Submarine mud volcanoes (MVs) are seafloor features commonly found in tectonically active margins with high sedimentation and compressional regimes. This study reports the first discovery of a prominent crater-like mud volcano on the Chilean margin, named the Cucao Mud Volcano (CMV), located ∼86 km offshore Chiloé Island (∼42°S) at a depth of 1800 m. Multichannel seismic data reveal that the CMV is structurally emplaced along the crest of a faulted anticline within a transpressional setting, indicating that tectonic deformation governs both its morphology and fluid pathways. A strong, continuous Bottom Simulating Reflector (BSR), seismic blanking, bright spots, and chaotic facies in the shallow subsurface suggest the presence of gas hydrates, free gas, and active fluid migration. High-resolution multibeam bathymetry and backscatter mosaics show a caldera-like edifice with a central crater, dome-shaped flanks, and surrounding depressions. Comparative data from 2012 to 2018 indicate reduced surface activity, possibly reflecting a transition to a quiescent phase. Additionally, dome-shaped reflectors above the BSR suggest diapir-like intrusions and vertical conduits associated with gas hydrate dissociation and overpressure. These findings underscore the complex interplay between tectonics, gas hydrate systems, and mud volcanism, positioning the CMV as a key site for understanding fluid dynamics along convergent continental margins.
{"title":"Discovery of an active crater-like mud volcano at ∼42°S on the Chilean margin: structural controls and gas hydrate associations","authors":"Cristian Rodrigo, Fernanda Ruiz, Nitza Garrido, Ximena Contardo","doi":"10.1016/j.marpetgeo.2025.107618","DOIUrl":"10.1016/j.marpetgeo.2025.107618","url":null,"abstract":"<div><div>Submarine mud volcanoes (MVs) are seafloor features commonly found in tectonically active margins with high sedimentation and compressional regimes. This study reports the first discovery of a prominent crater-like mud volcano on the Chilean margin, named the Cucao Mud Volcano (CMV), located ∼86 km offshore Chiloé Island (∼42°S) at a depth of 1800 m. Multichannel seismic data reveal that the CMV is structurally emplaced along the crest of a faulted anticline within a transpressional setting, indicating that tectonic deformation governs both its morphology and fluid pathways. A strong, continuous Bottom Simulating Reflector (BSR), seismic blanking, bright spots, and chaotic facies in the shallow subsurface suggest the presence of gas hydrates, free gas, and active fluid migration. High-resolution multibeam bathymetry and backscatter mosaics show a caldera-like edifice with a central crater, dome-shaped flanks, and surrounding depressions. Comparative data from 2012 to 2018 indicate reduced surface activity, possibly reflecting a transition to a quiescent phase. Additionally, dome-shaped reflectors above the BSR suggest diapir-like intrusions and vertical conduits associated with gas hydrate dissociation and overpressure. These findings underscore the complex interplay between tectonics, gas hydrate systems, and mud volcanism, positioning the CMV as a key site for understanding fluid dynamics along convergent continental margins.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107618"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145219115","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}
Pub Date : 2025-12-01Epub Date: 2025-08-09DOI: 10.1016/j.marpetgeo.2025.107580
Xiaocen Su , Rukai Zhu , Jingya Zhang , Chang Liu , Lei Gong , Xiaohua Jiang , Xiaofei Fu , Mehdi Ostadhassan
Bedding-parallel fractures play a critical role in enhancing storage capacity and horizontal permeability in tight shale reservoirs, significantly influencing the enrichment and productivity of shale oil. This study focuses on the continental shale of the Qingshankou Formation in the Songliao Basin, China, and systematically investigates the development characteristics and controlling factors of bedding-parallel fractures using a multi-scale dataset including core observations, image logs, scanning electron microscopy (SEM), and optical microscopy. Results show that bedding-parallel fractures are extensively developed across nano-to macro-scales, with nano-scale fractures reaching densities of up to 105 fractures/m. Fracture density is negatively correlated with both fracture scale and aperture. These fractures are generally sub-parallel to bedding or exhibit low-angle orientations (mostly <10°), and are typically discontinuous with limited lateral connectivity. Quantitative analyses indicate that fracture density is positively correlated with the contents of clay minerals, pyrite, and carbonate minerals, while showing weak or negative correlations with brittle minerals such as quartz and feldspar. Higher fracture densities are also observed in shales with elevated TOC content and higher thermal maturity. Furthermore, the type, thickness, and density of lamination significantly influence fracture development. At micro- and nano-scales, bedding-parallel fractures primarily act as hydrocarbon storage spaces and micro-flow conduits, whereas at the macro-scale, they mainly serve as horizontal flow pathways. These findings elucidate the multi-scale development mechanisms of bedding-parallel fractures in continental shale and underscore their dominant role in improving reservoir performance.
{"title":"Multi-scale characterization and control factors of bedding-parallel fractures in continental shale reservoirs: Insights from the Qingshankou Formation, Songliao Basin, China","authors":"Xiaocen Su , Rukai Zhu , Jingya Zhang , Chang Liu , Lei Gong , Xiaohua Jiang , Xiaofei Fu , Mehdi Ostadhassan","doi":"10.1016/j.marpetgeo.2025.107580","DOIUrl":"10.1016/j.marpetgeo.2025.107580","url":null,"abstract":"<div><div>Bedding-parallel fractures play a critical role in enhancing storage capacity and horizontal permeability in tight shale reservoirs, significantly influencing the enrichment and productivity of shale oil. This study focuses on the continental shale of the Qingshankou Formation in the Songliao Basin, China, and systematically investigates the development characteristics and controlling factors of bedding-parallel fractures using a multi-scale dataset including core observations, image logs, scanning electron microscopy (SEM), and optical microscopy. Results show that bedding-parallel fractures are extensively developed across nano-to macro-scales, with nano-scale fractures reaching densities of up to 10<sup>5</sup> fractures/m. Fracture density is negatively correlated with both fracture scale and aperture. These fractures are generally sub-parallel to bedding or exhibit low-angle orientations (mostly <10°), and are typically discontinuous with limited lateral connectivity. Quantitative analyses indicate that fracture density is positively correlated with the contents of clay minerals, pyrite, and carbonate minerals, while showing weak or negative correlations with brittle minerals such as quartz and feldspar. Higher fracture densities are also observed in shales with elevated TOC content and higher thermal maturity. Furthermore, the type, thickness, and density of lamination significantly influence fracture development. At micro- and nano-scales, bedding-parallel fractures primarily act as hydrocarbon storage spaces and micro-flow conduits, whereas at the macro-scale, they mainly serve as horizontal flow pathways. These findings elucidate the multi-scale development mechanisms of bedding-parallel fractures in continental shale and underscore their dominant role in improving reservoir performance.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107580"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144826897","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}
Pub Date : 2025-12-01Epub Date: 2025-07-05DOI: 10.1016/j.marpetgeo.2025.107536
Kanchana Kularatne , Nicolas E. Beaudoin , Pascale Sénéchal , Peter Moonen , Souhail Youssef , Fadi H. Nader
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.
{"title":"Pioneering data on detection, identification and quantification of key carbonate minerals using spectral tomography","authors":"Kanchana Kularatne , Nicolas E. Beaudoin , Pascale Sénéchal , Peter Moonen , Souhail Youssef , 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 MgCO<sub>3</sub> 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.% MgCO<sub>3</sub>. This estimate, while lower than the 46–50 mol.% MgCO<sub>3</sub> 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":"2025-12-01","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}
Pub Date : 2025-12-01Epub Date: 2025-07-14DOI: 10.1016/j.marpetgeo.2025.107559
Yong Ma , Qinhong Hu , Jianbin Xu , Binhao Feng , Fujie Jiang , Yanshan Wang , Haiping Huang
Low-maturity shale oil resources are widely developed in the Paleogene-aged Damintun Sag of the Bohai Bay Basin, yet the unclear pore architecture and reservoir space distribution have hindered its efficient exploitation. Focusing on the low-maturity Es4 shale, this study integrates core observations, geochemical tests, X-ray diffraction, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) data from Well S352 to investigate lithofacies-controlled pore structures and residual oil characteristics. Three lithofacies reservoirs are identified: laminated felsic shale (LFS), mixed shale (MS), and massive dolomitic mudstone (MDM). LFS and MS are rich in Type I kerogen excellent hydrocarbon generation and retention. LFS acts as both source and reservoir rock, featuring abundant mesopores, strong pore connectivity, and bedding-parallel fractures, making it a favorable sweet spot for in situ generation and light oil expulsion. MS serves as a transitional facies with moderate generative and physical properties. In contrast, MDM, with low TOC and poor pore connectivity, lacks generative capacity and instead functions as a secondary reservoir that stores migrated oil from adjacent LFS. Thermal maturity assessments show high Tmax values (up to 465 °C) indicative of peak oil generation, despite low measured Ro (∼0.6 %), likely suppressed by algal kerogen. Multiscale pore analyses reveal that LFS contains the highest cumulative pore volume and most developed pore–fracture networks, while MDM exhibits isolated, diagenetically altered pores. Geochemical zonation and gas chromatography fingerprinting distinguishes indigenous hydrocarbons in LFS/MS from migrated oils in MDM, confirming stratigraphically confined migration. Laminated shale—particularly those with interbedded MDM intervals—show optimal conditions for sweet spot development, as short-range migration enriches reservoir potential without requiring high maturity. This study underscores the viability of low-maturity shale oil systems and emphasizes the importance of integrating lithofacies, geochemistry, and pore network architecture to predict sweet spots for optimized exploration in lacustrine shale formations.
{"title":"Multidisciplinary characterization of migrated bitumen enrichment and pore network development in low-maturity Es4 shales of the Damintun Sag, East China","authors":"Yong Ma , Qinhong Hu , Jianbin Xu , Binhao Feng , Fujie Jiang , Yanshan Wang , Haiping Huang","doi":"10.1016/j.marpetgeo.2025.107559","DOIUrl":"10.1016/j.marpetgeo.2025.107559","url":null,"abstract":"<div><div>Low-maturity shale oil resources are widely developed in the Paleogene-aged Damintun Sag of the Bohai Bay Basin, yet the unclear pore architecture and reservoir space distribution have hindered its efficient exploitation. Focusing on the low-maturity Es<sub>4</sub> shale, this study integrates core observations, geochemical tests, X-ray diffraction, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) data from Well S352 to investigate lithofacies-controlled pore structures and residual oil characteristics. Three lithofacies reservoirs are identified: laminated felsic shale (LFS), mixed shale (MS), and massive dolomitic mudstone (MDM). LFS and MS are rich in Type I kerogen excellent hydrocarbon generation and retention. LFS acts as both source and reservoir rock, featuring abundant mesopores, strong pore connectivity, and bedding-parallel fractures, making it a favorable sweet spot for <em>in situ</em> generation and light oil expulsion. MS serves as a transitional facies with moderate generative and physical properties. In contrast, MDM, with low TOC and poor pore connectivity, lacks generative capacity and instead functions as a secondary reservoir that stores migrated oil from adjacent LFS. Thermal maturity assessments show high T<sub>max</sub> values (up to 465 °C) indicative of peak oil generation, despite low measured R<sub>o</sub> (∼0.6 %), likely suppressed by algal kerogen. Multiscale pore analyses reveal that LFS contains the highest cumulative pore volume and most developed pore–fracture networks, while MDM exhibits isolated, diagenetically altered pores. Geochemical zonation and gas chromatography fingerprinting distinguishes indigenous hydrocarbons in LFS/MS from migrated oils in MDM, confirming stratigraphically confined migration. Laminated shale—particularly those with interbedded MDM intervals—show optimal conditions for sweet spot development, as short-range migration enriches reservoir potential without requiring high maturity. This study underscores the viability of low-maturity shale oil systems and emphasizes the importance of integrating lithofacies, geochemistry, and pore network architecture to predict sweet spots for optimized exploration in lacustrine shale formations.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107559"},"PeriodicalIF":3.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633922","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}
Pub Date : 2025-12-01Epub Date: 2025-09-13DOI: 10.1016/j.marpetgeo.2025.107598
David Paul Canova , Gabriel Cofrade , Eduard Roca , Marco De Matteis , Oriol Ferrer
The Eastern Prebetics are part of the External Zone of the Betic Fold-and-Thrust Belt in SE Iberia where a significant amount of salt structures crops out including: diapirs, allochthonous sheets, welds, primary and secondary minibasins, and rafts. Our study focuses on the subsalt, syn-contractional, early to middle Miocene (Aquitanian-Langhian) stratigraphy of the Elda Salt Sheet, aiming to document the sub seismic scale deformation and salt-sediment interactions during allochthonous salt advance. Stratigraphic sections, halokinetic fold analysis, geologic field mapping and foraminiferal dating are used to characterize the subsalt sediments exposed in contact with the northwestern edge of the outcropping Elda Salt Sheet.
Based on the subsalt sedimentary and structural relationships we show that the Elda Salt Sheet advanced at least 8 km towards the north during the syn-orogenic Aquitanian – Langhian times before being buried during the latest Langhian - Serravallian times. This overall northward advance can be defined by six main phases. All the phases occur in submarine conditions in a carbonate ramp with water depths ranging from 10's to 100's of meters and are: (1) the extrusion of a salt sheet in an inner – outer carbonate ramp environment coeval to the onset of regional Oligocene-Miocene shortening corroborated by an Aquitanian aged flat and stranded intrasalt stringers along the subsalt flat; (2) Burdigalian-early Langhian burial of the salt sheet toe in an outer shelf – basinal environment where pinned inflation, and subsequent breakout of a confined salt sheet is evidenced by a hectometric halokinetic fold ramp and rafts of Burdigalian stratigraphy above the salt sheet. (3) early-middle Langhian rapid lateral advance of the salt sheet along a base salt flat which occurred in a deepwater basinal environment; (4) middle-late Langhian hindrance of the salt advance, development of subsalt decametric thick and decametric spaced halokinetic fold ramps in a basinal – outer shelf environment; (5) late Langhian salt sheet burial by shallow water carbonates and deepwater basinal marlstones; and (6) subsidence of secondary minibasins. These stages reflect a detailed history of a salt sheet lineage. This field-based study documents for the first time the structural and stratigraphic architecture of a subaqueous salt sheet lineage in a contractional setting.
{"title":"Where the salt sheet ends - submarine allochthonous salt advance and hindrance, The Elda Salt Sheet, Eastern Prebetics (Southern Iberia)","authors":"David Paul Canova , Gabriel Cofrade , Eduard Roca , Marco De Matteis , Oriol Ferrer","doi":"10.1016/j.marpetgeo.2025.107598","DOIUrl":"10.1016/j.marpetgeo.2025.107598","url":null,"abstract":"<div><div>The Eastern Prebetics are part of the External Zone of the Betic Fold-and-Thrust Belt in SE Iberia where a significant amount of salt structures crops out including: diapirs, allochthonous sheets, welds, primary and secondary minibasins, and rafts. Our study focuses on the subsalt, syn-contractional, early to middle Miocene (Aquitanian-Langhian) stratigraphy of the Elda Salt Sheet, aiming to document the sub seismic scale deformation and salt-sediment interactions during allochthonous salt advance. Stratigraphic sections, halokinetic fold analysis, geologic field mapping and foraminiferal dating are used to characterize the subsalt sediments exposed in contact with the northwestern edge of the outcropping Elda Salt Sheet.</div><div>Based on the subsalt sedimentary and structural relationships we show that the Elda Salt Sheet advanced at least 8 km towards the north during the syn-orogenic Aquitanian – Langhian times before being buried during the latest Langhian - Serravallian times. This overall northward advance can be defined by six main phases. All the phases occur in submarine conditions in a carbonate ramp with water depths ranging from 10's to 100's of meters and are: (1) the extrusion of a salt sheet in an inner – outer carbonate ramp environment coeval to the onset of regional Oligocene-Miocene shortening corroborated by an Aquitanian aged flat and stranded intrasalt stringers along the subsalt flat; (2) Burdigalian-early Langhian burial of the salt sheet toe in an outer shelf – basinal environment where pinned inflation, and subsequent breakout of a confined salt sheet is evidenced by a hectometric halokinetic fold ramp and rafts of Burdigalian stratigraphy above the salt sheet. (3) early-middle Langhian rapid lateral advance of the salt sheet along a base salt flat which occurred in a deepwater basinal environment; (4) middle-late Langhian hindrance of the salt advance, development of subsalt decametric thick and decametric spaced halokinetic fold ramps in a basinal – outer shelf environment; (5) late Langhian salt sheet burial by shallow water carbonates and deepwater basinal marlstones; and (6) subsidence of secondary minibasins. These stages reflect a detailed history of a salt sheet lineage. This field-based study documents for the first time the structural and stratigraphic architecture of a subaqueous salt sheet lineage in a contractional setting.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107598"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145094866","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}
Pub Date : 2025-12-01Epub Date: 2025-09-14DOI: 10.1016/j.marpetgeo.2025.107604
Philip T.S. Rose , Rene Jonk , Rachael Crowe , John Gibson , Andrew Dickson , Andrew Lind , Daniel Helgeson
Faults play an important role in controlling flow and retention of aqueous and petroleum fluids from overpressured basin centres (“kitchens”) to basin flanks. The Beryl Kitchen is a deep overpressured basin in the Beryl Embayment on the flanks of the Viking Graben in the UK northern North Sea and provides a data rich laboratory allowing these processes to be studied in detail. In this study we combine the results of detailed structural mapping, constrained by broadband seismic and abundant well control, with reservoir pressure data and hydrocarbon geochemistry. We use the data to demonstrate how the bounding faults of the Beryl Kitchen have acted as significant capillary seals, even with abundant porous and permeable reservoir juxtaposition across the key faults. The fault plane seals allowed the baffled escape of aqueous fluids, creating fault-bounded pressure compartments, while trapping significant hydrocarbon columns at the boundary between overpressured and normally pressured reservoirs. We demonstrate how the behaviour of some of these faults has evolved with progressive burial and increasing source rock maturity in the deepest parts of the basin. On the flanks of the Beryl Kitchen these processes have resulted in the preservation of hydrocarbon accumulations with unexpectedly tall columns and an unintuitive distribution of hydrocarbon water contacts in adjacent fault blocks. These accumulations provide valuable exploration analogues for the evaluation of the hydrocarbon potential of fault bound structures at the margins of overpressured basins.
{"title":"The static and dynamic behaviour of large faults as seals and conduits to aqueous and petroleum fluid flow at geological time-scales: Observations from the Beryl Embayment, UK North Sea","authors":"Philip T.S. Rose , Rene Jonk , Rachael Crowe , John Gibson , Andrew Dickson , Andrew Lind , Daniel Helgeson","doi":"10.1016/j.marpetgeo.2025.107604","DOIUrl":"10.1016/j.marpetgeo.2025.107604","url":null,"abstract":"<div><div>Faults play an important role in controlling flow and retention of aqueous and petroleum fluids from overpressured basin centres (“kitchens”) to basin flanks. The Beryl Kitchen is a deep overpressured basin in the Beryl Embayment on the flanks of the Viking Graben in the UK northern North Sea and provides a data rich laboratory allowing these processes to be studied in detail. In this study we combine the results of detailed structural mapping, constrained by broadband seismic and abundant well control, with reservoir pressure data and hydrocarbon geochemistry. We use the data to demonstrate how the bounding faults of the Beryl Kitchen have acted as significant capillary seals, even with abundant porous and permeable reservoir juxtaposition across the key faults. The fault plane seals allowed the baffled escape of aqueous fluids, creating fault-bounded pressure compartments, while trapping significant hydrocarbon columns at the boundary between overpressured and normally pressured reservoirs. We demonstrate how the behaviour of some of these faults has evolved with progressive burial and increasing source rock maturity in the deepest parts of the basin. On the flanks of the Beryl Kitchen these processes have resulted in the preservation of hydrocarbon accumulations with unexpectedly tall columns and an unintuitive distribution of hydrocarbon water contacts in adjacent fault blocks. These accumulations provide valuable exploration analogues for the evaluation of the hydrocarbon potential of fault bound structures at the margins of overpressured basins.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107604"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145094969","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}
Pub Date : 2025-12-01Epub Date: 2025-07-16DOI: 10.1016/j.marpetgeo.2025.107562
Guanyu Xie , Mengdi Sun , Yiquan Ma , Erfan Mohammadian , Mehdi Ostadhassan , Zhejun Pan , Xianggang Duan
The pore-fracture connectivity in unconventional shale systems is predominantly governed by laminae, necessitating comprehensive investigations through various perspectives. Thus, to quantitatively assess the influence of laminae and their characteristics on pore-fracture connectivity, optical microscopy and field emission scanning electron microscopy combined with Wood's metal impregnation are employed, integrated with mercury intrusion capillary pressure analysis, gas permeability testing, and nanoindentation experiments on Wufeng-Longmaxi marine shale samples from the southern Sichuan Basin, China. The results indicate that the level of pore-fracture connectivity (from good to poor) in three types of recognized lamina from petrographic observations of the samples follows: silty-organic rich laminae (η = 0.42–0.47) > silty-clay rich laminae (η = 0.36) > clay rich laminae (η = 0.20). Silty-organic rich laminae exhibit the best connectivity due to the higher abundance of organic matter, well-developed organic pores, and interlaminar fractures that facilitate their connectivity. In contrast, clay rich laminae demonstrate the poorest connectivity due to their low organic matter content and the predominance of isolated, elongated pores in clay minerals. Furthermore, permeability anisotropy of shale is primarily influenced by mineral composition and the degree of microfracture development where, silty-organic rich laminae exhibit the most extensive distribution of microfractures, supported by a rigid framework composed of brittle minerals. This results in the lowest pore-fracture compressibility coefficient, which helps maintain superior connectivity and fluid flow pathways. Nanoindentation experiments demonstrated that silty-organic rich laminae will have the highest elastic modulus (E > 30 GPa) and hardness (H > 2 GPa). With increasing clay content, these mechanical properties exhibit progressive reduction, promoting enhanced susceptibility to pore collapse and fracture closure, thereby significantly impairing pore-microfracture connectivity. Overall, the pore-fracture connectivity of different types of laminae controls the gas supply from matrix to the fractures, directly affecting the production and recovery rate of shale gas. During exploration, the silty-organic rich laminae in the middle-lower part of the TST of the Longmaxi Member 1 should be prioritized as the sweet spot. These findings have significant implications for evaluating favorable spots in shale reservoirs, for an optimized field development plans, specifically hydraulic fracturing, for higher gains and resource utilization.
{"title":"Impact of laminae characteristics on pore-fracture connectivity in the Wufeng-Longmaxi shale","authors":"Guanyu Xie , Mengdi Sun , Yiquan Ma , Erfan Mohammadian , Mehdi Ostadhassan , Zhejun Pan , Xianggang Duan","doi":"10.1016/j.marpetgeo.2025.107562","DOIUrl":"10.1016/j.marpetgeo.2025.107562","url":null,"abstract":"<div><div>The pore-fracture connectivity in unconventional shale systems is predominantly governed by laminae, necessitating comprehensive investigations through various perspectives. Thus, to quantitatively assess the influence of laminae and their characteristics on pore-fracture connectivity, optical microscopy and field emission scanning electron microscopy combined with Wood's metal impregnation are employed, integrated with mercury intrusion capillary pressure analysis, gas permeability testing, and nanoindentation experiments on Wufeng-Longmaxi marine shale samples from the southern Sichuan Basin, China. The results indicate that the level of pore-fracture connectivity (from good to poor) in three types of recognized lamina from petrographic observations of the samples follows: silty-organic rich laminae (η = 0.42–0.47) > silty-clay rich laminae (η = 0.36) > clay rich laminae (η = 0.20). Silty-organic rich laminae exhibit the best connectivity due to the higher abundance of organic matter, well-developed organic pores, and interlaminar fractures that facilitate their connectivity. In contrast, clay rich laminae demonstrate the poorest connectivity due to their low organic matter content and the predominance of isolated, elongated pores in clay minerals. Furthermore, permeability anisotropy of shale is primarily influenced by mineral composition and the degree of microfracture development where, silty-organic rich laminae exhibit the most extensive distribution of microfractures, supported by a rigid framework composed of brittle minerals. This results in the lowest pore-fracture compressibility coefficient, which helps maintain superior connectivity and fluid flow pathways. Nanoindentation experiments demonstrated that silty-organic rich laminae will have the highest elastic modulus (E > 30 GPa) and hardness (H > 2 GPa). With increasing clay content, these mechanical properties exhibit progressive reduction, promoting enhanced susceptibility to pore collapse and fracture closure, thereby significantly impairing pore-microfracture connectivity. Overall, the pore-fracture connectivity of different types of laminae controls the gas supply from matrix to the fractures, directly affecting the production and recovery rate of shale gas. During exploration, the silty-organic rich laminae in the middle-lower part of the TST of the Longmaxi Member 1 should be prioritized as the sweet spot. These findings have significant implications for evaluating favorable spots in shale reservoirs, for an optimized field development plans, specifically hydraulic fracturing, for higher gains and resource utilization.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107562"},"PeriodicalIF":3.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144654702","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}
Pub Date : 2025-12-01Epub Date: 2025-08-30DOI: 10.1016/j.marpetgeo.2025.107593
Min Wang , Yan Wu , Xuefeng Bai , Ming Li , Junhui Li , Xin Wang , Jinyou Zhang , Jinbu Li , Changqi Yu , Roufeida Bennani
The Cretaceous Qingshankou Formation in the Gulong Sag of the Songliao Basin, located in the eastern of the Eurasian Plate, exhibits unique shale oil properties, including high clay mineral content (>40 %), high organic matter maturity (>1.0 %), and low shale oil density (∼0.78 cm3/g). This represents the first globally documented shale oil produced from clay-rich shales. This study systematically investigates the characteristics and controlling factors of reservoir space, oil-bearing properties and the formation and enrichment processes of shale oil. Findings reveal that the Qing-1 Member predominantly comprises laminated argillaceous shale, bedded mixed shale, and massive calcareous shale. The kerogen is mainly Type I, characterized by well-developed lamalginite and high organic matter (OM) abundance, with an average Total Organic Carbon (TOC) of 2.27 %. Thermal maturity (Ro) in oil-producing intervals typically exceeds 1.0 %. The main pore types are intergranular pores, intragranular pores, OM-hosted pores, exposed pores after OM degradation, and microfractures, with pore development influenced by TOC, clay mineral content, and Ro. The Gulong shale is notably oil-rich, with oil films present observed in different types and sizes of pores, and oil content significantly affected by TOC and Ro. The coupling of hydrocarbon evolution, fault activity periods, and regional stress changes governs the in-situ retention of light oil within the sag and dictates the reservoir formation sequence and spatial distribution of tight and conventional oil outside the source rock. This study offers critical insights for the exploration and development of continental clay-rich shale oil reservoirs.
{"title":"Geological characteristics and in-situ retention mechanisms of clay-rich lacustrine shale oil in the Songliao Basin","authors":"Min Wang , Yan Wu , Xuefeng Bai , Ming Li , Junhui Li , Xin Wang , Jinyou Zhang , Jinbu Li , Changqi Yu , Roufeida Bennani","doi":"10.1016/j.marpetgeo.2025.107593","DOIUrl":"10.1016/j.marpetgeo.2025.107593","url":null,"abstract":"<div><div>The Cretaceous Qingshankou Formation in the Gulong Sag of the Songliao Basin, located in the eastern of the Eurasian Plate, exhibits unique shale oil properties, including high clay mineral content (>40 %), high organic matter maturity (>1.0 %), and low shale oil density (∼0.78 cm<sup>3</sup>/g). This represents the first globally documented shale oil produced from clay-rich shales. This study systematically investigates the characteristics and controlling factors of reservoir space, oil-bearing properties and the formation and enrichment processes of shale oil. Findings reveal that the Qing-1 Member predominantly comprises laminated argillaceous shale, bedded mixed shale, and massive calcareous shale. The kerogen is mainly Type I, characterized by well-developed lamalginite and high organic matter (OM) abundance, with an average Total Organic Carbon (TOC) of 2.27 %. Thermal maturity (R<sub>o</sub>) in oil-producing intervals typically exceeds 1.0 %. The main pore types are intergranular pores, intragranular pores, OM-hosted pores, exposed pores after OM degradation, and microfractures, with pore development influenced by TOC, clay mineral content, and R<sub>o</sub>. The Gulong shale is notably oil-rich, with oil films present observed in different types and sizes of pores, and oil content significantly affected by TOC and R<sub>o</sub>. The coupling of hydrocarbon evolution, fault activity periods, and regional stress changes governs the in-situ retention of light oil within the sag and dictates the reservoir formation sequence and spatial distribution of tight and conventional oil outside the source rock. This study offers critical insights for the exploration and development of continental clay-rich shale oil reservoirs.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107593"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144921642","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}
Pub Date : 2025-12-01Epub Date: 2025-07-09DOI: 10.1016/j.marpetgeo.2025.107539
Rui Ni , Yong Chen , Yifan Song , Hui Zhang , Yanwei Feng , Fang Hao , Xuesong Lu , Xingzhi Ma
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.
{"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 , Yong Chen , Yifan Song , Hui Zhang , Yanwei Feng , Fang Hao , Xuesong Lu , 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":"2025-12-01","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}
Pub Date : 2025-12-01Epub Date: 2025-08-09DOI: 10.1016/j.marpetgeo.2025.107579
Nikolaos Dimopoulos , Georgia Pe-Piper , David J.W. Piper , Nicolina Bourli , Elena Zoumpouli , George Iliopoulos , Avraam Zelilidis
Middle Jurassic limestones, deposited on deep-water highs in the Ionian Basin, include Fe-rich concretions. Mineralogical and textural studies by SEM show the concretions now consist of goethite with minor lepidocrocite, hematite and quartz. The cm-scale concretions include radiating spheres and pseudomorphs after ammonites, with cubic and pyritohedral pseudomorphs after pyrite. Smaller mm-scale concretions occur at limestone hardgrounds. Concretions have REE signatures and high Mo and V suggesting formation in hypoxic water overlying a local euxinic basin. Textures suggest the following sequence of events: (1) Sea floor diagenetic iron monosulphide and pyrite concretions and veins. (2) With burial, recrystallisation to cubes or pyritohedrons of pyrite. (3) Pseudomorphous alteration of pyrite to hematite, with the 5 % volume reduction resulting in sub-micron pores that filled with silica (now quartz). (4) Widespread alteration of hematite to goethite with texturally complex, coupled dissolution-reprecipitation reactions. (5) Widespread secondary porosity, with precipitation of fibrous goethite and minor lepidocrocite. (6) Late cross-cutting fractures have Mn-rich minerals, with exotic trace elements such as asbolane (Co, Ni) and romanechite (Ba). The original pyrite concretions persisted during burial diagenesis until Paleogene uplift of the basin margins allowed ingress of oxidising meteoric water, circulated by thermal anomalies related to salt domes. Pyrite was oxidized to hematite and micropores were filled by silica. Oligocene thrusting created a new fracture set, increased loading of basinal sediments and allowed ingress of abundant meteoric water creating supergene alteration. Both chert and Fe-rich concretions provide important insights into diagenetic and hydrothermal evolution of thick limestone successions. [249 words]
{"title":"Pseudomorphic changes after iron sulfide concretions in Jurassic limestones, Ionian Basin, Greece: tracking changes in basinal fluids","authors":"Nikolaos Dimopoulos , Georgia Pe-Piper , David J.W. Piper , Nicolina Bourli , Elena Zoumpouli , George Iliopoulos , Avraam Zelilidis","doi":"10.1016/j.marpetgeo.2025.107579","DOIUrl":"10.1016/j.marpetgeo.2025.107579","url":null,"abstract":"<div><div>Middle Jurassic limestones, deposited on deep-water highs in the Ionian Basin, include Fe-rich concretions. Mineralogical and textural studies by SEM show the concretions now consist of goethite with minor lepidocrocite, hematite and quartz. The cm-scale concretions include radiating spheres and pseudomorphs after ammonites, with cubic and pyritohedral pseudomorphs after pyrite. Smaller mm-scale concretions occur at limestone hardgrounds. Concretions have REE signatures and high Mo and V suggesting formation in hypoxic water overlying a local euxinic basin. Textures suggest the following sequence of events: (1) Sea floor diagenetic iron monosulphide and pyrite concretions and veins. (2) With burial, recrystallisation to cubes or pyritohedrons of pyrite. (3) Pseudomorphous alteration of pyrite to hematite, with the 5 % volume reduction resulting in sub-micron pores that filled with silica (now quartz). (4) Widespread alteration of hematite to goethite with texturally complex, coupled dissolution-reprecipitation reactions. (5) Widespread secondary porosity, with precipitation of fibrous goethite and minor lepidocrocite. (6) Late cross-cutting fractures have Mn-rich minerals, with exotic trace elements such as asbolane (Co, Ni) and romanechite (Ba). The original pyrite concretions persisted during burial diagenesis until Paleogene uplift of the basin margins allowed ingress of oxidising meteoric water, circulated by thermal anomalies related to salt domes. Pyrite was oxidized to hematite and micropores were filled by silica. Oligocene thrusting created a new fracture set, increased loading of basinal sediments and allowed ingress of abundant meteoric water creating supergene alteration. Both chert and Fe-rich concretions provide important insights into diagenetic and hydrothermal evolution of thick limestone successions. [249 words]</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107579"},"PeriodicalIF":3.6,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852019","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}
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