Organic chemical structure relationships to maturity and stability in shales

Longbottom, Todd L.; Hockaday, William C.; Daigle, Hugh; Harvey, Omar R.

doi:10.1016/j.coal.2020.103448

Cited by 11 publications

(20 citation statements)

References 58 publications

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“…The work by Longbottom et al shows that the temperature-dependent phenomena are determined by the chemical reaction rate of shale contained minerals . The temperature effect of the chemical reaction is commonly characterized by the Arrhenius relationship, which is expressed as r r 0 = exp [ E a R true( 1 T 0 − 1 T true) ] where r and r 0 represent the reaction rates (mol/s) at different temperatures of T and T 0 (K), respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The work by Longbottom et al shows that the temperature-dependent phenomena are determined by the chemical reaction rate of shale contained minerals . The temperature effect of the chemical reaction is commonly characterized by the Arrhenius relationship, which is expressed as where r and r 0 represent the reaction rates (mol/s) at different temperatures of T and T 0 (K), respectively.…”

Section: Discussionmentioning

confidence: 99%

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Investigation of the Temperature Dependence of the Chemical–Mechanical Properties of the Wufeng–Longmaxi Shale

Zhai

et al. 2022

ACS Omega

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Shale rocks have been widely investigated to evaluate the productivity of oil/gas. The high temperature generated by the explosive fracturing to stimulate the gas reservoir has a significant impact on the chemical−mechanical properties of shale rocks. Pioneering works have been carried out at temperatures below 500 °C, but little has been done to quantify the correlation between the chemical and mechanical properties of shale at temperatures above 500 °C. Therefore, an experimental study on the effect of temperature on the chemical−mechanical properties of shale rocks is presented in this paper. The temperatures used in our experiments are between 0 and 800 °C. Results indicate that there exist strong chemical reactions leading to a big reduction in the sample's weight and mechanical strength for a temperature over 500 °C. Thermogravimetric analysis data demonstrates that the weight of shale powders has little change below 400 °C and largely decreases after 600 °C. It shows that the chemical reaction rate corresponding to shale compositions varies with temperature. X-ray diffraction and Fourier transform infrared are integrated to quantify the occurrence of contained reactions including the decomposition of kerogen, carbonates, and quartz transition. This can provide a temperature range for all possible reactions. Changes in the compositional information of shale samples have been proven to significantly influence the mechanical properties. A 25% decrease in dynamic Young's modulus emerges as the temperature approaches 700 °C. As the brittle minerals, for instance, carbonates, decrease with temperature, a brittle-ductile transition happens in shale. This work provides very meaningful results different from that at low temperatures to help people better understand the effects of high temperatures in many fields, such as explosive fracturing and radioactive waste disposal.

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Section: Discussionmentioning

confidence: 99%

“…The work by Longbottom et al shows that the temperature-dependent phenomena are determined by the chemical reaction rate of shale contained minerals . The temperature effect of the chemical reaction is commonly characterized by the Arrhenius relationship, which is expressed as where r and r 0 represent the reaction rates (mol/s) at different temperatures of T and T 0 (K), respectively.…”

Section: Discussionmentioning

confidence: 99%

Investigation of the Temperature Dependence of the Chemical–Mechanical Properties of the Wufeng–Longmaxi Shale

Zhai

et al. 2022

ACS Omega

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“…Taking advantage of the rapid development of 13 C cross-polarization (CP) and the magic angle magnetic spin (MAS) technologies, the structural characterization of macromolecules by NMR has strongly improved. Thus, hydrocarbons, soils, asphalts, and kerogens can now be differentiated by NMR. − NMR results have complemented conventional organic geochemical analysis. However, most such studies have mainly focused on organic matters in marine settings. − Advanced solid-state NMR methods were performed on type I kerogen and for comparisons of kerogens with widely differing heteroatom contents. − The results of oil shale may be useful in setting NMR criteria for defining kerogen types (e.g., type I = aliphatic content >60%; type II = aliphatic content 40–60%; and type III = aliphatic content <40% or similar) .…”

Section: Introductionmentioning

confidence: 99%

“…Thus, hydrocarbons, soils, asphalts, and kerogens can now be differentiated by NMR. − NMR results have complemented conventional organic geochemical analysis. However, most such studies have mainly focused on organic matters in marine settings. − Advanced solid-state NMR methods were performed on type I kerogen and for comparisons of kerogens with widely differing heteroatom contents. − The results of oil shale may be useful in setting NMR criteria for defining kerogen types (e.g., type I = aliphatic content >60%; type II = aliphatic content 40–60%; and type III = aliphatic content <40% or similar) . It also summarizes some correlations between NMR parameters and bulk geochemical assays …”

Section: Introductionmentioning

confidence: 99%

“…However, compared with the NMR research of marine kerogen, the NMR study of lacustrine kerogen is unsubstantial. In particular, there are few studies on the low total organic carbon (TOC) samples and the relationship between NMR parameters and proxies of nonspectroscopic or bulk chemical assays remains not well-established. − These are the unresolved and critical issues in the study of NMR in organic geochemistry and the focus of our study.…”

Section: Introductionmentioning

confidence: 99%

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Application of Nuclear Magnetic Resonance (NMR) Spectroscopy to Lacustrine Kerogen Geochemistry: Paleogene Dongpu Sag, China

Gao

Cao

et al. 2021

Energy Fuels

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Solid-state nuclear magnetic resonance (NMR) spectroscopy has been widely used in organic geochemistry because of its utility in examining the chemical structures present in sedimentary organic matter (kerogen). Here, we present such an investigation of kerogens from the Paleogene Shahejie Formation in the Dongpu Sag, Bohai Bay Basin, eastern China. Results show that the NMR spectra and their parameters are sensitive to kerogen type as defined by elemental ratios. The NMR spectra of types I and II kerogens are similar and show that the dominant chemical structures are aliphatic functional groups (e.g., methylene and methyl carbons), followed by aromatic moieties, with relatively fewer structures containing heteroatoms. In contrast, type III kerogen is considerably different, having a much lower aliphatic than aromatic functional group content and a higher degree of aromaticity. Based on this, a formula is established in response to the source rock hydrogen index and hydrocarbon generation potential. Our data suggest that the chemical structural characteristics of lacustrine facies kerogens can be effectively studied by NMR in good response to hydrocarbon geochemistry. This implies that NMR is possibly a promising approach in lacustrine organic geochemistry and provides complements to the challenging study of paleoenvironment and organic matter accumulation in lacustrine systems due to the heterogeneity of source rock deposition.

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