China. The maximum yields of liquid components in confined pyrolysis experimnets (MCPΣC8+ ), which reflect oil potentials, have close correlations with the yields of n -alkanes + n -alkenes (FPΣ n -C7+ ) in flash Py-GC, but have poor correlations with Rock-Eval QI ((S1 + S2)/TOC) values. Thus, oil potentials of coals can be better predicted on the basis of FPΣ n -C7+ yields from flash Py-GC analysis. Coals with FPΣ n -C7+ yield >10.4 mg/g TOC can generate MCPΣC8+ yield >∼22.5 mg/g TOC or oil yield >∼40 mg/g TOC in confined pyrolysis or in natural systems and are effective oil source rocks. Although both Py-GC and Rock-Eval are open systems, the yields of total liquid components (FPΣC7+ ) obtained from flash Py-GC have poor correlations with, and are substantially lower than, Rock-Eval QI. In contrast, FPΣC7+ values have much better correlations with oil potentials (MCPΣC8+ ). Coals with higher oil potentials (MCPΣC8+ ) generate higher amounts of liquid components detected in flash Py-GC (FPΣC7+ ) than those with lower oil potentials but similar Rock-Eval QI. The correlations for parameters with gas to oil ratios (GOR) in confined pyrolysis are increasingly better in the sequence of Rock-Eval QI, H/C atomic ratios, MCPΣC8+, FPΣ n -C7+ and FPΣ n -C7+ /ΣC7+ ratios. GOR of petroleum generated from coals within oil generative window can be reasonably predicted on the basis of FPΣ n -C7+ /ΣC7+ ratio from flash Py-GC analysis.