Marine and Petroleum Geology最新文献

{"title":"Seismic evidence for magmatism-driven mud volcanism in the northern continental margin of the South China Sea","authors":"Junhui Yu ,&nbsp;Pin Yan ,&nbsp;Yanlin Wang ,&nbsp;Guangjian Zhong ,&nbsp;Changliang Chen","doi":"10.1016/j.marpetgeo.2025.107523","DOIUrl":"10.1016/j.marpetgeo.2025.107523","url":null,"abstract":"<div><div>The Chaoshan Depression in the northern South China Sea (SCS) margin is abundant with submarine mud volcanoes, and hosts two primary sets of hydrocarbon source rocks within its thick Mesozoic strata. However, the driving mechanism for submarine mud volcanism there remains enigmatic. Here multichannel seismic and ocean bottom seismometer data of line CS-L1 across several mud volcanoes in the Chaoshan Depression are processed and analyzed. Beneath the mud volcanoes, several vertical fuzzy reflection zones are imaged within the Mesozoic strata. They feature distinctly lower velocities than their host strata, and are interpreted as mud diapirs formed by vigorous fluid infilling. High-velocity bodies (HVBs) with Vp &gt; 7.0 km/s are widely imaged below the lower crust and interpreted as post-drift magma underplating bodies. Beneath the mud volcanoes, a thicker HVB extending upward to the depth of ∼15 km is observed, implying locally stronger magma underplating. Moreover, the overlying crust of this thicker HVB also features higher velocities than the surrounding crust. This crustal high-velocity zone extends upward to the shallow depth of ∼9 km, probably representing local magma intrusions sourced from the underlying magma underplating body. This strong association between the submarine mud volcanism and the stronger deep magma underplating and intrusion indicates that the mud volcanism in the Chaoshan Depression of the northern SCS margin was probably magmatism-driven. The deep magma underplating and intrusion firstly caused the surface uplift and the formation of high-angle normal faults. Subsequently, the heat from these intruded magmas promoted hydrocarbon gas generation of the Mesozoic source rocks and increased the pore-fluid pressure, generating mud diapirs within the Mesozoic strata with abundant fluid charging. The submarine mud volcanoes were finally formed with abundant fluids migrating from these mud diapirs to the seafloor along the high-angle faults.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107523"},"PeriodicalIF":3.7,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144336018","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":"Different AOM processes driving the formation of carbonate crusts and nodules in the Okinawa Trough","authors":"Yucheng Zhou ,&nbsp;Hong Cao ,&nbsp;Zhilei Sun ,&nbsp;Wei Geng ,&nbsp;Chenhui Liu ,&nbsp;Xilin Zhang ,&nbsp;Cuiling Xu ,&nbsp;Taiheng Lv ,&nbsp;Shixing Li ,&nbsp;Ye Chen ,&nbsp;Xuejun Jiang ,&nbsp;Dong Zhang ,&nbsp;Yunbao Sun ,&nbsp;Bin Zhai","doi":"10.1016/j.marpetgeo.2025.107510","DOIUrl":"10.1016/j.marpetgeo.2025.107510","url":null,"abstract":"<div><div>Anaerobic oxidation of methane (AOM) serves as a critical process that consumes methane formed in marine sediments and induces the precipitation of cold seep carbonates. However, the factors influencing sulfate-driven AOM (SD-AOM) and iron-driven AOM (Fe-AOM) during the formation of different types of carbonates remain unclear. In this study, mineralogical and geochemical studies were conducted on cold seep carbonate crusts and nodules in the northern Okinawa Trough (OT). Carbonate crusts exhibit rough surfaces with loose textures, while carbonate nodules are characterized by dense and homogeneous textures. The carbonate minerals in the crust samples are predominantly aragonite, whereas the primary carbonate minerals in the nodule samples are calcite and dolomite, as well as calcite and aragonite. The negative δ¹³C values of all samples indicate that the carbon is mainly sourced from biogenic methane. The δ¹⁸O enrichment suggests that the fluid involved in authigenic carbonate formation could be derived from the dissociation of natural gas hydrates. Mineralogical and rare earth element (REE) features reveal that carbonate crusts formed close to the seafloor under high methane fluxes, whereas carbonate nodules developed at greater depths under lower methane fluxes. The predominance of aragonite and low δ¹⁸O_CAS/δ³⁴S_CAS slope (carbonate-associated sulfate, CAS) indicate that SD-AOM drove the precipitation of carbonate crusts. In contrast, the presence of dolomite and siderite, iron-rich microbial structures, and elevated levels of carbonate-associated Fe collectively support the contribution of Fe-AOM during the formation of carbonate nodules. Our study highlights that the distinct formation conditions of carbonate crusts and nodules govern their differential AOM processes.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107510"},"PeriodicalIF":3.7,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321810","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":"Paleoenvironment and organic matter enrichment in the Kaijiang–Liangping Trough across the Emeishan Large Igneous Province (ELIP)","authors":"Mengxiang Yu ,&nbsp;Jianhua Zhao ,&nbsp;Keyu Liu ,&nbsp;Qinhong Hu ,&nbsp;Wei Wu ,&nbsp;Quanyou Liu ,&nbsp;Chao Luo ,&nbsp;Yang Chen ,&nbsp;Hongyu Ma ,&nbsp;Zhijun Jin","doi":"10.1016/j.marpetgeo.2025.107517","DOIUrl":"10.1016/j.marpetgeo.2025.107517","url":null,"abstract":"<div><div>The Emeishan Large Igneous Province (ELIP) substantially influenced Permian environmental conditions. This study focused on Middle–Late Permian strata in the Kaijiang and Liangping regions, located ∼800 km northeast of the ELIP center, integrating petrology and geochemistry to investigate the influence of the ELIP on the sedimentary environment and organic matter enrichment. Results indicate that the stratigraphic records preserve eruptive products from different developmental stages of the ELIP. The Kaijiang–Liangping Trough underwent initial uplift followed by subsidence from the late Capitanian to the Wuchiapingian, with organic enrichment patterns differing between northern and southern sections owing to tectonic and volcanic activity. In the north, organic matter is enriched in the siliceous mudstones of the Gufeng Member in the late Capitanian and the upper Wujiaping Formation of the Wuchiapingian age, whereas the south additionally contains coastal swamp facies shales at the base of the Wujiaping Formation. Organic matter enrichment was controlled by high productivity and anoxic conditions during the late Capitanian, whereas elevated sedimentation rates and enhanced terrigenous input attributable to volcanic activity became dominant factors in the early Wuchiapingian. Late Wuchiapingian Emeishan felsic volcanic eruptions might have triggered climatic cooling, promoting upwelling restoration and biotic recovery, with anoxic–euxinic conditions and high productivity jointly governing organic matter enrichment. The negative δ¹³C_org excursion during this period might reflect reduced terrestrial organic matter input caused by sea level rise. This study revealed the spatiotemporal coupling of volcanic and sedimentary processes, offering new insights into hydrocarbon source rock formation in large igneous provinces.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107517"},"PeriodicalIF":3.7,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321809","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":"Mercury in source rocks on the Norwegian Continental Shelf; link to maturity, depositional environment and age","authors":"Sverre E. Ohm ,&nbsp;Guro Skarstein ,&nbsp;Tomas Naeraa ,&nbsp;Fridtjof Riis ,&nbsp;Alejandro Escalona","doi":"10.1016/j.marpetgeo.2025.107511","DOIUrl":"10.1016/j.marpetgeo.2025.107511","url":null,"abstract":"<div><div>The source of mercury (Hg) in petroleum is debated in the literature and could stem from; Hg rich black shales producing petroleum, coals, proximity to deep faults acting as migration routes from deep Hg sources, and proximity to large igneous provinces. In an attempt to cast light on the source of Hg in oils on the Norwegian Shelf 268 mainly organic rich core samples from wells in the North Sea, Norwegian and Barents Sea were analysed for Hg and other heavy metals. In addition 5 core samples from Devonian and Permian reservoir sands and 6 oils from the Embla field were analysed. Our study shows that sediments with elevated Hg concentrations are associated with anoxic depositional environments. The study also show that Hg is mobilized in the source rock at the same temperature interval that generates oil and that the concentration of Hg in the source rock decreases with expulsion of oil. It is suggested that Hg in oil may carry information about the origin of the oil; source rock type and age.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107511"},"PeriodicalIF":3.7,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331071","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":"Thermal records of carbonate cements: Deciphering the hydrothermal imprint on Eocene Shahejie Formation sandstones in the northern Dongying Depression, China","authors":"Yishan Gao ,&nbsp;Shifa Zhu ,&nbsp;Hang Cui ,&nbsp;Wendian Cai ,&nbsp;Ruihang Zhang","doi":"10.1016/j.marpetgeo.2025.107513","DOIUrl":"10.1016/j.marpetgeo.2025.107513","url":null,"abstract":"<div><div>The carbonate cements in the sandstones of the Eocene Shahejie Formation in the Dongying Depression record crucial temporal and thermal information related to hydrothermal activity. This study presents a comprehensive investigation of these carbonate cements, detailing their diagenetic process, chronological formation, and material origins. Sedimentological evidence indicates that the sandstones in the study area were predominantly deposited in deltaic and marginal lacustrine settings, with a subdivision into matrix-rich and matrix-poor types at the microscale. Petrographic observation and electron probe microanalysis (EPMA) reveal that calcite is the predominant authigenic mineral phase, exhibiting variability in both abundance and morphology depending on sandstones maturity. Matrix-poor sandstones, characterized by higher maturity, predominantly exhibit blocky calcite cement, whereas those with a rich matrix and lower maturity tend to develop scattered patchy calcite. Fluid inclusion homogenization temperatures indicate that these calcite cements precipitated under abnormally high-temperature conditions, ranging from 85 to 350 °C. And the carbonate cements exhibit low δ¹³C (−11.8 to −3.1 ‰ VPDB) and δ¹⁸O (clustered tightly from −14.0 to −11.1 ‰ VPDB) values, interpreted to reflect a mixed source comprising magmatic CO₂, air CO₂, and a potential contribution from soil CO₂. <em>In situ</em> U-Pb isotopic dating of calcite constrains the timing of carbonate cement precipitation, with ages ranging from 39.4 ± 1.9 Ma to 42 ± 7.6 Ma. Ultimately, the results indicate that the calcium source for the carbonate cements in the Eocene Shahejie Formation sandstones of this region is primarily a mixture of primary alkaline formation waters and hydrothermal fluids. The carbon source is dominated by a mixture of magmatic CO₂ and air CO₂, with a potential minor contribution from soil CO₂. This study suggests that the hydrothermal activity influencing carbonate cementation in the study area was likely associated with the Cenozoic subduction of the New Pacific Plate. Through the integration of multiple advanced analytical techniques, this study elucidates the material origins and precipitation timing of hydrothermal derived carbonate cements, validating the potential application of advanced techniques such as <em>in situ</em> U-Pb isotopic dating of calcite in clastic rock research. Additionally, the hydrothermal activity age determined for the Shahejie Formation in this study provides crucial data support for the research on tectonic-magmatic activity in the Dongying Depression.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107513"},"PeriodicalIF":3.7,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298830","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":"Multistage fluid activity as a control on the Ediacaran carbonate reservoirs in the Sichuan Basin, SW China","authors":"Tao Luo ,&nbsp;Xiaowen Guo ,&nbsp;Tiago M. Alves ,&nbsp;Zhiliang He ,&nbsp;Ze Tao ,&nbsp;Yahao Huang","doi":"10.1016/j.marpetgeo.2025.107509","DOIUrl":"10.1016/j.marpetgeo.2025.107509","url":null,"abstract":"<div><div>The Ediacaran Dengying Formation (Z₂dn) of the Sichuan Basin, Southwestern China, experienced multi-stage fluid flow, which accompanied the reduction and modification of reservoir porosity. Porosity in the Z₂dn carbonate reservoir thus varies in different structural units. Fluid inclusion and implications for reservoir porosity were investigated by combining petrographic, geochemical, fluid inclusion, in-situ U-Pb geochronological, and basin modelling data. Three stages of dolomite cements (CD-1, CD-2, and CD-3) and one stage of dolomite veining (FD) were petrographically, geochemically, and geochronologically distinguished in reservoir rocks, and respectively dated at c. 453 Ma, 336 Ma, and 173 Ma. Two stages of dolomite and quartz cement formation (CD-1, CD-2, Qtz-1, and Qtz-2) were subsequently formed at c. 453 Ma, 298 Ma, 182 Ma, and 165 Ma. CD-1, CD-2 cements and FD veins were interpreted as diagenetic fluids and formed in the sealed environment during the Late Ordovician-Early Permian; they led to multi-stage cementation of reservoir intervals and a reduction in porosity. Importantly, the diagenetic sequences between bitumen and dolomite generation phases indirectly define the dates of two oil charging events. The first episode only occurred in the central Sichuan Basin during the Silurian, and its timing is constrained by the absolute ages of CD-1 and CD-2 cements. The second oil charging episode was the most important in the Sichuan Basin and occurred during Indosinian tectonics according to the trapping temperatures of bitumen-bearing inclusions in Qtz-1 veins. Also significantly, oil charge was able to inhibit the precipitation of authigenic minerals in reservoir intervals. Oil cracking in the Z₂dn reservoir occurred at 173-165 Ma, accompanied by weak overpressure generation in the southeastern Sichuan Basin and medium-intensity overpressure in the central Sichuan Basin. Once again, it prevented compaction and solution compaction to maintain reservoir porosity. Moreover, CD-3 and Qtz-2 cements were possibly derived from hydrothermal fluid, which led to the dissolution of the Z₂dn dolomite reservoir. As corollary, the numerous stages of dolomite cementation recorded here, the recognition of a single episode of oil charge, and weak reservoir overpressures, are the main factor contributing to a lower porosity development in the southeastern Sichuan Basin when compared to the central Sichuan Basin. These results have profound implications to the economic potential of similar oil and gas prospects deep in lower Paleozoic rocks across the world.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107509"},"PeriodicalIF":3.7,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288966","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":"A sequence boundary related aeolian sand record in a continental basin: The Cretaceous-Paleogene White Sandstone Member, Tabei Uplift, Tarim Basin, NW China","authors":"Xiaoyang Gao ,&nbsp;Luxing Dou ,&nbsp;Wenxiang He ,&nbsp;Qi Sun ,&nbsp;Zhenli Yi ,&nbsp;Bin Li ,&nbsp;Qiaolin He ,&nbsp;Jineng Jin ,&nbsp;Yong Hu ,&nbsp;Jingwen Yan ,&nbsp;Li Zhang","doi":"10.1016/j.marpetgeo.2025.107514","DOIUrl":"10.1016/j.marpetgeo.2025.107514","url":null,"abstract":"<div><div>A sequence boundary typically corresponds to an unconformity, with fluvial incised-valley fills representing a classic depositional model. However, aeolian deposits associated with sequence boundaries, though equally significant, have received less attention in studies of continental basins. Therefore, this study investigates aeolian sand sedimentary records near a sequence boundary in a continental basin based on an integrated analysis of 3D seismic volumes, wireline logs and cores from the Cretaceous-Paleogene deposits in the Tabei Uplift (Tarim Basin, NW China). The Cretaceous-Paleogene White Sandstone Member was formed in a salt-lake margin desert environment above a local unconformity surface that is well recognized on seismic profiles. The studied sandstone sequence is characterized by its friable texture and exhibits distinctive aeolian depositional features, including developed grainfall strata and grainflow strata within the core samples. Scanning electron microscopy (SEM) analysis reveals the presence of abundant dish-shaped impact pits on quartz grain surfaces, providing compelling evidence for the aeolian origin of these sandstones. During the Late Cretaceous to Paleogene period, the study area underwent significant geomorphological changes due to the tectonic uplift of the Tianshan and Kunlun Orogenic Belts. This tectonic activity resulted in the progressive erosion of Cretaceous strata in both the northwestern and southeastern regions of the research area. During this period, with regression of the Tarim Sea, aridity gradually increased, leading to the formation of extensive aeolian sands in the area. The aeolian sandstone pinches out from the southeast to the northwest in the area east of the WM7 fault belt. In the Paleogene, incised valleys were developed and transported eroded aeolian sands to the salt lake in the northwest. This study demonstrates the transformation of Cretaceous-Paleogene aeolian sand in a \"sandstone factory\" in the northern Tarim Basin during a greenhouse period. The \"sandstone factory\" provides an opportunity for research on sequence boundary-related aeolian sandstone unrelated to a fluvial incised valley in a continental basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107514"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331072","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":"Cutting-edge reverse time migration imaging of the hydrocarbon deposits in the Outer Carpathian fold-thrust belt","authors":"Tomasz Maćkowski ,&nbsp;Aurelia Zając ,&nbsp;Piotr Hadro ,&nbsp;Adam Cygal ,&nbsp;Michał Stefaniuk","doi":"10.1016/j.marpetgeo.2025.107515","DOIUrl":"10.1016/j.marpetgeo.2025.107515","url":null,"abstract":"<div><div>The Western Outer Carpathian fold-thrust belt is an example of strongly tectonically disturbed rock formations characterized by steeply dipping, narrow folds. The results of seismic surveys conducted in that region were used to evaluate the efficiency of the Pre-Stack Depth Migration using Reverse Time Migration (PreSDM RTM) processing workflow to enhance and detail the seismic imaging of geological structures. The analysis focused on seismic imaging of three hydrocarbon accumulations discovered using surface geological mapping methods long before the seismic methods were implemented into the hydrocarbon exploration.</div><div>The key problem in the application of the RTM algorithm is the construction of a highly accurate seismic velocity field. In this study, two inversion methods were used for this purpose: gravity inversion and the Early Arrival Waveform Inversion, employing as initial velocity model one derived from well-log data and standard refraction tomography. The effectiveness of the PreSDM RTM was assessed using both isotropic and anisotropic algorithms, particularly employing the TTI anisotropy variant due to the geological structure.</div><div>The results obtained showed that RTM migration enables the imaging of challenging details of strongly tectonically disturbed structures in the Carpathian fold-thrust belt, such as steep and tight folds or small-displacement faults. The best seismic imaging was achieved using TTI RTM algorithm, whose additional advantage is the accurate horizontal positioning of fold culminations being potential hydrocarbon traps, which is crucial for the proper location of drilling sites. The RTM efficacy was confirmed by good imaging of shallow hydrocarbon accumulations, whose geological structure is recognized by drillings.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107515"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331073","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":"Dynamic model for charging tight gas reservoirs: A case study from the Xujiahe Formation in the Sichuan Basin, China","authors":"Haoming Shao ,&nbsp;Min Wang ,&nbsp;Junfeng Cui ,&nbsp;Hui Jin ,&nbsp;Dianshi Xiao ,&nbsp;Yidong Jia ,&nbsp;Wei Li ,&nbsp;Xiaodie Guan ,&nbsp;Chen Zhao ,&nbsp;Tao Zhang","doi":"10.1016/j.marpetgeo.2025.107512","DOIUrl":"10.1016/j.marpetgeo.2025.107512","url":null,"abstract":"<div><div>As an important unconventional natural gas resource, the occurrence of tight gas is of great significance for the accumulation of natural gas. However, the charging process of tight gas is complex and diverse. Although previous studies have mainly focused on individual charging parameters, there is a lack of research on the coupling of multiple factors on the control of the charging process of tight gas. Consequently, this paper uses an example from the tight sandstones of the Upper Triassic Xujiahe Formation, Sichuan Basin, China, to elucidate insights by employing physical charging simulation of nuclear magnetic resonance (NMR) coupling displacement combined with physical property analyses, scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-pressure mercury injection (HPMI) experiments. The principal findings are: (1) The tight reservoirs of the Xujiahe Formation can be classified into four types based on the differences in pore structure. From Type I to IV reservoirs, chlorite coatings and dissolution progressively weaken, with pore characteristics (as shown by NMR T₂ spectra) transitioning from a bimodal distribution dominated by macropores to a unimodal distribution characterized by micropores. (2) The charging process of tight gas is divided into three stages: low-pressure rapid charging stage (A), medium-high pressure slow charging stage (B), and late non-continuous slow charging stage (C). Type I reservoirs are mainly charged in stage A, Types II and III reservoirs in stage B, and Type IV reservoirs in stage C. (3) The charging process of tight gas is controlled by a combination of charging pressure, pore structure, and water film. Higher charging pressure has a significant impact on the gas content of poor reservoirs. Under the same charging pressure, the gas saturation decreases with the decrease in of pore size. As the charging pressure increases, the influence of the water film diminishes. (4) Through multi-factor analysis, a tight gas saturation evaluation model is established that considers reservoir types and pressure and can predict the tight gas charging process and gas saturation in different types of tight reservoirs. This research not only aids in understanding the accumulation process of tight gas but also provides a theoretical foundation for the accurate prediction of tight gas sweet spots.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107512"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144307066","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":"Main controls on nitrogen cycling and Mo-U enrichment of the Middle Triassic Chang 7 Member in the Ordos Basin: Implications for redox and ultra-organic enrichment in a giant highly productive lake","authors":"Chuhan Zhao ,&nbsp;Xiaodong Liu ,&nbsp;Wanglu Jia ,&nbsp;Wenzheng Zhang ,&nbsp;Jian Chen ,&nbsp;Jinbu Li ,&nbsp;Ping'an Peng","doi":"10.1016/j.marpetgeo.2025.107508","DOIUrl":"10.1016/j.marpetgeo.2025.107508","url":null,"abstract":"<div><div>During the deposition of the Chang 7 Member (∼241.5 Ma) black shale from the Yanchang Formation in the Ordos Basin, a giant and deep perennial lake developed. This deposition represents a substantial organic carbon burial, and this lake serves as a significant focus for investigating the ecosystem recovery and environmental evolution following the end-Permian mass extinction (EPME). Due to potential influences from volcanic-hydrothermal activity and terrigenous detrital input, the primary controls on nitrogen (N) and redox-sensitive trace element enrichment remain unclear, leading to ongoing debates regarding the lake's redox conditions inferred from these proxies. This study examines the main controls on the different isotopic compositions of N species and the enrichment of redox-sensitive trace elements (RSTEs) in deep lake facies drill cores. The following conclusions can be drawn: (1) The high total N content (averaging 1.11 %) and inorganic N content (accounting for 65 % of total N) are likely influenced by terrigenous detrital input. This input also affects N isotope composition, leading to summarized results of bulk δ¹⁵N_bulk values being lower than δ¹⁵N_ker (δ¹⁵N of the kerogen) values (average 2.4 ‰). Other post-depositional factors, including thermal maturation and retained oil, do not significantly affect the organic N isotopes, thereby enhancing their reliability for N cycling analysis. (2) The notable enrichments of Mo and U in the Chang-7 source rocks, with Mo_EF values reaching 90.8 and U_EF values of 13.9, were primarily controlled by strong adsorption of metal sulfides and organic matter under anoxic-euxinic bottom water conditions, with additional input from hydrothermal activities. (3) Under anoxic-euxinic bottom water conditions, moderate δ¹⁵N_ker values (∼4.5 ‰) and decreasing δ¹⁵N_ker in deeper facies indicate a deep redox chemocline with an metalimnetic oxygen minimum near the lake's margin. N cycling was primarily dominated by denitrification but with a notable contribution from nitrogen fixation, while nitrates and ammonium were the primary bio-limiting nutrients in the metalimnetic oxygen minimum. Factors such as global cooling, which facilitated ecological recovery after the EPME, and local volcanic-hydrothermal activities that enhanced weathering and nutrient input, may have promoted primary production and development of anoxic bottom water in this large lake, ultimately fostering the anomalous accumulation of organic material.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107508"},"PeriodicalIF":3.7,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144272153","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}