Marine and Petroleum Geology最新文献

{"title":"Origin and accumulation of natural gas in the Sinian-Cambrian reservoirs of the central Sichuan Basin, southwest China: Implications from both closed and semi-open pyrolysis experiments","authors":"Xing Wang ,&nbsp;Haifeng Gai ,&nbsp;Peng Cheng ,&nbsp;Qin Zhou ,&nbsp;Tengfei Li ,&nbsp;Sui Ji ,&nbsp;Hui Tian","doi":"10.1016/j.marpetgeo.2025.107333","DOIUrl":"10.1016/j.marpetgeo.2025.107333","url":null,"abstract":"<div><div>Large amounts of natural gas have been discovered in the Sinian-Cambrian reservoirs of the central Sichuan Basin, southwest China. However, the gas origin and accumulation patterns remain unresolved due to a poor understanding of the geochemical signatures for natural gas derived from cracking of paleo-oils. In this study, a Cambrian sourced oil sample and its SARA (saturates, aromatics, resins and asphaltenes) fractions were pyrolyzed in closed systems to investigate the effects of oil fraction composition on the molecular signature and methane carbon isotope composition of the generated gas. Meanwhile, the oil sample and its asphaltene fraction were further pyrolyzed in stepwise, semi-open system to investigate how possibly the geological openness affects the generation potential and geochemical signatures of the resulted gas from the cracking of oil and asphaltene. It is revealed that although the carbon isotopes of methane (δ¹³C₁) generated from oils change with SARA compositions in the closed system, the δ¹³C₁ values of natural gas from both asphaltene (representing kerogen) and three types of oils with different SARA compositions are lighter than −40‰, and differ significantly from the δ¹³C₁ values of the present natural gas in the Sinian-Cambrian reservoirs. In semi-open systems, the generation potential of natural gases from residual asphaltenes and oils decrease drastically. The gases are dominated by methane with δ¹³C₁ values range from −39.8‰ to −29.4‰, which could even be heavier than the δ¹³C values of original asphaltenes and oils. The geochemical signatures of the natural gases in the Sinian-Cambrian reservoirs are similar to those of gaseous pyrolyzates in the semi-open systems, suggesting that early-generated natural gases may have been partly lost and the late gas derived from residual oils and kerogen forms the present gas pools. The geochemical variation of natural gases in different Sinian-Cambrian reservoirs is primarily controlled by paleostructures. Higher positions of the paleo-uplift contain a higher proportion of early-generated gases and thus have higher gas wetness and lighter δ¹³C₁ values, such as the natural gases in the Ziyang area and the Taihe area. In contrast, the natural gases in lower positions of the paleo-uplift have a higher proportion of late gases, characterized by lower gas wetness and heavier δ¹³C₁ values, such as those in the Weiyuan gases field and the Anyue gas field.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107333"},"PeriodicalIF":3.7,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143420672","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":"Variability in carbonate cementation induced by multistage fluid evolution in coal measures: Insights from the tight sandstones of the lower Jurassic Yangxia Formation, Kuqa Depression, Tarim Basin, China","authors":"Nianmin Zan ,&nbsp;Yingchang Cao ,&nbsp;Kelai Xi ,&nbsp;Guanghui Yuan ,&nbsp;Xianzhang Yang ,&nbsp;Guoding Yu ,&nbsp;Hao Wang ,&nbsp;Changjian Yuan ,&nbsp;Zilong Li ,&nbsp;Weikai Huang","doi":"10.1016/j.marpetgeo.2025.107329","DOIUrl":"10.1016/j.marpetgeo.2025.107329","url":null,"abstract":"<div><div>Carbonate cementation is a key factor in the densification of sandstone reservoirs in the Yangxia Formation of the Kuqa Depression; however, the formation mechanisms are not yet fully understood. The carbonate cements in the tight sandstones of the Yangxia Formation are primarily composed of siderite, ferroan calcite, ferroan dolomite, and ankerite. The δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr data indicate that the formation of these carbonate cements was controlled by the thermal evolution of the coal-bearing source rocks of the Yangxia Formation. Early-phase ferroan siderite (S1) and ferroan dolomite (D1) formed between 199.5 Ma and 170.54 Ma, with carbon derived from the reduction of CO₂ by methanogenic bacteria and calcium from the original formation water. Mid-phase ferroan calcite (C1) and ankerite (D2) formed between 72 Ma and 50 Ma, with carbon sourced from a mixture of inorganic CO₂ and CO₂ released during the thermal degradation of organic matter in the coal-bearing source rocks of the Yangxia Formation. Late-phase ferroan calcite (C2) formed between 18.6 Ma and 13.6 Ma, with carbon derived from a mixture of inorganic CO₂ and CO₂ released by the thermal decarboxylation of organic matter in the coal-bearing source rocks of the Yangxia Formation. The calcium in both mid-phase and late-phase carbonate cements was sourced from the smectite-to-illite transformation in the coal-bearing source rocks of the Yangxia Formation. Clumped isotope and fluid inclusion thermometry reveal that, prior to hydrocarbon charging, carbonate cementation significantly reduced the porosity and permeability of the sandstones in the Yangxia Formation, resulting in reservoir densification.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107329"},"PeriodicalIF":3.7,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143428118","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":"Stacking patterns in minibasins and intra-salt geometries as clues for reconstructing salt tectonic processes: The case of the Northern Santos Basin, Brazil","authors":"Giovana Rebelo Diório ,&nbsp;Barbara Trzaskos ,&nbsp;Leonardo Muniz Pichel ,&nbsp;Sérgio Francisco Leon Dias ,&nbsp;Vanessa da Silva Reis Assis","doi":"10.1016/j.marpetgeo.2025.107328","DOIUrl":"10.1016/j.marpetgeo.2025.107328","url":null,"abstract":"<div><div>Although research in Northern Santos Basin focuses on its hydrocarbon-rich pre-salt section, Aptian evaporites underwent complex salt tectonics, shaping intra-salt features and post-salt deposition. Seismostratigraphic mapping of a 3D seismic block identified five key-surfaces and four chronostratigraphic units, highlighting intra-salt features, as well as minibasins characteristics in plan-view (shape, thickness) and cross-sections (stacking patterns of depocenters). The non-planar base-salt has ramps (most up to 10°) trending NW-SE and NE-SW. The heterogenous Aptian evaporitic Ariri Fm. exhibits decreasing diapir maturity basinwards. In the north, E-W-salt walls and stocks contain upright folds, while in the south, N-S-directed salt anticlines with intra-salt asymmetric fold-and-thrust prevail. The Albian-Cenomanian Camburi Gr. (max. ∼800 m thick) features near-circular or E-W-elongated suprasalt depocenters, most with vertically stacked depocenters and some subbasins near the E-W Itapu-Búzios salt wall, recording salt movement towards the south and formation of density-driven minibasins above base-salt lows. Depocenters of the Turonian-Maastrichtian Frade Gr. (max. ∼2.2 km thick) show ubiquitous changes in plan-view (rounded to N-S elongated) and cross-section (most laterally shifting depocenters, followed by stacked dipping), marking the apex of two salt tectonics trends. Northern sedimentary input led to reactive diapirism and seaward-migrating depocenters, while southern E-directed salt translation formed N-S elongated minibasins, ramp syncline basins and contractive features within N-S salt bodies. Subcircular depocenters of the Cenozoic Itamambuca Gr. are laterally shifting and vertically stacked, reflecting decreasing salt tectonic activity. Identifying stacking patterns is crucial for unraveling minibasin nucleation and understanding local controls in evolution of salt tectonics in salt-bearing basins.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107328"},"PeriodicalIF":3.7,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143428119","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":"Seismic geomorphology of the karstified Upper Jurassic-Lower Cretaceous carbonate succession in the Carpathian Foredeep area, Poland","authors":"Jerzy Samojluk ,&nbsp;Jan Tveranger ,&nbsp;Jan Barmuta","doi":"10.1016/j.marpetgeo.2025.107331","DOIUrl":"10.1016/j.marpetgeo.2025.107331","url":null,"abstract":"<div><div>Characterization of subsurface reservoirs composed of soluble rock formations is commonly challenged by the presence of structures forming irregularly distributed, multi-scale inhomogeneities originating from karstification and karst degradation. Although the majority of paleokarst features occur at sub-seismic scales, seismic data interpretation can provide information on type and spatial distribution of meso-scale karst features. Integrating these with other data sources and a genetic understanding of karst formation provides a means to decipher former karst systems and their extent and potential impact on subsurface reservoirs. In turn this offers the potential for improved reservoir characterization and reducing exploration- and production-risks. The present work investigates the Upper Jurassic–Lower Cretaceous carbonate succession located in the Polish sector of the Carpathian Foredeep. From the Early Cretaceous to Middle Miocene, the stratigraphic record reveals that the region experienced two prolonged episodes of subaerial exposure, highlighting the potential for extensive overprinting of these formations by karst during these events. Using conventional 3D seismic data, supplemented by wireline logs, numerous karst-related features can be identified and mapped. Detailed structural, stratigraphic, and geomorphological analysis suggest that karst development was controlled by lithological and tectonic factors, as well as relative sea level change. The results are synthesized into a conceptual model for regional karst evolution and its impact on the Upper Jurassic–Lower Cretaceous carbonate succession in the Carpathian Foredeep. Our study demonstrates the utility of applying an integrated workflow when characterizing paleokarst systems in geologically complex, carbonate successions.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107331"},"PeriodicalIF":3.7,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394244","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":"Diagenetic controls on sweet spots pore types and reservoir quality of Permian tight sandstones in the Ordos Basin, China","authors":"Yaxin Shang ,&nbsp;Keyu Liu ,&nbsp;Ziyi Wang ,&nbsp;Bo Zhang","doi":"10.1016/j.marpetgeo.2025.107324","DOIUrl":"10.1016/j.marpetgeo.2025.107324","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Identification of sweet spots in tight sandstone reservoirs is crucial to the effective economic development of tight oil and gas. The pore types and porosity-permeability relationships in the sweet spots of tight sandstones are primarily controlled by sedimentary and diagenetic processes. All of the Permian tight sandstone sequences in the northeastern Ordos Basin were deposited under similar depositional environment with sediments supplied from the same source. Understanding the variations of the petrophysical properties of the Permian tight sandstones would thus provide insight into the control of reservoir quality by the diagenetic process. Petrographic and petrophysical analyses were conducted on the Permian tight sandstone sweet spot reservoir interval, revealing the distribution and characteristics of pore types that control reservoir quality. Pore types change from a mix pore type of primary intergranular, secondary dissolution porosity and undifferentiated microporosity in the shallower upper Permian reservoir interval to a secondary dissolution porosity- and microporosity-dominated one in the deeper lower Permian reservoir interval. Porosities decrease from 15.18% in the upper Permian to 10.43% in the lower Permian, while permeabilities decrease from 15.29 mD to 0.85 mD. The primary intergranular porosity decreases from 7.94% to 0%, while the secondary dissolution porosity increases from 4.75% to 6.22%. In contrast, microporosity increases from 3.60% to 4.52%. With increasing burial depth, the intergranular porosity decreases significantly due to mechanical compaction or occlusion by quartz cementation. The precipitation of authigenic clay minerals and ferrous carbonate cementation also contributes to the reduction of primary intergranular porosity. Although the dissolution of feldspars produced more secondary dissolution porosity with increasing burial depth, quartz cementation and authigenic clay minerals resulting from feldspar dissolution limit the porosity increase from mineral dissolution. Changes in pore type proportions and the reduction in total porosity with increasing burial depth alter porosity–permeability relationships. In the shallower upper and middle Permian reservoir intervals, primary intergranular porosity are well developed, typically exhibiting large pore throat sizes. The average medium pore throat radius in the upper and middle Permian reservoirs reaches 0.88 μm and 0.42 μm, respectively, resulting in high permeability. In contrast, the deeper lower Permian reservoir intervals lack primary intergranular porosity and primarily develop secondary dissolution porosity and microporosity, which connect to small pore throats. As a result, the lower Permian reservoir has an average medium pore throat radius of only 0.32 μm, resulting in low permeability. Because the lower Permian reservoirs are dominated by secondary dissolution porosity and microporosity, their porosity–permeability relationships have gentler ","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107324"},"PeriodicalIF":3.7,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378910","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":"Origin of reedmergnerite in sodium carbonate successions and environmental implications in a Late Paleozoic alkaline saline lake, NW Junggar Basin, China","authors":"Kuanhong Yu ,&nbsp;Xinyu Duan ,&nbsp;Yingchang Cao ,&nbsp;Shuo Du","doi":"10.1016/j.marpetgeo.2025.107323","DOIUrl":"10.1016/j.marpetgeo.2025.107323","url":null,"abstract":"<div><div>The Fengcheng Formation originated from a Late Paleozoic alkaline saline lake, characterized by abundant evaporites and serving as the primary source rocks within this evaporitic basin. Boron accumulation in this set of evaporitic deposits is primarily in the form of reedmergnerite (NaBSi₃O₈). Although reedmergnerite can be found in each sub-environment of this alkaline saline lake, it may dominate in evaporite successions near the evapocenter. However, its distribution pattern and origins within the evaporite succession remain unclear. Through comprehensive analyses of a reedmergnerite-rich evaporite core section, we propose the following: (1) boron originates from volcanic ash and hot spring; (2) diagenetic processes within a hydrothermal environment involve replacement of sodium carbonates by loughlinite (Na₂Mg₃Si₆O₁₆▪8H₂O) fibers followed by crystallization of reedmernerite within loughlinite during contemporaneous diagenesis; (3) vertical distributions of reedmergnerite within evaporitic successions are controlled by episodic volcanic eruptions, hot spring ejections, and climatic cycles; and finally, (4) significant volumes of reedmergnerite occur within sodium carbonate successions due to multiple stages of volcanic eruptions and hot spring ejections. Therefore, the boron accumulations within the sodium carbonate successions in the Fengcheng Formation provide compelling evidence of deep sources contributing to the formation of chemical deposits in an alkaline saline lake environment. The accumulation of reedmergnerite can be regarded as a boron resource that formed specifically within this type of alkaline saline lake setting. Furthermore, the presence of laminated reedmergnerite and louglinite can serve as indicators for identifying episodic volcanic activities and hot spring occurrences, thereby providing a basis for assessing the environmental conditions during source rock formation in an evaporitic basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107323"},"PeriodicalIF":3.7,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386831","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":"Sabkha deposition on an epicontinental-foredeep: The petroleum-bearing Cane Creek interval of the Pennsylvanian Paradox Formation, in the Paradox Basin, Utah, U.S.A.","authors":"Elliot A. Jagniecki ,&nbsp;Michael D. Vanden Berg ,&nbsp;Lauren P. Birgenheier ,&nbsp;Scott M. Ritter ,&nbsp;Gregor Maxwell ,&nbsp;Dave List","doi":"10.1016/j.marpetgeo.2025.107320","DOIUrl":"10.1016/j.marpetgeo.2025.107320","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Pennsylvanian Paradox Formation in the northern fold and fault belt of the foreland Paradox Basin, southeastern Utah, contains 4th and 5th order cyclothems of closed basin halite salt packages (60–92 m thick) interbedded with intervals of evaporitic-carbonate-siliciclastic (n = ∼30 cycles, each &lt;36 m thick). The cyclothems record rhythmic high-stand and low-stand deposition in an epicontinental foredeep marine basin influenced by subsidence, arid subtropical climate, and sea level changes that created continental inlets on the edge of the Panthalassic Ocean. Here, we document evaporitic-carbonate-siliciclastic facies of the unconventional hydrocarbon Cane Creek interval, clastic cycle 21, from eight cored drillholes spanning a northwest to southeast transect that represent sabkha-type deposition of an ancient interior seaway. This interpretation is collective from several past studies, however, a comparative sedimentological approach for the origin of depositional textures provides a finer scale description of parasequences that internally contain meter-scale shallowing upward successions. The successions are both allocyclic and autocyclic related to marine transgressions and regressions within a restricted, tidally influenced, marine basin and associated with subtidal, intertidal, and supratidal paleoenvironments. The Cane Creek is informally divided into three distinct stratigraphic zones: from top to bottom A, B, and C zones. The A and C zones are composed of fabric-destructive and laminated anhydrite laths, dolomitic mudstone, and algal-laminated source rock mudstones (15–20 wt % total organic carbon), interpreted as prograded supratidal flats during marine regressions. Anhydrite textures vary from finely laminated needles with dolomitic mud drape couplets, upward directed syntaxial crystalline fabric draped by silty dolomitic mud, and nodular laths. Volumetrically, smaller proportions of anhydrite occur in the C zone in the northwest part of the basin attributed to tidal inlet dilution. Intraclastic mudstone lag deposits composed of compacted mudrock clasts overlay anhydrite beds and are interpreted as diachronous storm or subaqueous debris flow deposits. The middle B zone is primarily low-permeable muddy sandstone to siltstone (0.009–0.202 mD; porosity 6%–17%) that contains bidirectional lenticular ripples, slack water mud drapes, trace fossil burrows, diagenetic anhydrite-dolomite-quartz-halite cements, and interbeds of organic-rich mudstone, and stratigraphically thickens to the northwest. Siliciclastic supply is interpreted as being sourced by fluvial drainage from the Uncompahgre Ancestral Rocky Mountains uplift and eolian processes that later were reworked by tidal and storm processes. Source rock analysis of interbedded organic-rich mudstones within all zones are mixed type I and II (lacustrine and marine) with more fluvial detrital type III in the southern part of the basin. Thin interbedded organic-rich mudstones (c","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107320"},"PeriodicalIF":3.7,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394243","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":"Development model of fracture-filling gas hydrates at the top of gas chimneys, the Songnan Low Uplift in Qiongdongnan Basin of the northern South China Sea","authors":"Tingwei Li ,&nbsp;Jinfeng Ren ,&nbsp;Zenggui Kuang ,&nbsp;Xiaoxue Wang ,&nbsp;Mengjie Xu ,&nbsp;Chenlu Xu ,&nbsp;Zhejun Pan","doi":"10.1016/j.marpetgeo.2025.107326","DOIUrl":"10.1016/j.marpetgeo.2025.107326","url":null,"abstract":"<div><div>Fracture-filling gas hydrates are consistently associated with gas chimneys; however, the causal mechanism remains unclear. The W07 orebody in the Songnan Low Uplift, located in the Qiongdongnan Basin of the northern South China Sea, was examined as a case study. By employing a combination of logging while drilling and seismic surveys, we aimed to elucidate the developmental model of fracture-filling gas hydrates within the structural context of gas chimneys and quantitatively assess the roles of the overlying strata and faults in the formation of leakage pathways. Gas of various origins migrates to the bottom of the gas hydrate stability zone through the gas chimney and subsequently flows laterally within the permeable sand strata. Pore-filling gas hydrates develop in the peripheral areas surrounding the gas chimney. The continuous accumulation of free gas in the central area leads to an increase in fluid pressure. Once the fluid pressure reaches the horizontal minimum principal stress, the overlying strata will undergo hydraulic fracturing, leading to the formation of a network of vertical hydraulic fractures that provide a pathway for the further upward migration of gas-bearing fluids. Fracture-filling gas hydrates form in high-angle cracks under appropriate temperature and pressure conditions. In terms of leakage, the overlying strata, with a minimum hydraulic pressure of 1.08 MPa, take precedence over the F07 fault, which has a minimum increment in fluid pressure of 1.12 MPa. Thus, the overlying strata, rather than the F07 fault, play a decisive role in the formation of leakage pathways.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107326"},"PeriodicalIF":3.7,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386840","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":"Improved representation of sub-wireline scale lithological heterogeneity in geological models","authors":"Achyut Mishra ,&nbsp;Seyed Ahmad Mortazavi ,&nbsp;Julie Dickinson ,&nbsp;Ralf R. Haese","doi":"10.1016/j.marpetgeo.2025.107322","DOIUrl":"10.1016/j.marpetgeo.2025.107322","url":null,"abstract":"<div><div>Siliciclastic reservoirs often comprise lithological heterogeneity at mm-to cm-scales in the form of fine laminations of intraformational baffles. Such heterogeneities enhance capillarity and are often enriched in clay minerals such as chlorites. These properties could significantly influence subsurface fluid flow and fluid rock reactions. However, these heterogeneities are difficult to represent in geological models primarily because they exist at a scale which is below the resolution of conventional wireline logs. This paper presents an approach for deducing such heterogeneities using a combination of core plug and wireline log data to derive rock types capturing variations in intraformational baffles. The rock types were further populated in geological models to honour a nested representation of heterogeneity ranging from seismic to core plug scale. We also present a new upscaling method to ensure that cm-scale discrete rock properties are not lost to averaging. The study shows that property models derived using the conventional geo-modelling approach could overestimate porosity by about 20–30% for the sections with cm-scale laminations. Additionally, wireline log derived permeability values were found to be inconsistent with heterogeneity in fine laminations as observed in core plugs. The proposed approach attempts to overcome this issue by upscaling permeability in a way that honours variations in intraformational baffles.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107322"},"PeriodicalIF":3.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378907","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":"Tight origin and hydrocarbon potential of shell interlayers in shale: A case of Lower Jurassic Dongyuemiao member, Sichuan Basin, China","authors":"Zhiyun Yu ,&nbsp;Benzhong Xian ,&nbsp;Zhenkui Jin ,&nbsp;Qianran Wu ,&nbsp;Yi Shu ,&nbsp;Haocheng Shi ,&nbsp;Junyang Geng ,&nbsp;Lin Zhao ,&nbsp;Yichen Liu","doi":"10.1016/j.marpetgeo.2025.107325","DOIUrl":"10.1016/j.marpetgeo.2025.107325","url":null,"abstract":"<div><div>Tight shell interlayers are widely distributed in global marine and lacustrine organic-rich shale successions, serving as key targets for reservoir prediction. However, the limited understanding of these interlayers presents challenges in characterising reservoirs and optimising hydrocarbon recovery in shell-rich shale formations. This study investigates the Lower Jurassic Dongyuemiao Member in the Sichuan Basin, Southwest China, using petrological, geochemical, and pore structure characterization techniques to differentiate shale from shell interlayers, and investigate the mechanisms underlying the tight properties of shell-rich interlayers. Results suggest that two shale lithofacies (e.g., laminated argillaceous shale and massive mixed mudstone) and two shell interlayer lithofacies (e.g., bedded-to-laminated shelly-bearing argillaceous mudstone and massive shell limestone) were identified. Porosity, permeability, and total organic carbon content of shale lithofacies are significantly higher than those of interlayer lithofacies. Special attention was therefore given to the analysis of sedimentary processes and diagenesis occurring in the two interlayer lithofacies. Shell interlayers were deposited by sediment gravity flows triggered by storm events. The two shell interlayers were considered the products of low-density turbidity currents and cohesive debris flows. Among the two shell interlayers, massive shell limestones exhibited the worst reservoir quality due to their fine mud-grade matrix compositions and non-lamellar textures. Differential compaction had a significant impact on the heterogeneous distribution of cements in interlayer lithofacies. Additionally, massive shell limestones experienced three distinct stages of cementation, including eogenetic calcareous cement and pyrite, and mesodiagenetic microquartz, which filled intergranular pores in the massive shell limestones and reduced reservoir quality. By contrast, the bedded-to-laminated shelly-bearing argillaceous mudstone also underwent three stages of cementation, comprising eogenetic pyrite, mesodiagenetic microquartz and ferroan calcite cement. However, close contact with black shales facilitated the development of dissolved pores within the lithofacies. Finally, based on sedimentary and diagenetic processes, tight models were established for different shell interlayers, making them applicable to other shell-rich shale successions for shale gas and oil exploration and production worldwide.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107325"},"PeriodicalIF":3.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403081","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}