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1
Hao, Nai, Yongliang Wang, Hao Cheng, Xiaochong Wu e Yi Zhao. "Hydration Absorption and Thermal Effects of Outcrop Porous Sandstone Based on Intelligent Experimental and Infrared Thermography Techniques". Energies 16, n. 22 (12 novembre 2023): 7540. http://dx.doi.org/10.3390/en16227540.
Testo completoAbstract (sommario):
Sandstones are enriched in deep energy reservoirs and also exist as outcrop rocks, where the pore characteristics of sandstone are influenced by hydration absorption and thermal effects. To study the influence of the initial temperature on the hydration absorption characteristics of outcrop porous sandstone in the Mogao Grottoes, China, an intelligent experimental device for rock hydration was used. The hydration absorption characteristics and temperature effects of sandstone were analyzed by using infrared thermography techniques to monitor the infrared radiation characteristics of the sandstone’s surface during hydration absorption. The experimental results show that the higher the initial temperature of the rock samples, the shorter the time it takes for the sandstone to absorb enough water to reach saturation. The temperature variation of sandstone with different initial temperatures was also determined; the variation in the hydration absorption of sandstone conforms to certain rules, which can be expressed by formulae containing certain parameters. The changing trend of hydration absorption in outcrop porous sandstone shows that the hydration absorption increases rapidly at first, and then the rate of increase slows down until the hydration absorption remains unchanged after saturation. The experimental technique and method provide feasible means and techniques to evaluate the hydration absorption and thermal effects of outcrop porous sandstone, for further detecting the weathering degree of rock grottoes and revealing the damage mechanisms.
2
Blake, Oshaine O., Ryan Ramsook, Uwaila C. Iyare e Ariana Osman. "Petrographic, Petrophysical, and Mechanical Characterisation of the Ultra- Tight Casa Cruz Sandstone, Moruga Formation, Southern Basin, Trinidad". West Indian Journal of Engineering 46, n. 2 (gennaio 2024): 79–90. http://dx.doi.org/10.47412/hzwe3939.
Testo completoAbstract (sommario):
Durability, compactness, and natural strength of sandstones are pivotal properties for its subsequent application as a building material. If a sandstone is tight and contains petroleum, then hydraulic fracturing is necessary to achieve commercial production. The Casa Cruz Sandstone Member, southern Trinidad, is currently being explored as a potential petroleum target and building material. This study investigates the petrographic, petrophysical, and mechanical characteristics of the Casa Cruz sandstone to understand the factors that control the quality of the sandstone and to determine the sandstone’s suitability as a natural resource. A thin-section analysis was performed to investigate the mineralogy, texture, and diagenesis of the sandstone. Permeability, porosity, density, P- and S-wave velocities, unconfined compressive strength (UCS) and confined compressive strength were measured. The elastic properties (Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio) were estimated from inversion of the P- and S-wave velocities. The results show that the Casa Cruz sandstone is one of the tightest sandstone types reported in the literature with porosity of 0.7% and permeability of 4.7 x 10-22 m2 (0.47 nD). Authigenic cementation and mechanical compaction are the main diagenetic processes that jointly controlled the quality of the sandstone. The sandstone was classified as a very strong (UCS of 128 MPa) quartz-arenite and is barren of petroleum and bioclasts. Brittle failure behaviour was exhibited, accompanied by axial splitting fractures and shear fractures under unconfined and confined conditions, respectively. The Casa Cruz sandstone is suggested to be an excellent building material as its petrophysical and mechanical properties are comparable to those of commercial industry grade of Westerly granite and Naparima Hill argillite.
3
Zheng, Dong-Yu, e Si-Xuan Wu. "Principal component analysis of textural characteristics of fluvio-lacustrine sandstones and controlling factors of sandstone textures". Geological Magazine 158, n. 10 (21 maggio 2021): 1847–61. http://dx.doi.org/10.1017/s0016756821000418.
Testo completoAbstract (sommario):
AbstractTextures are important features of sandstones; however, their controlling factors are not fully understood. We present a detailed textural analysis of fluvio-lacustrine sandstones and discuss the influences of provenance and depositional environments on sandstone textures. The upper Permian – lowermost Triassic Wutonggou sandstones in the Bogda Mountains, NW China, are the focus of this study. Sandstone thin-sections were studied by point counting and their textures were analysed using statistical and principal component analysis. Fluvial lithic, fluvial feldspathic, deltaic lithic, deltaic feldspathic, littoral lithic and littoral feldspathic sandstone were classified and compared. These comparisons indicate that lithic and feldspathic sandstones from the same depositional settings have significant differences in graphic mean, graphic standard deviation and roundness; in contrast, sandstones from different depositional settings but with similar compositions have limited differences in textures. Moreover, three principal components (PCs) are recognized to explain 75% of the total variance, of which the first principal component (PC1) can explain 44%. In bivariate plots of the PCs, sandstones can be distinguished by composition where lithic and feldspathic sandstones are placed in different fields of the plots along the axis of PC1. However, sandstones from different depositional settings overlap and show no clear division. These results indicate that provenance, mainly the source lithology, is the most significant controlling factor on sandstone texture, whereas the depositional environment has limited influence. This study improves our understanding of textural characteristics of fluvio-lacustrine sandstones and their controlling factors, and shows the potentiality of principal component analysis in sandstone studies.
4
Li, Yanzhi, Yue Wu, Weiguo Qiao, Shuai Zhang e Xungang Li. "The Permeability Evolution of Sandstones with Different Pore Structures under High Confining Pressures, High Pore Water Pressures and High Temperatures". Applied Sciences 13, n. 3 (30 gennaio 2023): 1771. http://dx.doi.org/10.3390/app13031771.
Testo completoAbstract (sommario):
Seepage from the pores of sandstone exposed in deep mines is difficult to block by grouting. In this paper, the permeability evolution of four subcategories of sandstone with different pore structures under different confining pressures, pore water pressures and temperatures is analyzed by experiments. (1) With increasing confining pressure, the permeabilities of the four tested subcategories of sandstone all decrease, but at different rates and to different extents. (2) With increasing pore water pressure, the permeability of subcategory I1, I2 and II1 sandstones increases linearly, while that of subcategory II2 sandstone decreases following a power function under low confining pressures and tends to be stable under high confining pressures. (3) With increasing temperature, the permeabilities of the four sandstone subcategories decrease at different rates. (4) The orthogonal experimental results show that the confining pressure has the greatest influence on the permeability, followed by the water pressure and temperature. (5) The confining pressure, pore water pressure and temperature produce stress-strain in sandstone and thus change the sandstone pore structure and permeability. The permeability evolution of sandstones varies with pore structure. The findings of this study can inform the classified grouting of deep sandstone and optimize grouting parameters.
5
Sørensen, Morten Kanne, e Ida Lykke Fabricius. "Clay squirt: Local flow dispersion in shale-bearing sandstones". GEOPHYSICS 82, n. 1 (1 gennaio 2017): MR51—MR63. http://dx.doi.org/10.1190/geo2015-0036.1.
Testo completoAbstract (sommario):
Dispersion of elastic-wave velocity is common in sandstone and larger in shaly sandstone than in clean sandstone. Dispersion in fluid-saturated shaly sandstone often exceeds the level expected from the stress-dependent elastic moduli of dry sandstone. The large dispersion has been coined clay squirt and is proposed to originate from a pressure gradient between the clay microporosity and the effective porosity. We have formulated a simple model that quantifies the clay-squirt effect on bulk moduli of sandstone with homogeneously distributed shale laminae or dispersed shale. The model predictions were compared with the literature data. For sandstones with dispersed shale, agreement was found, whereas other sandstones have larger fluid-saturated bulk modulus, possibly due to partially load-bearing shales or heterogeneous shale distribution. The data that agree with the clay-squirt model indicated nonuniform pore pressure in the high-frequency regime and uniform pore pressure in the low-frequency regime. Therefore, our model showed that clay-squirt dispersion can attain a sufficient magnitude to explain much of the large dispersion observed in shaly sandstone.
6
He, Yun, Hengwei Guo, Haoxiang Lan, Can Ling e Meiyan Fu. "The Effect of Single Sandstone Stacking Pattern on the Sandstone Reservoir Physical Properties—A Case Study from the Shanxi Formation in the Daniudi Area, Northeastern Ordos Basin". Energies 15, n. 13 (28 giugno 2022): 4740. http://dx.doi.org/10.3390/en15134740.
Testo completoAbstract (sommario):
The role of the single sandstone stacking pattern in controlling the physical properties of the sandstones deposited in the distribution channels of the deltaic plain is unclear. This study aims to reveal the effect of the single sandstone packing patterns on the reservoir qualities of sandstones from the Shanxi Formation in the Daniudi gas field of Ordos Basin. Based on the core observation, 2D-image analysis, and thin section identification, the lithofacies were identified, the stacking patterns of the single sandbody were divided, and the differences in minerals composition and diagenesis of different sandstone stacking patterns were analyzed. According to the sedimentary facies analysis, 10 types of lithofacies have been identified in the Shanxi Formation in the study area. The single sandstone stacking patterns include mixed stacking patterns of coarse to medium-grained sandstone, fining upwards stacking patterns of coarse- to medium-grained sandstone, and coarsening upwards stacking patterns of fine- to coarse-grained sandstone. Among these single sandstone stacking patterns, there is a greater percentage of lithofacies with high reservoir quality in the fining upwards stacking patterns of coarse- to medium-grained sandstone. Through a comparative study of the differences in minerals composition, the degree of compaction, and dissolution of sandstones, it is suggested that the high porosities and permeabilities of the coarse- to medium-grained sandstone lithofacies in the fining upwards stacking patterns are caused by the low content of the matrix in sandstone, relatively weak compaction, relatively high amounts of primary pores, and strong dissolution. The relatively high content of rigid clastic particles with coarser-grained size was favorable for the preservation of primary pores. The relatively high primary porosity could provide favorable passages for the late diagenetic fluid, leading to the development of dissolved pores. The study can provide an important basis for the exploration of high-quality sandstone reservoirs in the distributary channels of the delta plain.
7
Huang, Huazhou, Yuantao Sun, Xiantong Chang, Zhengqing Wu, Mi Li e Shulei Qu. "Experimental Investigation of Pore Characteristics and Permeability in Coal-Measure Sandstones in Jixi Basin, China". Energies 15, n. 16 (14 agosto 2022): 5898. http://dx.doi.org/10.3390/en15165898.
Testo completoAbstract (sommario):
The research of pore and permeability characteristics of tight sandstone reservoirs in coal-measure is critical for coal-measure gas development. In this study, the pore systems of tight sandstones were studied based on low-field nuclear magnetic resonance (LF-NMR) data. The permeability of tight sandstones was obtained by the tester based on the pulse transient method. The permeability variation with the effective stress, grains, and pore characteristics was analyzed. The results show that the tight sandstone reservoirs in the coal-measure have low total porosity (2.80–4.14%), low effective porosity (0.51–1.56%), and low permeability (0.351 × 10−6–13.910 × 10−6 um2). LF-NMR T2 spectra of the testing sandstones show that the micropores are the most developed, but most of the micropores are immovable pores. The pore characteristics are significantly affected by the grain size of sandstones. The pore connectivity ranks from good to poor with decreasing sandstone particle size. The total porosity and effective porosity increase with the grain size. There is a near-linear negative relationship between permeability and effective stress when the effective stress is between 405 psi and 808 psi. The greater the number of movable pores and the larger the effective porosity, the bigger the permeability of the sandstone. The effective porosity of sandstones is a sensitive indicator for evaluating the permeability of tight sandstone reservoirs. The stress sensitivity coefficient of permeability (Ss) increases with the increase of the effective stress. The sandstone with lower permeability, smaller effective porosity, and finer grains has a higher Ss. The particle size of sandstone from coal-measure has a great influence on both permeability and Ss. The findings will provide a better understanding of the characterization of pore structure and permeability in the process the coal-measure gas extraction, which is useful for the efficient development of coal-measure gas.
8
Knysh, Ivan, e Nadiya Kremin. "Zastinoche and budaniv sandstone deposits as potential geotourism objects of the Ternopil region". Visnyk of the Lviv University. Geology Series 35, n. 35 (2021): 111–26. http://dx.doi.org/10.30970/vgl.35.09.
Testo completoAbstract (sommario):
The article provides information on existing quarries for sandstone mining as promising geotourism locations within the Ternopil region (Western Ukraine). The study area is famous for its ancient mining of natural stone from Terebovlya sandstones. The object of research is located within the Eastern European platform on the territory of Zastinoche and Budanіv deposits. Since princely times, stone has been mined here for the construction of fortresses and defensive structures. Sediments of the Neogene and Devonian ages take part in the geological structure of the Zastinoche deposit. The mineral is represented by Devonian sandstone with an average thickness of 12 m, broken by horizontal and vertical cracks into boulders. Macroscopically, sandstone is represented by red-brown, brownish-red, greyish-red, reddish-grey, brownish-grey, pink-grey, greenish-grey and light grey variations. The Budaniv deposit is composed of Quaternary, Neogene, Cretaceous and Devonian rocks. The minerals here are the sandstones of the Ivanovo formation (Devonian), the sandstone stratum consists of two horizons. The average thickness of sandstones of the first horizon (red, thick-tiled) is 14.4 m, in the thickness of sandstones there are layers of argillites and siltstones. Sandstones of the second horizon are more thinly tiled, characterized by a thickness of 2.6 to 4.3 m. With depth, sandstones have a pink and pink-red colour. Both gray and pink variations of sandstones are fine-grained, quartz, feldspar-quartz, mica.. Cement is iron-clay; the clay part of it is sericite-silicon. Mining of sandstones at both deposits is carried out manually with the help of crowbars and wedges to the full depth. All processes for the extraction and manufacture of side and rubble stone are performed manually. Terebovlya sandstone is environmentally friendly, so it is used for the construction of facades as a natural heat insulator. Sandstone is frost-resistant and acid-resistant. It is widely used in modern architectural design and restoration of historical monuments in Europe; it is made of almost everything for facades. Among the architectural structures built of Terebovlya sandstone – a nine-arch railway bridge-viaduct near the village. Plebanivka, Terebovlya and Budaniv castles, Pidhoryany monastery of St. Basil the Great, a large number of churches and cathedrals. Geological and geotourism survey of Zastinoche and Budanіv sandstone quarries in the Ternopil region gives grounds to consider these locations as potential geotouristic objects.
9
Zhang, Jinliang, Zhongqiang Sun, Longlong Liu e Yang Li. "Sedimentary model of K-Successions Sandstones in H21 Area of Huizhou Depression, Pearl River Mouth Basin, South China Sea". Open Geosciences 11, n. 1 (31 dicembre 2019): 997–1013. http://dx.doi.org/10.1515/geo-2019-0077.
Testo completoAbstract (sommario):
Abstract The nearshore sand bar-sheet sedimentary system of the K-Successions sandstones of the Zhujiang Formation (23.8-16.5 Ma) in H21 Area of Huizhou Depression, Pearl River Mouth Basin has been identified in this research according to lithological characteristics, lithofacies, sedimentary sequence and seismic attributes. Seven lithofacies were recognized: fine-grained massive sandstone (Sm), fine-grained trough cross-bedded sandstone (St), fine-grained planar-bedded sandstone (Sp), fine-grained ripple cross-bedded sandstone (Sr), fine grained horizontally-bedded sandstone (Sh), laminated claystone with interbedded siltstone (Fl) and massive mudstone (Fm). Three sedimentary microfacies were further divided: sand bar, sand sheet and interbar. With the progradation and retrogradation process influenced by sea level changing, delta evolution of K-Successions sandstones in H21 area of Huizhou Depression can be divided into four stages: the early stage of the transgressive systems tract, A/S>1; the medium stage of the transgressive systems tract, A/S>1; the end stage of transgressive systems tract; the stage of the highstand systems tract, A/S<1. Different evolution stages controlled the sandstones distribution.
10
Huang, Wenbiao, Shuangfang Lu e Salad Hersi Osman. "Quality grading system for tight sandstone reservoirs in the Quantou 4 Member, southern Songliao Basin, Northeast China". Interpretation 5, n. 4 (30 novembre 2017): T503—T522. http://dx.doi.org/10.1190/int-2017-0067.1.
Testo completoAbstract (sommario):
A grading system for tight sandstone reservoir quality is needed to predict tight oil enrichment areas and assess the resources. To explore the establishment of the grading system, a variety of research methods, such as rate-controlled mercury injection, conventional mercury injection, contact angle measurement, and the mechanical equilibrium principle, are integrated to determine the upper and lower limits of the porosity, permeability, and pore-throat radius of tight sandstones and to establish a quality grading system. Based on the porosity [Formula: see text], permeability [Formula: see text], and pore-throat size [Formula: see text] properties of the studied samples from the [Formula: see text] Member, five sandstone classes have been identified. Three of these classes are tight sandstone reservoirs and include (1) high-quality tight sandstone reservoirs ([Formula: see text], [Formula: see text], and [Formula: see text]), (2) effective tight sandstone reservoirs ([Formula: see text], [Formula: see text], and [Formula: see text]), and (3) low-quality tight sandstone reservoirs ([Formula: see text], [Formula: see text], and [Formula: see text]). Sandstones with [Formula: see text], [Formula: see text], and [Formula: see text] parameters higher than the high-quality tight reservoirs are deemed to be conventional reservoirs, whereas those with parameters lower than the low-quality tight sandstone reservoirs are considered as nonreservoir sandstones. It is also noted that oil saturation of the tight sandstone reservoirs correlates positively with the throat radius rather than with the pore size. High-quality tight sandstone reservoirs are usually developed in the distributary channel sand bodies near faults and/or fractures, and they are capable of producing more petroleum.
11
Keppert, Martin, Jaromír Žumár, Monika Čáchová, Dana Koňáková, Petr Svora, Zbyšek Pavlík, Eva Vejmelková e Robert Černý. "Water Vapor Diffusion and Adsorption of Sandstones: Influence of Rock Texture and Composition". Advances in Materials Science and Engineering 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/8039748.
Testo completoAbstract (sommario):
The term sandstone is used for wide range of rocks containing quartz clasts which can be cemented by secondary precipitated quartz or calcite; moreover the space between clasts can be filled by matrix. These facts result in existence of numerous rocks having highly various properties. Sandstones have been used as construction materials due to their good accessibility and workability. Since most of sandstones are porous, water vapor can penetrate through sandstone constructions. The rate of water vapor diffusion, as well as the vapor sorption isotherm, was determined for range of sandstone types. The diffusion resistance factor was found to be dependent on the total porosity of sandstone but the sorption behavior was strongly influenced by nature of the particular sandstone; the specific surface area of stone and presence of clay matrix are determining its sorption isotherm. The published data enable estimating (i) diffusion resistance factor of a sandstone via knowledge of its total porosity and (ii) the sorption isotherm via knowledge of the stone’s nature and specific surface area. This approach can significantly reduce the time necessary to acquire vapor-related properties of a sandstone.
12
Deng, Jimei, Huan Zeng, Peng Wu, Jia Du, Jixian Gao, Fei Zhao e Zhixun Jiang. "Pore Structure Differentiation between Deltaic and Epicontinental Tight Sandstones of the Upper Paleozoic in the Eastern Linxing Area, Ordos Basin, China". Geofluids 2021 (30 agosto 2021): 1–17. http://dx.doi.org/10.1155/2021/9015041.
Testo completoAbstract (sommario):
Research on tight gas reservoirs in the eastern margin of the Ordos Basin, China, has recently become a hot spot. This paper mainly studies the reservoir characteristics of tight sandstone in the north-central area close to the provenance in eastern Linxing. Cast thin section, scanning electron microscopy, high-pressure mercury injection, and X-ray diffraction (XRD) were applied to discriminate the tight sandstone reservoir differences between the Permian Taiyuan and Shanxi formations in the study area. The results show that the deltaic tight sandstones in the Shanxi Formation are dominated by lithic quartz sandstone and lithic sandstone with an average porosity of 2.3% and permeability of 0.083 mD. The epicontinental tight sandstones in the Taiyuan Formation are mainly lithic sandstone and lithic quartz sandstone, with average porosities and permeabilities of 6.9% and 0.12 mD, respectively. The pore type is dominated by secondary dissolution pores, containing a small number of primary pores, and fractures are not developed. The capillary pressure curves of the Taiyuan Formation sandstone are mainly of low displacement pressure, high mercury saturation, and mercury withdrawal efficiency, while the Shanxi Formation sandstone is mainly of high displacement pressure, low mercury saturation, and withdrawal efficiency. The diagenetic evolution of sandstone in the Shanxi Formation is in meso-diagenesis stage A, and the Taiyuan Formation has entered meso-diagenesis stage B. The siliceous cement in the Taiyuan Formation sandstone enhanced the sandstone resistance to compaction and retained some residual intergranular pores. The pore types in the Shanxi Formation sandstone are all secondary pores, while secondary pores in the Taiyuan Formation sandstone account for approximately 90%. The results can be beneficial for tight gas production in the study area and similar basins.
13
Hu, Hai Yan. "Mechanism of Overpressure Formation in Deeply Burial Sandstone". Applied Mechanics and Materials 295-298 (febbraio 2013): 2736–39. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.2736.
Testo completoAbstract (sommario):
Overpressure is often encountered in the Jurassic tight and the overpressure is closely associated with gas generation. The pressure transfer from the over-pressurized mudstones to adjacent tight sandstones might occur through overpressure induced-fractures. The fine-grained coal containing Jurassic sandstone is sensitive to compaction, and the porosity decreases dramatically with the increase of overlying load. As gas migrates into the tight sandstones, it must overcome the capillary pressure which is greater than the hydrostatic pressure. The gas charging pressure in the tight sandstone must be higher than the capillary pressure, resulting in an overpressure buildup within the tight sandstones. Gas shows, low permeability and strong diagenesis in the overpressure of the tight sandstone system have been observed. Additionally, capillary seals are identified as playing an important role in the mechanism of the overpressure formation in tight sandstone reservoirs. Overpressure might be a driving force to create induced fractures in the interval, which has applications for crossing-formation migration and gas accumulation.
14
Zhao, Xiaodong, Xu Cai, Xingya Zhou, Zejin Lai, Qingwen Zhong, Zhaoxiang Chu, Guoqing Zhou e Hong Li. "Experimental Study on Compression and Torsion Fracture within 3D Printed Cementation-Weak and Porosity-High Sandstones". Geofluids 2023 (10 gennaio 2023): 1–18. http://dx.doi.org/10.1155/2023/6051378.
Testo completoAbstract (sommario):
Cretaceous sandstones have weak cementation and high porosity while exhibit a high apparent brittleness. Compression and torsion (C-T) fractures are widely distributed in Cretaceous sandstones due to asymmetric tectonic convergence action. However, studies on C-T fracture formation and the mechanisms causing variability in Cretaceous sandstones containing no oil or gas are rare due to the challenges in sampling intact sandstone cores, despite their significance to mine shaft sinking. Therefore, this study used binder jetting-based 3D printing to prepare artificial Cretaceous sandstone and developed a real-time X-ray computed tomography- (CT-) aided torsion shear apparatus to test them. The test results showed that the 3D printed (3DP) sandstone had characteristic indexes that approached and even exceeded the lower limits of Cretaceous sandstone cores, thereby accurately representing the unavailable cores. Furthermore, the 3DP sandstones had anisotropic properties comparable to the sandstone cores. Under C-T action, the 3DP sandstone exhibited a pronounced strain gradient of 2.0 %/mm perpendicular to fracture inclination. The inclination angles of fractures formed under C-T action tended to increase as the cell pressure increased, and that approached the orientation angles of maximal principal stress. The maximal and minimal principal stresses exerted inclination-slip and width-stretching effects, respectively, on C-T fractures. But the effect of inclination-slip on the C-T fractures was stronger than that of width-stretching. This insight into C-T fracture formation will guide future studies on the fracture evolution and its disaster-dominating mechanisms arisen from disturbances by shaft sinking.
15
Gong, Linxian, Lei Nie e Yan Xu. "Geometrical and Topological Analysis of Pore Space in Sandstones Based on X-ray Computed Tomography". Energies 13, n. 15 (23 luglio 2020): 3774. http://dx.doi.org/10.3390/en13153774.
Testo completoAbstract (sommario):
The pore geometry and topology properties of pore space in rocks are significant for a better understanding of the complex hydrologic and elastic properties. However, geometry and topology information about the sandstone pore structures is not fully available. In this study, we obtained the topological and geometrical pore parameters from a representative elementary volume (REV) for fluid flow in sandstone samples. For comparison, eight types of sandstones with various porosities were studied based on the X-ray micro-computed tomography technique. In this study, the REV size was selected based on the parameters from the respective pore network models (PNM), not just the porosity. Our analysis indicates that despite different porosity, all the sandstone samples have highly triangular-shaped pores and a high degree of pore structural isotropy. The high porosity group sandstones exhibit wider ranges of pore sizes than the low porosity group sandstones. Compared to the high porosity group sandstones, the low porosity group sandstones samples showing a higher global aspect ratio, indicating some pores exist in the form of bottlenecks. The pore topological properties of different sandstones show a high dependence of the porosity. The high porosity group sandstones obtain large coordination numbers, large connectivity densities and low tortuosities. The results from this study will help better understand the complex pore structure and the fluid flow in sandstone.
16
Barclay, S. A., K. Liu e D. Holland. "RESERVOIR QUALITY, DIAGENESIS AND SEDIMENTOLOGY OF THE PALE AND SUBU SANDSTONES: RE-VISITING THE EASTERN PAPUAN BASIN, PAPUA NEW GUINEA". APPEA Journal 43, n. 1 (2003): 515. http://dx.doi.org/10.1071/aj02027.
Testo completoAbstract (sommario):
Two shallow diamond drill holes (Subu–1 and Subu–2) continuously cored in August and September 2001 by InterOil Australia represent the first sub-surface penetrations of reservoir quality sandstones in the Eastern Papuan Basin of Papua New Guinea. These wells intersected two sedimentologically distinct thick quartz sandstones (>100 m). The upper sandstone unit is Campanian in age and is correlated with the Pale Sandstone, whereas the lower sandstone is of Turonian age and has not been reported previously, and is tentatively named as the Subu Sandstone in this paper.The core has been the subject of detailed reservoir quality and diagenetic study as part of a multi-disciplinary study conducted by CSIRO Petroleum. The results of the reservoir quality portion of this study form the basis of this report and demonstrate the following:There are two distinct depositional systems present with a lower sandy slope apron and basin floor fan system (Subu Sandstone) and a younger upper shoreface-shallow marine depositional system (Pale Sandstone).While the porosity and permeability data for subsurface samples (5 to 16% and 0.1 to 1000mD) are lower than previously reported by Boult and Carman (1990) for surface samples both the sandstone units demonstrate thick, good reservoir quality reservoir capable of holding significant volumes of hydrocarbons.Bitumen is present in the pore space through out the sandstones in both wells. The presence of biodegraded hydrocarbons demonstrates that liquid hydrocarbons have been generated in the basin and have either migrated through the Subu and Pale sandstone or have been reservoired in them.Associated with the bitumen is pyrite precipitated as an in-situ by-product of shallow biodegradation of the parent liquid hydrocarbon as indicated by sulphur isotope analysis.Diagenetic effects include compaction (the dominant control on reservoir quality), minor quartz cementation, minor secondary porosity generation, and in thin zones localised carbonate cementation.Despite their very different depositional settings and age difference the thin section petrology of the Pale and Subu sandstones are very similar. The subtle difference between them is textural (grain size, sorting) and detrital clay content. The Subu Sandstone is typically finer grained, displays a higher degree of sorting and has a higher detrital clay content than the Pale Sandstone.The character of these sandstones may have as much to do with provenance as with depositional environment and may indicate a separate quartz-rich depositional system sourcing sediment from the Australian craton independent of the Fly Platform Toro/Imburu systems.
17
Uchida, Etsuo, e Yoshimitsu Kobayashi. "Siliceous Sandstones Used in Local Khmer Temples in Battambang, Ta Keo, and Kampong Cham Provinces, Cambodia". Heritage 7, n. 2 (27 gennaio 2024): 608–20. http://dx.doi.org/10.3390/heritage7020029.
Testo completoAbstract (sommario):
Siliceous sandstones used in Khmer temples such as the Prasat Basset, Wat Ek Phnom, and Phnom Banan temples in Battambang Province, Phnom Chisor and Ta Prohm temples in Ta Keo Province, and Wat Nokor Bachey temple in Kampong Cham Province in Cambodia were investigated in this study to determine the supply source of the siliceous sandstones used in these temples. Chemical composition analyses and magnetic susceptibility measurements were conducted for the sandstone blocks used in these temples. Siliceous sandstone is the primary construction material in the investigated temples, except for the Phnon Chisor (bricks). Two types of siliceous sandstone, pale brown and red, were found. Pale brown siliceous sandstone was used for the construction of all the investigated temples. In contrast, red siliceous sandstone was found only in the Wat Ek Phnom, Prasat Basset, and Phnom Banan temples. It is suggested that the pale brown siliceous sandstone originated from the Phra Wihan Formation within the Khorat Group. Based on the chemical composition analysis, the pale brown siliceous sandstone in the Ta Prohm temple at Tonle Bati and the Wat Nokor Bachey temple may have been sourced from the lower level of the Phra Wihan Formation. In contrast, the pale brown siliceous sandstone used in the Prasat Basset, Wat Ek Phnom, Phnom Banan, and Phnom Chisor temples was likely sourced from the upper level. The origin of the red siliceous sandstone is proposed to be from the Sao Khua Formation, which is situated above the Phra Wihan Formation.
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Chaney, A. J., C. J. Cubitt e B. P. J. Williams. "RESERVOIR POTENTIAL OF GLACIO-FLUVIAL SANDSTONES: MERRIMELIA FORMATION, COOPER BASIN, SOUTH AUSTRALIA". APPEA Journal 37, n. 1 (1997): 154. http://dx.doi.org/10.1071/aj96009.
Testo completoAbstract (sommario):
Sedimentological analysis of cored sections within the Merrimelia Formation (basal Gidgealpa Group, Cooper Basin, S.A.) reveals a complex glacigenic environment, including glacio-lacustrine, deltaic, shorezone, fluvial, aeolian and other terrestrial facies. These facies are observed within terminoglacial and proglacial environments, and interfinger constantly throughout the Merrimelia Formation, exhibiting rapid environment change related to position of the ice sheet. Detailed sedimentological and petrological analysis, suggests that Tirrawarra sandstone-type facies belongs within the Merrimelia depositional realm. Provenance data indicates that the lithic component of the Tirrawarra Sandstone, is sourced from reworked Merrimelia coeval depositional facies. A high proportion of labile grains, which are commonly observed in the Merrimelia Formation, are only observed rarely in the Tirrawarra Sandstone (sensu stricto). It is proposed that the fluvial sandstones of the Merrimelia Formation are part of the same fluvial deposystem as the Tirrawarra Sandstone (sensu stricto) and the two sandstone sequences are the natural progression of coarsening sediment as more detritus was released from melting glaciers. It is suggested that there no longer remains any sedimentological, stratigraphical or petrographical reasons why the Tirrawarra Sandstone should not be included within the Merrimelia Formation. It is further proposed that all the braided glacio- fluvial sandstones within the Merrimelia Formation and Tirrawarra Sandstone (sensu stricto) be grouped together as 'Tirrawarra-type' facies within the Merrimelia glacigenic domain.The concept that the glacio-fluvial sandstones within the Merrimelia Formation are of the same genetic origin as the Tirrawarra Sandstone (sensu stricto), must point to the economic potential of similar sandstones found throughout the Merrimelia Formation. The thickness, sediment style and lateral extent of the proglacial braidplains is controlled by the duration of glacial melting. The Merrimelia Formation reveals a sequence of major freezing and thawing episodes with the overlying Patchawarra Formation representing the cessation of glacial influence in the Cooper Basin. Therefore, the youngest 'Tirrawarra-type' sandstone facies found at the top of the Merrimelia Formation is likely to contain the least amount of labile grains, a highly rigid siliceous framework and will be well sorted. The risk of lower reservoir quality increases down section where, with time, freezing dominated over thawing and the sediments were less rinsed, and where the resultant sandstones are more likely to be thin, more poorly sorted and chemically immature with a high proportion of labile framework grains. Thus compositional variation, controlling the diagenetic overprint, together with sandstone facies and bedform style exert profound control on the reservoir quality in the Tirrawarra-Moorari Field area, on potential gas reservoirs in the Merrimelia Formation.
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Rizal, Yan, e Aji Rahmat Gumilar. "The Architectural Element Distribution of Cinambo Formation in Jatigede Area, Sumedang District, West Java - Indonesia". Modern Applied Science 13, n. 7 (30 giugno 2019): 94. http://dx.doi.org/10.5539/mas.v13n7p94.
Testo completoAbstract (sommario):
This research is conducted in Jatigede subdistrict, Sumedang district, West Java Province, Indonesia, with a geographic position 175500 - 185000E and 9237800 -9242200 S. There are many different types of rocks scattered forming the Cinambo Formation including sandstones, mudstones, alternation claystones, conglomeratic sandstones, and conglomerate stones. Stratigraphic cross-section measurements on the Cimanuk River and Cinambo River traverses is carried out to figure out the distribution of the architectural elements of the Cinambo Formation. Nine lithofacies are obtained from both traverses: massive conglomerate (A1-1), graded bedding conglomerate and graded bedding conglomeratic sandstone (A2-3), conglomeratic sandstone (A2-1), massive sandstone (B1-1), graded bedding sandstone (B2-4), bedded sandstone (B2-1), alternation sandstone – mudstone (sandstone domination) (C2-2), alternation dense and thin alternation sandstone – mudstone, and mudstone intercalation sandy siltstone. The architectural elements that appear on Cimanuk River traverse are sandy lobe, proximal channel, distributary channel and proximal levee, while the elements that appear on the Cinambo River traverse are sandy lobe, proximal levee and distal levee. A vertical change of the architectural element can be observed on both traverses, which are likely to be caused by the fluctuation of sea level. Base on the architectural element data, it can be concluded that the Cinambo Formation was deposited in the upper fan-basin plain of a deep-marine fan system.
20
Fauziah, Cut Aja, Emad A. Al-Khdheeawi, Ahmed Barifcani e Stefan Iglauer. "Wettability measurements on two sandstones: an experimental investigation before and after CO2 flooding". APPEA Journal 60, n. 1 (2020): 117. http://dx.doi.org/10.1071/aj19099.
Testo completoAbstract (sommario):
Wettability of rock–fluid systems is an important for controlling the carbon dioxide (CO2) movement and the capacities of CO2 geological trapping mechanisms. Although contact angle measurement is considered a potentially scalable parameter for evaluation of the wettability characteristics, there are still large uncertainties associated with the contact angle measurement for CO2–brine–rock systems. Thus, this study experimentally examined the wettability, before and after flooding, of two different samples of sandstone: Berea and Bandera grey sandstones. For both samples, several sets of flooding of brine (5 wt % NaCl + 1 wt % KCl in deionised water), CO2-saturated (live) brine and supercritical CO2 were performed. The contact angle measurements were conducted for the CO2–sandstone system at two different reservoir pressures (10 and 15 MPa) and at a reservoir temperature of 323 K. The results showed that both the advancing and receding contact angles of the sandstone samples after flooding were higher than that measured before flooding (i.e. after CO2 injection the sandstones became more CO2-wet). Moreover, the Bandera grey samples had higher contact angles than Berea sandstone. Thus, we conclude that CO2 flooding altered the sandstone wettability to be more CO2-wet, and Berea sandstone had a higher CO2 storage capacity than Bandera grey sandstone.
21
Zobah, Theresa, Caspar Adenutsi, Godfrey Amedjoe, Matthew Wilson, Emmanuel Mensah, Cyril Boateng, Lydia Opuni, Sylvester Danuor e Hassan Karimaie. "Evaluation of porosity and permeability of sandstones within the Oti Group of the Volta Basin using petrophysical and petrographic techniques". Journal of the Ghana Institution of Engineering (JGhIE) 23, n. 3 (18 settembre 2023): 24–37. http://dx.doi.org/10.56049/jghie.v23i3.100.
Testo completoAbstract (sommario):
This study investigates the reservoir quality of sandstones in the Oti Group of the Volta Basin of Ghana. Geological field mapping, petrographic, petrophysical, mineralogical, and geochemical techniques are used to investigate the reservoir parameters of the sandstones by evaluating the fluid holding and transmission capabilities of the rocks. Results from the comprehensive study identified two sandstone formations of interest; viz. the Bimbila Sandstone and Yabraso Sandstone. Both sandstones were found to be quartz sandstones (sub-arkose and quartz arenites). The Bimbila Sandstones proved to have better porosity and permeability as compared to the Yabraso Sandstones. The Yabraso Sandstone showed porosity between 7-22 % with an average porosity of 13 % (helium gas) and permeability of 63.41 mD, which may be linked to intense cementation and intermediate compaction as well as grain size, shape and arrangement. The Bimbila Sandstones showed better porosity and permeability with a porosity range of 6-24 %, an average porosity of 14 % (helium gas) and 131.80 mD permeability. This is seen to be due to lower compaction supported by framework-stable quartz resulting in a well-connected pore system with high permeability. Further mineralogical data show that the clay minerals present are in minor concentrations. Also, the position of the Yabraso and Bimbila Sandstones in the project area as plotted on the geological map show that there is a close proximity relationship between these sandstones and the limestones; hence, forming a conducive system such that if hydrocarbons are produced by the possible source rocks (limestones), they can be housed by the sandstones.
22
Liang, Jiwei, Wenxing Tao e Xiaojun Ma. "Origin and paleoenvironmental reconstruction of phosphorus-bearing sandstones of the Cambrian Xinji Formation, southwestern margin of the Ordos Basin, China". Canadian Journal of Earth Sciences 57, n. 8 (agosto 2020): 903–17. http://dx.doi.org/10.1139/cjes-2019-0087.
Testo completoAbstract (sommario):
Increasing exploration interest in oil and gas hosted by early Cambrian strata has focused research efforts on early Cambrian sandstones. The origin of phosphorus and the paleoenvironment of phosphorus-bearing sandstones from the Xinji Formation are discussed in this paper. X-ray diffraction, optical microscopy, grain size analysis, total organic carbon, and the concentrations of major, trace, and rare earth elements (REEs) are analyzed in this work. The sandstones are mostly sublitharenite with calcareous cement. The content of the sandstone samples is quartz (39.8%–73.9%), with illite (7.9%–27.6%) and calcite (4.5%–29%). The mineral particles of sandstone samples are mainly well sorted with a fine particle size, suggesting strong paleohydrodynamic force. The value of SiO2 is 37.69%–78.19%, followed by Al2O3 (6.11%–13.67%). Compared with upper continental crust, the boron in the sandstone samples is relatively enriched, whereas Sc, Sr, and Ba are relatively depleted. The ΣREE content is 124.46–323.99 ppm. Phosphorus is of biogenic origin and enriched by upwelling current. The source of the Xinji Formation sandstone samples was mainly a mixture of sedimentary rock, granite, and alkali basalt, with the provenance of terrestrial clastic materials. The sandstone was deposited under oxic conditions and a warm and humid paleoclimate with saline to brackish features on a passive continental margin. Phosphorus occurring in sandstones is sensitive to paleoclimate and can be used as an indicator to judge paleoclimate, as it is more enriched in warm and humid weather.
23
Wu, Chao, Shengquan Wang, Delu Li e Xiaokang Wang. "NMR Experimental Study on Dynamic Process of Pore Structure and Damage Mechanism of Sandstones with Different Grain Sizes under Acid Erosion". Shock and Vibration 2020 (8 gennaio 2020): 1–13. http://dx.doi.org/10.1155/2020/3819507.
Testo completoAbstract (sommario):
In many engineering projects, it is critical to consider the acid erosion of rock. This study investigates dynamic changes in pore structure and damage mechanisms in sandstones subjected to acid erosion. Specimens with three grain sizes were immersed in acid solution and tested by the nuclear magnetic resonance technique. Changes in solution pH, specimen mass and porosity, T2 spectrum distribution, and area were analyzed. Damage mechanisms are discussed, and relationships between porosity and acid erosion damage variables are established. The results show that acid erosion has significant effects on pore structure and erosion damage in sandstone. With increasing soaking time, new micropores formed in sandstone, while existing micropores and mesopores gradually expanded into macropores, causing the T2 spectrum distributions to change greatly. The porosity, acid erosion damage, and T2 spectral areas of sandstones with different grain sizes all increased gradually. Under acid erosion, sandstones became gradually weakened, but the effects varied greatly according to grain size. Pore structure changes and acid erosion damage were greatest in coarse-grained sandstone, followed by medium- and fine-grained sandstone.
24
Arif, Subhan, Nurul Dzakiya, Samuel Kristiyana e Rohmad Bagus Abadi. "Identification of the Potential Quartz Sandstone in the Sambong Area By the Dipole-Dipole Configuration of Resistivity Method". Journal of Applied Geospatial Information 7, n. 1 (15 maggio 2023): 813–19. http://dx.doi.org/10.30871/jagi.v7i1.5276.
Testo completoAbstract (sommario):
The presence of quartz sandstone outcrops in the southeast of the study site suggests the presence of quartz sandstones in the northwest, according to the strike direction. This geoelectrical measurement aims to determine the distribution of these sandstones below the surface. The method used is geoelectric with a dipole dipole configuration.
Measurements were made on four track lines. Tracks A and B indicate the existence of a layer of sandstone below the surface. Tracks C and D do not show any layers of quartz sandstone. This is caused by the presence of faults or folds that cause the layer to shift from the previously predicted path.
25
Zhang, LiKuan, Xiaorong Luo, Mingze Ye, Baoshou Zhang, Hongxing Wei, Binfeng Cao, Xiaotong Xu, Zhida Liu, Yuhong Lei e Chao Li. "Small-Scale Diagenetic Heterogeneity Effects on Reservoir Quality of Deep Sandstones: A Case Study from the Lower Jurassic Ahe Formation, Eastern Kuqa Depression". Geofluids 2021 (24 marzo 2021): 1–25. http://dx.doi.org/10.1155/2021/6626652.
Testo completoAbstract (sommario):
The Lower Jurassic Ahe Formation is an important exploration target for deep clastic reservoirs in the eastern Kuqa Depression. The Ahe Formation sandstones show heterogeneous porosity and permeability petrophysical properties. These properties have been poorly understood, limiting forecast of petroleum accumulations and making it difficult to develop the reservoirs. Based on cores, thin sections, SEM, and fluid inclusions, this study examined sandstone composition and texture and diagenetic heterogeneity at the core scale. The aim was to understand the influence of variations in detrital composition and texture on diagenetic and reservoir quality evolution. The Ahe Formation sandstones are dominantly fine- to coarse-grained litharenites, with minor feldspathic litharenites. In fining-up sand beds, detrital grain size determines the degree of mechanical compaction and, consequently, the abundance of porosity through ductile grains and muddy matrix. Local complete calcite cementation is a noticeable exception to this general trend. Three sandstone petrofacies have been defined based on texture and framework composition, detrital matrix, diagenesis, and pore types: (1) ductile-lean sandstone, (2) ductile-rich sandstone, and (3) tightly calcite-cemented sandstone. Different petrofacies experienced contrasting diagenetic and porosity evolution pathways. Ductile-lean sandstones underwent lower degree of compaction relative to ductile-rich sandstones during the eodiagenesis stage, and extensive grain dissolution occurred. The petrofacies remained relatively porous and permeable before early oil arrival. With continued burial, the porosity and permeability in the sandstones were further reduced by cementation. The petrofacies still had moderate porosity and permeability and were substantially charged when late petroleum migrated into the reservoirs. Thus, ductile-lean sandstones constitute effective reservoir rocks in deep reservoirs. By translating petrofacies to signatures of well logs, the effective properties of the reservoir rocks can be forecasted at the well scale.
26
Al-Mashaikie, Saad Z. A. Kader, e Younis A. Mohammed. "ANATOMY OF CARBONATE BRECCIAS, TURBIDITE FACIES AND DEPOSITIONAL SYSTEMS OF GERCUS FORMATION IN DOKAN AREA, NORTHERN IRAQ". Iraqi Geological Journal 50, n. 1 (30 giugno 2017): 90–103. http://dx.doi.org/10.46717/igj.50.1.7ms-2017-06-29.
Testo completoAbstract (sommario):
Four facies associations are classified based on facies types, sedimentary structures and facies successions, these are; distal slope apron siliciclasticcalciturbidites (siliciclastic/ carbonate dominated), proximal marine siliciclasticcalciturbidites (carbonate/ siliciclastic dominated), distal basinal fan siliciclastic turbidites (siliciclastic dominated) and proximal basinal fan siliciclasticcalciturbidites (carbonate/ siliciclastic dominated). The most important characteristic representative facies types are; ball and pillows dolomite (reported here for the first time), thick fissile shale, slump/ slide limestone, slump/ slide sandstone, channeled sandstone, ball and pillow sandstone, slump sandstone, convolute sandstone, crossbedded sandstone, sigmoidal channeled sandstone, disturbed sandstones, red argillaceous mudstone, gray massive claystone, flute scoured sandstone with slump carbonate breccias types. The carbonate breccias are the most important characteristic facies types observed in the formation and reported here for the first time and it is strong indication for marine environment. Examinations and anatomy of facies types and associations suggest developed marine environment, effected mainly by gravity flows and turbidity currents, forming sequences of submarine fans including high density turbidity currents in deeper margins.
27
Singh, Paritosh, e Thomas Davis. "Advantages of Shear Wave Seismic in Morrow Sandstone Detection". International Journal of Geophysics 2011 (2011): 1–16. http://dx.doi.org/10.1155/2011/958483.
Testo completoAbstract (sommario):
The Upper Morrow sandstones in the western Anadarko Basin have been prolific oil producers for more than five decades. Detection of Morrow sandstones is a major problem in the exploration of new fields and the characterization of existing fields because they are often very thin and laterally discontinuous. Until recently compressional wave data have been the primary resource for mapping the lateral extent of Morrow sandstones. The success with compressional wave datasets is limited because the acoustic impedance contrast between the reservoir sandstones and the encasing shales is small. Here, we have performed full waveform modeling study to understand the Morrow sandstone signatures on compressional wave (P-wave), converted-wave (PS-wave) and pure shear wave (S-wave) gathers. The contrast in rigidity between the Morrow sandstone and surrounding shale causes a strong seismic expression on the S-wave data. Morrow sandstone shows a distinct high amplitude event in pure S-wave modeled gathers as compared to the weaker P- and PS-wave events. Modeling also helps in understanding the adverse effect of interbed multiples (due to shallow high velocity anhydrite layers) and side lobe interference effects at the Morrow level. Modeling tied with the field data demonstrates that S-waves are more robust than P-waves in detecting the Morrow sandstone reservoirs.
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Savage, Jeni E., Margaret A. Bradshaw e Kari N. Bassett. "Marginal marine depositional setting and correlation of the Devonian Sperm Bluff Formation (Taylor Group), southern Victoria Land, Antarctica". Antarctic Science 25, n. 6 (16 aprile 2013): 767–90. http://dx.doi.org/10.1017/s0954102013000205.
Testo completoAbstract (sommario):
AbstractAnalysis of conglomerates and sandstones of the Sperm Bluff Formation at the base of the Taylor Group (Devonian) between the Mackay Glacier and Bull Pass provides new insights into the nature of initial coarse-grained deposition on basement along the northern side of the McMurdo sedimentary basin. Six lithofacies are recognized in the Sperm Bluff Formation: conglomerate lithofacies, pebbly sandstone lithofacies, cross-bedded sandstone lithofacies, low-angle cross-stratified sandstone lithofacies, bioturbated sandstone lithofacies and interbedded siltstone/sandstone lithofacies. Sedimentary environments ranged from wave-dominated delta, estuary or lagoon to shoreface and inner shelf. The assemblage is thought to reflect changes in sea level. Rhyolite is the most abundant clast type in the coarse lithofacies, but is unknown in outcrop in southern Victoria Land. The rhyolites correlate in age and geochemistry with Cambrian granites in the basement. Coarse beds also contain numerous quartzite clasts, probably derived from the late Precambrian Skelton Group. Palaeocurrents on Mount Suess indicate a strong unimodal flow to the west, but other sites show polymodal palaeoflow. The Sperm Bluff Formation is correlated with Terra Cotta Siltstone, New Mountain Sandstone and Altar Mountain formations based on the lithology of sandstones and their ichnology. A northward onlap during the Early Devonian is indicated.
29
Laasch, H., T. Medic e A. Wieser. "TOWARDS ASSESSING SANDSTONE SURFACE MOISTURE AND DEGRADATION LEVEL FROM RADIOMETRICALLY CORRECTED TLS INTENSITY DATA". ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences X-1/W1-2023 (5 dicembre 2023): 567–74. http://dx.doi.org/10.5194/isprs-annals-x-1-w1-2023-567-2023.
Testo completoAbstract (sommario):
Abstract. Water is a prevalent deterioration agent for historic masonry works, especially those made of clay-bearing sandstones. To preserve cultural heritage made of sandstone, it is important to monitor, and then detect the regions with water retention or stone deterioration. To that aim, we investigate the prospects of terrestrial laser scanner (TLS) intensities for quantifying moisture in sandstone. Through a series of experiments following the drying processes of sandstone samples, we verify that TLS intensities can serve as moisture proxies for remote-sensing water retention. We identify the theoretically most suitable wavelengths, systematic effects requiring mitigation, and promising mitigation strategies. However, we also observe that the intensities are significantly affected by the type of sandstone and its level of degradation. Our results indicate that it is possible to distinguish different sandstones and levels of artificial degradation by observing and analyzing TLS-intensity time series during the drying process.
30
Al-Khdheeawi, Emad A., Doaa Saleh Mahdi, Yujie Yuan e Stefan Iglauer. "Influence of Clay Content on CO2-Rock Interaction and Mineral-Trapping Capacity of Sandstone Reservoirs". Energies 16, n. 8 (17 aprile 2023): 3489. http://dx.doi.org/10.3390/en16083489.
Testo completoAbstract (sommario):
The injection of carbon dioxide (CO2) is an essential technology for maximizing the potential of hydrocarbon reservoirs while reducing the impact of greenhouse gases. However, because of the complexity of this injection, there will be many different chemical reactions between the formation fluids and the rock minerals. This is related to the clay content of sandstone reservoirs, which are key storage targets. Clay content and clay types in sandstone can vary substantially, and the influence of these factors on reservoir-scale CO2-water-sandstone interactions has not been managed appropriately. Consequently, by simulating the process of CO2 injection in two different clay-content sandstones (i.e., high- and low-clay content), we investigated the effect of the sandstone clay concentration on CO2-water-sandstone interactions in this article. High clay content (Bandera Grey sandstone) and low clay content (Bandera Brown sandstone) were considered as potential storage reservoirs and their responses to CO2 injection were computationally assessed. Our results indicate that the mineralogical composition of the sandstone reservoir significantly varies as a result of CO2-water-sandstone interactions. Clearly, the high clay-content sandstone (Bandera Grey) had a higher maximum CO2 mineral-trapping capacity (6 kg CO2/m3 sandstone) than Bandera Brown Sandstone (low clay content), which had only 3.3 kg CO2/m3 sandstone mineral-storage capacity after 400 years of storage. Interestingly, pH was decreased by ~3 in Bandera Grey sandstone and by ~2.5 in Bandera Brown sandstone. Furthermore, porosity increased in Bandera Grey sandstone (by +5.6%), more than in Bandera Brown Sandstone (+4.4%) after a 400-year storage period. Overall, we concluded that high clay-content sandstone shows more potential for CO2 mineral-trapping.
31
Wang, Jing, Fawang Ye, Chuan Zhang e Zhaodong Xi. "Factors That Control the Reservoir Quality of the Carboniferous–Permian Tight Sandstones in the Shilounan Block, Ordos Basin". Processes 11, n. 8 (28 luglio 2023): 2279. http://dx.doi.org/10.3390/pr11082279.
Testo completoAbstract (sommario):
The Carboniferous–Permian, coal-bearing, sedimentary succession on the eastern edge of the Ordos Basin in the Shilounan Block contains large accumulations of hydrocarbon resources. During the exploration of coalbed methane and tight sandstone gas in the study area, multiple drilling wells in the tight sandstone reservoirs have yielded favorable gas logging results. The Benxi, Taiyuan, Shanxi, Shihezi, and Shiqianfeng formations contain multiple sets of sandstone reservoirs, and the reservoir quality and the controlling factors of its tight sandstones were affected by sedimentation, diagenetic alteration, and pore structure. This study comprehensively examines the sedimentary environment, distribution of sand bodies, and physical characteristics of tight sandstone reservoirs through drilling, coring, logging, and experimental testing. The results indicate that the Carboniferous–Permian tight sandstones are mainly composed of lithic sandstone and lithic quartz sandstone. The reservoir quality is relatively poor, with an average permeability of 0.705 mD and porosity of 6.20%. The development of reservoirs in the study area is primarily influenced by diagenesis and sedimentation. Compaction and cementation, which are destructive diagenetic processes, significantly reduced the porosity of the sandstone reservoirs in the study area. Compaction primarily causes a reduction in porosity and accounts for over 70% of the overall decrease in porosity. Dissolution, as a constructive diagenetic process, has a limited effect on porosity and is the primary reason for the relatively tight nature of these reservoirs. The macroscopic and microscopic characteristics of tight sandstone reservoirs were used to establish the evaluation and classification criteria, after which the sandstone reservoirs in the study area were divided into three types. The poor quality type II and type III reservoirs are predominant, while high quality type I reservoirs are primarily limited to the Shihezi Formation.
32
Peng, Xiaoxia, Zexin Fang, Xin Cheng, Ling Guo e Jianni Liu. "Sedimentological and Geochemical Characterization of the Early Cambrian Eastern Yunnan, Southwestern China". Minerals 14, n. 5 (24 aprile 2024): 445. http://dx.doi.org/10.3390/min14050445.
Testo completoAbstract (sommario):
The accurate reconstruction of the early Cambrian paleoclimate and paleoceanographic conditions on the Yangtze Plate is crucial for understanding the ancient environment during the Cambrian Explosion. It is also a key factor in understanding the ecological habits of organisms during the Cambrian Explosion. The study utilized field outcrops, thin section analysis, and major and trace elements to investigate the sedimentary environment, provenance, paleoweathering, and paleoclimate of the Lower Cambrian Hongjingshao (HJS) Formation (Cambrian Stage 3, ~515 Ma) in the Yangtze Basin, eastern Yunnan, SW China. The HJS sandstones are composed of 10 lithofacies, including massive and weakly bedded gravel supported by coarse sandstone (Gm), trough cross-bedded sandstone (St), planar cross-bedded sandstone (Sp), ripple cross-laminated sandstone (Sr), horizontal bedded sandstone (Sh), scour-fill sandstone (Se), massive sandstone (Sm), fine to medium sandstone with thin bed muddy siltstone (Fl), muddy siltstone (Fsc), and mudstone (Fm). On the basis of these lithofacies, channel fill and over-bank deposits in delta and shallow shelf depositional environments are suggested for HJS Formation. The major elements-based provenance discriminant function and mineral composition indicate that felsic rocks from the recycled orogen and continental block are the main sediment source terrane for the HJS sandstones of the study area. CIA, PIA, and CIW values range from 71.29 to 93.72, indicating an intermediate to intense chemical weathering and semiarid to humid climate conditions in Cambrian Stage 3. The research findings have clarified the paleoclimate and paleoceanographic environment of the Early Cambrian in the Yangtze region, which is of significant importance for understanding the early biological and ecological marine environment in the study area.
33
Li, Jian, Zhao-Wen Du e Zhong-Ping Guo. "Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone". Advances in Materials Science and Engineering 2020 (12 agosto 2020): 1–19. http://dx.doi.org/10.1155/2020/5072534.
Testo completoAbstract (sommario):
Rock destruction under high-temperature conditions is a key issue for nuclear waste treatment projects, underground coal gasification, and improvement of the use of geothermal energy for heating. Therefore, in this study, various methods and techniques were integrated to study the changes in mechanical properties, mineral composition, and microscopic fracture characteristics of Sichuan sandstone treated at 600°C. First, the fracture toughness and indirect tensile strength of untreated sandstones and high-temperature treated sandstones were tested by the MTS testing machine, and the double-K model (DKFM) was used to estimate the unstable fracture toughness. Then, the diffraction spectra of sandstone were analyzed with an X-ray diffractometer to determine the mineral composition change after heat treatment. Finally, the microscopic features of sandstone were observed through a scanning electron microscope (SEM) and optical microscope. The results show the following. (1) There is no significant change in the tensile strength and fracture toughness of Sichuan sandstone treated at 600°C. (2) The brittleness of Sichuan sandstone decreases and the ductility increases after high-temperature treatment. (3) The unstable fracture toughness value Kun obtained by the double-K model (DKFM) is significantly larger than the apparent fracture toughness value Kif. (4) After treatment at 600°C, the clay minerals in the sandstone changed significantly. Kaolinite is dehydroxylated to metakaolinite, which may increase the ductility of the rock.
34
Li, Fu Lai, Wen Shuai Li, Zhong Feng Duan e Yan Deng. "Petrologic Characteristics of Dawsonite-Bearing Sandstones in Dongying Sag of Bohai Bay Basin, China". Advanced Materials Research 1010-1012 (agosto 2014): 1376–79. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.1376.
Testo completoAbstract (sommario):
A large number of dawsonite-bearing sandstones has been found in Dongying Sag of Bohai Bay basin. The petrological characteristics of these sandstones, such as the framework clastic composition, cements, authigenic minerals and diagenetic paragenesis succession are investigated by polarizing microscope, SEM, and Alizarin Red-S staining etc. The results show that these kinds of dawsonite-bearing sandstone are feldspathic sandstone or debris-feldspar sandstone with mainly fine or fine to medium particle size, poor to mediocre sorting features, poor psephicity and dot-line contact. The cements and authigenic minerals are dominated by overgrowth quartz, dawsonite, calcite, ferrocalcite, ankerite and clay minerals. The amount of dawsonite accounts for 15% by volume. The paragenesis sequence are illite/montmorillonite mixing layer, kaolinite, overgrowth quartz-calcite, ferrocalcite, dawsonite and ankerite.
35
Lin, Wen, David Kynaston, Curtis Ferron, Janok P. Bhattacharya e William Matthews. "Depositional and sequence stratigraphic model of transgressive shelf sandstone: The Late Cretaceous Tocito Sandstone, San Juan Bain, New Mexico, U.S.A." Journal of Sedimentary Research 91, n. 4 (1 aprile 2021): 415–32. http://dx.doi.org/10.2110/jsr.2020.121.
Testo completoAbstract (sommario):
ABSTRACT There has long been debate about the origin of long, linear, isolated shallow marine sandstones. In the 1980s these were routinely interpreted as wave- or tide-modulated shelf sandstones. With the advent of sequence stratigraphy, many of these sandstones were reinterpreted as top-truncated forced-regressive to lowstand delta or shoreface, inviting the question regarding whether the concept of a shelf sandstones remain a viable depositional model. More recent syntheses demonstrate that shelf sands tend to be derived by reworking of underlying sediment through transgressive erosion and show varying levels of detachment and reworking into discrete ridges and bars by wave and tidal processes as they become more evolved. The Late Cretaceous Tocito Sandstone in the Western Interior Seaway, which overlies the regressive Gallup Formation, is a candidate for a transgressive shelf sandstone. In this study, we present detailed facies analysis, based on sedimentological sections measured from well-exposed outcrops of the Tocito Sandstone and its related stratigraphic units in northwest New Mexico, USA. With high-resolution sequence stratigraphic control, facies analysis, detrital-zircon anatomy, and petrographic analysis are integrated to investigate the sequence stratigraphic evolution and depositional processes of the Tocito Sandstone. Detrital zircons indicate that the Tocito, Torrivio, and Gallup deposits are derived from different source areas, and therefore imply separate sequence stratigraphic origins. The Tocito Sandstone is interpreted to have been deposited as shelf sand ridges in retrogradational estuarine to drowned-barrier-system environments with tidal and wave influence, characterized by intense bioturbation. The Tocito was deposited in an overall transgressive systems tract and sourced from reworking of the underlying Torrivio and Gallup units through processes of transgressive erosion.
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Jiu, Bo, Wenhui Huang, Jing Shi e Mingqian He. "Growth Mechanism of Siliceous Cement in Tight Sandstone and Its Influence on Reservoir Physical Properties". Energies 11, n. 11 (13 novembre 2018): 3133. http://dx.doi.org/10.3390/en11113133.
Testo completoAbstract (sommario):
To investigate the effect of siliceous cementation on the densification of sandstone and the forming process of tight sandstone, based on cathodoluminescence, scanning electron microscopy and thin section analysis, the growth mechanism and characteristics of quartz particles in tight sandstone formations are explored. Meanwhile, combined with conventional core analysis and X-ray diffraction experiments, the factors affecting the crystallization of quartz particles, including the chlorite content, grain size and clay mineral, are analyzed, respectively. The entire siliceous cementation is divided into two processes. The first part is the process in which the weathered and rounded particles in the formation are restored to the hexagonal dipyramid crystal by siliceous cementation. The second part is the process of coaxial growth that the hexagonal dipyramid crystal continues to increase with the form of micro-quartz film. As siliceous cements continue to increase, the petrological characteristics of sandstones are constantly changing. The tight sandstone developed in the study area is composed of lithic sandstone and quartz lithic sandstone. Based on the analysis results, 2D and 3D evolution models are established for densification of two different lithic sandstones. When the content of siliceous cement in the study area is less than 17%, the porosity of tight sandstone increases with the increase of cement. When the content of cement is more than 17%, the porosity of tight sandstone is negatively correlated with the content of cement. When the cement content is greater than 10%, the reservoir permeability is negatively correlated with it. Furthermore, the particle size mainly affects the permeability of reservoir, and the particle size is negatively correlated with the permeability of tight sandstone. The most high-quality tight sandstone reservoir in the study area is in the first cementation stage when siliceous cements are distributed in porphyritic texture with the content of 10–15% and a grain size of 0.2–0.3 mm. In addition, the relatively high-quality reservoir is the one developing clay mineral film with a content of cementation about 5–12%.
37
Ehling, Angela. "Cretaceous building sandstones in northern Germany". Geological Society, London, Special Publications 486, n. 1 (19 dicembre 2018): 205–15. http://dx.doi.org/10.1144/sp486.7.
Testo completoAbstract (sommario):
AbstractCretaceous sandstones occur mainly in the north and NE of Germany. Some of them have been quarried for more than a thousand years and they have been transported to other regions, even abroad, from as early as medieval times. These are the Elbe Sandstones in Saxony, the Wealden Sandstones and the Bentheimer Sandstone in Lower Saxony and the Baumberger Sandstone in North Rhein-Westfalia. All of these are still quarried, and all can be used as building stone as well as for sculptures. They are introduced with their special features and their use over the centuries.
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Li, Kuizhou, Xuehui Han, Hao Zhang, Tao Fang, Xingping Luo e Junguang Nie. "Effects of clay types and fractions on elastic properties of artificial clay-bearing sandstones: an experimental study". Journal of Geophysics and Engineering 20, n. 1 (18 gennaio 2023): 103–16. http://dx.doi.org/10.1093/jge/gxac099.
Testo completoAbstract (sommario):
Abstract Experimentally understanding the effects of clay type and fraction on the elastic properties of clay-bearing sandstone is crucial for exploring hydrocarbon reservoirs. Therefore, we artificially synthesized a series of pure clay rocks and clay-bearing sandstones with different clay types and fractions, and conducted the ultrasonic measurements to investigate the elastic behaviors. According to experiments on pure clay rocks, illite rocks have the highest porosity, followed by montmorillonite rocks and chlorite rocks. In terms of elastic properties, illite rocks show the highest ultrasonic P- and S-wave velocities, followed by chlorite rocks and montmorillonite rocks. For clay-bearing sandstones, the measured results indicate that clay types and fractions significantly influence both the physical and elastic properties. Specifically, the porosity of chlorite-bearing sandstone is systematically lower than that of illite-bearing and montmorillonite-bearing sandstone. The chlorite-bearing sandstone has the highest P- and S-wave velocities, followed by illite-bearing and montmorillonite-bearing sandstone. Moreover, the clay fraction also affects porosity–velocity trends. The porosity first falls and then increases as the clay fraction rises, while the P- and S-wave velocities first rise and then fall and, in turn the turning point occurs at the ∼30% clay fraction. The potential mechanism of the turning point is analyzed based on the microscopic distribution of clay and sandstone. Additionally, the clay fraction and distribution also affect the electrical conductivity and permeability of the clay-bearing sandstone, implies that the clay types, clay fraction and clay distribution are non-negligible factors in reservoir evaluation.
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Wieczorek, Andrzej N., Iwona Jonczy, Krzysztof Filipowicz, Mariusz Kuczaj, Arkadiusz Pawlikowski, Kamil Mucha e Anna Gerle. "Effect of the Mineralogical Composition of Sandstones on the Wear of Mining Machinery Components". Coatings 14, n. 7 (9 luglio 2024): 859. http://dx.doi.org/10.3390/coatings14070859.
Testo completoAbstract (sommario):
The paper provides and comments on the results of studies of the effect of sandstone-based abrasives and quartz sand alone on the wear of martensitic surfaces of wear-resistant steels. The wear process was examined on a ring-on-ring test rig seeking to determine the mass decrement parameter which characterised wear. In addition, SEM microscopy, optical profilometry and XRF analysis were used to analyse the abrasives used and damaged surfaces. The tests were conducted for three sandstone varieties, Carboniferous, Permian, and Cretaceous, and they made it possible to determine that the most intense process of deterioration of wear-resistant steels took place in the presence of quartz sand grain, while less intense wear was observed in the case of sandstone-based abrasives. The mass decrement values established in the presence of the sandstones in question did not differ significantly between individual sandstone varieties. Based on a surface damage analysis, the basic damage mechanism was found to be micro-scratching; however, with regard to the sandstones examined, it was also determined that individual grains could be pressed into surface irregularities and that films of soft hematite cement developed in the Permian sandstone and that inclusions of carbonaceous matter were formed in the Carboniferous sandstone. With reference to the wear process observations, a wear model was described for the surface of the steels examined in the presence of sandstone-based abrasives. This model presents the possibility of capturing wear products by unstable binder layers and changing the form of wear from three-body to two-body.
40
Xie, Dao Lei, Jiu Chuan Wei, Hui Yong Yin, Jian Bin Guo, Song Zhou, Min Gao e Bing Sheng Li. "Comprehensive Prediction about Water Abundance of NO.5 Coal Seam Roof’ Sand in Yili NO.1 Coal Mine". Advanced Materials Research 706-708 (giugno 2013): 483–87. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.483.
Testo completoAbstract (sommario):
Collect geological and hydrogeological data of Yili NO.1 coal mine and analyze Hydrogeological Characteristics of sandstone aquifers in the roof of No5 coal seams; predict the water abundance and classify sandstone aquifers’ water abundance with considering the sandstone’s thickness, content and lithology structure index, and provide the basis for controlling the sandstone water of NO.5 coal seam’s roof.
41
Greig, Iain P., Andrew Morton, Dirk Frei e Adrian Hartley. "Establishing Provenance from Highly Impoverished Heavy Mineral Suites: Detrital Apatite and Zircon Geochronology of Central North Sea Triassic Sandstones". Geosciences 13, n. 1 (30 dicembre 2022): 13. http://dx.doi.org/10.3390/geosciences13010013.
Testo completoAbstract (sommario):
A study of Triassic sandstones in the central North Sea, UK, has shown that combined detrital zircon and apatite geochronology and apatite trace element analysis is a powerful tool for reconstructing provenance for sandstones with diagenetically impoverished heavy mineral suites. Sandstones in the earlier part of the succession (Bunter Sandstone Member and Judy Sandstone Member) have characteristics that indicate derivation from Moinian–Dalradian metasediments affected by Caledonian tectonothermal events, in conjunction with a Palaeoproterozoic-Archaean source unaffected by Caledonian metamorphism. Palaeogeographic reconstructions indicate that the sediment cannot have been input directly from either of these cratonic areas. This, in conjunction with the presence of common rounded apatite, indicates that recycling is the most likely possibility. The zircon-apatite association in the younger Joanne Sandstone Member sandstones indicates derivation from lithologies with mid-Proterozoic zircons (either crystalline basement or metasediments in the Caledonian Nappes), subjected to Caledonian metamorphism to generate early Palaeozoic apatites. This combination is compatible with a source region in southern and western Norway. The low degree of textural maturity associated with the detrital apatite, together with the unimodal Caledonian age grouping, indicates the Joanne sandstones have a strong first-cycle component.
42
Lv, Gui You. "Research on Character of Sandlayer in Heidimiao Oil Layer in Yingtai Area". Advanced Materials Research 734-737 (agosto 2013): 426–31. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.426.
Testo completoAbstract (sommario):
Based on the division and correlation of sand groups in Heidimiao, synthesizing the information of 3D seism data, drilling data, logging data and core data, well ties profile, sandstone contrast diagram and oil reservoir profile are drawn in this article in a way of combining the data of logging and seism. Furthermore, spatial distribution rules of sandlayer in Heidimiao oillayer are expected to be analyzed in this article through the data of stratum thickness, sandstone thickness, the thickness ratio of sandstone to stratum, and porosity isogram. The rules are described as: the Heidimiao oil layer is thick in east and north but thin in the west and south as a whole. Little sandstone is found in H3 (Nen 2) but that is highly developed in H2 (Nen 3) and H1 (Nen 4) in which lenticular sandlayer can also be found. Sandstones in each oil group are developed with varying thickness, great depth difference and complex lateral connectivity. What’s more, sandstones in the research area manifest a decline in layers and thickness from east to west. The thinner and smaller-scale sandstones in the west have weak lateral connectivity but strong control of oil and water distribution, which results in the formation of concealed lithological reservoir uncontrolled by geological structure.
43
Groh, Melanie, Jeanette Orlowsky e Robert Schulte Holthausen. "Analysing the Porosity Distribution in Stone Surfaces by Means of Unilateral NMR after Long-Term Outdoor Weathering". Materials 15, n. 13 (30 giugno 2022): 4604. http://dx.doi.org/10.3390/ma15134604.
Testo completoAbstract (sommario):
Porosity changes in the near-surface area of sandstones due to long-term weathering can produce deterioration. Therefore, porosity analyses on weathered sandstones are significant for detecting possible influences on the pore structure. Classical methods for determining the porosity and pore size distribution in sandstones can only investigate the entire sample volume. In contrast, in this publication, the porosity was analysed in 0.2 mm steps over a depth of 5 mm by means of single-sided NMR measurements on water-saturated sandstones under vacuum. Evaluations of Obernkirchener and Schleeriether Sandstones that were weathered outdoors in Germany for over 30 years are presented. The results showed that the water content in Vol.-% strongly correlated with the normalised NMR signal. The unweathered sandstones showed a uniform distribution of micro and capillary pores throughout the stone depth. As a result of 30 years of outdoor weathering, changes in the pore structure occurred at the sandstone surface due to weathering down to depths of about 0.6 mm. The porosity of the Schleeriether Sandstone samples, mainly the microporosity, clearly increased in this region. Due to the dominance of capillary pores in the Obernkirchener Sandstone, the changes were not as pronounced, but a shift towards smaller pores in the surface area was observable.
44
Ugwueze, C. U., e K. O. Okengwu. "Textural characteristics and sediment transport dynamics of the sandstones of the Nkporo group, Southern Anambra Basin (Nigeria): evidence for the upper cretaceous sea-level lowstand". Scientia Africana 22, n. 2 (10 ottobre 2023): 177–202. http://dx.doi.org/10.4314/sa.v22i2.17.
Testo completoAbstract (sommario):
The Anambra sedimentary basin is one of the major inland basins in Nigeria. It covers an area of approximately 30,000 square kilometres and is named after the Anambra River, which traverses the basin. The geology of the basin is characterized by a complex sequence of sedimentary rocks that record a long history of deposition and tectonic activity. Detailed and systematic field investigation of its rock sequences exposed at Leru junction and adjoining localities revealed five dominant lithologic units consisting of massive sandstone facies, argillaceous sandstone facies, fissile black shale and mudstone facies, planar and ripple laminated sandstone facies, and massive and pebbly sandstone facies. The area is dominated by transgressive facies characterized by alternating sequences of thinly and parallel laminated fissile black shales, mudstones, and argillaceous sandstones overlain by regressive deposits dominated by massive and partly pebbly sandstones. The transgressive sequences perhaps represented shelf mud sedimentation that was probably interrupted by episodic influxes of sands rich in argillaceous materials transported down the shelf probably by shoreface waves or gravity-driven flows, while the regressive facies may have probably been emplaced by liquefied sand flows of the frontal slope of an advancing mouth bar. The erosion of the shelf deposits by the pebbly sandstones possibly reflected seaward migration of shallow distributary channels during sea-level low stand. Thus, facies transition from argillaceous sandstones to massive and pebbly sandstones within the continental shelf perhaps signified a fall in the relative sea level possibly triggered by the erosion of the shelf or perhaps a high rate of sediment supply.
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Cieszkowski, Marek, Anna Waśkowska, Justyna Kowal-Kasprzyk, Jan Golonka, Tadeusz Słomka, Andrzej Ślączka, Patrycja Wójcik-Tabol e Rafał Chodyń. "The Upper Cretaceous Ostravice Sandstone in the Polish sector of the Silesian Nappe, Outer Western Carpathians". Geologica Carpathica 67, n. 2 (1 aprile 2016): 149–66. http://dx.doi.org/10.1515/geoca-2016-0010.
Testo completoAbstract (sommario):
Abstract The Ostravice Sandstone Member was identified and described as a lithostratigraphic unit in the Polish part of the Outer Carpathians. This division occurs in the lowermost part of the Godula Formation, is underlain by variegated deposits of the Mazák Formation or directly by the Barnasiówka and Lhoty formations, and overlain by the Czernichów Member of the Godula Formation. Domination by thick- and very thick-bedded sandstones, conglomeratic sandstones and conglomerates rich in calcareous clasts, mostly of the Štramberk-type limestones, is typical for the Ostravice Sandstone Member. These deposits are widespread between the Moravskoslezské Beskydy Mountains in the Czech Republic and the Ciężkowice Foothills in Poland. The documentation of the Ostravice Sandstone Member occurrence as well as the petrological, sedimentological features, and inventory of the carbonate clasts are presented here.
46
Surlyk, Finn, e Rikke Bruhn. "Flood-generated hyperpycnal delta front sands of the Brora Arenaceous Formation (upper Callovian–middle Oxfordian) of the Inner Moray Firth, Scotland, record the onset of rifting". Scottish Journal of Geology 56, n. 2 (3 luglio 2020): 159–74. http://dx.doi.org/10.1144/sjg2020-004.
Testo completoAbstract (sommario):
Sandstones of the Middle–Upper Jurassic Brora Arenaceous Formation of the Inner Moray Firth, NE Scotland have hitherto been interpreted as representing coastal, tidally-influenced bars. The formation is exposed close to the northern basin-bounding Helmsdale Fault, and the middle member of the formation, the Clynelish Quarry Sandstone, consists of thick, mainly structureless sandstone beds with wavy, commonly amalgamated boundaries. It also includes sandstone bodies with sigmoidal clinothems, erosional surfaces and backset beds. Rich marine faunas dominated by bivalves and ammonites occur at a few levels, whereas trace fossils are rare or absent. The Clynelish Quarry Sandstone is here reinterpreted as reflecting deposition by hyperpycnal sandy density flows in flood-generated marine, subaqueous, delta-scale clinoforms and lobes in front of local mountain streams. The reinterpretation of these sandstones implies the presence of a tectonically controlled, relatively steep basin margin along the line of the Helmsdale Fault. The Brora Arenaceous Formation thus dates the onset of Jurassic rifting in the Inner Moray Firth to the latest Callovian rather than the late Oxfordian as previously interpreted from seismic data.
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DRUMMOND, CARL N. "ON THE CLASSIFICATION OF SANDSTONES". Earth Sciences History 42, n. 1 (1 gennaio 2023): 215–32. http://dx.doi.org/10.17704/1944-6187-42.1.215.
Testo completoAbstract (sommario):
ABSTRACT Over the last three-quarters of a century various grain-based classification systems have been developed in order to categorize sandstones on the basis of the relative abundances of their three most common components: quartz, feldspar, and rock fragments. A review of the historical development of sandstone classification is undertaken to elucidate evolution in geological understanding represented by various methodologies of classification. The compositional fields defined in traditional sandstone classifications are found to be largely incompatible with subpopulations of sandstones grouped according to interpreted sedimentary tectonic provenance. The origin of this incompatibility between descriptive classifications and genetic classifications arose from the fact that neither approach established classification field boundaries on the basis of processes known to control the origin and evolution of sandstone composition. The development of the study of a range of factors that influence sandstone petrogenesis and grain composition are reviewed along with the introduction of several critical statistical techniques applicable to multicomponent grain abundance analysis. From the understandings gained by the evaluation of these advances in classification practice a set of potential topics for future consideration are introduced.
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Wang, Liping, Xiaotong Chen, Wan Zhang, Yanzhe Tian e Shuanhai Xu. "Study on Changes in Physical and Mechanical Properties and Integrity Decay of Sandstone Subjected to Freeze–Thaw Cycling". Applied Sciences 13, n. 12 (20 giugno 2023): 7316. http://dx.doi.org/10.3390/app13127316.
Testo completoAbstract (sommario):
To investigate the effects of long-term freeze–thaw cycles on the physical and mechanical properties as well as the attenuation trend of rocks, this study conducted saturated freeze–thaw tests on coarse sandstone and fine sandstone samples collected from the slopes of Muli Coal Mine in Qinghai Province. The samples underwent different numbers of freeze–thaw cycles, and their porosity, longitudinal wave velocity, and uniaxial compression strength were studied. The variations in the physical and mechanical properties of the two types of sandstone with respect to the number of freeze–thaw cycles were analyzed. Take uniaxial compressive strength (UCS) as the integrity index, and decay laws of rock integrity were analyzed based on the decay equation suggested in previous studies. We found that the decay index λ, which is commonly assumed to be constant, varies with the number of freeze–thaw cycles. Furthermore, the λ values varied between different rock types. For fine sandstone, the λ decreases with an increase in the number of freeze–thaw cycles, ranging from 0.00385 to 0.005. However, for coarse sandstone, the λ initially decreases and then increases with an increase in the number of freeze–thaw cycles. The range of λ for coarse sandstone is between 0.00376 and 0.00481. Finally, we established a relationship between the decay index, porosity, and longitudinal wave velocity in the fine sandstones. This relationship provides a more straightforward way to evaluate the integrity of fine sandstones subjected to different numbers of freeze–thaw cycles.
49
Yang, Yuru, Wenping Li e Qinggang Lu. "Acoustic Emission Characteristics of the Water Weakening Effect on Cretaceous Weakly Cemented Sandstone". Sustainability 15, n. 10 (22 maggio 2023): 8390. http://dx.doi.org/10.3390/su15108390.
Testo completoAbstract (sommario):
Rock mass stability is often affected by water–rock interaction in underground engineering construction. Cretaceous sandstones often have weak cementation, low strength and strong water-holding capacity, and their rock mass strength is easily weakened by these activities. In this paper, the uniaxial compressive strength (UCS) and tensile strength (TS) of weakly cemented Cretaceous sandstones from different sedimentary facies under natural and saturated conditions were tested, and the loading process was monitored by the acoustic emission (AE) technique. The results show that the existence of water obviously weakened the mechanical properties of weakly cemented sandstone. The UCS and TS of saturated braided river facies sandstone decreased to 41.24% and 35.95% of their natural states, respectively, while those of desert facies sandstone decreased to 32.90% and 26.98% of their natural states, respectively. The AE characteristics of sandstone from different sedimentary facies were similar during loading due to weakening by water, including a decrease in cumulative AE energy, b-value fluctuation and reduction in the peak frequency distribution range. Fracture in the Brazilian splitting test was mainly due to the rapid initiation and coalescence of microcracks near the peak point. However, in the uniaxial compression test, the macro fractures were caused by many microcracks that occurred continuously during loading and finally connected. The high quartz and low feldspar contents strengthened the mechanical properties of braided fluvial facies sandstone compared to those of desert facies sandstone and lessened the effect of water weakening.
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Qiao, Peng, Yiwen Ju, Jianchao Cai, Jun Zhao, Hongjian Zhu, Kun Yu, Yu Qi et al. "Micro-Nanopore Structure and Fractal Characteristics of Tight Sandstone Gas Reservoirs in the Eastern Ordos Basin, China". Journal of Nanoscience and Nanotechnology 21, n. 1 (1 gennaio 2021): 234–45. http://dx.doi.org/10.1166/jnn.2021.18743.
Testo completoAbstract (sommario):
The complex pore system in tight sandstone reservoirs controls the storage and transport of natural gas. Thus, quantitatively characterizing the micro-nanopore structure of tight sandstone reservoirs is of great significance to determining the accumulation and distribution of tight gas. The pore structure of reservoirs was determined through polarizing microscopy, scanning electron microscopy (SEM), and the combination of mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) experiments on Late Paleozoic conventional and tight sandstone samples from the Linxing Block, Ordos Basin. The results show that in contrast to conventional sandstone, dissolution pores, with diameters less than 8 μm, are the main contributors to the gas storage space of tight sandstone reservoirs. The pore size distribution derived from the MICP experiment demonstrates that the main peak of tight sandstones corresponds to a pore radius in the range of 247 nm to 371 nm, while the secondary peak usually corresponds to 18 nm. The results of the NMR test illustrate that the T2 spectra of tight sandstones are unimodal, bimodal and multimodal, and the main NMR peak is highly related to the MICP peak. Fractal theory was proposed to quantitatively characterize the complex pore structure and rough porous surface. The sandstones show fractal characteristics including nanopore fractal dimension DN obtained from the MICP and large pore fractal dimension DL obtained from the NMR experiment. Both DN and DL are positively correlated with porosity and negatively correlated with permeability, demonstrating that complex and heterogeneous pore structure could increase the gas storage space and reduce the connectivity.