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The aim of this work is to follow the generation of NSO compounds during the artificial maturation of an immature Type II kerogen and a Type III lignite in order to determine the different sources of the petroleum potential during primary cracking. Experiments were carried out in closed system pyrolysis in the temperature range from 225 to 350 °C....
Contexts in source publication
Context 1
... samples are thermally immature, as indicated by geochemical data in Table 1. Elemental compositions for isolated kerogen from the Toarcian Type II source rock and for the initial Wilcox lignite are in Table 2. ...
Context 2
... steady state of the n-pentane NSOs yield is shifted to a higher TR range 45-90% than that of the DCM NSOs. Table 4 Comparison of transformation ratio (TR) using bulk kinetics from Table 3 (TR 1) with that using parameters from Table 3 (TR 2): DTR = TR 2 À TR 1 ...
Context 3
... indicates, as suspected, that kero- gen conversion is faster in closed than in open pyro- lysis system. Examples of conversion for kerogen cracking in open and closed pyrolysis systems are given in Table 12 at 325 °C for heating times between 1 and 72 h. In terms of distribution of pyro- lysis products, thermal cracking of kerogen in a closed system leads to more than 70% DCM NSOs and 17% kerogen 2. This means that the main mech- anism of kerogen decomposition is the generation of a very viscous liquid containing polar products of high molecular weight. ...
Citations
... The oils were then mixed with n-hexane, the asphaltene fraction was precipitated, and then the other components were filtered into saturates, aromatics and resins using a column liquid chromatography method (Zhang et al., 2014). The asphaltenes and resins were weighed after solvent evaporation and were collectively classified as NSOs, which were composed of heteroatomic (i.e., N, S, O) compounds (Behar et al., 2008). ...
... Mud gas in the Gulong shale shows a normal trend in δ 13 C (i.e., δ 13 C 1 < δ 13 C 2 ) and mainly distribute near the point between pre-rollover and rollover (Fig. 11b), indicating the beginning of secondary cracking of oil (Tilley and Muehlenbachs, 2013;Dai et al., 2014). The measured Ro (1.3%-1.5%) of K 2 qn OM in GY8 (Fig. 7) confirms the intensive cracking of early generated NSOs and C 15+ HCs to generate wet gas in source rocks (Behar et al., 2008). By the pyrolysis experiments involving Type-II kerogen, Huang et al. (1999) have established a correlation between δ 13 C 1 and Ro for oil-related gas. ...
... Different approaches are used in artificial maturation experiments: anhydrous open and closed systems (Berner and Faber, 1996;Behar et al., 1997Behar et al., , 2008, hydrous closed (Lewan, 1985), and semi-open systems (Stockhausen et al., 2019;Hou et al., 2020). There is no consensus as to which conditions best mimic the natural process involved in kerogen thermal transformation. ...
... Despite kerogen type II is mostly composed by C and H, the presence of heteroatoms (N, S and O) plays a major role during kerogen cracking and hydrocarbon generation (Behar et al., 2008) and therefore are important to understand the mechanisms during thermal maturation. Fig. 6 shows the total sulfur and nitrogen content determined by XPS. ...
Artificial maturation of kerogen is a widely used technique to assess the hydrocarbon potential of shale rocks and to observe thermal transformations of organic matter in the laboratory. However, the degree of reproducibility of natural geological transformation at the molecular level is still not fully established. In the present work, a set of kerogens isolated from Vaca Muerta Formation core samples at varying levels of thermal maturity were studied. Another set of samples was obtained by anhydrous pyrolysis of kerogen in a closed system. Molecular structures measured by solid-state techniques (13C NMR, XPS and FTIR) were compared in natural and artificially matured samples at equivalent levels of thermal maturation. We observed that heating in an anhydrous closed system accurately reproduces most of the molecular structural changes observed during natural thermal maturation, with exceptions related to the branching degree and oxygen containing groups. The evolution of some parameters, such as N and S content, are highly variable in the natural samples because of differences in their deposition environments. In these cases, artificial thermal maturation changes are smaller and follow more clearly defined trends because variables other than thermal changes are not present. This is the first work comparing natural and artificial thermal maturation in the Vaca Muerta Formation and add valuable data regarding the limitation of artificial maturation that can be extrapolated to other formations.
... Kerogen cracking to generate oil and gas is a complicated chemical process that is mainly affected by kinetic effects [8,9]. A large number of pyrolytic experiments have been conducted in closed, semiclosed, or open systems to investigate the hydrocarbon generation process and calculate the kinetic parameters [7,[10][11][12][13][14][15][16]. These studies indicated that petroleum products generated from organic-rich shale depend on the features of shale and pyrolytic conditions. ...
... To explore the generation process of oil and gas, the evolution of kerogen pyrolytic products in a closed system was studied in detail [7,12,14,54]. In general, pyrolytic products generated from kerogen can be described as follows [7,[10][11][12][13][14][15][16]: Figure 2 shows the change in the relative mass content of different products during the nonisothermal pyrolysis of a typical kerogen [7]. ...
... To explore the generation process of oil and gas, the evolution of kerogen pyrolytic products in a closed system was studied in detail [7,12,14,54]. In general, pyrolytic products generated from kerogen can be described as follows [7,[10][11][12][13][14][15][16]: Figure 2 shows the change in the relative mass content of different products during the nonisothermal pyrolysis of a typical kerogen [7]. At the early mature stage (Easy%Ro < 0.80%), NSO content visibly increases and is higher than the generated HC component. ...
Petroleum was the most-consumed energy source in the world during the past century. With the continuous global consumption of conventional oil, shale oil is known as a new growth point in oil production capacity. However, medium–low mature shale oil needs to be exploited after in situ conversion due to the higher viscosity of oil and the lower permeability of shale. This paper summarizes previous studies on the process of kerogen cracking to generate oil and gas, and the development of micropore structures and fractures in organic-rich shale formations during in situ conversion. The results show that the temperature of kerogen cracking to generate oil and gas is generally 300–450 °C during the oil shale in situ conversion process (ICP). In addition, a large number of microscale pores and fractures are formed in oil shale formation, which forms a connecting channel and improves the permeability of the oil shale formation. In addition, the principles and the latest technical scheme of ICP, namely, conduction heating, convection heating, reaction-heat heating, and radiation heating, are introduced in detail. Meanwhile, this paper discusses the influence of the heating mode, formation conditions, the distribution pattern of wells, and catalysts on the energy consumption of ICP technology in the process of oil shale in situ conversion. Lastly, a fine description of the hydrocarbon generation process of the target formation, the development of new and efficient catalysts, and the support of carbon capture and storage in depleted organic-rich shale formations after in situ conversion are important for improving the future engineering efficiency of ICP.
... Lignite comprises organic matter that has shown intermediate thermal maturity in the course of coalification, and soluble bitumen extract from lignite consists of partially defunctionalized aromatic and saturated compounds [180]. These compounds include labile functionalities, cyclic compounds with 1-2 aromatic rings, unsaturated cyclic functionalities with 1-2 double bonds, heterocycles, etc. [180][181][182][183][184][185][186]. Biochemical coalification at this rank involves alkylation, the loss of methoxyl groups by dehydroxylation and demethylation processes, and the cleavage of aryl ether bonds [25]. ...
Coal bed methane (CBM) extraction has astounding effects on the global energy budget. Since the earliest discoveries of CBM, this natural gas form has witnessed ever-increasing demands from the core sectors of the economy. CBM is an unconventional source of energy occurring naturally within coal beds. The multiphase CBM generation during coal evolution commences with microbial diagenesis of the sedimentary organic matter during peatification, followed by early to mature thermogenic kerogen decomposition and post-coalification occurrences. Indeed, the origin of the CBM and, moreover, its economically valuable retention within coal seams is a function of various parameters. Several noticeable knowledge gaps include the controls of coal make-up and its physico-chemical position on the CBM generation and genetic link through fossil molecular and stable isotopic integration with the parent coal during its evolution. Therefore, this manuscript reviews the origin of CBM; the influences of coal properties and micropetrographic entities on CBM generation and storage; and its genetic molecular and stable isotope compositions in India and the world's major coal reservoirs. Moreover, analyses of and outlooks on future development trends in the exploration, production, and application of coalbed methane are also addressed. Finally, as India has the fifth largest proven coal reserves, this brief review of the recent CBM discoveries and developments provides a plausible scope for microbially enhanced CBM production from these basins.
... One is the sequential hydrocarbon generation model, whereby kerogen first generates macromolecular NSOs and these are then cracked into smaller hydrocarbons. Behar et al. [44,45] conducted kerogen pyrolysis experiments under closed pyrolysis conditions and verified this mechanism. In Behar's research on Toarcian shale (type II), the components of oil and bitumen were divided into volatile components (saturates and aromatics) and heavy components (NSOs), and NSOs were further divided into n-pentane NSOS (resins) and DCM NSOs (asphaltenes) according to their solubility in organic solvents. ...
Affected by the complex mechanism of organic–inorganic interactions, the generation–retention–expulsion model of mixed siliciclastic–carbonate sediments is more complicated than that of common siliciclastic and carbonate shale deposited in lacustrine and marine environments. In this study, mixed siliciclastic–carbonate shale from Lucaogou Formation in Junggar Basin was selected for semi–closed hydrous pyrolysis experiments, and seven experiments were conducted from room temperature to 300, 325, 350, 375, 400, 450, and 500 °C, respectively. The quantities and chemical composition of oil, gases, and bitumen were comprehensively analyzed. The results show that the hydrocarbon generation stage of shale in Lucaogou Formation can be divided into kerogen cracking stage (300–350 °C), peak oil generation stage (350–400 °C), wet gas generation stage (400–450 °C), and gas secondary cracking stage (450–500 °C). The liquid hydrocarbon yield (oil + bitumen) reached the peak of 720.42 mg/g TOC at 400 °C. The saturate, aromatic, resin, and asphaltine percentages of bitumen were similar to those of crude oil collected from Lucaogou Formation, indicating that semi–closed pyrolysis could stimulate the natural hydrocarbon generation process. Lucaogou shale does not strictly follow the “sequential” reaction model of kerogen, which is described as kerogen firstly generating the intermediate products of heavy hydrocarbon compounds (NSOs) and NSOs then cracking to generate oil and gas. Indeed, the results of this study show that the generation of oil and gas was synchronous with that of NSOs and followed the “alternate pathway” mechanism during the initial pyrolysis stage. The hydrocarbon expulsion efficiency sharply increased from an average of 27% to 97% at 450 °C, meaning that the shale retained considerable amounts of oil below 450 °C. The producible oil reached the peak yield of 515.45 mg/g TOC at 400 °C and was synchronous with liquid hydrocarbons. Therefore, 400 °C is considered the most suitable temperature for fracturing technology.
... From Lower Thoar clays of Paris basin the oil was obtained at temperature higher than 350°C [1]. In works [6,7] on the basis of experiments the two-stage model of formation of oil from kerogen has been proved: at the first stage from kerogen large high-molecular organic compounds (bitumens) are formed, and then from them hydrocarbons are formed. Apart from theoretical significance these works have practical application. ...
... The carried out modeling of stage formation of oil as a whole agrees with results of experimental works. According to [6,7] at the first stage transformation of kerogen occurs: separation of non-hydrocarbon components (CO 2 , H 2 S, H 2 O), asphaltenes and resins containing heteroatoms, a small amount of lighter hydrocarbons. Then in the second stage lighter hydrocarbons are formed from high-molecular compounds by aqueous cracking. ...
The thermodynamic model of stage oil formation has been proposed: (1) transformation of sedimentary kerogen at increasing temperature and pressure and (2) subsequent transformation of newly formed immature oil (bitumoid) in the reservoir rock. Calculations have shown that immature aromatic-asphaltene oil is formed in the source rock, starting from a temperature of 50 °C. With further increase of temperature and pressure the tendency to change the hydrocarbon composition of bitumoid in the direction of the aromatic-mixed type is observed, and at 325 °C there is a sharp increase in the amount of oil formed and a fundamental change in the hydrocarbon composition (alkanes are dominated). An even lighter oil is formed from bitumoid in the reservoir reservoir at 325 °C in the presence of liquid water in the system. It is shown that water is a necessary component for the formation of light hydrocarbons from high molecular weight ones. The results allow to make the following conclusions: (1) high-molecular hydrocarbons can be an intermediate element in crude oil formation; (2) light alkane oils are the result of their transformation in the process of hydrocracking in the reservoir.
... This process has also been demonstrated in published studies [50]. Due to the closed nature of the gold tube system, the products have strong secondary cracking characteristics under high thermal pressure, and the main reaction in the late oil window was the secondary cracking or coking of already-produced hydrocarbons [51][52][53][54][55]. NSOs reached a maximum at an Easy%Ro of 0.89 and then began to decline ( Table 2, Fig. 4), decomposing into oil, gas and insoluble residue with increasing maturity [32,53]. ...
Lacustrine type II kerogen is widely distributed in China and has important hydrocarbon potential, but the study of its structural evolution is not comprehensive enough. In this study, a closed gold tube system was used to simulate the maturation of kerogen extracted from the Nengjiang Formation of the Songliao Basin to investigate a model of hydrocarbon generation and molecular structure change in lacustrine type II kerogen. The pyrolysis products at two heating rates were collected and quantitatively analyzed, and the Easy%Ro of 20 solid kerogen residue samples (solid pyrolysis products after extraction of methylene chloride and methanol) ranged from 0.69 to 2.49. From elemental analysis and ¹³C nuclear magnetic resonance (¹³C NMR), the molecular structure evolution of kerogen was clearly determined, and four average molecular models of kerogen were established. The results show that with increasing maturity, the aliphatic fractions of kerogen decreased, and the aromatic fractions increased. Before the main oil window (Easy%Ro < 0.89), the main products were nonhydrocarbon heteroatomic functional groups (NSOs: asphaltene and resin). The oil peak occurred at an Easy%Ro of approximately 1.1 when hydrocarbon C14+ production reached the maximum and kerogen residue was the lowest. After the oil peak, aromatic groups became dominant in the structure. C14+ began to decrease, and the kerogen residue proportion increased, which was related to the occurrence of secondary coking reactions after the main oil window. The hydrocarbon generation capacity of kerogen was exhausted after the oil peak, and the kerogen likely became the precursor of generated gaseous products. In the gas window (Easy%Ro > 1.53), the large quantity of C1-5 was mainly due to the secondary cracking of hydrocarbons. The number of aromatic structures caused by alkyl bond breaking and condensation was estimated. It was found that before the oil peak, the number of aromatic structures caused by alkyl bond breaking decreased and was higher than that of aromatic structures caused by condensation. After the oil peak, the latter structures were obviously dominant, which further indicates that polymerization is the main structural change mechanism of kerogen evolution.
... The thermal decomposition of the initial kerogen (primary OM) during burial first generates heavy compounds (asphaltenes) at the oil-window thermal maturity stage, then generates low-molecular weight resins and liquid hydrocarbons from the secondary cracking of asphaltenes (e.g. Behar et al., 2008). The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. ...
... The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. Behar et al., 2008; and references therein). ...
Accurate source rock characterizations via geochemical and optical methods require advanced knowledge of the processes of their formation and the factors that control their development. The current chapter starts by addressing the fundamentals of sedimentary organic matter’s origin and chemical compositions and how they interact with the atmosphere, lithosphere, and hydrosphere through comprehensive elucidations of the biogeochemical cycles of carbon, nitrogen, sulfur, and phosphorus. Then, it discusses the deposition and transportation of organic matter in different habitats and the physical and chemical factors that affect its preservations. The third part of the chapter provides insights into the kerogen formation pathways, classifications, and alteration processes. Finally, the chapter introduces the common terrestrial and marine source rock depositional environments and the processes that control the organic productivity and source rock development richness and quality. The knowledge in this chapter represents a reliable base for accurate source rocks and petroleum data interpretations. Furthermore, it can assist in explaining the changes in organofacies and thermal maturity, identifying sweet spots in unconventional resources, types of generated hydrocarbons (sweet versus sour oils), and maturing basin modeling calibrations.
... The thermal decomposition of the initial kerogen (primary OM) during burial first generates heavy compounds (asphaltenes) at the oil-window thermal maturity stage, then generates low-molecular weight resins and liquid hydrocarbons from the secondary cracking of asphaltenes (e.g. Behar et al., 2008). The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. ...
... The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. Behar et al., 2008; and references therein). ...
The progressive increase in the demand for unconventional resource assessments such as gas and oil shale, as well as shale gas and oil plays in the last two decades, boosted the development of source rock characterization methods and techniques. Additionally, it advanced more research in geochemistry, palynology, and organic microscopy. The interpretation of source rocks appears straightforward; therefore, many industry professionals and researchers make common mistakes when interpreting source rocks. These are repeatedly observed, especially in kerogen typing, thermal maturity assessments, and disregarding the drilling-fluid contamination effects. This chapter addresses the leading causes of these interpretation errors and provides a detailed review of sampling techniques and analytical methods with their advantages and limitations. The methods mainly characterize source rocks for their richness, quality, and thermal maturity. The approaches include thermal oxidation, pyrolysis, organic microscopy, molecular geochemistry (e.g., biomarkers), isotope geochemistry (including mud gas isotopes), inorganic geochemistry, palynology, and other advanced techniques.
... The thermal decomposition of the initial kerogen (primary OM) during burial first generates heavy compounds (asphaltenes) at the oil-window thermal maturity stage, then generates low-molecular weight resins and liquid hydrocarbons from the secondary cracking of asphaltenes (e.g. Behar et al., 2008). The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. ...
... The onset and outcome of these stages are controlled by the kerogen's hydrocarbon generation kinetics which themselves reflect the depositional organofacies (e.g. Behar et al., 2008;Tissot & Espitalié, 1975 and references therein). ...
Organic matter rich rocks are the basis of any petroleum system. The nature and variability of organofacies in sedimentary rocks have been well documented for a large number of source rocks. Significant effects of these organofacies heterogeneities on the source rocks hydrocarbon generation potential and kinetics have also been reported, therefore highlighting the importance of numerical source rocks prediction tools in petroleum systems analysis. Efforts to numerically model organic matter deposition through earth’s history have been made with various degrees of success. However, none of these efforts have yet been integrated in hydrocarbon exploration workflows due to the time and resource needed to properly do so. In this chapter, we present a new methodology to model marine organic matter. The advantage of this methodology is that it is coupled with an established forward stratigraphic modelling workflow, therefore requiring minor additional input and time to provide a quantification of source rocks distribution and properties. The integration of this approach with traditional petroleum systems modelling solutions makes it a value adding tool in petroleum exploration efforts.
