Hydrous pyrolysis of Monterey asphaltenes

Hydrous pyrolysis of asphaltenes has been tested as a method to reconstruct the chemical composition of biodegraded oils and oil seeps. The asphaltenes of three oils (a nondegraded oil, a biodegraded oil, and a biodegraded oil seep) from the Monterey Formation were studied. Results show that the aliphatic fraction generated by hydrous pyrolysis is very similar in chemical composition to the non-degraded oil. This makes the method very useful in correlation studies of biodegraded and nondegraded oils. It also allows to roughly estimate the maturity of the source of the biodegraded oil or oil seep.     

Kerogen-mineral reactions at raised temperatures in the presence of water

Kerogen has been artificially matured under “hydrous pyrolysis” conditions in the presence of various minerals in order to investigate the influence of the latter on the organic products. In addition to three clay minerals (montmorillonite, illite, kaolinite), calcium carbonate and limonite were also employed as inorganic substrates. Kerogen (Type II) isolated from the Kimmeridge Blackstone band was heated in the presence of water and a 20-fold excess of mineral phase at two different temperatures (280 and 330°C) for 72 hr. Control experiments were also carried out using kerogen and water only and kerogen under anhydrous conditions. This preliminary study describes the bulk composition of the pyrolysates with detailed analyses of the aliphatic hydrocarbon distributions being provided by gas chromatography and combined gas chromatography-mass spectrometry.In the 280°C experiments, considerably more organic-soluble pyrolysate (15% by weight of original kerogen) was produced when calcium carbonate was the inorganic phase. At 330°C, all samples generated much greater amounts of organic-soluble products with calcium carbonate again producing a large yield (40% wt/wt). Biomarker epimerisation reactions have also proceeded further in the 330°C pyrolysate formed in the presence of calcium carbonate than with other inorganic phases. Implications of these and other observations are discussed.     

Long-chain carboxylic acids in pyrolysates of Green River kerogen

Long-chain fatty acids (C₁₀-C₃₂), as well as C₁₄-C21 isoprenoid acids (except for C₁₈), have been identified in anhydrous and hydrous pyrolyses products of Green River kerogen (200–400°C, 2–1000 hr). These kerogen-released fatty acids are characterized by a strong even/odd predominance (CPI: 4.8-10.2) with a maximum at C₁₆ followed by lesser amounts of C₁₈ and C₂₂ acids. This distribution is different from that of unbound and bound geolipids extracted from Green River shale. The unbound fatty acids show a weak even/odd predominance (CPI: 1.64) with a maximum at C₁₄, and bound fatty acids display an even/odd predominance (CPI: 2.8) with maxima at C₁₈ and C₃₀. These results suggest that fatty acids were incorporated into kerogen during sedimentation and early diagenesis and were protected from microbial and chemical changes over geological periods of time. Total quantities of fatty acids produced during heating of the kerogen ranged from 0.71 to 3.2 mg/g kerogen. Highest concentrations were obtained when kerogen was heated with water for 100 hr at 300°C. Generally, their amounts did not decrease under hydrous conditions with increase in temperature or heating time, suggesting that significant decarboxylation did not occur under the pyrolysis conditions used, although hydrocarbons were extensively generated.     

Simulated diagenesis and catagenesis of marine kerogen precursors: Melanoidins as model systems for light hydrocarbon generation

Amino acids and sugars are principal constituents of marine organisms. The condensation of amino acids and sugars is one possible nonenzymatic, early diagenetic pathway for the incorporation of these compounds into more complex geopolymers. In this study, aqueous solutions consisting of l-lysine, l-histidine, l-arginine and d-(+)-glucose were heated (100°C) for up to 288 h. Portions of the melanoidin polymer isolated after heating were reheated in the presence of water (hydrous pyrolysis) for 72 h at 325°C. Reaction products were identified by GC and GC/MS. Stable isotopic (δ¹³C) and elemental analyses were used to follow thermal evolution.While the initial melanoidin was synthesized from a simple, four component system, the products generated during hydrous pyrolysis are of considerable complexity, and include straightchain and branched alkanes, alkadienes, alkynes, indole, dimethyl indane, ethyl phenol, quinoline, and xylenes, in addition to a multitude of as yet, unidentified components. Stable carbon isotopic values for the reactants and products correspond to trends observed for naturally generated geopolymers and light gases. Elemental analyses of the melanoidin prior and subsequent to hydrous pyrolysis indicate a kerogen evolution pathway similar to that observed for natural samples. Considering the intractable nature of kerogen, laboratory simulation studies of simple systems can provide an alternative approach for elucidating the origins of geopolymers and their potential for hydrocarbon generation.     

On the chemical mechanism of kerogen thermal transformation. Study of the transformation of sporopollenin

Experiments were carried out on the thermal decomposition of sporopollenin, isolated from a marine algae (Lycopodium clavatum) at constant temperature (380°C) and pressure (around 200 atm), but for varying pyrolysis times.The decomposition products were separated into groups, analysed by chromatography and infra-red spectroscopy, and their elemental composition determined. The thermal evolution of sporopollenin proceeds in three distinct steps: first, a partial decomposition of the initial substance occurs with the formation of soluble materials. This is followed by a full decomposition of the sporopollenin and disappearance of the non-soluble residue. Finally, a non-soluble material reappears. It is proposed that, due to secondary reactions, the evolution of kerogen of the sapropelic type is similar to what has been observed in mild pyrolysis experiments.     

Relation entre évolution de la matière organique et caractéristiques géostructurales : exemple du bassin yprésien en Tunisie centro-septentrionale

The geochemical analysis of the organic-rich facies from the Ypresian basin in central–northern Tunisia shows that the organic matter is marine originated (type II) and displays a low thermal maturity level in outcropping samples. This study proves that the distribution, conservation and, therefore, the composition of the organic matter have been controlled by the dynamic of the Ypresian basin. The Ypresian period corresponds to an anoxic event, which led to the accumulation and preservation of good quantities of organic matter derived from a high primary production. To cite this article: A. Arfaoui, M. Montacer, C. R. Geoscience 338 (2006).     

不同升温速率下树皮体的热重特征变化

中国特有煤种——树皮煤,因具有高氢、高挥发分及高焦油产率等特点而备受关注,而其中富含的特殊显微组分——树皮体,其热性质一直未得到深入研究,直接影响树皮煤的合理利用。采用热重分析仪对不同升温速率下树皮体、镜质体及原煤(树皮煤)的热解失重特征进行了对比研究,并结合工业分析和元素分析结果,讨论了树皮体的化学性质。研究表明:随着升温速率的增加,树皮体、镜质体和树皮煤的TG和DTG曲线均不同程度的向右侧高温区移动,最大失重速率相应减小,升温速率对树皮体的DTG曲线变化影响较大。尽管使用的升温速率不同,而树皮体的DTG曲线峰形均具有窄而尖的特点,说明树皮体的受热变化比较剧烈。同时,树皮体的总失重量均大于镜质体和树皮煤。     

Determination of hydrocarbon generation potential of a non-isothermal pyrolysis of Faraghun and Sarchahan Formations in Coastal Fars and the Persian Gulf,Iran

Source rock assessment is a key step in any petroleum exploration activity. The results of Rock-Eval analysis showed that Sarchahan Formation was in the late oil window, while the Faraghun and Zakeen Formations were just in the early stages of the oil window. Furthermore, Sarchahan, Zakeen and Faraghun Formations exhibited different kerogen types (types-Ⅱ, types-Ⅲ and type-Ⅲ, respectively). Refining the kinetic parameters using the OPTKIN software, the error function returned error values below 0.1, indicating accurate optimization of the kinetic parameters. Based on the obtained values of activation energy, it was clear that Sarchahan Formation contained type-Ⅱ kerogen with an activation energy of 48–52 kcal/mol, while Zakeen and Faraghun Formations contained type-III kerogen with activation energies of 70–80 kcal/mol and 44–56 kcal/mol, respectively. The geographical distribution of the samples studied in this work, it was found that the organic matter (OM) quantity and quality increased as one moved toward the Coastal Fars in Sarchahan Formation. The same trend was observed as one moved from the southern coasts of Iran toward the shaly and coaly portions of Faraghun Formation in the center of the Persian Gulf.©2021 China Geology Editorial Office.     

Investigation of Hydrous Pyrolysis on Type-II Kerogen-bearing Source Rocks from Iran and its Application in Geochemical and Kinetic Analyses of Hydrocarbon Products

Hydrous pyrolysis (HP) practiced on type-II kerogen-bearing oil shale samples from the Sargelu Formation in the Ghali-Kuh Area, western Iran, using a specially designed apparatus was performed at different temperatures (250–350°C), with hydrocarbon generation evaluated at each temperature. For comparison, the samples subjected to Rock-Eval pyrolysis before proceeding to HP resulted in Tmax = 418°C, HI = 102, and TOC = 4.33%, indicating immaturity and hence remarkable hydrocarbon (especially oil) generation potential, making them appropriate for HP. Moreover, the samples were deposited in a low-energy reductive marine environment, with maximum oil and gas generation (739 mg and 348 mg out of 50 g of rock sample, respectively) observed at 330°C and 350°C, respectively. The oil generated at 330°C was subjected to gas chromatography (GC) and isotopic analyses to assess hydrocarbon quality and composition. The hydrocarbon generation data was devised to estimate kinetic indices of the Arrhenius equation and to investigate the gas–oil ratio (GOR) and overall conversion yield. Based on the producible hydrocarbon quantity and quality, the findings contribute to the economic assessment of oil shales across the study area. The developed kinetic model indicates the history of hydrocarbon generation and organic matter (OM) maturity.     

高压-工频电加热裂解油页岩技术室内试验及 氧的驱动效应分析

高压-工频电加热原位裂解油页岩是吉林大学与俄罗斯托木斯克理工大学合作研究的具有占地面积小、污染小、工艺简单等优点的油页岩开采技术。先对油页岩使用高压电击穿,再使用电加热的二步法,可以达到快速裂解油页岩的效果。为了确定裂解油页岩的工艺参数,以及更好地掌握高压-工频电加热裂解油页岩技术,本文对油页岩在有、无氧气条件下的裂解过程进行了热分析试验。试验表明,在有氧与无氧加热条件下,都可完成油页岩的裂解,且裂解过程是相同的,都属于二段式裂解过程。氧在油页岩加热裂解时具有驱动作用,可以降低油页岩的裂解温度、节省能量、提高裂解速度。