Coal-derived gas theory and its discrimination

Dai, Jianhua

doi:10.1360/n972018-00303

Cited by 29 publications

(11 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Maturity has a significant effect on the d 13 C 1 relative to the d 13 C 2 , whereas the d 13 C 2 may be predominantly controlled by their source rather than maturity (Dai et al, 2005b;Galimov, 2006). Therefore, the d 13 C 1 is usually used as a proxy to ascertain the maturity of gas source rocks, whereas the d 13 C 2 is the common and effective indicators to distinguish coal-derived from oil-type gas (Dai, 2018;Dai et al, 2005b;Galimov, 2006). Numerous empirical studies of gas geochemistry in sedimentary basins have suggested a cutoff point in the d 13 C 2 for differentiating the origin of thermogenic gases in these basins (Dai, 2018;Dai et al, 1992;Galimov, 2006;Gang et al, 1997).…”

Section: Genetic Types Of Natural Gasmentioning

confidence: 99%

“…Numerous empirical studies of gas geochemistry in sedimentary basins have suggested a cutoff point in the d 13 C 2 for differentiating the origin of thermogenic gases in these basins (Dai, 2018;Dai et al, 1992;Galimov, 2006;Gang et al, 1997). Generally, the d 13 C 2 less than -29.0& is oil-type gas generated from sapropelic kerogen (Galimov, 2006), while the value greater than -28.0& is coal-derived gas generated from humic kerogen (Dai, 2018;Dai et al, 1992;Gang et al, 1997). The gases from Cretaceous and Tertiary in Kuqa Depression, Tarim Basin, Triassic Xujiahe Formation in central Sichuan Basin, and C-P in Sulige and Yulin gas field, Ordos Basin are mainly coalderived gases, while the gases produced from Mississippian Barnett Shale in the Fort Worth Basin are mainly oil-type gas based on the values of d 13 C 2 (Figure 1).…”

Section: Genetic Types Of Natural Gasmentioning

confidence: 99%

“…Therefore, the δ 13 C 1 is usually used as a proxy to ascertain the maturity of gas source rocks, whereas the δ 13 C 2 is the common and effective indicators to distinguish coal-derived from oil-type gas (Dai, 2018; Dai et al., 2005b; Galimov, 2006). Numerous empirical studies of gas geochemistry in sedimentary basins have suggested a cutoff point in the δ 13 C 2 for differentiating the origin of thermogenic gases in these basins (Dai, 2018; Dai et al., 1992; Galimov, 2006; Gang et al., 1997). Generally, the δ 13 C 2 less than –29.0‰ is oil-type gas generated from sapropelic kerogen (Galimov, 2006), while the value greater than –28.0‰ is coal-derived gas generated from humic kerogen (Dai, 2018; Dai et al., 1992; Gang et al., 1997).…”

Section: Geochemical Characteristics and Genesis Of Natural Gasmentioning

confidence: 99%

“…In addition, the maturities of their source rocks are systematically lower than that of three other areas (Figure 3). Oil-type gas will enrich 12 C, while coal-derived gas will enrich 13 C at the same maturity on account of stable carbon isotope inheritance effect of source rocks (Dai et al., 1992; Galimov, 2006). Stahl and Carey (1975) and Dai (1992) established the relationship between the δ 13 C 1 of oil-type, coal-derived gas and R o of source rock based on the chemical and isotopic compositions of natural gas from numerous basins as follows …”

Section: Geochemical Characteristics and Genesis Of Natural Gasmentioning

confidence: 99%

“…Chemical and isotopic compositions are the most important parameters for characterizing the geochemical properties of natural gases. In particular, methane and ethane components and their isotopes are widely used in genetic type analysis, maturity estimation, gas source rock correlation, migration tracer, and secondary transformation identification of natural gas (Dai, 2018;Dai et al, 2012;Galimov, 2006;Jenden et al, 1988;Kotarba and Lewen, 2013;Prinzhofer and Huc, 1995;Schoell, 1983;Sechman et al, 2017). Due to the influence of isotopic fractionation caused by pyrolysis, methane and higher hydrocarbons should become increasingly enriched in the 13 C isotope with increasing thermal stress, i.e.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Significance and evolution characteristics of the isobutane/n-butane ratio of natural gas

Liu

Qiu

et al. 2019

Energy Exploration & Exploitation

View full text Add to dashboard Cite

In previous studies, two conflicting conclusions existed, which were: (a) the isobutane/n-butane ratio of natural gas increases with the increasing maturity (Ro) of source rocks and (b) decreases with the increasing Ro. In this paper, the correlations between the isobutane/n-butane ratios, dryness of natural gases, and the Ro values of source rocks of 77 gas samples from Cretaceous and Tertiary in Kuqa Depression, Tarim Basin, Triassic Xujiahe Formation in central Sichuan Basin, Carboniferous–Permian in Sulige and Yulin gas field, Ordos Basin, China, and 80 shale gas samples from Mississippian Barnett Shale in the Fort Worth Basin, the United States are analyzed to reveal the evolution of the isobutane/n-butane ratios, then mathematical models of the isobutane/n-butane ratios and Ro are attempted to be established. Results show that the isobutane/n-butane ratio initially increases and then decreases with increasing Ro, both coal-derived gas and oil-type gas. Diverse types of kerogens may be responsible for the different corresponding Ro values when the isobutane/n-butane ratios of gases reach their maximum values. The initial increase in the isobutane/n-butane ratios with increasing Ro is the reason that isobutane is mainly generated at a higher rate by carbonium ion reaction of α-olefins with protons during kerogen primary cracking at lower maturity, whereas free radical reactions to form n-butane relatively quickly during oil cracking at higher maturity and isobutane cracked at a higher rate during the wet gas cracking stage may result in the terminal decreases in the isobutane/n-butane ratios. Besides, mathematical models of the isobutane/n-butane ratios of different types of natural gas and maturity are established. Therefore, the maturity of gas source rock can be obtained quickly based on the models using the isobutane/n-butane ratio combined with other component information (such as dryness, wetness, etc.), which is of great significance to the characterization of natural gas maturity and gas source rock correlation.

show abstract