Generation Of Light Hydrocarbons Research Articles

Parametric evaluation of clean syngas production from pine forest residue by chemical looping gasification at the 20 kWth scale

In the framework of the EU H2020 CLARA project, jet biofuel production via Fischer-Tropsch synthesis is intended from syngas generated by Biomass Chemical Looping Gasification (BCLG). BCLG is based on the lattice oxygen transference between a solid oxygen carrier and the biofuel to energetically support the biomass gasification. This process produces low tar and nitrogen-free syngas under autothermal conditions, and at the same time includes an intrinsic separation of carbon compounds from nitrogen in air, avoiding future carbon capture costs. This work evaluates the syngas production from pine forest residue (PFR) through the BCLG process with ilmenite as the oxygen carrier. The effects of several key operating variables, including temperature, oxygen-to-biomass ratio and mean residence time of solids, on the performance of the BCLG process were analyzed at 20 kWth scale. The syngas yield depended on the oxygen-to-biomass ratio and improved with the char conversion in the fuel reactor. Temperature and mean residence time of solids in the fuel reactor were identified as the primary factors affecting char conversion. A dedicated study was performed to assess the impact of the biomass size on char conversion, as well as the relevance of a carbon stripper unit on the improvement on char gasification due to its role either as a secondary gasifier or as a char-oxygen carrier separator. Higher char conversion values were achieved with the lowest biomass particle size (1–2 mm vs. pellets 6 mm Ø) due to lower restrictions to gas diffusion inside the particles. The carbon stripper may act as a secondary gasifier, thus improving the char conversion, but it was not able to take away the unconverted char particles from ilmenite in any case due to it was designed for powdered fuels. Besides, the generation of light hydrocarbons was hardly affected by any operating variables. The tar content remained below 4.5 g/kg dry biomass. The ilmenite showed a good performance during the continuous operation without signs of defluidization.

Stable carbon isotopic compositions of individual light hydrocarbons in the C5–C7 range in natural gas from the Qaidam Basin, China

C5–C7 light hydrocarbons are important components in petroleum and are extensively employed as an auxiliary approach in petroleum research. Consensus on the mechanism of light hydrocarbon generation has not yet been achieved. In this study, 20 gas samples were collected from the western part and northern margin of the Qaidam Basin. The molecular and carbon isotopic compositions of C1–C3 gaseous hydrocarbons and C5–C7 light hydrocarbons, as well as the carbon isotopes of oils were analyzed. Based on the relationships between carbon isotopes (13C) of individual light hydrocarbons and calculated vitrinite reflectance, it suggests that organic matters play a fundamental role in the carbon isotopes of light hydrocarbons, and maturity mainly affects the carbon isotopes of n-alkanes in light hydrocarbons. In addition, carbon isotopic differences between n-, iso- and cyclo-alkanes indicate that light hydrocarbons with different structures are produced from various biological precursors. Besides, carbon isotopes of individual light hydrocarbons can be used to estimate the δ13Ckerogen and distinguish cracked gas. On the one hand, small isotope fractionation between iso-alkanes and kerogen is observed. Average carbon isotopic compositions of iso-pentane ( i-C5), 2-methylpentane (2-MC5) and 3-methylpentane (3-MC5) can provide a similar δ13Ckerogen with actual values. On the other hand, the carbon isotopic difference between 2-MC5 and n-C6 generally decreases with increasing maturity. Combined with the parameter (2-MC6 + 3-MC6)/ n-C6, kerogen-cracked gases are characterized by high δ13C2MC5–δ13CnC6 and low (2-MC6 + 3-MC6)/ n-C6 values, whereas oil-cracked gases exhibit the opposite features.

Kinetic and equilibrium reactions on natural and laboratory generation of thermogenic gases from Type II marine shale

The phenomenon that laboratory pyrolysis experiments produce much wetter gases than those in natural reservoirs is a long-recognized and debated problem in the investigation of natural gases in sedimentary basins. In this study, we explore the discrepancy by pyrolyzing a type II kerogen from the Woodford Shale in Oklahoma, compared with the previous results on the produced natural gases from the Arkoma Basin generated from the same source rock (Liu et al., 2019) with the discussion of gas and isotopic compositions at bulk and position-specific (PS) levels. An improved GC-pyrolysis-GC IRMS method is applied for the determination of PS δ13C of propane produced in the pyrolysis of the Woodford Shale at Easy %Ro from 0.76 to 3.27. Kinetic and thermodynamic considerations of the chemical and isotopic compositions of the natural and laboratory pyrolysis gases suggest that the generation of light hydrocarbons involves uni-directional cracking reactions, exchange reactions with water, and likely reversible reactions among light hydrocarbons and other H-containing volatiles. After the gas generation in the unconventional Woodford Shale reservoirs, the C1-C4 gases might have approached close to chemical equilibrium of C1-C3 and isotope equilibrium of C2-C1 and C3-C1 pairs at their peak temperatures. The capping H for the generation of C1-C4 in the Woodford Shale gases appears to have experienced at least partial exchange with the water, while that in the pyrolysis gases is only originated from organic-bound compounds with large kinetic isotope effects (KIE). Our findings indicate that elevated compound-specific and PS δ13C values of propane in the wet-gas cracking stage are significantly influenced by the breakdown of the thermally stable compounds (e.g., remaining kerogen, residues). A first synthesis of PS δ13C and δ2H isotopic compositions of propane from this study and the literature data suggests relatively similar isotopic structures of propane precursors in kerogens. This study demonstrates that PS isotope analysis of propane can contribute to identifying various geological (e.g., maturation, wet-gas cracking, H exchange, diffusion) and biodegradation processes.

Improved light hydrocarbons collection method for the pyrolysis of crude oil in gold tube closed system experiments

Light hydrocarbons (C6–C13) are the major components of light oils and condensates and contain abundant geochemical information. Hence, they are widely used as important supplements to biomarker analysis. Due to high volatility, it is often difficult to collect light hydrocarbons completely after pyrolysis experiments. The traditional liquid hydrocarbon (TLH) collection method is usually applied to collect liquid hydrocarbon products after gold tube closed-system pyrolysis experiments. However, this method is difficult to adequately inhibit the evaporation of light hydrocarbons, which may cause deviations in the evaluation of generation potential, applications of parameters, and stable carbon isotopic compositions of light hydrocarbons. Hence, we have developed an alternative method of liquid nitrogen direct freezing (LNDF) to collect liquid hydrocarbon products after pyrolysis of a crude oil in closed gold tubes. The yields, molecular and stable carbon isotopic compositions of light hydrocarbons collected are compared with the TLH method to evaluate any differences. In addition, the influence of thermal alteration on the characteristics of light hydrocarbons are discussed. The yields of light hydrocarbons by the TLH method are 10–75% less than that by the LNDF method, which may bring about an underestimate of light hydrocarbon generation potential. The maturity corresponding to the maximum light hydrocarbon yield determined by the TLH method is at Easy%Ro = 1.08, much lower than Easy%Ro = 1.67 by the LNDF method. Relative to the LNDF method, the TLH method reveals significant differences in some light hydrocarbon parameters and C6–C8 carbon isotopes, which may cause deviations in their geochemical applications such as oils correlation and thermal maturity evaluation. In addition, thermal maturation has significant effects on some light hydrocarbon parameters. The LNDF method can effectively avoid evaporative loss to reveal the original geochemical information of light hydrocarbons.

Characterization of Pyrolysis Kinetics of Continental Shale: Comparison and Enlightenment of the Parallel Reaction Model and the Overall Reaction Model

A total of nine immature–low maturity oil shale samples from Fushun and Maoming, the main oil shale producing areas in China, and three mature shale samples from the Jiyang Depression, China, were selected for use in hydrocarbon generation thermal simulation experiments in an open system and a closed system. The parallel first–order reaction kinetic model and the overall nth–order reaction kinetic model were used to calibrate the pyrolysis kinetic parameters of the samples. This comparative study revealed following conclusion. The generation period of the gaseous hydrocarbons (C1–5) was the longest, and the generation period of the heavy hydrocarbon (C14+) was the shortest. The activation energy of the hydrocarbon generation reaction was closely related to the maturity of the organic matter, i.e., the higher the maturity of the sample, the higher the activation energy of the reaction, which indicates that oil shale/shale oil conversion requires higher temperature conditions. The parallel first–order reaction model regards the hydrocarbon generation reaction as a series of first–order reactions, and it has a better fitting effect for the longer hydrocarbon generation period reactions, such as generating gaseous hydrocarbons (C1–5) and light components (C6–14) from organic matter. The overall nth–order reaction treats the reaction as a nth–order reaction, and the nth–order reaction has a better fitting effect for reactions with a narrow hydrocarbon generation window, such as generating heavy components from organic matter. In the process of generating hydrocarbons from organic matter, the order of the reaction is the sum of the orders of the sub–reactions. The more hydrocarbon–generating parent material, the higher order of hydrocarbon–generating reaction. The reaction order sequence of the generation of different hydrocarbons from organic matter is as follows: generation of gaseous hydrocarbons > generation of light hydrocarbons > generation of heavy hydrocarbons.

Catalytic effect and mechanism of in-situ metals on pyrolysis of FR4 printed circuit boards: Insights from kinetics and products

Pyrolysis is a promising method for the recovery of waste printed circuit boards (WPCBs), but few researches have noticed the influence of in-situ metals. This study conducted a series of comparisons between metal-free leftover pieces (LP) and intact boards (IB), including pyrolysis characteristics, volatile emission, kinetics, and thermodynamic parameters. The thermo-gravimetry (TG) analyses indicated that both the samples presented predominant mass loss in narrow temperature intervals, and characteristic pyrolysis temperatures of IB were approximately 15 °C lower than those of LP. Dominant constituents in evolved gases were detected by Fourier-transform infrared spectrometry as CO2, phenol, bromophenol, ethers, ketones, and aldehydes, and metals accelerated the generation of light hydrocarbons and aromatic compounds. The activation energy and thermodynamic parameters were calculated and compared, and the results verified the presence of in-situ metals led to a lower energy barrier and higher reaction extent. Moreover, conversion behaviors of Cu, Fe, Sn, and Pb manifested the formation of metal bromides and implied the reduction of brominated volatiles. The obtained results confirmed the catalytic effect of in-situ metals on PCBs pyrolysis and their bromine fixation abilities. This study contributes to fundamental knowledge that can be used to guide the pyrolysis of WPCBs.

Thermal Cracking of Oil under Water Pressure up to 900 Bar at High Thermal Maturities: 2. Insight from Light Hydrocarbon Generation and Carbon Isotope Fractionation

In this study, pyrolysis experiments were conducted with a saturate-rich Tertiary source rock-derived oil from the South China Sea basin using a fixed-volume pressure vessel at temperatures from 35...

Prediction of gaseous products from Dachengzi oil shale pyrolysis through combined kinetic and thermodynamic simulations

The characteristics of gas evolution from Dachengzi oil shale pyrolysis under different temperatures were experimentally investigated using a fixed bed reactor and then were evaluated by integrating thermodynamic equilibrium simulation employing HSC Chemistry program and Sandia PSR kinetics simulation in this paper. The experiment results indicate that the non-condensable gases contain much higher CO2, CH4 and H2 and lower CO and C2–C4 hydrocarbons in terms of volume percentages, and mainly consist of CO2 and CH4 as well as some minor gases in terms of mass distribution. CO2, CO and H2 are firstly produced followed by the generation of light hydrocarbons. The HSC calculation results present that some C2 and C2+ hydrocarbons disappear in the predicted gaseous products thermodynamically, and the nitrogen- and sulfur-containing gases mainly are N2 and H2S, respectively. Then, the normalized HSC species are inputted into the Sandia PSR code by three methods, i.e., the CHO input method, the regional input method and the individual input method, considering the potential kinetic constraints. Some C2 and C2+ hydrocarbons appear in the predicted gaseous products based on the three methods. The regional input method demonstrates that more H2 and CO are produced at higher temperature, which agrees with the experimental results. And more C2H4 and C2H2 release at higher temperature depending on the enhanced secondary gas cracking reactions. The peak concentration of every gas product is obtained at higher temperature with lower value compared to the experimental results possibly due to ignoring the effect of the shale ash. The individual input method indicates that C2 and C3 hydrocarbons are generated after the formation of CH4, CO, CO2 and H2. The change trends of CO2, CO and H2 obtained from the experiment and simulation with rising temperature are very similar, but those for CH4 are different, due to most likely certain limitations of a fixed bed reactor as a reaction system. Combining the HSC and PSR calculations, the obtained gas products are closer to the realistic situation.

Destruction of Kerogen in the Presence of Pyrite and Cobalt-Based Catalyst

Objectives: The investigation of the process of the kerogen in situ catalytic transformation accompanied by the synthetic oil production. Methods: To develop kerogen-rich deposits, such technologies as in situ combustion and retorting, presupposing productive layers warming-up, can be employed. The intensification of the light hydrocarbon generation under the kerogen cracking is achieved while using nano-dimensional catalysts based on the transition metals. Finding: The cracking catalyst on the cobalt basis alongside with the impact on the organic substance can promote to the transformation of pyrite into mixed iron oxides, the latter also being the catalysts of the processes under discussion. Under the thermocatalytic effect on the kerogen-containing rocks, the processes of the destructive hydrogenation with the formation of liquid hydrocarbons take place. The processes above are quite catalytic, accompanied by the hydrocarbons molecules activation with power and chemical methods. Iron-containing minerals of all other ones found in the thermal transformation of kerogen. Pyrite under thermal treatment transforms into hematite which is a hydrocracking process. Conclusion: The influence of the nano-dimensional catalyst based on cobalt aims at the organic substance cracking.

Destruction of Kerogen in the Presence of Pyrite and Cobalt-Based Catalyst

Objectives: The investigation of the process of the kerogen in situ catalytic transformation accompanied by the synthetic oil production. Methods: To develop kerogen-rich deposits, such technologies as in situ combustion and retorting, presupposing productive layers warming-up, can be employed. The intensification of the light hydrocarbon generation under the kerogen cracking is achieved while using nano-dimensional catalysts based on the transition metals. Finding: The cracking catalyst on the cobalt basis alongside with the impact on the organic substance can promote to the transformation of pyrite into mixed iron oxides, the latter also being the catalysts of the processes under discussion. Under the thermocatalytic effect on the kerogen-containing rocks, the processes of the destructive hydrogenation with the formation of liquid hydrocarbons take place. The processes above are quite catalytic, accompanied by the hydrocarbons molecules activation with power and chemical methods. Iron-containing minerals of all other ones found in the thermal transformation of kerogen. Pyrite under thermal treatment transforms into hematite which is a hydrocracking process. Conclusion: The influence of the nano-dimensional catalyst based on cobalt aims at the organic substance cracking.

Effect of the Nature of the Metal Co-Catalyst on CO2 Photoreduction Using Fast-Grown Periodically Modulated Titanium Dioxide Nanotube Arrays (PMTiNTs)

ABSTRACTAnodically formed TiO2 nanotube arrays composed of the anatase phase with periodically modulated diameters (PMTiNTs) are excellent photocatalysts for the sunlight-driven transformation of carbon dioxide into hydrocarbons. Exploiting the full potential of this nanoarchitecture for CO2 photoreduction requires integration with metal nanoparticles that function as catalytic promoters for multistep electron transfer reactions. We studied the effect of different metallic and bimetallic nanoparticles on the rate of generation of light hydrocarbons by the photoreduction of CO2. All the metal nanoparticles were loaded on to the TiO2nanotubes using the technique of photodeposition, which standardized the coating process and enabled examination purely of the effect of different metals. Photodeposition was used not only due to its simplicity but also because it enabled us to engineer very fine coatings possessing excellent uniformity and depth penetration into the nanotubes. The best performing co-catalysts were found to be CuPt (atomic ratio of 0.33:0.67), Pt and NiPt (1:2), which when loaded onto the PMTiNTs yielded total hydrocarbon generation rates of 3.5, 0.85 and 0.8 mL g-1 hr-1 respectively. The time required to form PMTiNTs was reduced by a factor of 160 by using a recently reported recipe based on fluoride ion bearing electrolyte containing lactic acid. PMTiNTs formed using the ultrafast growth lactic acid-based electrolytes exhibited similar photocatalytic properties to samples obtained more slowly using conventional ethylene glycol-based electrolytes.

Glycerol and bioglycerol conversion in supercritical water for hydrogen production

Catalytic transesterification of vegetable oils leads to biodiesel and an alkaline feed (bioglycerol and organic residues, such as esters, alcohols…). The conversion of bioglycerol into valuable organic molecules represents a sustainable industrial process leading to the valorization of a renewable organic resource. The physicochemical properties in the supercritical domain (T>374°C, P>22.1 MPa) transform water into a solvent for organics and a reactant favouring radical reactions. In this context, the conversion of bioglycerol in supercritical water (SCW) into platform molecules and/or high energetic gases (hydrogen, hydrocarbons) could represent an interesting valorization process. The reported research results concern the conversion of bioglycerol compared to pure glycerol. The experiments have been done in batch autoclaves (5 ml and 500 ml stirred). Solutions of pure (5 or 10 wt%) and crude (3.5 wt%) glycerol have been processed with or without catalyst (K2CO3 1.5 wt%) in the range of 450–600°C. The molecular formula of bioglycerol was determined as C4.3H9.7O1.8Na0.1Si0.08. Glycerol was partially decomposed in the batch systems during the heating (42% before reaching 420°C) and some intermediates (propanediol, ethylene glycol …) were quantified, leading to a proposition of a reaction pathway. Acrolein, a valuable platform molecule, was mainly produced in the absence of catalyst. No solid phase was recovered after SCW conversion of pure and bioglycerol in batch reactors. The optimal parameters for gasification were 600°C, 25 MPa for bioglycerol and 525°C, 25 MPa, for pure glycerol. In these operating conditions, 1 kg of pure or bioglycerol leads to 15 and, respectively, 10 mol of hydrogen. Supercritical water gasification of crude glycerol favoured the generation of light hydrocarbons, while pure glycerol promoted H2 production. SCW conversion of glycerol (pure and crude) allows to obtain simultaneously energetic gases (respectively 2600 and 4000 kcal/kg glycerol) and valuable platform molecules.

Generation of light hydrocarbons through Fischer–Tropsch synthesis: Identification of potentially dominant catalytic pathways via the graph–theoretic method and energetic analysis

The Fischer–Tropsch synthesis (FTS) for the production of widely distributed hydrocarbons through the catalytic hydrogenation of carbon monoxide (CO) has been intensively and extensively explored. This is attributable to its immense theoretical as well as practical importance. Naturally, such exploration would be greatly facilitated if the feasible or dominant catalytic pathways (mechanisms) of FTS can be determined. The stoichiometrically feasible and independent catalytic pathways (IP i 's) of FTS have been exhaustively identified via the rigorous graph–theoretic method based on P-graphs (process graphs). The most extensive set of elementary reactions available, which numbers 26, has yielded 24 IP i 's in less than 1 s on a PC. The plausibly dominant pathways have been selected from the stoichiometrically feasible pathways through the analysis of their activation energies. Naturally, the dominant pathway or pathways need ultimately be discriminated among these plausibly dominant pathways via various means, e.g., in situ spectroscopic measurements of intermediates.

Processing of hydrocarbons in an AC discharge nonthermal plasma reactor: An approach to generate reducing agents for on-board automotive exhaust gas cleaning

Light hydrocarbons and H 2 can be used to enhance NO x reduction efficiency and regenerate sulfur-poisoned NO x storage catalysts, and therefore are valuable for automotive exhaust gas cleaning. The processing of hydrocarbons in an alternating current (AC) discharge nonthermal plasma reactor was studied for the instant generation of light hydrocarbons and H 2 at room temperature and atmospheric pressure. n-Octane and n-hexane were used as model hydrocarbons. Effects of hydrocarbon feedstock, electrode diameter, applied voltage, flow rate of carrier gas, gap size, and residence time of hydrocarbon molecules, were investigated systematically. Cracking is the only detected reaction during n-octane conversion (which might be very attractive for the cracking of heavy oil), and is the dominant reaction during n-hexane conversion. Catalytic dehydrogenation, catalytic addition, and noncatalytic cracking reactions, were discussed. The cleavage mode of single carbon–carbon bonds is revealed to be relevant to the carbon number of hydrocarbon molecules. Conversions, yields, power consumption, energy efficiencies, generation of hydrogen, etc, were determined and discussed. This study is of importance to novel processing of hydrocarbons at room temperature and atmospheric pressure, instant generation of hydrogen, cleaning of automotive exhaust gas, and chemistry in nonthermal plasma reactors.

The origin of light hydrocarbons in petroleum: Ring preference in the closure of carbocyclic rings

In a proposal for the generation of light hydrocarbons (LHs), n-alkane parents are catalytically transformed into daughter isoalkanes and cycloalkanes through the closure of three-, five-, and six-membered rings. Three reaction rate constants, k 3: →- isoalkanes; k 5: → cyclopentanes; k 6: → cyclohexanes, control this catalytic process, and thus the compositions of LHs. A catalyst that preferentially promotes ring-closure of a specific carbon number is said to express ring preference (RP) in that carbon number. For example, a catalyst that preferentially generates isoalkanes over cycloalkanes would be expressing three-ring preference (3RP), meaning that k 3 is greater than k 5 and k 6 in the catalytic process generating LHs. Oils show large compositional variations in LHs, with ratios of isoalkanes to cycloalkanes showing coefficients of variation on the order of 100%, reflecting large variations in RP. Genetically related oils (homologous oils), however, are either invariant in composition (invariant in RP) or they display systematic changes in RP. In a striking example of this latter case, RP progressively shifts to smaller rings, 6RP → 5RP → 3-RP, as parent concentrations increase. This paper addresses a curious paradox, apparently unique to the LHs: homologous oils, displaying a uniform overall geochemical composition (i.e., gravity, sulfur concentration, isotopic composition, biomarker composition, and so on), show remarkable changes in LH composition reflecting systematic changes in RP. These apparent contradictions, on the one hand a uniform overall composition reflecting a static system and on the other hand systematic changes in LH composition reflecting a dynamic system, are analyzed in the context of a steady-state catalytic hypothesis.

Novel Applications of Light Hydrocarbons Chemistry in Petroleum Exploration

The light hydrocarbons in petroleum are products of a kerogen-specific catalytic process. The catalysts are believed to be the transition metals entrained in kerogen. The process is controlled by the metals in the active sites and the kerogenous organic structures surrounding the active sites. Different catalytic sites are suggested to yield distinct distributions of light hydrocarbons. The author recognizes three dominant (primary) distributions, with all other distributions adequately represented by some linear combination of the three primary distributions. Three catalytic sites, therefore, can be associated with the generation of light hydrocarbons. He introduces a simple and inexpensive procedure using cross plots of various product ratios to correlate oils and source rocks. It has proven to be a remarkably articulate and powerful tool for deconvoluting diverse oils into genetic groups. The light hydrocarbons are also indicators of oil-generation temperature and other physical parameters associated with oil generation. The analysis of light hydrocarbons from this perspective is new. It provides the exploration geochemist with a novel technique for gaining insight into the fundamental chemistry of petroleum generation.

C 1[sbnd]C 8 hydrocarbons in sediments from Guaymas Basin, Gulf of California—Comparison to Peru Margin, Japan Trench and California Borderlands

Surface seafloor sediments, hydrothermal vent samples, and Deep Sea Drilling Project sediments (Hole 481A) from the Guaymas Basin were examined for C 1 C 8 hydrocarbons. The proportions of various classes of compounds were examined and compared to those from other geographic areas (Peru upwelling region and Japan Trench) to gain insight into the relative importance of thermal generation, migration and biodegradation. Concentrations of C 2 C 7 hydrocarbons were about 10–10,000 times higher in geothermally warm (estimated to have been exposed to maximum temperatures in the range of 30–150°C) Guaymas Basin sediments in comparison to the low concentrations (0.1–10 ppb per compound) typical of geothermally cold (maximum thermal exposure less than 20°C) seafloor and DSDP diatomaceous sediments. However, one sediment sample from DSDP Site 477, estimated to have been exposed to temperatures of 300°C or higher in the past, showed only a limited hydrocarbon composition, consisting of C 1 C 3 alkanes and aromatic hydrocarbons only. Alkene/alkane ratios of 0.1 or greater were typical of both geothermally cold sediments and also of very hydrocarbon-rich Alvin samples recovered from the seafloor. Because little or no alkene was generally detected in buried sediments exposed to geothermal temperatures greater than 30°C, it is suggested that the alkenes are produced by biogenic processes. Normal alkenes predominated over cyclic and branched structures in geothermally cooler (<20°C) sediments, with the proportion of cyclic and branched compounds increasing in hotter sediments. Concentrations of gem-dimethyl and aromatic compounds generally remained approximately constant or increased slightly with temperature in comparison with geothermally cold shallow sediments. Similarities in compositions of branched and cyclic compounds were observed in some pairs of bitumen-rich Guaymas seafloor samples recovered from different areas, suggesting common mechanisms of light hydrocarbon generation and/or migration. Localized increases in ratios of specific cycloalkane ratios were observed adjacent to sill intrusions.

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 ( δ 13C) 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.

Geochemistry of low molecular weight hydrocarbons in two exploration wells of the Elmworth gas field (Western Canada Basin)

The Elmworth gas field is situated in the deep part of the Western Canada Basin (“Deep Basin”). Almost the entire Mesozoic sedimentary sequence in this area is gas-saturated and represents a typical low-porosity, low-permeability gas accumulation of major importance. Various aspects of the geochemistry of light hydrocarbons are studied in a series of about 200 type III kerogen and coal-bearing rock samples (cuttings) from two exploration wells in the Elmworth area, comprising a sedimentary sequence of Cretaceous to Mississippian age. Based on a combined “hydrogen-stripping”- thermovaporization/capillary gas chromatography technique the concentrations of the C 2–C 8 hydrocarbons are determined. Concentrations and compositional details are discussed in terms of light hydrocarbon generation including possible migration phenomena. Both the relative cyclopentane content and the concentration ratio of the 1,2-dimethylcyclopentane stereoisomers can clearly be correlated with the vitrinite reflectance data in the two wells.

ORIGIN OF LIGHT HYDROCARBONS IN CARBONATE OOLITES

The excellent porosity and permeability characteristics of oolitic carbonates have been used to explain their notably superior production of hydrocarbons, when compared with most other reservoir rocks. However, we have found that Recent ooid sands contain light hydrocarbons which we believe to be authigenic. The significance of these hydrocarbons is not the fact of their occurrence, but in the ratio of methane to the other hydrocarbons present (ethane, propane, etc.). To our knowledge, no similar discovery has been reported. This paper seeks to account for the formation of these hydrocarbons, and to relate the process to an overall scheme of petroleum genesis. In addition to providing a new insight into the timing, depth and nature of light hydrocarbon generation, the results present the possibility of the role of oolites as source rock.