Marine and Petroleum Geology最新文献

{"title":"Do red marine carbonates represent oxic environments? New understanding from the Upper Ordovician marine limestone in Tarim Basin, China","authors":"Mu Liu ,&nbsp;Daizhao Chen ,&nbsp;Haoran Ma ,&nbsp;Yi Ding","doi":"10.1016/j.marpetgeo.2024.107166","DOIUrl":"10.1016/j.marpetgeo.2024.107166","url":null,"abstract":"<div><div>Marine red beds (MRBs), typically colored by Fe- and Mn-rich minerals, are often interpreted as indicators of bottom water oxygenation. However, their continuous formation requires long-term input of aqueous derived Fe-Mn oxides and/or stable sources of Fe²⁺ and Mn²⁺ ions, challenging the traditional concept of “red equals oxic environment.” This study investigates two coeval Upper Ordovician Sandbian MRB carbonate intervals in the Tarim Basin. Previous studies attributed the pigment origin to hematite. Th/U values and total rare earth element and yttrium (REY) contents increased in the MRB interval, indicating a terrestrial source of iron. Hematite was observed within the intercrystal pores of calcite precipitating from porewater, consistent with high Ni_carb abundance and MREE-enriched bulge pattern in the red intervals. Both sections exhibit high Fe_carb and Mn_carb, pointing to substantial reductive dissolution of Fe and Mn oxides. Simulation shows that isotopic discrimination (Δ¹³C) between carbonate and organic carbon could be biased by increasing benthic Fe-Mn flux, leading to decreased Δ¹³C values in MRB intervals. Ce/Ce∗ values in the high-Mn_carb interval reflect the releasing of Ce by reductive dissolution of Mn oxides. The commonly used carbonate-based redox proxy I/(Ca + Mg) ratio is correlated positively with Mn_carb in the shallower section and with TOC in the deeper section, while it is negatively correlated with TOC in the shallower horizon, suggesting that iodine behavior may be influenced by adsorption and releasing of Mn hydro-oxides and organic matter besides oxygen contents. This study links MRB coloring to Fe and Mn mineral cycling in pore water through reductive dissolution and oxidative precipitation, and highlights potential biases of carbonate-based redox proxies that might be susceptible to other electron acceptors/donors such as Fe-Mn oxides and organic matter, in addition to free oxygen in seawater.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107166"},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled evolution of basin structure and fluids recorded by microfractures: A case study of deep-buried ordovician in the tarim basin","authors":"Jian Wang ,&nbsp;Dongping Tan ,&nbsp;Yingchang Cao ,&nbsp;Jun Han ,&nbsp;Haijun Yang ,&nbsp;Yin Liu ,&nbsp;Keyu Liu","doi":"10.1016/j.marpetgeo.2024.107161","DOIUrl":"10.1016/j.marpetgeo.2024.107161","url":null,"abstract":"<div><div>The fluid activity in the deep strata of sedimentary basins is commonly related to tectonic activity, and the cements filled in fractures are a good carrier for the tectonic-fluid coupling evolution. Compared to macrofractures, microfractures have characteristics of high frequency and easy identifiable periods. Abundant microfractures infilled by carbonate cements (MCCFs) developed in carbonates of the Ordovician Yingshan and Yijianfang formations in the platform basin area of the Tarim Basin. Based on the study of petrology, U-Pb dating, and geochemical characteristics, this study determined the stages of MCCFs and clarified the tectonic-fluid coupling evolution process recorded by MCCFs in the study area. The formation order of these MCCFs is D1, C1, C2, D2, C3, and C4. The precipitation times of MCCFs have a good correspondence with orogeny around the Tarim Basin and active times of strike-slip faults in the platform basin area. The six stages of MCCFs in the Ordovician Yingshan and Yijianfang formations in the SLU recorded the tectonic-fluid coupling evolution process of concentrated seawater in the late Middle Ordovician, meteoric water at late Ordovician, organic acids during the Silurian, Mg-rich hot brine at the end Devonian-early Carboniferous, and magmatic hydrothermal fluids during the Permian. This not only indicates a close connection between fluid activity and tectonic activity in sedimentary basins, but also confirms that the formation of MCCFs in carbonate formations is closely related to regional tectonic-fluid coupling activities. This study provides a good example for studying macro scale tectonic-fluid coupling activities in basins using microfractures.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107161"},"PeriodicalIF":3.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The rare earth elements and yttrium (REY) geochemistry of the upper Carnian (Upper Triassic) carbonates from northwestern Sichuan Basin (South China)","authors":"Yixing Du ,&nbsp;Nereo Preto ,&nbsp;Alberto Zanetti ,&nbsp;Manuel Rigo ,&nbsp;Marco Franceschi ,&nbsp;Bao Guo ,&nbsp;Xin Jin","doi":"10.1016/j.marpetgeo.2024.107164","DOIUrl":"10.1016/j.marpetgeo.2024.107164","url":null,"abstract":"<div><div>Rare earth elements and yttrium (REY) serve as valuable tracers of the geochemical properties of paleo-seawater and diagenetic processes. Four different carbonate components, ooids, microbalites, cements and brachiopods, from upper Carnian (Upper Triassic) of the northwestern Sichuan Basin were analyzed for REY geochemistry. Petrographic and cathodoluminescence analyses were employed to identify diagenetic features. The bright luminescent microspar calcite cement, ooids and the microbialites from the lower part of Qingyangou (HWQ) section exhibit bell-shaped REY_SN patterns. Microbialites from the upper part of HWQ section have relatively high REY concentrations with a flat REY_SN pattern. The high content of ΣREY and terrigenous elements (e.g., Al, Zr, Th) in ooids and microbialites reflect the input of terrigenous clastic in the northwestern Sichuan Basin during Late Carnian. Articulated terebratulid brachiopods in the study area display a generally modern seawater-like REY_SN pattern. However, this pattern may be influenced by the presence of sparry cement that has infilled the cracks and punctae of the brachiopod shells. The ooids, microbalites, cements and brachiopods are unsuitable for reconstructing the REY characteristics of Carnian seawater in the northwestern Sichuan Basin due to diagenetic alteration and terrigenous input. This study also highlights the necessity of thoroughly evaluating carbonate components for diagenetic effects and terrigenous contamination when employing them for REY characteristic reconstruction.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107164"},"PeriodicalIF":3.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation for subsidence control in CO2 storage and methane hydrate extraction","authors":"Chico Sambo,&nbsp;Ipsita Gupta","doi":"10.1016/j.marpetgeo.2024.107160","DOIUrl":"10.1016/j.marpetgeo.2024.107160","url":null,"abstract":"<div><div>Gas hydrates are increasingly viewed as a promising alternative to traditional fossil fuels. However, their extraction process poses risks to structural integrity, potentially causing significant subsidence. In this study, we developed a Thermo-Hydro-Mechanical-Chemical (THMC) model to analyze the impact of gas hydrate extraction on seabed subsidence. Our investigation focused on the influence of bottom hole flowing pressure, initial hydrate concentration, gas saturation, permeability, porosity, and rock thermal conductivity on subsidence during gas hydrate extraction via depressurization.</div><div>The results show that seabed subsidence is affected by various factors such as bottom hole flowing pressure, initial hydrate concentration, gas saturation, permeability, porosity, and rock thermal conductivity. It was noted that significant subsidence is associated with low initial hydrate concentration, high permeability, porosity, low gas saturation, low rock thermal conductivity, and a notable pressure drop of 79.31%.</div><div>To address this issue, we propose a seabed subsidence mitigation strategy involving CO₂ injection. This approach not only safeguards offshore infrastructure and coastal communities but also helps reduce CO₂ emissions, aligning with global climate change mitigation efforts. In our model, CO₂ injection occurs in the subsurface reservoir at the interface between the free water zone and hydrate-bearing formations. The CO₂ hydrates formation process releases heat, which dissociates methane hydrates, allowing the methane to be replaced by CO₂ molecules and move towards the production well.</div><div>Our analysis reveals that increasing injection temperature and rate significantly reduces subsidence. Additionally, the range of investigated injection pressures, which included pressures equal to and more than double the initial reservoir pressure, showed inconsequential impacts on seabed subsidence.</div><div>The effectiveness of subsidence reduction is significantly enhanced by injecting a CO₂/N₂ mixture compared to pure CO₂ injection. The most substantial reduction in subsidence occurred when a mixture of CO₂ and N₂ in a 50/50 vol/vol ratio was injected at a high rate.</div><div>These findings offer crucial insights for optimizing the efficiency and control of gas hydrate extraction methods. They emphasize the importance of employing balanced injection strategies to minimize environmental risks and ensure sustainable energy extraction.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107160"},"PeriodicalIF":3.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inhomogeneous strain partitioning in the Cenozoic Bohai Bay Basin controlled by pre-existing crustal fabrics and oblique subduction: Insights from the Jizhong and Huanghua subbasins","authors":"Yumeng Su ,&nbsp;Wuke Chen ,&nbsp;Lei Wu ,&nbsp;Hongdan Deng ,&nbsp;Liguang Mao ,&nbsp;Chunxiao Wang ,&nbsp;Tinghui Li ,&nbsp;Wanfu Zhang ,&nbsp;Ancheng Xiao ,&nbsp;Hanlin Chen","doi":"10.1016/j.marpetgeo.2024.107156","DOIUrl":"10.1016/j.marpetgeo.2024.107156","url":null,"abstract":"<div><div>The tectonic features and geodynamics of the Bohai Bay Basin (BBB) have been extensively studied over several decades. It is generally accepted that the Cenozoic BBB was subjected to a superimposed extensional and strike-slip stress field. However, the specific basin-forming mechanism remains ambiguous. Basin-scale studies with high spatial and temporal resolution reveal how strain migrates and localizes during multiphase rifting. Understanding these strain-related processes is crucial for deciphering the formation mechanisms and controlling factors of rift basins. This study investigates the rift-related evolution and strain partitioning in the Jizhong and Huanghua subbasins, the western half of the BBB. Using high-resolution 3D and 2D seismic datasets and well data, we present detailed geological sections, residual thickness maps, and fault systems, showing two distinct patterns of strain partitioning in the Cenozoic. In the Jizhong Subbasin, strain migrated inwards from the NE-trending boundary faults and finally became localized along the NE-trending rift axis; in the Huanghua Subbasin, strain migrated northeastwards from the southern part and then was largely localized along the near E–W-trending faults in the northeastern part. By integrating our results with previous studies of other subbasins, we identify two separate extensional domains within the Cenozoic BBB. The suborthogonal extensional domain in the Jizhong Subbasin is dominated by relatively stable NW–SE extension. In contrast, the extended areas to the east (i.e., the Huanghua, Bozhong, and Liaohe-Liaodongwan subbasins) comprise the oblique extensional domain, characterized by asymmetric transtensional pull-apart deformation and subjected to a clockwise-rotated extensional stress field from NW–SE to NNW–SSE. We suggest that the spatially inhomogeneous strain partitioning in the BBB has developed since the middle Eocene, and was controlled by the interaction of pre-existing crustal fabrics (e.g., the Tan-Lu Fault Zone) and the oblique subduction of the Pacific Plate. The boundary between the two domains may represent a transition zone where the margin-parallel residual velocity component of the oblique convergence decreased considerably landwards. Our study highlights the Cenozoic strain evolution and the associated geodynamics in the BBB, emphasizing the strain complexity within the back-arc rift basin under the oblique subduction background.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107156"},"PeriodicalIF":3.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Triassic to present-day tectono-thermal history of the coastal part of the Asturian basin: Implications for hydrocarbon exploration and for the North-Iberian margin evolution","authors":"Hodei Uzkeda ,&nbsp;Josep Poblet ,&nbsp;Mayte Bulnes","doi":"10.1016/j.marpetgeo.2024.107158","DOIUrl":"10.1016/j.marpetgeo.2024.107158","url":null,"abstract":"<div><div>The Asturian Basin, situated on the North Iberian margin, is a Permian-Mesozoic extensional basin developed over a Variscan Palaeozoic basement, subsequently inverted during the Cenozoic Alpine orogeny. The compilation of cartographic, structural, biostratigraphic and vitrinite reflectance data collected in a Late Triassic-Jurassic succession, excellently exposed along the Cantabrian Sea coast, has allowed us to gain insight into the Mesozoic and Cenozoic tectono-thermal history of this basin. The oldest recorded event occurred in Middle-Late Jurassic times and consisted of uplift, development of a large syncline, and normal faulting accompanied by circulation of hydrothermal fluids along the faults. The basin emersion caused an angular unconformity, together with a change in the sedimentary environment that passed from marine to continental. A second event, whose age was probably Late Jurassic-Early Cretaceous, was responsible for extensional reactivation of previous normal faults accompanied by a weaker fault-related hydrothermal episode. In Cenozoic (Eocene-Miocene) times, as a consequence of the Alpine orogeny some of the previous faults were reactivated as reverse and/or strike-slip faults, and folds developed. Here we analyse which structures were active during each event, their relationship with the hydrothermal fluids, the control they exerted on the hydrocarbon generation, and how the large-scale models proposed for this portion of the North Iberian margin fit the onshore field observations, in particular regarding the structural position of the Asturian Basin within the Iberian Plate Mesozoic rifts and the role of the Ventaniella Fault.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107158"},"PeriodicalIF":3.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Petroleum system analysis of Fujairah basin, eastern offshore of the United Arab Emirates","authors":"Ahmed Abdelmaksoud ,&nbsp;Mohammed Y. Ali","doi":"10.1016/j.marpetgeo.2024.107157","DOIUrl":"10.1016/j.marpetgeo.2024.107157","url":null,"abstract":"<div><div>The Fujairah basin, located on the eastern margin of the United Arab Emirates, forms part of the hinterland basin of the Oman-UAE mountains. Despite its geological significance, the hydrocarbon potential of this basin remains unexplored. This study aims to address this knowledge gap by using 2D seismic reflection data, three exploration wells, geochemical data from one well, a 2D velocity section, and two pseudo-wells. The study began with the interpretation of the seismic profiles and then proceeded to create depth maps for the most significant units. We used Rock-Eval pyrolysis plots to identify the primary source rocks and to classify their kerogen types. The seismic interpretation formed a basis for the 1D and 2D basin modeling techniques that are used to determine the petroleum system of the basin. Our results identify the Pliocene, Miocene, and Eocene sequences as potential source rocks in the basin with TOC values less than 1 wt% and low expulsion efficiencies. The Pliocene and Miocene source rocks are mainly type-II kerogen, whereas most Eocene samples are characterized as type-III kerogen. The Pliocene and Miocene source rocks are immature in the basin. The Eocene is mature depending on the burial within the sub-basins. The Eocene started expelling hydrocarbons during the Burdigalian, which was linked to the collision of the Arabian and Central Iran plates along the Zagros suture zone. Structural and stratigraphic traps may have entrapped the generated hydrocarbons. The three drilled wells in the basin lack good reservoir rocks. However, low-velocity anomalies and bright spots indicate possible hydrocarbon accumulations in the basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107157"},"PeriodicalIF":3.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"A modified surface to volume (SVR) method to calculate nuclear magnetic resonance (NMR) surface relaxivity: Theory and a case study in shale reservoirs","authors":"Jinbu Li ,&nbsp;Min Wang ,&nbsp;Wanglu Jia","doi":"10.1016/j.marpetgeo.2024.107159","DOIUrl":"10.1016/j.marpetgeo.2024.107159","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Surface relaxivity (&lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt;) is a critical parameter for converting nuclear magnetic resonance (NMR) T&lt;sub&gt;2&lt;/sub&gt; data to pore size distribution (PSD). The surface-to-volume ratio (SVR) method, known for its simplicity and ease of operation, has been widely used for &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; calculation in unconventional reservoirs. However, previous studies often overlooked the equivalence of pore ranges characterized when directly applying the classical SVR model. Moreover, shale reservoirs generally develop layered fractures, whose &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; values are different from matrix pores. The logarithmic mean value of the T&lt;sub&gt;2&lt;/sub&gt; distribution (T&lt;sub&gt;2LM&lt;/sub&gt;) is significantly influenced by layered fractures, therefore, relying solely on the T&lt;sub&gt;2LM&lt;/sub&gt; value of a whole sample under fluid-saturated state will lead to inaccurate &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; values of matrix pores, particularly in laminated shales where fractures are well developed. However, insufficient attention has been paid to the effect of fractures on the &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; calculation. In this study, a modified SVR method based on the theory of NMR relaxation in partially fluid-saturated pores was proposed to characterize the &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; of shale matrix pores. Twenty-four shale core samples from the Shahejie Formation in the Jiyang Depression, China were selected, and subjected to series of NMR experiments at varying oil-bearing conditions, and low-temperature nitrogen adsorption (LTNA) analysis. The results indicate a strong linear correlation (&lt;em&gt;R&lt;/em&gt;&lt;sup&gt;2&lt;/sup&gt; &gt; 0.85) between the inverse T&lt;sub&gt;2LM&lt;/sub&gt; (1/T&lt;sub&gt;2LM&lt;/sub&gt;) and the inverse fluid saturation (1/&lt;em&gt;f&lt;/em&gt;) when oil molecules across the entire surface layer participate in the exchange process. For a whole core sample, &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; values obtained using the modified SVR model are higher than those obtained using the classical SVR model, especially in samples with numerous fractures. The modified SVR method effectively reduces the impact of fractures on the characterization of &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; of matrix pores. For shale pore &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; characterization, the classical SVR model may be more suitable for pores smaller than 300 nm, with a recommended T&lt;sub&gt;2&lt;/sub&gt; range of &lt;33 ms. Additionally, &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; values for different pore ranges (&lt;25 nm, 25–100 nm, and &gt;100 nm) within individual samples were estimated. It is found that the &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; values of smaller pores is greater than those of larger pores, which may be due to differences in mineralogy of the pores across various size ranges. The small pores are more associated with clay minerals while large pores are surrounded by quartz and rigid minerals. In addition, &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; is lower in larger pores and fractures that do not contain organic matter and clays, thus the underestimation of &lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;2&lt;/sub&gt; by the classical SVR met","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107159"},"PeriodicalIF":3.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface geochemistry as a key to understanding the petroleum system in regions of complex geology - Polish Outer Carpathians","authors":"Anna Twaróg ,&nbsp;Krzysztof Starzec ,&nbsp;Henryk Sechman ,&nbsp;Wojciech Schnabel","doi":"10.1016/j.marpetgeo.2024.107155","DOIUrl":"10.1016/j.marpetgeo.2024.107155","url":null,"abstract":"<div><div>The goal of the study is to investigate the relationships between soil gas composition and geological structures in a structurally complex area of the Carpathian fold and thrust belt. Surface geochemical surveys, aimed at determining the molecular and isotopic composition of soil gas samples, were carried out in the central part of the Polish Outer Carpathians in two major tectonic units, the Magura Unit and the Fore-Magura Group of units, which outcrop at the front of the former and within it as a tectonic window (the so-called Mszana Dolna Tectonic Window, MDTW). The tectonic structure of the area has numerous deformations, such as folds, thrusts, and strike-slip faults, that are accompanied by broad zones of mélange. In all 572 soil gas samples, the concentrations of light alkanes, gaseous alkenes as well as non-hydrocarbon (e.g. hydrogen) components were determined, and part of the samples were analysed to test the carbon isotope composition of methane and carbon dioxide.</div><div>The results of the surface geochemical survey showed significant differences in the recorded microconcentrations of hydrocarbons within the tectonic units of the Outer Carpathians. Significantly higher concentrations of total alkanes C₂-C₅ were mainly recorded in the MDTW, although the distribution of total alkane values within the Window shows strong connections with the arrangement of strata and the strike of faults and thrusts. Generally, the sealing is insufficient within the MDTW to support the existence of conventional economically viable hydrocarbon accumulations. Our data confirms the sealing role of the Magura Unit in the Carpathian oil system. Therefore, hydrocarbon sources (i.e. potential hydrocarbon accumulations) may be expected within the Fore-Magura Group beneath the cover of the Magura Unit.</div><div>Our results are also of key importance for the interpretation of surface geochemistry data in other oil and gas provinces with a complex geological structure.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107155"},"PeriodicalIF":3.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Organic geochemical characterization and hydrocarbon generation modeling of Paleozoic-Paleogene shales, Wadi Sirhan basin, south-eastern Jordan","authors":"Abdelrahman Qteishat ,&nbsp;Moataz El-Shafeiy ,&nbsp;Sherif Farouk ,&nbsp;Fayez Ahmad ,&nbsp;Khaled Al-Kahtany ,&nbsp;Thomas Gentzis ,&nbsp;Dina Hamdy","doi":"10.1016/j.marpetgeo.2024.107152","DOIUrl":"10.1016/j.marpetgeo.2024.107152","url":null,"abstract":"<div><div>The Wadi Sirhan Basin in Jordan originated from the Arabian Platform and served as a stable shelf during the Paleozoic era. The Lower Paleozoic-Eocene sequence in the Wadi Sirhan Basin contains numerous shales, found, in ascending order the Upper Ordovician Dubeidib, Lower Silurian Mudawwara, Maastrichtian Ghareb, Paleocene Taqiyeh, and Eocene Sara fms. These strata warrant investigation of their source-rock potential and hydrocarbon generation modeling, to precisely elucidate the timing of petroleum generation. To achieve this, datasets were utilized from various analytical approaches, including Rock-Eval pyrolysis, visual kerogen analysis, pyrolysis-GC, and lipid biomarker geochemistry. The aim of this study is to assess these source rocks regarding organic matter quantity and quality, paleoenvironmental implications, thermal maturity, and petroleum generation depth/time. The Lower Paleozoic Dubeidib and Mudawwara shales are identified as effective source rocks, containing kerogen types II, II-III, and III. A high proportion of well-preserved, weakly fluorescent amorphous organic matter suggests an origin from marine plankton-derived alginite in an oxygen-deficient setting. These formations reached the peak oil window during the Devonian (∼405-380 Ma) and Carboniferous (∼320-300 Ma). The Dubeidib Fm experienced late-stage oil generation during the Early Triassic (∼255-250 Ma), with a transformation ratio (TR) of 68%. The Ghareb Fm predominantly contains type II kerogen, while the Taqiyeh and Sara fms mainly contain type I kerogen with minor type II kerogen. Thermal maturity assessments using integrated parameters indicate that the Dubeidib and Mudawwara shales have entered the main phase of hydrocarbon generation, while the Ghareb, Taqiyeh, and Sara shales remain immature. Furthermore, analysis of biomarker ratios reveals the dominance of marine over terrestrial organic matter in the studied strata. These clay-rich sediments were deposited under reducing conditions, which further facilitated the rearrangement of steranes into diasteranes. The modeled TRs indicate the generation and subsequent expulsion of hydrocarbons, but the absence of suitable reservoirs and/or improper trapping system, owing to the major Hercynian unconformity, led to an incomplete petroleum system in the basin. Additional investigation is required to evaluate the potential of the Early Paleozoic shales as subsurface unconventional resources, considering parameters such as brittleness index and hydraulic fracturing. This study holds important implications for future hydrocarbon exploration and development in the Wadi Sirhan Basin. The insights gained from such investigations could help mitigate the risk of petroleum exploration failures in the Wadi Sirhan Basin, guiding future exploration and development efforts towards promising approaches.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107152"},"PeriodicalIF":3.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}