Monoaromatic Steroid Hydrocarbons Research Articles

The La Luna Formation, Venezuela: A prospective unconventional reservoir

Since the early 2000s, the exploitation of unconventional reservoirs has become very important to the oil and gas industry because of their high potential source of energy and economic value. Venezuela possesses a world-class hydrocarbon source rock in one of the most prolific hydrocarbon basins in the world, namely the Cretaceous La Luna Formation in the Maracaibo Basin. Outcrop and core samples collected from the northwestern Maracaibo Basin provide the database for this study. A comprehensive multiscale characterization of the samples is undertaken to unravel the stratigraphic properties of the petroleum system. In addition, a geochemical approach is taken to evaluate the prospectivity of the La Luna Formation as an unconventional resource in the Maracaibo Basin. Rock-Eval pyrolysis and biomarker data indicate that the La Luna Formation is dominated by type II kerogen, indicating an oil-prone marine organic matter origin. Total organic carbon values range between 3.85 wt% and 9.10 wt%. Distributions of isoprenoids, steranes, and terpanes including gammacerane and monoaromatic steroid hydrocarbons indicate a hypersaline, marine carbonate anoxic depositional environment. Thermal maturity parameters indicate that most of the cores are currently in the oil window. This combined stratigraphic geochemical study indicates that the La Luna Formation has excellent potential as an unconventional reservoir for oil and gas in the study area.

Aromatic hydrocarbons as parameters of oil formation conditions

Aromatic hydrocarbons in the oils of Absheron and Baku archipelago, as well as in coastal zones have been identified via the method of chromato-mass-spectrometry. Geochemical estimation of distribution character of main biomarkers and their correlations as well is presented. The similarity in the distribution of monoaromatic and triaromatic steroid hydrocarbons, as well as benzogopane and sekabenzogopans has been specified, which suggests that studied oils are associated with one source rock or organic facies. The varieties observed in the distribution of saturated steranes are most likely the result of differences in the values of thermal maturity or the processes of secondary alterations.

Steroidal Aromatic ‘Naphthenic Acids’ in Oil Sands Process-Affected Water: Structural Comparisons with Environmental Estrogens

The large volumes, acute toxicity, estrogenicity, and antiandrogenicity of process-affected waters accruing in tailings ponds from the operations of the Alberta oil sands industries pose a significant task for environmental reclamation. Synchronous fluorescence spectra (SFS) suggest that oil sands process-affected water (OSPW) may contain aromatic carboxylic acids, which are among the potentially environmentally important toxicants, but no such acids have yet been identified, limiting interpretations of the results of estrogenicity and other assays. Here we show that multidimensional comprehensive gas chromatography-mass spectrometry (GCxGC-MS) of methyl esters of acids in an OSPW sample produces mass spectra consistent with their assignment as C(19) and C(20) C-ring monoaromatic hydroxy steroid acids, D-ring opened hydroxy and nonhydroxy polyhydrophenanthroic acids with one aromatic and two alicyclic rings and A-ring opened steroidal keto acids. High resolution MS data support the assignment of several of the so-called 'O3' species. When fractions of distilled, esterified, OSPW acid-extractable organics were examined, the putative aromatics were mainly present in a high boiling fraction; when examined by argentation thin layer chromatography, some were present in a fraction with a retardation factor between that of the methyl esters of synthetic monoalicyclic and monoaromatic acids. Ultraviolet absorption spectra of these fractions indicated the presence of benzenoid moieties. SFS of model octahydro- and tetrahydrophenanthroic acids produced emissions at the characteristic excitation wavelengths observed in some OSPW extracts, consistent with the postulations from ultraviolet spectroscopy and mass spectrometry data. We suggest the acids originate from extensive biodegradation of C-ring monoaromatic steroid hydrocarbons and offer a means of differentiating residues at different biodegradation stages in tailings ponds. Structural similarities with estrone and estradiol imply that such compounds may account for some of the environmental estrogenic activity reported in OSPW acid-extractable organics and naphthenic acids.

Hydrous pyrolysis of cholesterol under various conditions

The alteration products of cholesterol subjected to hydrothermal conditions have been analyzed by gas chromatography–mass spectrometry. Four sets of experiments were conducted at temperatures ranging between 150 and 300 °C for 24 h. The reaction mixtures of the first set included only cholesterol and water, whereas those of the second, third and fourth sets also contained oxalic acid, natural sediment and montmorillonite, respectively. The alteration rate and the number of observed alteration products increased with higher temperature and acidity of the reaction mixtures. At lower temperatures cholestenes and cholestenones were major compounds. Cholestene concentrations increased at higher temperatures in all sets and were highest at 200 °C in acidic medium, at 250 °C in the presence of sediment and at 300 °C with montmorillonite. Cholestane concentrations also increased at elevated temperatures, being greatest in the absence of both sediment and montmorillonite. Diacholestenes were detected in an acidic medium at all temperatures and with montmorillonite at >200 °C. Monoaromatic steroid hydrocarbons were found above 200 °C. Thus, backbone rearrangements were the major alteration processes and bond cleavage (cracking) was predominant in an acidic medium, whereas aromatization was enhanced in the presence of both sediment and montmorillonite. These products confirm that reductive biomarker alteration in hydrothermal systems occurs rapidly and at high temperatures (>250 °C).

Feasibility study on direct coal liquefaction in Indonesia

The distributions of steroidal and triterpenoidal alkanes and aromatic hydrocarbons and, where appropriate, triterpenoid alkenes and ketones, in nine oils, nine coals and three shales from the Mahakam Delta have been examined by gas chromatography-mass spectrometry. In all of the fractions there are high relative abundances of components of higher-plant origin, in keeping with the previous assignment of the organic matter in Mahakam sediments as type III. Comparison of molecular maturity measurements for the sediments and the oils extends earlier ideas that the source for the Handil oils must have a present depth of at least 3000 m. No major difference was observed here in the maturity (based on the molecular measurements) measured for coal-shale pairs with similar burial depths.In the oils, variations in the relative abundances of the monoaromatic steroid hydrocarbons relative to the triaromatic steroid hydrocarbons, taken with the results of earlier studies of the oils, have been ascribed tentatively to a migration effect.

Characterisation of a unique ‘asphalt’ sample from the early 19th century Hafkenscheid painting materials collection by analytical pyrolysis MS and GC/MS

Asphalt has been used since antiquity for various purposes and by painters since the 17th century. Asphalt as a pigment material with a known pre-19th century provenance is extremely rare. The analytical pyrolysis techniques of direct temperature-resolved mass spectrometry (DTMS) and pyrolysis gas liquid chromatography coupled with mass spectrometry (Py-GC/MS) were applied to characterise a unique ‘asphalt’ sample from a painting materials collection dating from the early 19th century. The provenance of this sample was investigated by comparison with a sample from a present day floating asphalt from the Dead Sea. DTMS demonstrated a complex envelope of ions from hydrocarbons ranging past m/z 1000 in both samples. Both samples showed evaporating sets of compounds as well as pyrolysing materials evolving from asphaltenes. Asphaltene network polymers were marked by aliphatic cross-links releasing alkenes and alkanes, and aromatic centres releasing alkylbenzenes, alkylnaphthalenes, alkylanthracenes, alkylphenanthrenes, and alkylbenzothiophenes. Hopanoid hydrocarbons and C-ring monoaromatic steroid hydrocarbons were among the biomarker compounds identified. Particularly striking were homologous series of alkylbenzothiophenes and alkyldibenzothiophenes with long hydrocarbon chains that could be traced with DTMS and confirmed by DTMS/MS. The results indicate that the early 19th century ‘asphalt’ sample from the Hafkenscheid collection is indeed a true asphalt that shows many similarities to the Dead Sea asphalt sample, which is therefore proposed as the possible region of provenance.

Quantitative separation of aliphatic and aromatic hydrocarbons using silver ion--silica solid-phase extraction

A solid-phase extraction (SPE) method employing silver nitrate impregnated silica has been developed and evaluated for the separation of defined aliphatic and aromatic hydrocarbons from crude oils. The versatility of the SPE method is demonstrated using a light crude oil from the North Sea and a heavy crude oil from Orcutt field (Monterey, California, U.S.A.). The coefficients of variation for a number of geochemical parameters measured on both aliphatic and aromatic hydrocarbons were excellent. The separation efficiency of SPE is demonstrated using quantification of monoaromatic steroid hydrocarbons which are notoriously difficult to efficiently sequester into the aromatic hydrocarbon fraction using traditional liquid chromatographic procedure. The selectivity and efficiency of the SPE technique is comparable with that of silica gel TLC. However, losses of volatile compounds such as naphthalene are limited during SPE since the sample remains in solvent. We conclude that solid-phase extraction affords rapid sample turnover suitable for processing large sample numbers with high reproducibility.

Computerized GC/MS detection of monoaromatic and triaromatic steroid hydrocarbons in Alamein crude oil

AbstractSeries of C‐ring monoaromatic steroid hydrocarbons (C21, C22, C27  C29) and triaromatic steroid hydrocarbons (C20, C21, C26  C28) have been recognized in the aromatic hydrocarbon fraction of Alamein crude oil from the western desert, Egypt. Detection of these compounds were based on mass fragmentography of the key ions m/z 253 and m/z 231 and comparison of the mass spectra and relative retention times with literature data. The predominance of the C29 monoaromatic steroids and C28 triaromatic steroids provide further evidence for a land plant origin of Alamein oil. The results substantiate previous evidence of the occurrence of an aromatization process with increasing maturation and indicate a moderate maturity level for Alamein oil.

Diterpanes, triterpanes, steranes and aromatic hydrocarbons in natural bitumens and pyrolysates from different mimic coals

There is a significant difference in the distribution of terpanes in natural bitumen extracted from four coals identified as Rocky Mountain coal (RMC), Australian Gippsland Latrobe Eocene coal (GEC), Australian Gippsland Latrobe Cretaceous coal (GCC), and Texas Wilcox lignite (WL). Whereas pentacyclic triterpanes are dominant in GEC, GCC and WL, diterpanes strongly predominate in the bitumen of RMC. This indicates that resin is a more important constituent of RMC than in the other coals and releases the diterpenoids at an early stage of diagenesis. Furthermore, the composition of diterpanes is also different among these coals. For example, tricyclic diterpanes are the only diterpanes present in RMC, whereas tetracyclic and tricyclic diterpanes are both present in GEC and GCC and tetracyclic diterpanes are most abundant in GEC. However, diterpanes are nearly absent in WL. Surprisingly, the diterpenoid content is negligible in the pyrolysates of all coals. The sterane and triterpane distributions in the natural bitumen of coals are very different from those in pyrolysates. C 31 αβ 22R hopane predominates in the m/z 191 mass fragmentograms of the natural bitumens, whereas a homologous series of hopanes (C 27–C 35 ; except C 28) is present in the coal pyrolysates. C 29 steranes dominate in all of the coal bitumens as well as pyrolysates. C 27 steranes are absent in the natural bitumen, but are generated in pyrolysates during lengthy heating of coal kerogen. This indicates that formation of secondary steranes occurs by cracking the side chain. C 29 monoaromatic steroid hydrocarbons are abundant in the natural bitumen of the four coals. The m/z 253 distribution is similar for GEC, RMC and WL, but it differs from the more mature GGC, which has a lower content of 20R of both 5 α and 5β C 29 MA-steroids. Triaromatic steroid hydrocarbons are only present in GCC, whereas significant amounts of tetra- and triaromatic triterpenoid hydrocarbons are present in the other three coals (GEC, RMC and WL). The ratio of benzo(e)pyrene/perylene may be potentially useful as a maturity parameter because the amount of benzo(e)pyrene increases with thermal stress, whereas perylene decreases with heating time. Benzohopanes are widely present in four humic coals but become unstable after 10 h heating at 300°C.

Biodegradation of tar-sand bitumens from the Ardmore and Anadarko Basins, Carter County, Oklahoma

A series of tar-sand bitumens collected from a single shallow well in the Ardmore Basin, Carter County, Oklahoma has been characterized by various geochemical techniques. Particular emphasis has been placed on determination of variations in biomarker distributions, both hydrocarbons and porphyrins, as a function of biodegradation. The tar-sand bitumens have been severely biodegraded and most of the n-alkanes, low molecular weight cycloalkanes, isoprenoid alkanes, C 27C 29 steranes, light aromatics and sulfur compounds have been removed. In addition, the hopane distributions have been altered to differing degress with the pseudohomolugoues above C 30decreasing in concentration prior to the C 20–21 The triaromatic steroid hydrocarbons were also altered with preferential removal of 20R epimers (C 20–21 and C 27–28). Diasterane and C 30-sterane distributions appear to be relatively unaffected by biodegradation. The high resistance of tricyclic terpanes, The C 24-tetracyclic terpane and monoaromatic steroid hydrocarbons to biodegradation indicate that the distributions of these compounds are well suited to serve as correlation parameters in heavily altered samples. It was also observed in this study that the main ring structure of the porphyrin molecule was not affected by these very high levels of biodegradation. Previously hypothesized changes in porphyrin structure, due to biodegradation, have included n-alkyl side chain cleavage and possible conversion from DPEP- to ETIO-type porphyrins. An investigation has also been made with an active seep collected from Sulphur in the Anadarko Basin, Oklahoma and the results show that the relative rate of biodegradation of various classes of biomarkers differs between these two locations, although it was proposed that the original oil responsible for these two seeps is derived from the same source rock formation.

A biomarker study of petroleum from the Neogene Tertiary sedimentary basins in Northeast Japan.

Crude oils and condensates from the Japanese Neogene Tertiary sedimentary basins were analyzed for steroid and triterpenoid hydrocarbons, using GC/MS. Most crude oils show incomplete side chain epimerization of C29 steranes. This is possibly due to an insufficient reaction time and temperature for epimerization since the Miocene age. All oils show a good correlation between nuclear isomerization and side chain epimerization of C29 steranes. The correlation curve appears to be different from that previously reported, which may have resulted from a difference in thermal histories. On the basis of the extents of side chain cleavages of saturated and triaromatic steroid hydrocarbons as well as upon the extents of configurational isomerizations of steranes and hopanes, the condensates are considered to be distinctly maturer than the crude oils. This fact suggests that the condensates have undergone higher temperatures than the crude oils. Among the crude oils, those from the Niigata basin are significantly maturer than those from the Akita-Yamagata basin. This is probably due to the difference between the oil source rocks in the two basins, which may cause a difference in the stage of primary migration of oils. The conversion of monoaromatic to triaromatic steroid hydrocarbons does not correlate well with the side chain epimerization of steranes. This may be due to preferred migration of monoaromatics by geochromatographic separation. There is a significant difference between the crude oils from the Niigata basin and those from the Akita-Yamagata basin in respect of the C27/C29 ratios of steroid hydrocarbons. This difference is consistent with the previous report on visual kerogen compositions of oil source rocks from these basins. The relative abundance of C27 to C29 of monoaromatic steroid hydrocarbons is thought to be less affected by thermal stress than that of steranes. This could thus be a more useful organic source indicator in the case off matured oils such as condensates in Japanese Tertiary sedimentary basins.

Geochemical Study of Oils, Source Rocks, and Tar Sands in Pauls Valley Area, Anadarko Basin, Oklahoma: ABSTRACT

An organic geochemical study of numerous oils and source rocks from the Anadarko basin has been undertaken in an attempt to determine the number of genetically related families of oils in the Pauls Valley area of the Anadarko basin, in addition to determining the potential source rocks for these oils. In the study area it was found that, of the oils examined, there were basically two families of oils. The majority of oils examined from the Oil Creek, Bromide, Hunton, and other sands appeared to have a similar source which appeared to be the Woodford Shale. A smaller and distinct group of oils appeared to be source and reservoired in the Viola Limestone. The correlations were made by determination of the various classes of biomarkers in the oils and source rock extract. The compounds examined included n-alkanes, isoprenoids, steranes, hopanes, and monoaromatic steroid hydrocarbons. The distributions of these compounds will be discussed in addition to the way in which the data are used to make the above-mentioned correlations. In the course of this study, a number of tar-sand samples in Upper Mississippian tar sands from Carter County, Oklahoma, were also examined in some detail. These samples were of particular interestmore » since they presented an opportunity to study samples that had been biodegraded to differing degrees. Hence several classes of biomarkers, namely alkanes, steranes, hopanes, mono and tri-aromatic steranes, and porphyrins, were analyzed from these different tar sands. The aims of the study were two-fold, with the first being to study the in-situ effects of progressive biodegradation on a series of samples derived from the same source. The second was to determine the origin of the oil responsible for the tar sands.« less

長岡周辺新第三系ガス田の生物指標化合物

Cuttings materials from Katagai Gas Field in the vicinity of Nagaoka City, Niigata Prefecture, were analyzed for biological markers (triterpenoid and steroid hydrocarbons) in order to evaluate their validity as maturity indicies, with the following results.(1) Isomerization of both steranes and triterpanes are recognized from immature to oil generation zone.(2) The most reliable criteria in the immature zone and the oil generation zone are inferred to be the isomerization of hopane nucleus and the epimerization of stigmastane side chain, respectively.(3) Change of monoaromatic steroid hydrocarbons into triaromatics seems to occur from the immature to oil generation zone.(4) Cracking reactions in the side chains of C26, 27, 28-triaromatic steroid hydrocarbons into C20, 21-triaromatics appear to take place from the late stage of oil generation zone to the overmature zone. This reaction may be useful as a maturity index of crude oils or gas condensates, which cannot be measured for vitrinite reflectance.

Effects of thermal maturation on steroid hydrocarbons as determined by hydrous pyrolysis of Phosphoria Retort Shale

Hydrous pyrolysis experiments on the Phosphoria Retort Shale generate bitumen extracts and expelled oils that have steroid hydrocarbons with m/z 217-, 231-, and 253-mass Chromatographic distributions that are similar to those of bitumens and crude oils in the natural system. These experiments agree with the natural observations that diasteroid hydrocarbons increase relative to their regular counterparts with increasing thermal stress, while their C 27 through C 29 proportionality shows a slight enrichment in C 27. Relative concentrations of 20S to 20R configurations of 24-ethyl-14α,17α-cholestane show the expected increase with increasing thermal stress into the early part of the primary oil generation stage, but thereafter decrease with increasing thermal stress. If this reversal is found in high maturity sections of the natural system, the utility of this transformation as a maturity index will be limited. Triaromatic- to monoaromatic-steroid hydrocarbon concentrations increase with increasing thermal stress as observed in the natural system. Preferred migration of monoaromatic steroid hydrocarbons from bitumen extracts to expelled oils places considerable doubt on currently employed kinetic models for this aromatization reaction. As in the natural system, the experiments show relative concentrations of low-molecular weight- to high-molecular weight-triaromatic steroid hydrocarbons to increase with increasing thermal stress. Assuming a first-order reaction rate, the apparent activation energy and pre-exponential factor for this apparent side-chain cleavage reaction are 175.59 kJ mol −1 and 2.82 × 10 13 hr −1, respectively. These kinetic parameters are geologically reasonable and are similar to those for the overall generation of expelled oil.

Novel rearranged ring C monoaromatic steroid hydrocarbons in sediments and petroleums

Two series of novel rearranged ring C monoaromatic steroid hydrocarbons (C 21,C 22, C 27–C 29) occurring in sediments and petroleums have been characterised by synthesis of C 21 and C 27 homologues 1 and 2 .

Biological marker distribution and significance in oils and rocks of the Monterey Formation, California

The biological marker distributions of several oils, core extracts and solid bitumens of the Monterey Formation of California have been studied. Sterane, terpane and monoaromatic steroid hydrocarbons were analyzed in samples from the San Joaquin, Los Angeles, Ventura and Santa Maria Basins. The sterane patterns of both oils and extracts are characterized by 1. (a) low relative concentrations of diasteranes, 2. (b) low 20S/20R-5α,14α,17α-ethylcholestane ratios, 3. (c) relatively high concentrations of cholestane ( vs. methyl- and ethylcholestane) isomers. San Joaquin Basin samples contain significant amounts of the 5β isomer, which is generally absent in samples from other basins. The carbon number distribution of 5α,14α,17α,20R steranes is similar for all oils, regardless of API gravity, depth or basin location, and is suggestive of open marine depositional conditions for the source material involved. 17α(H),l8α(H),21β(H)-28,30-Bisnorhopane is present in almost all samples. Certain San Joaquin Basin oils and extracts contain 1. (a) a series of 25-nor hopanes, including 25,28,30-trisnorhopane, 2. (b) a distinctive monoaromatic steroid hydrocarbon distribution, 3. (c) an aliphatic hydrocarbon fraction devoid of n-paraffins. Biological marker characteristics suggest that the Monterey oils examined originated early in the maturational sequence, from elastics-poor source material. API gravities of the Monterey Formation oils examined vary monotonically with 1. (a) bisnorhopane/hopane ratios, 2. (b) aromatized/regular sterane ratios and 3. (c) the concentration of monoaromatized steranes relative to terpanes and regular steranes. These oil gravity correlations exist regardless of sample depth or basin location.

Synthesis of ring C monoaromatic steroid hydrocarbons occuring in Geological samples

Several series of ring C monoaromatic steroid hydrocarbons (C 21, C 22, C 27-C 29) widespread in sediments and petroleums have been identified by synthesis of the C 21, C 22 and C 27 homologues ( 1 - 3 ) obtained by reductive alkylation of the corresponding cyclopentanophenanthrenes.

Isomerization and Aromatization of Hydrocarbons and the Paleothermometry and Burial History of Alberta Foreland Basin

The hydrocarbon fractions extracted from 34 Cretaceous shales from a cross section of the Alberta basin have been analyzed using gas chromatography-mass spectrometry. Particular attention has been paid to the extents to which three temperature-dependent geochemical reactions have occurred: isomerization of steranes at C-20; isomerization of hopanes at C-22; and aromatization of C-ring monoaromatic steroid hydrocarbons. Estimates of the kinetic constants of these reactions have been published previously; therefore, constraints may be put on the maximum temperature experienced by the sediments and the time for which this temperature existed. The subsidence history of the Alberta basin is simulated using a lithospheric flexural model in which the lithosphere is downwarped by the loading of overthrusts in the adjacent Cordilleran orogene. When overthrusting ceases, erosion of the overthrusted region lightens the load and the lithosphere rebounds, causing uplift and erosion of the foreland basin. Major overthrusting and therefore deep burial occurred during the Laramide orogeny of Late Cretaceous to mid-Tertiary time. The extent of chemical reactions suggests that the present maturity of the Cretaceous shales is almost entirely a reflection of burial and heating during the Laramide orogeny in a manner that is consistent with the lithospheric flexural model for the basin. The chemical reactions suggest that the paleogeothermal gradient increased systematically away from the foothills of the Rocky Mountains along the profile studied. That a similar trend exists today suggests this situation has persisted at least since the early stages of the Laramide orogeny. This variation is best explained by advective heat transfer. Water entering the basin in the faulted and topographically higher foothills is heated at depth, thereby depressing the geothermal gradient. This hot water then migrates updip and away from the foothills to enhance the geothermal gradients in the Edmonton area and beyond. The route of the migrating hot water is similar to that taken by hydrocarbons from Devonian and Cretaceous source rocks in the deep basin, updip to the oil and tar-sand accumulations of Alberta.

A biological marker study of coals, shales and oils from the Mahakam Delta, Kalimantan, Indonesia

The distributions of steroidal and triterpenoidal alkanes and aromatic hydrocarbons and, where appropriate, triterpenoid alkenes and ketones, in nine oils, nine coals and three shales from the Mahakam Delta have been examined by gas chromatography-mass spectrometry. In all of the fractions there are high relative abundances of components of higher-plant origin, in keeping with the previous assignment of the organic matter in Mahakam sediments as type III. Comparison of molecular maturity measurements for the sediments and the oils extends earlier ideas that the source for the Handil oils must have a present depth of at least 3000 m. No major difference was observed here in the maturity (based on the molecular measurements) measured for coal-shale pairs with similar burial depths. In the oils, variations in the relative abundances of the monoaromatic steroid hydrocarbons relative to the triaromatic steroid hydrocarbons, taken with the results of earlier studies of the oils, have been ascribed tentatively to a migration effect.

Laboratory simulation studies of steroid aromatisation and alkane isomerisation

Laboratory heating experiments have been carried out using a mixture of isomeric C 27 monoaromatic steroid hydrocarbons and 6(R), 10(S) pristane as organic substrate, each on a different sediment matrix. Under free radical conditions in the presence of elemental sulphur triaromatic steroid hydrocarbons and the 6(R), 10(R) and 6(S), 10(S) isomers of pristane were formed, respectively. Both the aromatisation and isomerisation reactions follow pseudo-first-order kinetics and rate constants have been measured. A qualitative investigation of the isomerisation of 5α(H)-cholestane shows that a complex mixture of C 27 isomeric steranes is formed.