Demethylation as a mechanism for isotopic reversals of shale gas generated at over maturity

Mi, Jingkui; Wang, Huitong; He, Kun; Bai, Jingfang; Liu, Changyue

doi:10.1016/j.jaap.2018.08.015

Cited by 12 publications

(5 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The above results indicate that the correlation between different carbon isotopes of hydrocarbon gas and ORR is obviously different, which may be due to the different formation paths of carbon isotopes of hydrocarbon gas during thermal evolution . In a step pyrolysis experiment of kerogen and bitumen, the carbon isotopes of hydrocarbon gas will be significantly changed by retained bitumen, and heavy hydrocarbon gas has a different generating pathway compared to CH 4 . However, the differences between the carbon isotopes of CH 4 and C 2 H 6 are not significantly affected; thus, we further plot δ 13 C CH 4 –C 2 H 6 versus ORR.…”

Section: Discussionmentioning

confidence: 96%

Carbon Isotope Fractionation Characteristics during the Oil Shale Water Extraction Process and Its Implications

et al. 2022

View full text Add to dashboard Cite

In this work, Huadian oil shale was extracted by water at 350, 365, and 385 °C with a time series (2−100 h) under a closed system to better investigate the carbon isotope fractionation character and its use in predicting the oil recovery rate (ORR). The results revealed that the gas carbon isotope fractionation was controlled by two factors: kinetic and thermal equilibrium processes, the former through primary (ORR increasing stage) and secondary cracking (ORR decreasing stage) during the decomposition of organic matter, and the latter related to the gas−water−rock interaction process after gas decomposing from organic matter. Different from the continuous increase of carbon isotope in the kinetic process, in the thermodynamic equilibrium process, the oxidation/hydration process will increase the δ 13 C CO 2 −CH 4 value, while the water−rock interaction process decreases the δ 13 C CO 2 −CH 4 value. This competition strength controlled by gas generation rate caused δ 13 C CO 2 −CH 4 to show two obvious "turning" points at the beginning of oil generation and the maximum generation of oil. And these "turns" decreased with increasing temperature, which both exist in subcritical and supercritical water. In addition, different from the carbon isotopes of heavy hydrocarbon gas, δ 13 C CH 4 shows a much better relationship with the ORR evolution during the main oil-generation area (the highest R 2 can reach 0.99), even though it has been altered by the thermodynamic equilibrium process after generation. Thus, the carbon isotope and its fractionation character can be used to constrain the oil-generation character and help optimize the heating process during the oil shale exploitation process and lower the production costs.

show abstract

Section: Discussionmentioning

confidence: 96%

Carbon Isotope Fractionation Characteristics during the Oil Shale Water Extraction Process and Its Implications

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Aromatic =C−H bonds (670-860 cm −1 and 966-1096 cm −1 ) and aromatic C=C bonds (1586 cm −1 ) were identified at all selected temperatures, indicating a high content of aromatic-compound-bearing organic matter in shale [16]. In addition, the cracking of kerogen also contributed to the generation of aliphatic hydrocarbons containing −CH 3 radicals (2875-2965 cm −1 ) [9]. The characteristic bands at 3500-4000 cm −1 were identified as the stretching vibrations of O-H bonds from the organic hydroxides and the decomposition of clay minerals [49,50].…”

Section: Tg-ftir Analysismentioning

confidence: 94%

“…The generation of thermogenic gases in shale formation (e.g., CH 4 , C 2 −C 5 and CO 2 ) is strongly related to the cleavage of chemical bonds in organic matter [8]. As kerogen matures, longchain organic molecules (e.g., kerogen and residual oil) crack into simpler molecules, such as light hydrocarbons [9]. This leads to the relatively weak gas generation potential of overmatured kerogen in shale [10,11].…”

Section: Introductionmentioning

confidence: 99%

Gas Generation and Its Carbon Isotopic Composition during Pyrite-Catalyzed Pyrolysis of Shale with Different Maturities

et al. 2022

View full text Add to dashboard Cite

In this study, two shale samples with different maturities, from Geniai, Lithuania (Ro = 0.7%), and Wenjiaba, China (Ro = 2.7%), were selected for open-system pyrolysis experiments at 400 °C and 500 °C, respectively. The generation of isotopic gases from the shales with different maturities was investigated, and the effects of pyrite catalysis on the carbon isotopic compositions were also studied. It was found that CO2, CH4 and their isotopic gases were the main gaseous products of the pyrolysis of both shales, and more hydrocarbon gases were generated from the low-maturity Geniai shale. The δ13C1 values fluctuated from −40‰ to −38‰, and δ13C2 showed higher values (−38‰~−34‰) for the Geniai shale. In addition, its δ13CCO2 values ranged from −28‰ to −26‰. Compared with the Geniai shale, lower δ13C1 values (−43‰~−42‰) and higher δ13CCO2 values (−19‰~−14‰) were detected for the Wenjiaba shale. As temperature increased, CH4 became isotopically lighter and C2H6 became isotopically heavier, which changes were due to the mass-induced different reaction rates of 12C and 13C radicals. Furthermore, the pyrite made the kinetic isotope effect stronger and thus made the CH4 isotopically lighter for both shales, especially at the lower temperature of 400 °C.

show abstract

“…Additionally, the rise of unconventional oil and gas has promoted the hot development of simulation experiments. Hydrocarbon generation and expulsion simulation experiments with their different, for example, experimental systems, conditions and samples, have been widely used in the basic theoretical research of shale gas (Horsfield & Dueppenbecker 1991;Behar et al 1997;Tang et al 2000;Hill et al 2007;Tian et al 2012;Gao et al 2014;He et al 2018;Mi et al 2018;Su et al 2020). These experiments mainly include the evaluation of the gas-forming potential of organic-rich shale (Mani et al 2014;Wang et al 2017;Gai et al 2018;Ma et al 2021), hydrocarbon generation and expulsion of shale (Li et al 2017a(Li et al , 2017bZhao et al 2018), and influence factors on the formation and development of shale pores (Bai et al 2012;Tiwari, et al 2013;Sun et al 2015Sun et al ,, 2019b.…”

Section: Introductionmentioning

confidence: 99%

Response model of fluid–rock ratio to reservoir space in primary formation of shale oil during hydrous pyrolysis

Sun

Fu²,

Zhang³

et al. 2022

Earth and Environmental Science Transactions of the Royal Society of Edinburgh

View full text Add to dashboard Cite

Due to the presence of geological fluid under actual geological conditions, water–rock interaction will occur between the fluid and reservoir. Thus, to analyse the influence of the water–rock interaction on storage space during the organic matter evolution stages, this study conducted a series of simulation experiments on shales by using a closed autoclave: four temperatures, 250°C, 300°C, 350°C, 400°C, and five fluid–rock ratios (FRRs), 0:20, 4:20, 10:20, 15:20, and 20:20. Low pressure N2 adsorption measurement was conducted on the solid residues. The experimental results show that the effect of temperature on the yield and pore structure of oil shale was the same as the result when the FRR was = 0:20, 4:20 and = 10:20, 15:20, 20:20, respectively. This result showed that temperature remained the main factor that affected the thermal evolution of hydrocarbon generation. Additionally, temperature was beneficial to the generation and storage of shale oil within a certain range, but only occupied the storage space of shale oils or connected a certain storage space beyond a certain range. The variation trend of shale oil yield with increasing FRR under the same simulated temperatures, 250°C and 400°C, was most affected by the FRR, but little change occurred at 300°C and 350°C. This further proved that the ratio of fluid to rock was an indirect acting factor, which affected the evolution of organic matters and then the development of pore structures. Before the oil window (350°C), the lower evolution degree, the higher water content and the more significant effect. In the higher evolution stage, the higher the water content, and the more complete the kerogen reaction, which was also more conducive to the development of pore structures. Therefore, this study promotes the establishment of linear equations on FRR to the gas adsorption capacity, which further provides a theoretical basis and guidance for the exploration and development of shale oil.

show abstract

Demethylation as a mechanism for isotopic reversals of shale gas generated at over maturity

Cited by 12 publications

References 38 publications

Carbon Isotope Fractionation Characteristics during the Oil Shale Water Extraction Process and Its Implications

Carbon Isotope Fractionation Characteristics during the Oil Shale Water Extraction Process and Its Implications

Gas Generation and Its Carbon Isotopic Composition during Pyrite-Catalyzed Pyrolysis of Shale with Different Maturities

Response model of fluid–rock ratio to reservoir space in primary formation of shale oil during hydrous pyrolysis

Contact Info

Product

Resources

About