Organic Geochemistry最新文献

{"title":"Three major types of trimethyl-alkylbenzenes and significance for the genesis of reservoir bitumens from the northwestern Sichuan Basin, South China","authors":"Mingyue Tao , Susu Wang , Wanglu Jia , Yongge Sun , Lian Jiang , Jian Chen , Ping’an Peng","doi":"10.1016/j.orggeochem.2025.104997","DOIUrl":"10.1016/j.orggeochem.2025.104997","url":null,"abstract":"<div><div>Trimethyl-alkylbenzenes in oil are an important class of molecular marker for determining biological sources, source rock depositional environment and maturity. They can be classified into three major types based on the type of side chain, including trimethyl-isoprenoid-, trimethyl-isohexyl-, and trimethyl-<em>n</em>-alkyl-benzenes. Although they have been studied separately for many years, recent studies have elucidated complicated co-elution of trimethyl-isoprenoid-benzenes and trimethyl-<em>n</em>-alkyl-benzenes on commonly used chromatographic columns. Moreover, simultaneous detections of these three types of trimethyl-alkylbenzenes were rarely reported. Reservoir bitumens, widely distributed along the northwestern margin of the Sichuan Basin, exhibit maturity characteristics that provide crucial insights for regional petroleum exploration in this ancient, giant petroliferous basin. So far, there has been no report on detection of these compounds from these reservoir bitumens, which may have suffered from severe biodegradation resulting in challenges to the understanding of genesis of these bitumens. In this study, asphaltenes, which are resistant to biodegradation, were carefully examined and asphaltene-bound hydrocarbons were compared to free hydrocarbons for the distribution of trimethyl-alkylbenzenes. Three main conclusions were drawn. Firstly, three major types of trimethyl-alkylbenzenes were detected through comparisons with available standards and well-characterized oils. These are 2,3,6-trimethyl-aryl isoprenoids (2,3,6-TMIPBs), 2,3,6-trimethyl-isohexylbenzene (2,3,6-TMiHB, C<sub>15</sub>), and trimethyl-<em>n</em>-alkylbenzenes (TMnABs, mainly 2,4,5-/2,3,5-, 2,3,6-, 2,3,4-trimethyl series), which show significant differences in concentrations for both free and asphaltene-bound hydrocarbons. Secondly, four groups of reservoir bitumens having distinct isotopic compositions also show large differences in the distributions of 2,3,6-TMIPBs and 2,3,6-TMiHB, providing further constraints on both biological sources and depositional environments for their source rocks. For the major group mainly sourced from the upper Ediacaran to lower Cambrian source rocks, abundant 2,3,6-TMIPBs and isorenieratane were detected. This finding, combined with global distributions of multiple kinds of C<sub>40</sub> aromatic carotenoids (isorenieratane, chlorobactane, okenane) in the upper Ediacaran to lower Cambrian source rocks and their generated oils, indicates that photic zone euxinia was prevalent in ancient oceans, which may be of great significance for biological evolution in this key geological period. Thirdly, the ratios of 2,3,6-TMIPBs and 2,3,6-TMiHB to TMnABs have suggested subtle differences in the maturity of free hydrocarbons and asphaltenes, which can be used to reveal complex genetic processes for these bitumens, including at least two oil charging phases, different degrees of secondary cracking of asphaltenes mainly from early charg","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"205 ","pages":"Article 104997"},"PeriodicalIF":2.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating pressure effects on oil stability in deep-buried strata via chemical kinetics","authors":"Jun Shi ,&nbsp;Hua Wang ,&nbsp;Huajun Gan ,&nbsp;Zhao-Wen Zhan ,&nbsp;Yun Li ,&nbsp;Wenmin Jiang","doi":"10.1016/j.orggeochem.2025.104992","DOIUrl":"10.1016/j.orggeochem.2025.104992","url":null,"abstract":"<div><div>The effect of pressure on the oil stability in reservoirs, particularly in deep to ultra-deep strata, is a topic of significant interest. A series of crude oil cracking experiments were conducted in closed gold-tube pyrolysis systems under compressible and incompressible conditions without added water to quantitatively investigate this phenomenon. Crude oil samples with a thermal maturity of 0.74% <em>R</em>o were heated from 354 ℃ to 600 ℃ at rates of 2 ℃/h and 20 ℃/h. Constant confining pressures of 50 MPa and 100 MPa were maintained throughout the experiments. Additionally, experiments were conducted at programmed temperatures corresponding to thermal maturities of 1.0% EasyRo (380 ℃), 1.5% EasyRo (420 ℃), and 2.1% EasyRo (454 ℃), with heating rates of 2 ℃/h, and under two variable fluid pressures of approximately 50 MPa (ranging from 0 to &gt;50 MPa) and approximately 100 MPa (ranging from 0 to &gt;100 MPa). The results indicate that confining pressure has a marginal impact on the hydrocarbons generation and cracking. Whereas, the fluid pressure initially promotes cracking reactions and subsequently exerts a retardation effect. This was demonstrated by the variations in alkane yields (methane, C₂–C₅, C₆–C₁₂, and C₁₃₊ hydrocarbons). A kinetic analysis shows that the temperatures required for 51% and 62.5% conversion levels of liquid hydrocarbons vary marginally (by 1–5 ℃). This indicates that from a chemical kinetics perspective, pressure has a marginal impact on oil stability compared with temperature. This study introduces a novel approach to investigate the effects of pressure on oil stability and to elucidate the complex dynamics process of hydrocarbon reactions under varying pressure conditions in deep-ultra-deep reservoirs.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"205 ","pages":"Article 104992"},"PeriodicalIF":2.6,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determining carbon isotopic compositions of benzothiophenes and dibenzothiophenes in crude oils and potential geochemical implications","authors":"Yili Mao ,&nbsp;Ke Du ,&nbsp;Xiaofeng Xia ,&nbsp;Zhiwei Gao ,&nbsp;Qilin Xiao ,&nbsp;Quan Shi ,&nbsp;Yongge Sun","doi":"10.1016/j.orggeochem.2025.104944","DOIUrl":"10.1016/j.orggeochem.2025.104944","url":null,"abstract":"<div><div>Benzothiophenes (BTs) and dibenzothiophenes (DBTs) are an important organic sulfur compounds (OSCs) in crude oils, primarily as proxies for thermal maturity and secondary alteration, though their biological sources and depositional environments remain debated. Compound-specific stable carbon isotopic measurements could provide new insights into their origins. In this study, we employed improved methylation/demethylation reactions for selective separation of thiophenic and sulfidic compounds from crude oils to measure the stable carbon isotopic compositions of individual BTs and DBTs. Experiments with model compounds show no significant isotopic fractionation of BTs and DBTs through entire procedure, while small fractionation occurs for sulfidic compounds. Pre-removal of alkanes and additional purification by alumina column chromatography effectively reduced co-elution interference, enhancing the accuracy of isotopic measurements. To demonstrate the method’s applicability, two crude oils from Chinese petroliferous basins were analyzed, integrating δ³⁴S values of individual DBTs. In the low maturity, non-biodegraded lacustrine oil, the DBTs exhibit highly ¹³C-depleted values (av., −35.2 ‰) compared to oil fractions and non-sulfurized individual organic compounds. With the exception of 1-methyldibenzothiophene (−29.1 ‰), the BTs are enriched in ¹³C relative to DBTs by up to ∼5.5 ‰, suggesting the distinct organic sources. In the biodegraded marine oil, although a small discrepancy in δ¹³C values (∼1 ‰) remains, similar δ¹³C values of oil components indicate a shared source, as shown by δ¹³C values of pristane (–33.0 ‰) and phytane (–33.7 ‰). δ³⁴S values of individual DBTs (21–23 ‰) suggest a common source for organic sulfur given its moderate maturity (equivalent vitrinite reflectance of ∼0.9 %<em>R_equ</em>). While OSCs formation in oils from the Tarim Basin is attributed to the incorporation of TSR-H₂S into labile compounds in biodegraded oils, we propose that OSCs in these oils form mainly from sulfur re-incorporation, followed by cyclization and/or aromatization into functionalized aromatic and alkyl cyclohexane compounds at the early stage of diagenesis. This leads to similar carbon and sulfur signatures in BTs and DBTs. Therefore, successful carbon isotope measurements of individual BTs and DBTs could provide new insights into their sources and formation pathways, and application limitations. Future studies on samples from diverse geological settings could further demonstrate the methods potentials.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"205 ","pages":"Article 104944"},"PeriodicalIF":2.6,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel protocol for extracting 3-hydroxy fatty acids from soil with microwave-assisted acid digestion","authors":"Ting Chen ,&nbsp;Canfa Wang ,&nbsp;Zhiguo Li ,&nbsp;Huan Yang ,&nbsp;Yi Yang ,&nbsp;Shucheng Xie","doi":"10.1016/j.orggeochem.2025.104988","DOIUrl":"10.1016/j.orggeochem.2025.104988","url":null,"abstract":"<div><div>In recent years, bacterial 3-hydroxy fatty acids (3-OH-FAs) have gained increased interest in paleoclimate reconstruction due to their ubiquitous distributions and potential as paleoclimate proxies in palaeo- and modern environmental samples. However, the current extraction method for 3-OH-FAs is time-consuming and not feasible for samples with low lipid concentrations, which greatly hinders the broad application of 3-OH-FA-based proxies. Therefore, it is vital to improve the extraction method to shorten the extraction time and increase the extraction efficiency and stability. Here, we report a novel extraction protocol with microwave-assisted acid digestion for 3-OH-FAs extraction. The operating conditions (such as HCl concentration, heating temperature, and irradiation time) of this novel protocol are optimised via orthogonal array experimental design by analysing 3-OH-FAs from surface soil samples collected from Mt. Yujia, central China. The optimum digestion condition is recommended to be 3 mol/L HCl heated at 130 °C for 55 min. The yield of 3-OH-FAs obtained by the optimised microwave-assisted acid digestion method is about twice as much as that of the traditional acid digestion method, with relatively better reproducibility. Moreover, we re-treated the same soil samples previously reported by <span><span>Wang et al. (2021)</span></span> with the optimised microwave-assisted acid digestion method and found that the distribution of 3-OH-FAs and calculated 3-OH-FA-based proxies are identical to those extracted by the traditional acid digestion method. Furthermore, a comparative investigation was conducted on other lipids, such as <em>n</em>-alkanes, fatty acids (FAs), and glycerol dialkyl glycerol tetraethers (GDGTs), among several prevalent methods, including ultrasonic extraction, accelerated solvent extraction, conventional microwave-assisted extraction, traditional acid digestion and microwave-assisted acid digestion established in this study. Our findings show that different extraction methods may produce varying amounts of lipids and values of lipid-based proxies. Consequently, the differences caused by different extraction methods should be considered in comparison and palaeoclimate reconstruction.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104988"},"PeriodicalIF":2.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exceptionally high contents of rearranged hopanes in a late Permian section, southern Sydney Basin, Australia","authors":"Inna Kampoli,&nbsp;Simon C. George","doi":"10.1016/j.orggeochem.2025.104986","DOIUrl":"10.1016/j.orggeochem.2025.104986","url":null,"abstract":"<div><div>A suite of 19 late Permian–early Triassic outcrop samples from the southern Sydney Basin were analysed by gas chromatography-mass spectrometry. Three series of rearranged hopanes were identified in the samples: 18α(H)-neohopanes, 17α(H)-diahopanes, and the early-eluting 9,15-dimethyl-25,27-bisnorhopane homologues. There is very large variability in the relative abundance and distribution of rearranged hopanes compared to the 17α(H)-hopanes between samples. There is one group of samples, associated with the “dead zone” after the Permian-Triassic mass extinction event, and deposited above the uppermost coal seam, where rearranged hopanes are not present, while in other samples their abundance is very high, and the C₃₀ diahopane/C₃₀ αβ hopane ratio reaches 93. No dependency on thermal maturity or depositional water salinity were observed, and there is no correlation between the presence and distribution of rearranged hopanes and diasteranes. There is a positive correlation between the presence of monomethylalkanes, interpreted to be associated with cyanobacterial input, and a high relative abundance of rearranged hopanes. The samples with the highest relative abundances of rearranged hopanes and monomethylalkanes are from the Tongarra Coal at Austinmer Beach, where three coal seams are separated by laterally-continuous pale-coloured ash-fall tuffs. The high abundance of terrigenous organic matter, deposited under fresh water sub-oxic conditions, together with extensive volcanic activity, may be the main factors contributed to the formation and enrichment of these exceptional amounts of rearranged hopanes in the Sydney Basin.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104986"},"PeriodicalIF":2.6,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of novel sulfur-containing petroporphyrins in a natural bitumen: Potential biomarkers for aerobic organisms","authors":"Fang Zheng ,&nbsp;Weisheng Yang ,&nbsp;Yanbin Wang ,&nbsp;Mi An ,&nbsp;Da Huo ,&nbsp;Chunyan Wang ,&nbsp;Qing Cao ,&nbsp;Jing He ,&nbsp;Quan Shi ,&nbsp;Yongge Sun","doi":"10.1016/j.orggeochem.2025.104987","DOIUrl":"10.1016/j.orggeochem.2025.104987","url":null,"abstract":"<div><div>In this study, a serial of novel sulfur-containing petroporphyrins were identified in a natural bitumen by chemical derivatization and solvent extraction. In contrast to previously reported sulfur-containing petroporphyrins, the new petroporphyrins exhibit reduced unsaturation and are characterized by a reduced number of double-bond equivalences (number of rings plus double bonds). Molecular structures of these sulfur-containing petroporphyrins were further elucidated by multiple collision-induced dissociation in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicate that sulfur atoms are present as cyclic thioether on the side chain of porphyrin, suggesting that these compounds may have evolved from <em>heme</em> <strong><em>a</em></strong> or <em>heme</em> <strong><em>o</em></strong> in aerobic organisms. We thereby propose a potentially diagenetic pathway of these compounds. Due to the relative stability of cyclic thioethers in the porphyrin structure, potential geochemical information could be carried by these compounds, which warrants further investigation.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104987"},"PeriodicalIF":2.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nanometer-scale relationships between sedimentary organic matter molecular composition, fluorescence, cathodoluminescence, and reflectance: The importance of oxygen content at low thermal maturities","authors":"Aaron M. Jubb ,&nbsp;Paul C. Hackley ,&nbsp;Ryan J. McAleer ,&nbsp;Jing Qu","doi":"10.1016/j.orggeochem.2025.104990","DOIUrl":"10.1016/j.orggeochem.2025.104990","url":null,"abstract":"<div><div>Molecular characterization of sedimentary organic matter (SOM), termed macerals, is a common goal when seeking to understand petroleum generation as well as other geologic processes in deep time. However, unambiguous measurement of discrete macerals is challenging due to the small size of organic particles in sedimentary rocks, the proximity of different organic matter types to one another, mineral-organic matter interactions, and maceral mixing that occurs during SOM isolation prior to ex situ analysis. The recent advent of infrared spectrometers capable of nanometer-scale resolution and the application of these technologies to geologic samples has enabled advances in rapid, in situ molecular characterization of SOM allowing for insights into paleoenvironmental processes, such as organic matter productivity and preservation, among others. Here we employ one such technology, optical photothermal infrared (OPTIR) spectroscopy, to map SOM functional group distributions at 500-nm resolution in a sample from the Lower Cretaceous Sunniland Limestone of the South Florida Basin. Examined fields of view include occurrences of amorphous organic matter (AOM), inertinite, micrinite, solid bitumen, telalginite, and vitrinite. OPTIR data from these macerals are compared against traditional organic petrographic data from the same organic grains including fluorescence intensity and white light reflectance as well as against cathodoluminescence response, an emerging organic petrographic approach. Maceral oxygen content (using carbonyl functional group abundance as a proxy) is observed to vary widely between maceral types but correlates strongly with fluorescence and cathodoluminescence intensity as well as against reflectance. These findings highlight the important role that oxygen content plays in determining the optical properties of SOM and further demonstrate the ability of OPTIR to discriminate subtle molecular differences between SOM types.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104990"},"PeriodicalIF":2.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical inconsistencies in the measurement and reporting of IP25, IPSO25 and related biomarkers for paleo sea ice reconstruction","authors":"Simon T. Belt ,&nbsp;Lukas Smik","doi":"10.1016/j.orggeochem.2025.104989","DOIUrl":"10.1016/j.orggeochem.2025.104989","url":null,"abstract":"<div><div>IP₂₅ and related biomarkers are commonly used for Arctic and Antarctic sea ice reconstruction. With a growing number of laboratories performing their measurement, we reviewed many publications spanning the period 2007–2024 in order to assess analytical rigour. We found a number of common shortfalls in analytical protocols, or at least how they are reported, which may have important implications for future synthesis studies and meta-data analyses. Here, we outline some of these shortcomings and provide suggestions of how to improve both data acquisition and reporting.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104989"},"PeriodicalIF":2.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143724185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry Articles – January 2025","authors":"","doi":"10.1016/j.orggeochem.2025.104984","DOIUrl":"10.1016/j.orggeochem.2025.104984","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104984"},"PeriodicalIF":2.6,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry Articles – February 2025","authors":"","doi":"10.1016/j.orggeochem.2025.104985","DOIUrl":"10.1016/j.orggeochem.2025.104985","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"204 ","pages":"Article 104985"},"PeriodicalIF":2.6,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}