Assessment of Oil Potentials for Humic Coals on the Basis of Flash Py-GC, Rock-Eval and Confined Pyrolysis Experiments

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 (MCP Sigma C8+), which reflect oil potentials, have close correlations with the yields of n-alkanes + n-alkenes (FP Sigma 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 FP Sigma n-C(7+ )yields from flash Py-GC analysis. Coals with FP Sigma n-C7+ yield >10.4 mg/g TOC can generate MCP Sigma C8+, yield >similar to 22.5 mg/g TOC or oil yield >similar to 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 (FP Sigma C7+) obtained from flash Py-GC have poor correlations with, and are substantially lower than, Rock-Eval Ql. In contrast, FP Sigma C7+ values have much better correlations with oil potentials (MCP Sigma C8+). Coals with higher oil potentials (MCP Sigma C8+) generate higher amounts of liquid components detected in flash Py-GC (FP Sigma C7+) than those with lower oil potentials but similar Rock-Eval Ql. 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, MCP Sigma C8+, FP Sigma n-C7+ and FP Sigma n-C7+/Sigma C7+ ratios. GOR of petroleum generated from coals within oil generative window can be reasonably predicted on the basis of FP Sigma n-C7+/Sigma C7+ ratio from flash Py-GC analysis. (C) 2020 Elsevier Ltd. All rights reserved.