Marine and Petroleum Geology最新文献

{"title":"Isotopic equilibrium constraints on CO2 dissolution and carbon isotopic reversal in a thermogenic coalbed gas system associated with the Zhuzang syncline, Guizhou, China","authors":"Xiangrui Chen ,&nbsp;Yunpeng Wang ,&nbsp;Mingxin Tao ,&nbsp;Zheng Zhou ,&nbsp;Meng Wei","doi":"10.1016/j.marpetgeo.2025.107554","DOIUrl":"10.1016/j.marpetgeo.2025.107554","url":null,"abstract":"<div><div>Natural gas is a vital energy resource. The isotopic composition of natural gas plays a critical role in understanding its origin, thermal maturity, and secondary alteration. Both kinetic and equilibrium isotopic fractionations have been observed in various natural gas systems. However, the dominant mechanism (either equilibrium or kinetic) that controls the isotopic compositions of the primary natural gas is still unclear. Coalbed gas (CBG), formed and stored in situ coalbeds, is an ideal natural gas for studying this key issue. We collected CBG and coproduced water samples from the Zhuzang syncline in China. This study shows that the CBG is an over-mature thermogenic gas formed during the Yanshanian orogeny. The CH₄-C₂H₆-CO₂ system was likely near carbon isotope equilibrium during the CBG formation. However, later alterations, such as meteoric water recharge, CO₂ dissolution, and CBG recovery led to obvious isotopic disequilibrium of the CH₄-C₂H₆-CO₂-DIC (dissolved inorganic carbon) system. Carbon isotope reversals (δ¹³C_CH4 &gt; δ¹³C_C2H6) were observed in the CBG samples, resulting from decreasing δ¹³C_C2H6 values after CBG formation. Based on isotopic equilibrium, the δ¹³C values of the primary ethane were estimated. Some hypotheses often used to explain isotope reversals in natural gas cannot explain the isotope reversals of the CBG samples. We propose that the CBG recovery process led to more negative δ¹³C_C2H6 and thus δ¹³C_CH4 &gt; δ¹³C_C2H6. Model-estimated 53–99 % CO₂ generated during thermogenic or microbial CBG formation has dissolved into coalbed water to become DIC. Hence, dissolution trapping is an important mechanism for CO₂ storage in coalbeds over geological timescales. This study implies that isotopic equilibrium fractionation plays a vital role in understanding the primary geochemical composition and secondary alteration of CBG.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107554"},"PeriodicalIF":3.7,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144614855","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":"Genesis and developmental pattern of Middle Permian dolomite in Northwestern Sichuan, China","authors":"Zhidian Xi ,&nbsp;Fei Huo ,&nbsp;Huachuan Jiang ,&nbsp;Xingzhi Wang ,&nbsp;Huiwen Huang ,&nbsp;Yuhan Huang ,&nbsp;Yi Hu ,&nbsp;Xueyan Wu ,&nbsp;Yang Li ,&nbsp;Wenli Xu ,&nbsp;Anqing Chen","doi":"10.1016/j.marpetgeo.2025.107555","DOIUrl":"10.1016/j.marpetgeo.2025.107555","url":null,"abstract":"<div><div>The formation of large-scale dolomite reservoirs in the Middle Permian of Northwest Sichuan shares a good temporal correlation with the occurrence of major events in the Emeishan Large Igneous Province (ELIP). However, because the dolomitized fluids, the timing of dolomitization and the genesis mechanism of the dolomites are not comprehensively understood, its developmental pattern requires further analysis. This paper identified the diagenetic fluids of different types of dolomites via petrological characteristics of dolomites, carbon and oxygen isotopes, strontium isotopes, and other geochemical data, as well as fluid inclusions and laser U-Pb isotope dating. The dolomite genesis model related to the dynamical formation mechanism of the ELIP was also reconstructed. The Middle Permian dolomites in Northwest Sichuan are divided into matrix dolomite (Md) and cement dolomites (Cd). Importantly, the matrix dolomites include very finely to finely crystalline matrix dolomite (Md1), finely to medium crystalline matrix dolomite (Md2), and medium to coarsely crystalline matrix dolomite (Md3). The dolomites were primarily modified by three phases of dolomitizing fluids. The Md1 phase yields a U-Pb age of 262 ± 9.2 Ma, consistent with the host stratigraphic age, and exhibits ⁸⁷Sr/⁸⁶Sr ratios matching Permian seawater values. These features indicate Md1 formed dominantly through penecontemporaneous seawater reflux dolomitization. In contrast, the Md2 phase shows a U-Pb age of 261.3 ± 7.4 Ma—also stratigraphically consistent—but contains later-stage subsurface cements with a distinct U-Pb age of 245.7 ± 1.9 Ma. This significant age offset demonstrates that Md2 resulted from overprinting by multiple dolomitizing fluid phases. These fluids were mainly formed owing to the temperature difference between the warming stratigraphic water and the cold seawater in the ELIP under the geothermal warming effect. The cold seawater on the slope creates a fluid potential energy difference, generating lateral open circulation and causing thermal convection. Furthermore, Md3 and Cd have negatively skewed δ¹⁸O values, along with higher Th and Eu/Eu∗ values, suggesting that the diagenetic fluids were substantially shallow buried strata water, which resembled Permian seawater. They were mostly produced under the higher geothermal temperatures during the ELIP active period, which generated a substantial fluid potential energy difference, and were driven by a more rapid thermal convection cycle. This study quantitatively constrains the timing of dolomitization using laser U-Pb isotope dating, aiming to give a reliable and valuable reference for the impact of tectonic activities on dolomite genesis caused by the Large Igneous Province.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107555"},"PeriodicalIF":3.7,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633914","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":"Sequence stratigraphic and reservoir modeling of KOC Field onshore Niger Delta Basin: implication for mature oilfield revitalization","authors":"Amoke Aniebonam Ignatius ,&nbsp;Ayonma Wilfred Mode ,&nbsp;Ikechukwu Onyema Njoku ,&nbsp;Eze Martins Okoro","doi":"10.1016/j.marpetgeo.2025.107553","DOIUrl":"10.1016/j.marpetgeo.2025.107553","url":null,"abstract":"<div><div>Recently, the exploration focus in the onshore areas of the Niger Delta Basin has been targeted towards extending the economic viability of “shallow hanging” producing reservoir units whilst searching wider and deeper for new oil and gas pools beyond known depths. The need therefore arises to deploy improved technologies for accurate mapping of prospect opportunities located at intermediate and deeper intervals within the basin. In this study, integrated sequence stratigraphic and reservoir modeling of the KOC Field onshore Niger Delta Basin was carried out using well logs, 3D seismic, and biostratigraphic data to assess the hydrocarbon potentials and also uncover the reservoir geometry, stratigraphic configuration, and structural framework of the study area. Logging and biofacies information from seven (7) wells, as well as key stratal surfaces including three (3) sequence boundaries (SB) and three (3) maximum flooding surfaces (MFS) provided in Well 001 and Well 039, formed the basis for chronostratigraphic correlation across the field. Two genetic sequences bounded at the top and base by maximum flooding surfaces were mapped and designated as Genetic Sequence 1 (G_SEQ1) and Genetic Sequence 2 (G_SEQ2). Three main stacking patterns (progradational, retrogradational and aggradational) interpreted as Lowstand Systems Tract (LST), Highstand Systems Tract (HST) and Transgressive Systems Tract (TST) were delineated from each of the identified genetic sequences. Lithological correlation of the wells revealed two hydrocarbon-bearing sand units with good reservoir quality characteristics. These reservoirs designated as R12 Sand and R15 Sand belonged to the LST and TST of G_SEQ2, and were interpreted to be basin floor fans and channel fill complexes, deposited within the neritic to bathyal environments. 3D geological modelling of the reservoirs showed good structural closures with thick sedimentary packages, suggesting that they are good locations for hydrocarbon accumulation. The major faults constitute good reservoir seals due to stratigraphic juxtapositions that may have prevailed in the cause of the dip slip movement.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107553"},"PeriodicalIF":3.7,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144662041","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":"Inconsistencies in organosulfur compounds during natural and artificial maturation","authors":"Poorna Srinivasan ,&nbsp;Constantin Sandu ,&nbsp;Estefania M. Endara Arguello ,&nbsp;Ibrahim Atwah","doi":"10.1016/j.marpetgeo.2025.107541","DOIUrl":"10.1016/j.marpetgeo.2025.107541","url":null,"abstract":"<div><div>Hydrous pyrolysis techniques are valuable for understanding and quantifying petroleum yield, thermal maturity, compositional variations, and kinetics across different kerogen types. Such data is essential for basin modeling and well planning. Previous studies have shown that sulfur-rich Type II-S kerogen generates hydrocarbons at lower temperatures due to its lower activation energy, resulting in early cracking. Consequently, organosulfur presents a challenge in numerous basins worldwide, as sulfur-rich source rocks from various regions must be examined closely to accurately predict hydrocarbon generation in each basin. Additional factors, such as total organic carbon content and mineralogy, also influence the timing and yield of oil generation. Methyldibenzothiophene isomers have proven to be reliable maturity indicators in sulfur-rich source rocks, often providing more accurate maturity predictions than biomarkers at higher maturity levels. However, few studies have closely examined the compositional and isomeric changes of alkylated methyldibenzothiophene compounds under hydrous pyrolysis conditions. In this study, hydrous pyrolysis experiments were conducted on three sulfur-rich source rocks and one sulfur-rich crude oil at temperatures between 275 and 360 °C to monitor and quantify changes in alkylated MDBT compounds as well as other aromatic hydrocarbons. The results were compared to four naturally matured Type II-S source rocks, spanning the immature to condensate windows, to evaluate the effects of hydrous pyrolysis on aromatic compounds. Significant differences in thermal maturity parameters were observed in the kerogen, bitumen, and expelled oil. While the increase in the 4-MDBT/1-MDBT ('MDR') ratio provided consistent thermal maturity estimates in natural samples, the hydrous pyrolysis experiments revealed that these geochemical markers are inconsistent under artificial thermal conditions, potentially due to additional sulfur species forming in the reactor, buffering reactions in the closed system reactor, the limited temperature range of the experiments, or other matrix-controlled interactions that are found in nature but are not occurring in the reactor. In contrast, aromatic biomarkers such as triaromatic steroids showed a positive increase in their isomer ratios relative to the experimental run temperature. The chemical differences between these organosulfur-rich samples (e.g., TOC, hydrogen index, mineralogy) suggest that the original source material—not solely the sulfur content—plays a critical role in the kinetics of alkylated dibenzothiophene compounds.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107541"},"PeriodicalIF":3.7,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144654697","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":"Cenomanian channel system evolution of Mundaú Sub-basin deepwater, Brazilian Equatorial Margin: Reservoir characterization using machine learning techniques","authors":"Ian de Oliveira Souza Cerdeira ,&nbsp;Karen Maria Leopoldino Oliveira ,&nbsp;Jorge de Jesus Picanço Figueiredo ,&nbsp;Heather Bedle ,&nbsp;Narelle Maia de Almeida ,&nbsp;Ana Clara Braga Souza","doi":"10.1016/j.marpetgeo.2025.107540","DOIUrl":"10.1016/j.marpetgeo.2025.107540","url":null,"abstract":"<div><div>Submarine channel systems have garnered significant attention in recent years due to their importance in petroleum exploration and favorable reservoir characteristics. Specifically, the Brazilian Equatorial Margin basins have attracted considerable interest from various sectors because of substantial hydrocarbon discoveries in adjacent basins. In the Mundaú Sub-basin (Ceará Basin, NE Brazil), recent studies have identified a series of sand-rich structures associated with a Cenomanian submarine channel system. However, despite these advancements, the depositional elements, sedimentary architecture, and stratigraphic sequences remain poorly understood. This paper aims to integrate robust quantitative geophysical techniques, including unsupervised machine learning methods, multi-attribute analysis, and RGB blending, to clarify the main evolutionary stages of the Cenomanian submarine channel-lobo system in the central portion of the aforementioned Sub-basin and their controlling factors. We utilized data from four exploration wells drilled in the deep waters of the Mundaú Sub-basin, along with a 2200 km² seismic volume covering the study area. Our integrated approach identified three main evolutionary stages. The first stage is characterized by straight to low-sinuosity confined channels on the upper to middle slope, alongside poorly confined channels and splays on the lower slope to basin floor, primarily comprising sand-prone layers developed during a Falling Stage System Tract. The second stage exhibits low to moderate sinuosity confined channels in the upper to middle slope, with significantly poorly confined channels and splays on the lower slope to basin floor, also dominated by sand-prone layers developed in a Lowstand Tract System. The final stage features a high-sinuosity confined channel with dominant sand-prone and sand/mud-prone layers developed in a Transgressive System Tract. all stages and across almost the whole region, sand-prone and sand/mud-prone facies were identified and associated with various depositional elements at different scales. the presence of sand-prone layers in all stages is thought to result from high-density turbidity currents driven by a narrow shelf and stepped slope. The mapped features and predicted facies indicate an unexplored area with sand-rich layers likely possessing good lateral and vertical connectivity. Important structures that may facilitate oil migration were identified, highlighting the high exploration potential of the Cenomanian submarine channel system in the Mundaú Sub-basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107540"},"PeriodicalIF":3.7,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144604136","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":"Reconstructing hydrocarbon accumulation and burial history of Permian reservoirs in northwest Sichuan Basin, China: Integrated fluid inclusion thermometry and U-Pb dating","authors":"Rui Ni ,&nbsp;Yong Chen ,&nbsp;Yifan Song ,&nbsp;Hui Zhang ,&nbsp;Yanwei Feng ,&nbsp;Fang Hao ,&nbsp;Xuesong Lu ,&nbsp;Xingzhi Ma","doi":"10.1016/j.marpetgeo.2025.107539","DOIUrl":"10.1016/j.marpetgeo.2025.107539","url":null,"abstract":"<div><div>The western Sichuan basin is a typical foreland basin, and great discovery of oil and gas exploration has been done here, but the history of hydrocarbon accumulation and burial history evolution is still uncertain. Fluid inclusion thermometry and isotopic dating are employed in this study to reconstruct the burial history and hydrocarbon accumulation of the Western Sichuan Foreland Basin. Furthermore, research was conducted research on the diagenesis, reservoir-forming stages and differences of the Qixia Formation reservoirs at different tectonic locations in the northwest of Sichuan. The results show that in the Shuangyushi area (concealed front-edge belt), the upper reservoirs of the Qixia Formation are mainly composed of sparry dolomitic limestone, with a diagenesis mineral sequence of: (1) the early microcrystalline calcite, (2) recrystallized calcite, (3) quartz, albite, pore bitumen in the surrounding rock, and (4) dolomite and calcite in fractures. In the Longmen Mountain piedmont area (thrust nappe belt), the outcrop rock of the Qixia Formation is mainly dolomitic limestone, with a diagenesis mineral sequence: (1) microcrystalline calcite, (2) recrystallized calcite, (3) quartz and bitumen, and (4) calcite filled in both pores and fractures. In the Shuangyushi area, the reservoirs of the Qixia Formation underwent crude oil charging from the Middle Triassic to Middle Jurassic, subsequent natural gas charging in the Late Cretaceous, and final natural gas reservoir destruction and adjustment at Late Cretaceous (81.2 ± 8.4 Ma). While, the outcrop of the Qixia Formation in the Longmen Mountain piedmont area recorded oil charging from the Lower Cambrian source rocks at Late Triassic (217.1 ± 0.9 Ma) and the destruction of oil reservoirs during the Miocene to Pleistocene (i.e., Himalayan orogeny). By comparing the petrological characteristics, fluid inclusion development and reservoir-forming periods of the two areas, it is considered that these disparities arise from the areas’ distinct tectonic positions within the foreland basin, leading to divergent responses to the Indosinian and Himalayan orogeny, as well as the resulting hydrocarbon accumulation processes.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107539"},"PeriodicalIF":3.7,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144604137","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":"Porosity estimation using deep learning and ImageJ: Implications for reservoir characterization in Central Luconia Miocene carbonates","authors":"Abdulrahman Danlami Isa ,&nbsp;Haylay Tsegab Gebretsadik ,&nbsp;Abdulrahman Muhammad ,&nbsp;Hassan Salisu Mohammed ,&nbsp;Ibrahim Muhammad Kurah ,&nbsp;Adamu Kamaliddeen Salisu","doi":"10.1016/j.marpetgeo.2025.107538","DOIUrl":"10.1016/j.marpetgeo.2025.107538","url":null,"abstract":"<div><div>Accurate porosity prediction is essential for effective reservoir characterisation, particularly in heterogeneous carbonate systems. This study investigates applying deep learning techniques to predict porosity from petrographic thin-section images of Miocene carbonate reservoirs in Central Luconia, offshore Malaysia. Four semantic segmentation models—UNet, SegNet, PSPNet, and Fully Convolutional Network (FCN)—were trained and evaluated, with UNet achieving the highest performance across all metrics: accuracy (0.990), precision (0.849), recall (0.940), F1 score (0.892), and Intersection over Union (IoU) (0.805). These results were benchmarked against traditional image analysis using ImageJ, where UNet predictions showed strong alignment, highlighting its reliability. SegNet also performed robustly, while PSPNet and FCN demonstrated lower predictive accuracy. The study further explored the impact of data augmentation, revealing performance degradation in SegNet and PSPNet due to distortion of micropore structures. A classification scheme based on UNet output identified porosity ranges, with 71.90 % of samples exhibiting &lt;5 % porosity, reflecting a low-porosity-dominated system. A spatial porosity distribution map was also generated using UNet to visualise heterogeneity across thin-section samples. It is important to note that this map is a conceptual representation and does not reflect the actual porosity distribution of the broader reservoir. Instead, it serves as a hypothetical visualisation to enhance understanding of porosity characteristics and heterogeneity within the analysed thin-section images. This work demonstrates the advantages of deep learning over conventional techniques for pore-scale analysis. It offers a scalable framework for integrating artificial intelligence in quantitative reservoir quality assessment.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107538"},"PeriodicalIF":3.7,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144571261","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":"Differential diagenetic controls on petrophysical heterogeneity of lacustrine beach-bar tight sandstones: Insights from the Boxing Sag, eastern China","authors":"Cunfei Ma ,&nbsp;Haowen Song ,&nbsp;Yuqi Wu ,&nbsp;Xiaopeng Cao ,&nbsp;Haicheng Liu ,&nbsp;Huafeng Zhang ,&nbsp;Yong Fu ,&nbsp;Wei Wang ,&nbsp;Chao Huang ,&nbsp;Xianxu Fang","doi":"10.1016/j.marpetgeo.2025.107537","DOIUrl":"10.1016/j.marpetgeo.2025.107537","url":null,"abstract":"<div><div>The Bohai Bay Basin is rich in petroleum resources, and the lacustrine beach-bar tight sandstone facies in the upper part of the fourth Member of the Paleogene Shahejie Formation (Es4s) of the Boxing Sag is a key exploration target. However, the heterogeneity in petrophysical properties caused by differential diagenesis during burial impacts its development. In this study, an integrated approach is used that includes core and thin section descriptions, scanning electron microscopy (SEM), carbon and oxygen isotope analysis, fluid inclusion analysis, rock physical properties, and high-pressure mercury injection analyses to investigate the differential diagenesis of the beach-bar tight sandstone reservoirs and its effects on petrophysical heterogeneity. Key findings include: (1) The sequence of diagenetic evolution of the reservoirs is: mechanical compaction and spherical pyrite cementation → calcite and dolomite cementation → feldspar dissolution, authigenic kaolinite precipitation, and quartz overgrowth → ferro-calcite and ankerite cementation → secondary dissolution and quartz overgrowth → late agglomerate pyrite cementation, reflecting alternating alkaline and acidic diagenetic environments. (2) Mechanical compaction and cementation are the dominant factors responsible for the reduction in reservoir quality. (3) Four distinct diagenetic facies are identified: an intense compaction with intergranular dissolution diagenetic facies (DF-I), an intense compaction with residual intergranular porosity diagenetic facies (DF-II), a weak-moderate compaction with intergranular cementation diagenetic facies (DF-Ⅲ), an intense compaction with matrix occlusion diagenetic facies (DF-Ⅳ). DF-I and DF-II exhibit superior reservoir quality (porosity &gt;10 %, permeability &gt;0.1 mD), making them effective reservoirs. (4) The genesis and spatial distributions of these facies are controlled by the petrological structure, petrographic composition, sand-mud interface, mudstone thickness, and distance from oil-source faults. By integrating multiple factors, this study elucidates the genetic mechanisms of the four diagenetic facies and establishes their vertical distribution patterns. This provides a basis for predicting favorable reservoir distribution and guiding future exploration.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107537"},"PeriodicalIF":3.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144572714","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":"Pioneering data on detection, identification and quantification of key carbonate minerals using spectral tomography","authors":"Kanchana Kularatne ,&nbsp;Nicolas E. Beaudoin ,&nbsp;Pascale Sénéchal ,&nbsp;Peter Moonen ,&nbsp;Souhail Youssef ,&nbsp;Fadi H. Nader","doi":"10.1016/j.marpetgeo.2025.107536","DOIUrl":"10.1016/j.marpetgeo.2025.107536","url":null,"abstract":"<div><div>In this study, we present, for the first time, the spectral computed tomography (sp-CT) signatures of key carbonate rock-forming minerals namely, calcite, magnesian calcite, dolomite, and magnesite. Although the raw spectra of these phases may not be readily distinguishable, we demonstrate that they appear in clusters on a multi-energy histogram derived from laboratory sp-CT. These clusters show a strong correlation with the MgCO₃ mol.% of the carbonate phases. In addition to discriminating among these carbonate phases, we demonstrate the capability of time-resolved sp-CT to monitor mineral replacement reactions in carbonates. As an example, we analyze a series of time-lapse sp-CT images of a carbonate sample undergoing hydrothermal dolomitization in the laboratory. The results reveal a progressive transformation of pure calcite into an Mg-rich carbonate, with the sp-CT data indicating a final composition of approximately 32 mol.% MgCO₃. This estimate, while lower than the 46–50 mol.% MgCO₃ determined through complementary chemical analysis, provides a valuable first-order approximation. This contribution introduces a novel methodology for visualizing, monitoring, and quantifying such chemical reactions in multi-phase carbonate systems, in 2D, 3D and even 4D, offering advantages over destructive techniques such as 3D FIB-tomography. Our findings pave the way to further exploration of carbonate diagenesis and open up new perspectives for the application of spectral tomography in Earth sciences.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107536"},"PeriodicalIF":3.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144654698","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":"Pyrite morphologies in Bazhenov Formation source rocks: diversity, systematic classification, sulfur isotopic composition and insights into sedimentation and diagenesis processes","authors":"Alina Karamova,&nbsp;Tagir Karamov,&nbsp;Mikhail Spasennykh","doi":"10.1016/j.marpetgeo.2025.107535","DOIUrl":"10.1016/j.marpetgeo.2025.107535","url":null,"abstract":"<div><div>Pyrite is a common authigenic mineral in organic-rich source rocks, which is diverse in morphology and carries valuable genetic information about geological processes. This study proposes comprehensive genetic morphological classification of pyrite aggregates in organic-rich shales of the Bazhenov Formation – one of the world largest source rock located in the Western Siberia. Scanning electron microscopy was used to analyze over 530 samples from 17 wells, identifying various types of pyrite such as framboids (with corresponding subtypes based on orderliness of the internal structure, crystallographic shape of microcrystals, infilling of internal structure, and integrity), euhedral crystals, and pyrite pseudomorphosis. The obtained sulfur isotopic composition for framboidal pyrite, which turned out to be the lightest (δ³⁴S vary in the range from −55.38 ‰ to −26.02 ‰), is indicative of anoxic conditions on seafloor. Euhedral pyrite develops in diagenesis under limited sulfate supply, reflecting slow growth in pore-water depleted in ³²S (δ³⁴S values range from +15.05 ‰ to +26.49 ‰). Described morphological types cover the diversity of pyrite forms in other similar geological objects around the world, which allows pyrite to be used as a geochemical proxy for paleoenvironmental reconstructions and hydrocarbon exploration, enhancing understanding of sulfur cycle and basin evolution.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107535"},"PeriodicalIF":3.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144588495","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}