Changes in the Macromolecular Structure of a Type I Kerogen during Maturation

Larsen, John W.; Li, Shang

doi:10.1021/ef970007a

Cited by 37 publications

(35 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…50 The kerogen molecules typically possess on average 2-5-ring PAH units that are highly substituted, [51][52][53] and during thermal maturation, kerogen is transformed from a macromolecule characterized by a significant aliphatic component to one containing shorter chains dominated by more condensed PAH structures. [54][55][56][57] From their basic geochemical origin, it can be concluded that asphaltenes should contain multiple PAH units inside their molecules, which is consistent with the PAH distribution produced from their pyrolysis.…”

mentioning

confidence: 72%

Discussion on the Structural Features of Asphaltene Molecules

Liao¹,

Zhao²,

Creux³

et al. 2009

Energy Fuels

View full text Add to dashboard Cite

Asphaltenes are a class of complex mixtures in petroleum fluids, which are defined as the fraction in petroleum oils soluble in aromatic solvents, such as toluene, whereas insoluble in saturated hydrocarbons, such as n-heptane, and asphaltenes are prepared from crude oils by this simple principle. From this operational definition, asphaltenes are anticipated as a group of complex compounds, 1,2 which are highly polydispersed and cannot be absolutely prescribed by some simplex physicochemical parameters. 3,4 There are fewer large aggregates and narrower distributions once asphaltenes are in infinite-diluted systems of higher temperatures and better solvents; however, they still exhibit a real polydispersity. [1][2][3][4] The average molecular weight (MW) is not necessarily a good parameter to characterize asphaltenes, simply because asphaltenes are defined through their solubility in aliphatic hydrocarbons. 1 Time-resolved fluorescence depolarization (TRFD) was applied to determine the average MW and structural features of asphaltenes by the research group of Mullins, [5][6][7][8][9][10][11][12] and the authors arrived at three primary conclusions: (1) petroleum asphaltenes have an average molecular mass of ∼750 Da (even smaller as 500 Da for coal-derived asphaltenes), with a full width at half-maximum of 500-1000 Da; (2) asphaltenes are dominated by molecules with one polycyclic aromatic hydrocarbon (PAH) unit per molecule; and (3) the most likely asphaltene PAH has roughly 7 rings. However, this method (TRFD) has been reported as being unsuitable for the study of asphaltenes. 2,13,14 The fundamental properties of asphaltenes,

show abstract

mentioning

confidence: 72%

Discussion on the Structural Features of Asphaltene Molecules

Liao¹,

Zhao²,

Creux³

et al. 2009

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…Similar values for retention of EGME before and after OM removal from sedimentary samples were observed by Tiller and Smith (1990) and Kennedy et al (2002), and so suggested that OM does not react with EGME. In contrast, Larsen and Li (1997) and Larsen et al (2002) presented evidence that Type I and Type II kerogens of different degrees of maturation react chemically with organic molecules and swell in polar organic liquids, although those liquids seem to react differently depending on the various major constituents of OM (Cornelissen et al, 2005 and references therein). The similarity of kerogen (Larsen and Li, 1997;Larsen et al, 2002) and soil humic acid (Chiou et al, 1988) reactions with various organic liquids suggests that sedimentary OM may retain EGME via the mechanism demonstrated by Chiou et al (1993) for soil OM.…”

Section: Egme Retention and Cec Measurement In Organic-rich Rocksmentioning

confidence: 98%

On the Problems of Total Specific Surface Area and Cation Exchange Capacity Measurements in Organic-Rich Sedimentary Rocks

Derkowski

Bristow

2012

Clays and clay miner.

View full text Add to dashboard Cite

The increasing exploration and exploitation of hydrocarbon resources hosted by oil and gas shales demands the correct measurement of certain properties of sedimentary rocks rich in organic matter (OM). Two essential properties of OM-rich shales, the total specific surface area (TSSA) and cation exchange capacity (CEC), are primarily controlled by the rock's clay mineral content (i.e. the type and quantity). This paper presents the limitations of two commonly used methods of measuring bulk-rock TSSA and CEC, ethylene glycol monoethyl ether (EGME) retention and visible light spectrometry of Co(III)-hexamine, in OM-rich rocks. The limitations were investigated using a suite of OM-rich shales and mudstones that vary in origin, age, clay mineral content, and thermal maturity.Ethylene glycol monoethyl ether reacted strongly with and was retained by natural OM, producing excess TSSA if calculated using commonly applied adsorption coefficients. Although the intensity of the reaction seems to depend on thermal maturity, OM in all the samples analyzed reacted with EGME to an extent that made TSSA values unreliable; therefore, EGME is not recommended for TSSA measurements on samples containing >3% OM.Some evidence indicated that drying at 5200ºC may influence bulk-rock CEC values by altering OM in early mature rocks. In light of this evidence, drying at 110ºC is recommended as a more suitable pretreatment for CEC measurements in OM-rich shales. When using visible light spectrometry for CEC determination, leachable sample components contributed to the absorbance of the measured wavelength (470 nm), decreasing the calculated bulk rock CEC value. A test of sample-derived excess absorbance with zero-absorbance solutions (i.e. NaCl) and the introduction of corrections to the CEC calculation are recommended.

show abstract

“…There have been extensive experiments on the adsorption of gases in shales and kerogens. − However, experiments on gas sorption-induced shale swelling are limited. , The extensive experiments performed on liquid sorption-induced kerogen swelling − have mainly been conducted at room conditions. Larsen et al − have measured swelling of different types of kerogen; the measured swelling is in the range of 10 to 25% in normal pentane ( n -C 5 H 12 ) and normal heptane ( n -C 7 H 16 ). Kelemen et al report that Type II kerogen can swell 23 and 21% in normal decane ( n -C 10 H 22 ) and normal hexadecane ( n -C 16 H 34 ), respectively.…”

Section: Introductionmentioning

confidence: 99%

Kerogen Swelling in Light Hydrocarbon Gases and Liquids and Validity of Schroeder’s Paradox

Firoozabadi

2021

J. Phys. Chem. C

View full text Add to dashboard Cite

Kerogen is often the organic part of the shale and provides the pore space for a large part of the hydrocarbons in place. Kerogen molecules are flexible like polymer molecules, and may swell when in contact with specific solvents. The difference in swelling of a polymer when exposed to a pure liquid versus its saturated vapor is known as Schroeder’s paradox, which has a long history of controversy. To the best of our knowledge, kerogen swelling induced by a hydrocarbon in both gas and liquid states has not been investigated. We investigate the sorption of gaseous and liquid propane, normal butane, and normal pentane in kerogen and kerogen swelling at various pressures. A flexible kerogen matrix is created using molecular dynamics simulations. The large pores are created and maintained with a dummy particle and nailed atoms, respectively. The hydrocarbon sorption and kerogen swelling induced by the sorption of hydrocarbon gases and liquids are investigated by the hybrid molecular dynamics-grand canonical Monte Carlo simulations. Results show that smaller hydrocarbon molecules in both gas and liquid states have higher sorption and induce higher swelling and structural changes in the kerogen matrix. Hydrocarbon liquids have higher sorption and induce higher kerogen swelling than the corresponding gases at saturation pressure in agreement with Schroeder’s paradox. Hydrocarbon gases lead to the moderate kerogen swelling from expansion of large pores; hydrocarbon liquids swell the kerogen more significantly not only by expanding the large pore but also by creating new pores and throats. Liquid-inducing kerogen swelling is accompanied by hydrocarbon dissolution in the kerogen matrix altering significantly the pore surface area, porosity, and pore size distribution. The work sets the stage for further studies considering the effect of production on shale volumetric strain.

show abstract

Changes in the Macromolecular Structure of a Type I Kerogen during Maturation

Cited by 37 publications

References 10 publications

Discussion on the Structural Features of Asphaltene Molecules

Discussion on the Structural Features of Asphaltene Molecules

On the Problems of Total Specific Surface Area and Cation Exchange Capacity Measurements in Organic-Rich Sedimentary Rocks

Kerogen Swelling in Light Hydrocarbon Gases and Liquids and Validity of Schroeder’s Paradox

Contact Info

Product

Resources

About