Evolution Of Hydrocarbons Research Articles

Hydrocarbon migration and accumulation in buried hills based on quantitative fluorescence techniques, fluid inclusion, and 1D basin modeling: Shulu sag, Bohai Bay basin, NE China

Interpreting the hydrocarbon generation, migration, and accumulation process is significant for understanding hydrocarbon evolution and finding exploration targets. The buried hills of Shulu Sag exhibit great potential for hydrocarbon exploration. However, the variations observed in different oil reservoirs highlight the complexity of hydrocarbon migration and accumulation in this region. In this study, 1D basin modeling, fluid inclusion analysis, and quantitative fluorescence techniques were used to investigate the thermal maturation history of the source rock, the timing of hydrocarbon charging, the pathway of hydrocarbon migration, and the oil-water contact. Hydrocarbons in the buried hills in the Western Slope and Paleo-uplift are derived from the source rocks at the edge and center of the sag, respectively, which have different thermal maturation histories. The source rocks in the center of the sag mainly supply hydrocarbons to the Paleo-uplift through faults, while the hydrocarbons generated from the source rocks in the edge of the sag can be rapidly transported to the Western Slope through clast-supported terrigenous carbonate rudstone. Differences in oil sources result in different hydrocarbon charging histories for the Western Slope and Paleo-uplift. The Western Slope experienced a single low-mature oil charging event at 5-0 Ma, while the Paleo-uplift encountered two hydrocarbon charging events, including low-mature oil charging at 35-25 Ma and high-mature oil charging at 5-0 Ma. As a result of secondary changes controlled by the hydrological environment, the oil reservoirs in the Western Slope have undergone varying degrees of adjustment or even destruction, resulting in variations in the oil quality of different buried hills. The results provide a detailed understanding of hydrocarbon migration and accumulation in the study area, which can be used as a reference for hydrocarbon exploration.

Presence of oxygen in catalytic pyrolysis of lignin impacts evolution of both coke and aromatic hydrocarbons

Coking is a major issue in catalytic pyrolysis of biomass over zeolite catalysts. Using oxidative gas might mitigate formation of carbonaceous deposits. This was verified herein by catalytic pyrolysis of lignin with different oxygen concentrations (0 %, 3 %, 6 %, 9 % and 12 %) in carrier gas using ZSM-5 as the catalyst at 600 °C. The results indicated that the O2 introduced oxidized both volatiles and biochar, reducing bio-oil yield from 29.2 to 20.7 % and biochar yield from 56.8 to 53.7 % with increasing O2 concentration from 0 to 12 %. Oxidation of intermediates in “hydrocarbon pool” on surface of catalyst decreased the yield of BTX from 11.5 % in inert gas to 6.1–8.0 % and also other aromatics with 1 or 2 benzene rings. The aromatics with rigid polycyclic aromatic structures were more resistant towards oxidation. However, toluene, xylene, and other aromatic hydrocarbons or phenolics with side chains were more prone to be oxidized, abundance of which decreased more significantly at high O2 concentrations. Such results were also observed in catalytic pyrolysis of guaiacol or vanillin. The benefit of using O2 was diminished formation of coke and/or precursors of coke over ZSM-5. Characterization of reaction intermediates in catalytic pyrolysis of lignin with in-situ IR showed that O2 presence remarkably decreased the abundance of aliphatic intermediates containing –OH, -C-H and C=O through oxidation reactions and also interrupted aromatization organics in both coke and biochar.

Solid bitumen Rhenium-Osmium (Re–Os) isotope geochronology and existing problems: Sampled of Sinian-Cambrian gas reservoir in Sichuan Basin, China

Understanding the key timings related to petroleum evolution is crucial for optimizing exploration targets and assessing oil/gas resources, attract petroleum geologists’ attention worldwide. Recently, hydrocarbon (oil and bitumen) Re–Os isotope dating has been innovatively applied to constrain the timing related to oil/gas generation, however, the resulting Re–Os isochron ages can be complex and challenging to interpret. This study utilizes various geochemical and geochronological data from Sinian to Cambrian natural gas reservoirs in the Sichuan Basin to reconstruct the hydrocarbon evolution process and discuss the significance of different bitumen Re–Os dating results. The gas accumulation in the Sinian-Cambrian reservoirs experienced four stages of evolution: (1) initial oil generation during the Ordovician to Silurian periods, (2) secondary oil generation during the Triassic period, (3) gas generation through thermal cracking of liquid oil from the Jurassic to Cretaceous periods, and (4) gas reservoir redistribution since the late Cretaceous. The Re–Os dates (ca. 485 Ma) of low maturity and biodegraded bitumen from the western Sichuan Basin record the oil generation during the Ordovician before the Caledonian tectonic event. The Re–Os dates (ca.184–128 Ma) of highly mature bitumen associated with MVT Pb–Zn deposits in northern Sichuan Basin provide insights into both liquid oil-cracking and thermochemical sulfate reduction (TSR) processes. The complex Re–Os dates (ca.414 Ma, ca.154 Ma) of highly mature bitumen from the central Sichuan Basin may represent different periods related to either oil or gas generation. Future studies should explore the genetic type, maturity, thermal cracking, or TSR degrees of bitumen to better understand the significance of Re–Os dates.

Simulation of lower Cambrian oil and gas generation and phase evolution process in ZH1 of Tazhong area

The Lower Cambrian petroleum system in the Tarim Basin has undergone multiple periods of tectonic movements, leading to successive hydrocarbon expulsion events and adjustments. The complex process of hydrocarbon accumulation occurred under deep burial conditions, persisting at depths of nearly 6,000 m over an extended period. This has resulted in the current occurrence of various phases including light oil, condensate, and gas in the deep-ultradeep strata of the Tarim Basin. The intricacies of formation of hydrocarbon accumulations and phase evolution have posed challenges to understanding the accumulation mechanisms and enrichment patterns of the Cambrian in the Tarim Basin, consequently lowering the success rate of oil and gas exploration. Such characteristics of multi-stage accumulation and adjustment are prevalent in deep hydrocarbon systems. Therefore, based on data from Well ZH1 in the Tazhong Uplift, combined with basin simulation, Compositional kinetics model, and PVT performance simulation, this study investigates the hydrocarbon generation and phase evolution processes in the deep hydrocarbon systems of the Tazhong Uplift. The results indicate that Well ZH1 entered the hydrocarbon generation peak during the Late Ordovician, followed by secondary cracking as the predominant hydrocarbon evolution process. Hydrocarbon fluids within the Lower Cambrian reservoir transitioned into the condensate phase towards the end of the Cambrian, with increasing depth resulting in higher gas-oil ratios and a decreasing trend in viscosity and density.

Novel interpretation of the crustal structure and hydrocarbon evolution within the South Caspian and Kura sedimentary basins, Azerbaijan

Novel interpretation of the crustal structure and hydrocarbon evolution within the South Caspian and Kura sedimentary basins, Azerbaijan

Origin and microbial degradation of thermogenic hydrocarbons within the sandy gas hydrate reservoirs in the Qiongdongnan Basin, northern South China Sea

Large-scale natural gas hydrate accumulations (generally over one billion cubic meters of natural gas) in coarse-grained marine sediments are the most valuable types for commercial exploration and exploitation. The formation of such a gas hydrate deposit generally requires a sufficient natural gas supply such as deeply buried thermogenic gas source. However, the worldwide discovered thermogenic gas hydrate deposits are rare, leaving relatively a poor understanding of their formation and evolution. Based on the geochemical and microbial analyses of eleven hydrate-related gas and five sediment samples from the thermogenic gas hydrate deposits in the Qiongdongnan Basin in northern South China Sea, we systematically investigated the origin and evolution of thermogenic hydrocarbons within sandy gas hydrate reservoirs. Results show that natural gas within high saturated gas hydrate-filled sandy sediments is predominately of thermogenic (the proportion is 57.1–70.5%), characterized by “dry gas” (99.38–99.7% C1, 0.26–0.47% C2 and <0.5% C3+), relatively lower C1/(C2+C3) ratio (187–376), and heavier δ13C–C1 values (−55.0 to −31.3‰). In addition, typical biomarkers (including the alkanes, tricyclic terpanes, hopanes and steranes) generated from mature source rocks were detected in the hydrate-filled fine sand reservoir, as well as the biomarker indicators (including the unresolved complex mixtures (UCMs) hump and the 25-norhopane homologous series) for severe hydrocarbon biodegradation. Furthermore, large amounts of hydrocarbon degrading bacteria (50.5% of bacteria) and methanogenic archaea (34.3% of archaea) were detected within hydrate-filled sandy sediment. Our results indicated that the deeply buried thermogenic source can indeed provide sufficient gas supply for the formation of a large-scale gas hydrate deposit, but thermogenic liquid hydrocarbons within gas hydrate reservoirs are very susceptible to be degraded and consumed by hydrocarbon degrading bacteria. In addition, we also found that the clay components of argillaceous gas hydrate reservoirs can adsorb and store large amounts of in situ immature organic matter, which can significantly obscure or cover up the original geochemical signatures of thermogenic hydrocarbons therein. These findings suggest that the relative contribution of deeply buried thermogenic source for gas hydrate accumulation worldwide may be underestimated, because we have previously ignored the fact that thermogenic hydrocarbons within gas hydrate reservoirs would be significantly consumed by hydrocarbon degrading microbes or diluted by in situ immature sedimentary organic matter. Our findings are highly significant for the evaluation and exploration of thermogenic gas hydrate accumulations worldwide.

Position-specific and clumped isotope equilibria in propane: Ab initio calculations beyond the harmonic and Born-Oppenheimer approximations

Position-specific and clumped isotope compositions that reveal intramolecular isotope distributions can offer novel insights into the physical and chemical properties of substances. In particular, the intramolecular isotope effects observed in propane have demonstrated significant potential for constraining the formation and evolution of hydrocarbons. To calibrate measurements and interpret observations, a comprehensive understanding of equilibrium isotope fractionation within propane is required. However, previous studies yielded inconsistent calculations of position-specific isotope equilibria, and lacked any prediction of clumped isotope equilibria in the methyl group of propane. Here, we employ quantum chemical calculations beyond the harmonic approximation and the Born-Oppenheimer approximation to study the intramolecular isotope equilibria in propane. Benchmark coupled cluster calculations (CCSD(T)) were used to produce reliable frequencies of propane isotopologues. By integrating the CCSD(T) outcomes with effects beyond the harmonic and Born-Oppenheimer approximations, we present high-accuracy equilibrium carbon and hydrogen isotope fractionation between the methylene and methyl sites, and report for the first time the equilibrium Δ13CH2D and Δ12CHD2 signatures of the methyl group in propane. Our results of position-specific isotope equilibria can serve as a reference frame for calibrating both theoretical calculations and experimental measurements. The equilibrium Δ13CH2D and Δ12CHD2 values provide a theoretical framework for further studies of 13CD and DD clumping in methyl groups of alkanes, and are valuable for tracing the sources and sinks of methyl groups as well as processes related to methylation.

The implication of kinetics characteristics of modern organisms for the hydrocarbon generation evolution of organic matter components in the lacustrine source rocks: A case study of the Dongying Formation from the Bozhong Sag, Bohai Bay Basin

The hydrocarbon generation evolution characteristics of lacustrine source rocks are crucial for understanding hydrocarbon resources. In this research, we focus on the mudstone found in the third member of the Paleogene Dongying Formation (E3d3) within the Bozhong Sag of the Bohai Bay Basin as a case study. An analysis of the discrepancy in geochemical characteristics and kinetic parameters was carried out by utilizing the modern organisms (pine pollen and benthic algae) analogies to the organic matter (OM) components (Pinaceae sporopollen and benthic algae amorphous). Furthermore, the bulk hydrocarbon evolution of the Dongying Formation mudstones was further discussed in combination with a water-added sealing thermal simulation experiment and basin simulation. Our findings indicate that the pine pollen and benthic algae have higher OM abundance compared to the E3d3 mudstones, and their OM types are both Ⅱ1-Ⅱ2, which possess excellent potential for oil generation. In contrast, the E3d3 mudstones are predominantly in the low mature to mature thermal evolution stage. When we compare hydrocarbon generation rates and transformation ratios using Rock-Eval pyrolysis, it becomes evident that modern organisms are more prone to generate large amounts of hydrocarbons even at a low mature stage. The kinetic parameters of pine pollen are notably higher compared to those of benthic algae and the E3d3 mudstone samples. In parallel first-order reactions, the activation energy obtained by the single-frequency factor model (SFFP model) displays a narrow distribution range, while the activation energy distribution range of the multi-frequency factor model (MFFP model) is broader. The MFFP model focuses more on the variations of hydrocarbon kinetic parameters throughout the entire process, which is more in conformity with the actual geological process. The enclosed thermal simulation experiment and basin simulation analysis unveil the presence of two distinct phases of hydrocarbon generation within the Dongying Formation. Furthermore, it becomes evident that abundant benthic algae and Pinaceae sporopollen components play vital roles in both of these phases. In conclusion, the method of applying modern organisms to analogize the hydrocarbon generation evolution characteristics of the parent components of lacustrine source rocks seems feasible. Meanwhile, the Dongying Formation in the Bozhong Sag also possesses broad exploration prospects for hydrocarbon resources.

Kinetics of thermal decomposition of crude oils: Insights from principal component analysis and products characterization

Energy demand is souring, and fossil fuel reserves are dwindling, making heavy oil resources more attractive. In this study, thermogravimetric and Py-GC/MS analyses were conducted on Iranian crude oil samples to compare high and low API (American Petroleum Institute) crude oils. A kinetic study based on mass loss of crude oil was performed using three model-free methods and distributed activation energy model (DAEM). To do that, TG analysis carried out, the temperature was increased from room temperature to 1000 °C with heating rates of 10, 20, and 30 °C min−1. Activation energy (Ea) and pre-exponential factor (A0) were estimated from Friedman, Kissinger–Akahira–Sunose (KAS), and Ozawa-Flynn–Wall (OFW) methods for oil sample. The Ea and A0 for heavy crude oil (Koroosh) pyrolysis varied between 59.85 and 193.83 kJ mol−1 and 1.34 × 105 to 4.36 × 1011 s−1, respectively. For light crude oil sample Lavan, the Ea and A0 ranged between 35.93 to 62.89 kJ mol−1 and 337.41–722.65 s−1, respectively. Pearson's correlation analysis found that the activation energy barrier increases as the reaction progresses and the temperature rises. This makes it harder to form the activated complex, which is a key step in the reaction. Principal component analysis supported these findings. Saturated and aromatic hydrocarbons were liberated at mild temperature while the resins and asphaltenes consecutively released in favorable condition for developing sustainable heavy oil recovery systems. Py/GC–MS analysis shows the evolution of saturated hydrocarbon in Koroosh-oil and aromatic hydrocarbons in Lavan-oil and demonstrates their suitability for fuel applications.

In situ U-Pb dating of carbonate veins in Cambrian shales constrains fluid flow and hydrocarbon evolution at the southeastern margin of the Upper Yangtze platform, southwestern China

Fluid flow in sedimentary basins not only impacts redistribution of the geothermal cycle and precipitation of ore deposits, but also exerts control on hydrocarbon migration and accumulation. However, reconstructing the history of fluid flow in basins that have experienced multiple tectonic deformation events is exceedingly difficult. Here, we examined petrography, in situ U-Pb geochronology, and rare earth element (REE) and C-O isotope geochemistry, as well as fluid inclusion microthermometry of fracture fillings within the Cambrian Niutitang Formation shales at the southeastern margin of the Upper Yangtze platform, southwestern China. The results show that four main fluid flow pulses are identified based on cathodoluminescence images, U-Pb ages, and geochemical data, namely, 446−428 Ma (fibrous calcite and barytocalcite), 343−329 Ma (calcite I), 113 Ma (calcite II), and 63 Ma (calcite III). The fibrous calcite (ca. 446 Ma) and barytocalcite (ca. 428 Ma) veins, corresponding to the late Caledonian Orogeny, show significantly positive Eu-Y anomalies, negative Ce anomalies, and enrichment in heavy REE, similar to their host rocks, suggesting that the mineral-forming fluids were derived mainly from dissolution of the host rocks. An abundance of bitumen inclusions with homogenization temperatures (Th) of 93.1−137.4 °C and high salinities (5−8 wt%) indicate that the first fluid flow pulse occurred during the oil generation stage in a closed fluid system. Calcite I (ca. 343−329 Ma) exhibits REE depletion and high Y/Ho ratios, a low fluid inclusion salinity (2−10 wt%) with Th = 78.4−125.8 °C, and C-O isotopic compositions similar to the underlying marine carbonates. This suggests that calcite I formed in an open fluid system, which was related to the transition from compression to extension during the Hercynian Orogeny. The pre-existing faults were reactivated and opened, resulting in the leakage and reconstruction of hydrocarbon reservoirs. Calcite II (ca. 113.4 Ma) has similar REE+Y patterns and C-O isotopic compositions to the host rocks. It contains abundant single-phase hydrocarbon gas (CH4) inclusions with high Th (164.1−211.1 °C) and salinity (6−14 wt%) values, indicating that the third phase fluid was derived largely from the host rocks and migrated during the early Yanshanian Orogeny. Lastly, calcite III (ca. 62.7 Ma) exhibits extremely low REE concentrations, low δ13CPDB [Peedee belemnite] values (−6.74‰), and low fluid inclusion salinities (0.3−7.0 wt%) with Th = 61.9−97.1 °C, suggesting that the fourth fluid flow pulse was affected by meteoric water to some extent. This can be interpreted to represent an open fluid system, which caused gas dispersion in the Niutitang Formation shales. Our findings provide important references for reconstructing the history of fluid flow in tectonically complex basins worldwide.

Differences and identification on multi-time hydrocarbon generation of carboniferous-permian coaly source rocks in the Huanghua Depression, Bohai Bay Basin

Coal is a solid combustible mineral, and coal-bearing strata have important hydrocarbon generation potential and contribute to more than 12% of the global hydrocarbon resources. However, the deposition and hydrocarbon evolution process of ancient coal-bearing strata is characterized by multiple geological times, leading to obvious distinctions in their hydrocarbon generation potential, geological processes, and production, which affect the evaluation and exploration of hydrocarbon resources derived from coaly source rocks worldwide. This study aimed to identify the differences on oil-generated parent macerals and the production of oil generated from different coaly source rocks and through different oil generation processes. Integrating with the analysis of previous tectonic burial history and hydrocarbon generation history, high-temperature and high-pressure thermal simulation experiments, organic geochemistry, and organic petrology were performed on the Carboniferous-Permian (C–P) coaly source rocks in the Huanghua Depression, Bohai Bay Basin. The oil-generated parent macerals of coal’s secondary oil generation process (SOGP) were mainly hydrogen-rich collotelinite, collodetrinite, sporinite, and cutinite, while the oil-generated parent macerals of tertiary oil generation process (TOGP) were the remaining small amount of hydrogen-rich collotelinite, sporinite, and cutinite, as well as dispersed soluble organic matter and unexhausted residual hydrocarbons. Compared with coal, the oil-generated parent macerals of coaly shale SOGP were mostly sporinite and cutinite. And part of hydrogen-poor vitrinite, lacking hydrocarbon-rich macerals, and macerals of the TOGP, in addition to some remaining cutinite and a small amount of crude oil and bitumen from SOGP contributed to the oil yield. The results indicated that the changes in oil yield had a good junction between SOGP and TOGP, both coal and coaly shale had higher SOGP aborted oil yield than TOGP starting yield, and coaly shale TOGP peak oil yield was lower than SOGP peak oil yield. There were significant differences in saturated hydrocarbon and aromatic parameters in coal and coaly shale. Coal SOGP was characterized by a lower Ts/Tm and C31-homohopane22S/(22S+22R) and a higher Pr/nC17 compared to coal TOGP, while the aromatic parameter methyl dibenzothiophene ratio (MDR) exhibited coaly shale TOGP was higher than coaly shale SOGP than coaly TOGP than coaly SOGP, and coal trimethylnaphthalene ratio (TNR) was lower than coaly shale TNR. Thus, we established oil generation processes and discriminative plates. In this way, we distinguished the differences between oil generation parent maceral, oil generation time, and oil production of coaly source rocks, and therefore, we provided important support for the evaluation, prediction, and exploration of oil resources from global ancient coaly source rocks.

The evolution of the majiang paleoreservoir, west margin of xuefeng uplift: Insights from in situ calcite U–Pb dating and bitumen and shale trace element analysis

The Majiang Reservoir, situated within the Yangtze Block, is the largest paleoreservoir in the region. Employing a comprehensive methodology involving the analysis of trace and rare earth elements in bitumen and shale, in situ U–Pb dating of hydrocarbon-associated calcite, and incorporating previously published data on oil-source correlation and significant stages of reservoir development, we successfully reconstructed the complete evolution of the Majiang Reservoir quantitatively. The bitumen trace elements data show the ratio of V/(V + Ni) ranging from 0.64 to 0.82, Ni/Co exceeding 7.0 and Zr/Cr below 1.0. PAAS-normalized rare earth element distribution patterns of both bitumen and Cambrian shales present zig-zags distributions. In addition, biomarker distribution acquired by catalytic hydropyrolysis and bulk δ13C values of both bitumen and Cambrian shales (−29.1‰ to −34.7‰ vs −30.2‰ to −32.3‰) also show similarity. All the geochemical parameters together indicate that the primary source of bitumen stems from Early Cambrian shales. Integrating fluid inclusion analysis, specifically examining two Th groups with temperatures of 97.2 °C and 142.6 °C, and U–Pb dating on hydrocarbon-bearing calcite (∼300 Ma), referencing prior Re–Os dates on bitumen (∼430 Ma) and pyrobitumen (∼80 Ma) and quartz fluid inclusion Ar–Ar dating (∼225 Ma), we successfully reconstructed the entire hydrocarbon evolution. The findings reveal that initial oil generation occurred during the Caledonian event, followed by secondary continuous oil and gas generation and migration, influenced by the Indosinian event. The combination of fluid inclusion analysis and isotopic geochronology data exemplifies immense potential in precisely determining the progression of petroleum evolution.

Evolution of Hydrocarbons and Carboxylic Acids in Heavy Oil during In Situ Combustion in Xinjiang Oilfield

Evolution of Hydrocarbons and Carboxylic Acids in Heavy Oil during In Situ Combustion in Xinjiang Oilfield

Effects of inorganic CO2 intrusion on diagenesis and reservoir quality of lacustrine conglomerate sandstones: Implications for geological carbon sequestration

Mantle-sourced fluids are common in rift basins and often migrate into the reservoir along deep faults. They have a significant role in hydrocarbon evolution and reservoir quality modifications. In this study, we selected Chagan Sag in China as an example and applied reactive transport modeling to explore the influence of mantle-derived CO2 on diagenesis and reservoir quality evolution in the Lower Cretaceous Bayingebi conglomerate reservoirs. The geochemical modeling constrained by natural CO2 reservoirs provides beneficial information on the underground physical processes and chemical reactions during CO2 injection. This is also an efficient means of validating geological carbon sequestration models. Petrographic, geochemical, and modeling data reveal that CO2 intrusion could reduce the reservoir porosity and permeability via significant CO2-water-mineral interactions. Ankerite and illite are the dominant diagenetic minerals responsible for reservoir quality reduction. Among the different lithologies, the higher reservoir quality conglomerate is mainly caused by its high initial porosity and small quantities of clay minerals, with relatively weak carbonate cementation. The lower reservoir quality finer-grained conglomeratic siltstone is caused by intensive albitization, carbonation, and illitization. In the long-term CO2-water-rock interaction process, CO2 can be sequestered through the precipitation of secondary carbonate minerals such as ankerite and dolomite.

Polycyclic aromatic hydrocarbons (PAHs) and soot formations under different gasifying agents: Detailed chemical kinetic analysis of a two-stage entrained flow coal gasifier

The injection of CO2 with coal into coal gasifier is a promising approach to achieve CO2 recirculation. Predicting the formation and evolution of polycyclic aromatic hydrocarbons (PAHs) and soot during coal gasification is particularly important as their presence poses challenges to the gasifier operation and environment. However, the effect of CO2 injection on their formation must be elucidated in more detail to optimize the gasifier design. This work investigates PAHs and soot formations in gas-phase reactions under different gasifying agents (Air, O2/CO2, O2/H2O) in a two-stage entrained flow coal gasifier using a detailed chemical kinetic model (DCKM). Under the O2/CO2– and O2/H2O-blown conditions, aromatics reforming was progressed whereas the yields of tar and soot were effectively suppressed. The benzene was observed as the most abundant PAHs species, followed by naphthalene and acenaphthalene. Regarding the relative oxygen concentration, the conversion behavior of aromatics was significantly influenced in the O2/CO2-blown condition, while the somewhat effect was found in the O2/H2O-blown condition. Tar yield peaked at 50% relative oxygen concentration in the O2/CO2-blown condition. The present finding may have practical significance in the O2/CO2-blown gasifier to facilitate CO2 recirculation for the oxy-fuel IGCC system.

Crude Oil Pyrolysis Studies: Application to In Situ Superheat Steam Enhanced Oil Recovery

This work focuses on the occurrence and composition of flammable pyrolysis gases which can be expected from stimulation of heavy oil with superheat steam. These gases can have commodity value or be used to fire a conventional boiler to generate steam vapor for superheater feed. Seven oil samples taken from different US locations were tested via thermogravimetric analysis (TGA) with off-gas analysis of light hydrocarbons via mass spectrometry (MS). The samples were heated up to 500 °C at 5 °C/min in a gas flow of moist carbon dioxide and held at 500 °C until no further mass loss was noted. Then, carbonaceous residue was exposed to air at 500 °C to determine enthalpy of combustion by differential scanning calorimetry (DSC). To demonstrate that pyrolysis was indeed occurring and not simple de-volatilization, a high-molecular-weight reagent-grade organic molecule, lactose, was first demonstrated to produce components of interest. After treatment under moist CO2 at 500 °C, all samples were found to lose around 90% of mass, and the follow-up combustion process with air further reduced the residual mass to between 2% and 12%, which is presumed to be mineral matter and char. The light hydrocarbons methane, ethane, and propane, as well as hydrogen, were detected through MS during pyrolysis of each oil sample. Heavier hydrocarbons were not monitored but are assumed to have evolved, especially during periods where additional mass loss was occurring in the isothermal process, with minimal light hydrocarbon evolution. These results correspond to a possible concept of subsequent in situ combustion drive with or without heat scavenging following high-temperature pyrolysis from in situ superheat steam injection.

The photochemical evolution of polycyclic aromatic hydrocarbons and nontronite clay on early Earth and Mars

The photochemical evolution of polycyclic aromatic hydrocarbons (PAHs), an abundant form of meteoritic organic carbon, is of great interest to early Earth and Mars origin-of-life studies and current organic molecule detection efforts on Mars. Fe-rich clay environments were abundant on early Earth and Mars, and may have played a role in prebiotic chemistry, catalyzing the breakdown of PAHs and freeing up carbon for subsequent chemical complexification. Current Mars is abundant in clay-rich environments, which are most promising for harboring organic molecules and have comprised the main studied features by the Curiosity rover in search of them. In this work we studied the photocatalytic effects of the Fe-rich clay nontronite on adsorbed PAHs. We tested the effect of ultraviolet radiation on pyrene, fluoranthene, perylene, triphenylene, and coronene adsorbed to nontronite using the spike technique, and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in a Mars simulation chamber. We studied the infrared vibrational PAH bands with first order reaction kinetics and observed an extensive decrease of bands of pyrene, fluoranthene, and perylene, accompanied by the formation of PAH cations, while triphenylene and coronene remained preserved. We further analyzed our irradiated samples with nuclear magnetic resonance (NMR). Our study showed certain PAHs to be degraded via the (photo)Fenton mechanism, even under a dry, hypoxic atmosphere. Using solar spectra representative of early Earth, early Mars, and current Mars surface illumination up to 400 nm, the processes occurring in our set up are indicative of the UV-induced photochemistry taking place in Fe-rich clay environments on early Earth and Mars.

Unconventional Pathway in the Gas‐Phase Synthesis of 9H‐Fluorene (C13H10) via the Radical–Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5)

AbstractThe simplest polycyclic aromatic hydrocarbon (PAH) carrying a five‐membered ring—9H‐fluorene (C13H10)—is produced isomer‐specifically in the gas phase by reacting benzyl (C7H7⋅) with phenyl (C6H5⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1‐(6‐methylenecyclohexa‐2,4‐dienyl)benzene intermediates (C13H12) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical‐radical reactions are initiated through recombination at their radical centers. The structure of 9H‐fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.

Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C13H10) via the Radical - Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5).

The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring - 9H-fluorene (C13H10) - is produced isomer-specifically in the gas phase by reacting benzyl (C7H7•) with phenyl (C6H5•) radicals in a pyrolytic reac-tor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenyl-methane and unexpectedly 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C13H12) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.

Термодинамическая модель глубинного происхождения нефти и ее фазового «замерзания»

Based on the deep inorganic concept of the origin of oil and gas deposits, the evolution of these petrogenic reservoirs in the lithosphere is considered. The analysis of phase diagrams and experimental data made it possible to determine two trends in the evolution of non-methane hydrocarbons in the Earth's interior. In the upper mantle, the "metastability" of heavy (with a lower H/C ratio) hydrocarbons increases with depth. However, at temperatures and pressures corresponding to the surface mantle-crustal hydrothermal conditions, the “relative metastability” of heavy hydrocarbons increases with approach to the surface. When deep HCs fluids rise to the surface, petrogenic oil reservoirs are formed as a result of a drop in hydrogen fugacity and a gas → liquid oil phase transition. Under the physical and chemical conditions of an oil reservoir, metastable reversible phase equilibria are established between liquid oil, gas hydrocarbons and CO2 and solid (pseudocrystalline) "mature" and "immature" kerogens of "oil source" rocks. A decrease in hydrogen pressure and temperature leads to a stoichiometric phase transition (“freezing”) of liquid oil into solid kerogens. This occurs as a result of oil dehydrogenation in the processes of high-temperature CO2 fixation and low-temperature hydration of oil hydrocarbons, which are the main geochemical pathways for its transformation into kerogen. Thus, the formation of carbon matter in petrogenic reservoirs is the result of regressive metamorphism of deep hydrocarbon fluids, natural gas, liquid oil, and emerging accumulations of naphthides.