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1
Wang, Ziwen, Jifang Du, Shuaifeng Wu, Yingqi Wei, Jianzhang Xiao, Wenxi Han, Di Pan, and Binbin Zheng. "Water Softening Mechanism and Strength Model for Saturated Carbonaceous Mudstone in Panzhihua Airport, China." Advances in Civil Engineering 2020 (December 9, 2020): 1–12. http://dx.doi.org/10.1155/2020/8874201.
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To identify the water softening mechanisms that caused landslides in Panzhihua Airport, China, property and saturation tests of the mudstones extracted from a representative landslide were proposed. In this paper, water saturation tests were carried out on samples of carbonaceous mudstone collected from the east side of the No. 12 landslide at the airport. A number of different analytical techniques and mechanical tests were used to determine changes in chemical composition, mineral assemblages, and mudstone structural characteristics, including shear strength, after the mudstone had been softened. Three kinds of changes caused by water and three mudstone softening stages are proposed. The results show that the water has a significant influence on the properties of the mudstone, so the stability of the mudstone in the watery period is a big threat to the upper structure. A model for water immersion mudstone strength softening is developed. The model incorporates a permeability coefficient, the hydraulic gradient, and time; the model can be used to determine the mudstone’s shear strength and internal friction angle. This study provides a reference for the study of rock softened by water immersion.
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Feng, Chong, and Hua Cai. "Seepage Mechanics Mechanism of Undercompacted Mudstone's Formation." Applied Mechanics and Materials 459 (October 2013): 693–97. http://dx.doi.org/10.4028/www.scientific.net/amm.459.693.
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Buried mudstones general have undercompacted phenomenon. Undercompacted mudstones have the characteristics that the porosity and pore fluid pressure are abnormal bigger. In order to disclosure the seepage mechanics mechanism of undercompacted mudstones formation, this paper has summed up the seepage mechanics relationship when fluid flows through the mudstone, and has verified the relationships between the key physical quantities with the minimal pressure (pressure that can let the fluid flow in the mudstone) by the experiments in physics. This paper has also analysis the formations process of undercompacted mudstone. The result shows that, the flow regime of fluid in the mudstone is the low speed seepage, and it is not applicable by Darcy equation; the fluid what flow through the thick and heavy compacted mudstone has the big minimal pressure. At the beginning or during the deposit, the rule of fluid flow in the mudstone decides that the fluid inside of the mudstone is more difficult to flow out than the fluid surface of the mudstone, and the inside mudstone becomes undercompacted. Because of the undercompacted mudstone is more important for the exploration of oil and gas, it has theoretic and practical sense to analysis the formations mechanism of the undercompacted mudstone.
3
Feng, Zheyuan, Qi Xu, Xinyu Luo, Ruyu Huang, Xin Liao, and Qiang Tang. "Microstructure, Deformation Characteristics and Energy Analysis of Mudstone under Water Absorption Process." Energies 15, no. 20 (October 12, 2022): 7511. http://dx.doi.org/10.3390/en15207511.
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In geological engineering, a series of safety problems caused by expansive mudstone are common, such as slope instability and roadbed up-arch. In this paper, the mineral composition of mudstones in the Xining area was analyzed by X-ray diffraction (XRD), and the microstructural and morphological changes of mudstones after water absorption were observed by scanning electron microscopy (SEM) test to analyze the internal factors and microstructural evolution patterns of water absorption and swelling of mudstones. Based on the microstructural units, the mudstones were defined into two categories, one is N-type mudstone with flat sheet-like stromatolite units, and the other is SN-type mudstone with more clastic particle units. Water absorption experiments were conducted on the rock samples to study the microstructure of these two types of mudstones under different water absorption conditions. The pore characteristics of the mudstones were analyzed by using Image-Pro Plus to reveal the water absorption mechanism. The results show that the pore area of N-type mudstone is smaller, as well as the distribution of pore diameter. The pore area of N-type mudstone develops rapidly, in the early stage of water absorption, lots of pores are produced, and the pore area of SN-type mudstone shows an overall decreasing trend. The pore area and the number of SN-type mudstones are at a low level after full water absorption. Under the condition of full immersion, water enters the pores rapidly and soluble salts are dissolved in large quantities. The change of water absorption rate of mudstone with time can be divided into the stage of sudden increase, decrease and stability of water absorption rate. Then, based on the stress theory, the relationship between the macroscopic expansion process and the microstructure of mudstone was analyzed. Finally, the energy basis of mudstone water absorption is discussed. In the swelling of mudstone, the energy gradually turns into swelling strain energy.
4
Zhang, Xue Juan, Lei Zhang, and Zhi Ru Yang. "Seismic Prediction Method for Dark Mudstone Thickness of the Second Member of the Denglouku Formation in Northern Songliao Basin." Advanced Materials Research 616-618 (December 2012): 411–20. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.411.
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The hydrocarbon source rocks in Denglouku formation of Northern Songliao Basin are mainly the grey mudstones in Deng 2 member. Combined with well and seismic information, this paper forecasts the mudstone thickness distribution of study area applying multiple seismic attribute quantitative prediction based on sedimentary characteristics. We also predict the plane distribution of dark mudstone-mudstone thickness ratio with stratigraphic sedimentary thickness information, horizontal result of seismic facies interpretation and dark mudstone-mudstone thickness ratio materials of well point. Eventually, we obtain the plane dark mudstone prediction result. Analysis indicates that the source rocks of Deng 2 member in Northern Songliao Basin mainly consist of three larger dark mudstone development areas and other sporadic small-scale development areas adjacent, which have the maximum dark mudstone thickness of about 357m located near Songji 6 well.
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Zhu, Rui, Ying-hao Huang, Zhu Song, and Feng Zhou. "Volume Changes and Mechanical Properties of Expansive Mudstone below Canals under Wet-Dry/Wet-Dry-Freeze-Thaw Cycles." Advances in Civil Engineering 2021 (June 5, 2021): 1–11. http://dx.doi.org/10.1155/2021/3791692.
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The complex environment in northern China is the main reason for degradation of expansive mudstone below the canals, which resulted in instability and damage of canal slopes. In this study, a serial of laboratory tests was conducted to explore the volume changes and mechanical behaviors of expansive mudstone below the canals in Xinjiang. The experimental program includes wet-dry (WD) and wet-dry-freeze-thaw (WDFT) tests, volume measurement, and unconfined compression tests. The test results show that during the WD cycles, the volume changes of expansive mudstones with a higher dry range would be more significant. The freeze-thaw process in the WDFT cycles resulted in a decrease of volume change ranges when the expansive mudstones had a relatively smaller dry range and a slight increase of volume change ranges when the expansive mudstones had a relatively larger dry range. In the meantime, the stress-strain relationships of expansive mudstones with different dry ranges all presented strain softening under the cycles of WD or WDFT. The first cycle resulted in a significant decrease of failure strength. After seven WD/WDFT cycles, the failure strength of expansive mudstones with different dry ranges decreased by 37.2%∼59.1%. In addition, the freeze-thaw process in the WDFT cycles promoted the softening of the stress-strain relationships and aggravated the failure strength attenuation of expansive mudstones. Through this study, we expect to provide a preliminary basis for the construction and maintenance of expansive mudstone canals in Xinjiang.
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Douma, Lisanne A. N. R., Jeremie Dautriat, Joel Sarout, David N. Dewhurst, and Auke Barnhoorn. "Impact of water saturation on the elastic anisotropy of the Whitby Mudstone, United Kingdom." GEOPHYSICS 85, no. 1 (January 1, 2020): MR57—MR72. http://dx.doi.org/10.1190/geo2019-0004.1.
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Mudstones are often anisotropic, which complicates depth conversion in seismic exploration and monitoring subsurface reservoirs during injection or production. In addition, the physical and mechanical properties of mudstones are highly sensitive to their water content. The elastic anisotropy of mudstones is not well understood because of their complex nature and the lack of laboratory experiments performed on well-preserved samples. Triaxial deformation tests were performed on mudstone core plugs to investigate the impact of water saturation on the elastic anisotropy of the Whitby Mudstone (United Kingdom). The mechanical and physical properties of the Whitby Mudstone were estimated from stress-strain and ultrasonic wave velocity data obtained on core plugs with different water saturations under isotropic and anisotropic stress conditions. The Whitby Mudstone has extremely high intrinsic elastic anisotropy (0.3–0.4) due to its composition and lamination. This elastic anisotropy increases with decreasing water content. There are three competing mechanisms that play a key role in the anisotropy increase due to dehydration such as (1) density contrast in the pore space (i.e., the presence of purely brine or a mixture of brine and air in the pore space), (2) formation of dehydration fractures, and (3) frame stiffening. Increasing the mean effective stress leads to a decrease in Thomsen’s anisotropy parameters [Formula: see text] and [Formula: see text] because of the closure of defects, such as natural and dehydration fractures, and the formation of stress-induced fractures. The relationship between the wavefront anellipticity factor [Formula: see text] and the mean effective stress is nonmonotonic and can be related to the onset of inelastic deformation.
7
Zhou, Yi Bo, Guang Di Liu, and Jia Yi Zhong. "Identification and Distribution of Lower Cretaceous Source Rocks in Ying’er Sag, Jiuquan Basin." Advanced Materials Research 616-618 (December 2012): 69–72. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.69.
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Based on the sequence stratigraphy study, the relation between dark mudstone ratio and sedimentary facies in different system tracts is observed and used to forcast the distribution of dark mudstones in the main formation combining with seismic data and well log. However, not all dark mudstones can generate hydrocarbon, so the source rock quality is quoted to calculate the thickness of the source rock within mudstone. The results show that the favored source rock in lake progressive system tracts and the bottom of highstand system tracts of Xiagou Formation and Chijinpu Formation are related to a group of reflectors with medium-strong amplitude, medium-low frequency and medium to comparatively good lateral continuity. The source rock of Xiagou Formation with high organic content and wide-range distribution is the major hydrocarbon source in Ying’er Sag, while Chijinpu Formation with thick dark mudstones is the potential source rock and the target of the further exploration.
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Cruden, D. M., S. Thomson, and P. C. Tsui. "The geotechnical characteristics of an ice-thrust mudstone, Wabamun Lake area, Alberta." Canadian Geotechnical Journal 26, no. 2 (May 1, 1989): 227–34. http://dx.doi.org/10.1139/t89-032.
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This first detailed report of the geotechnical characteristics of ice-thrust soft rock examines Upper Cretaceous, once heavily overconsolidated mudstones in the Highvale coal mine, Alberta. The fissured and brecciated sample from an ice-thrust shear zone in the mine behaves as a lightly overconsolidated sediment in laboratory tests and shows a non-brittle mode of shear deformation with a maximum shear strength close to residual. This behaviour is due to weathering and glaciotectonic deformation, which have jointed, sheared, and remoulded the mudstone, thus eliminating the fabric formed by overconsolidation.In the ice-thrust mudstone, platy clay minerals dominate and have been grouped into aggregations or shear-remoulded matrices. The strength of the brecciated portion of the mudstone ranges from peak to residual. The strength along principal displacement shears is at or close to residual, as back analysis of a slope failure shows. Key words: ice-thrust shear zone, glaciotectonic deformation, consolidation, nonbrittle deformation, principal displacement shears, shear strength.
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Haq, Izhar Ul, Eswaran Padmanabhan, and Omer Iqbal. "Depositional Heterogeneities and Brittleness of Mudstone Lithofacies in the Marcellus Subgroup, Appalachian Basin, New York, U.S.A." Energies 14, no. 20 (October 14, 2021): 6620. http://dx.doi.org/10.3390/en14206620.
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Organic-rich rocks of the Marcellus subgroup in the study area consist of a diverse suite of mudstone lithofacies that were deposited in distinct facies belts. Lithofacies in the succession range in composition from argillaceous to siliceous, calcareous, and carbonaceous mudstone. Heterogeneities in the succession occurs in the form of varying mineralogical composition, slightly bioturbated to highly bioturbated chaotic matrix, organic-rich and organic-lean laminae, scattered fossil shells in the matrix, and fossils acting as lamination planes. Lithofacies were deposited in three facies belts from the proximal to the distal zone of the depositional system. Bedded siliceous mudstone (BSM) facies occur in the proximal facies belt and consists of a high quartz content in addition to clay minerals and pyrite. In the medial part of the facies belt lies the laminated argillaceous mudstone (LAM), bedded calcareous mudstone (BCaM), and bedded carbonaceous mudstone (BCM). The size of detrital mineral grains in the lithofacies of the medial facies belt is larger than bedded argillaceous mudstone (BAM) of the distal facies belt, characterized by clay-rich matrix with occasional fossil shells and horizontally aligned fossils. Two types of horizontal traces and one type of fecal string characterize the proximal mud-stone facies, whereas only single horizontal trace fossil is found in the mudstones of the medial and distal facies belt. Parallel alignment of fossil shells and fossil lags in lithofacies indicate that bed-load transport was active periodically from the proximal source of the depositional system. Bioturbation has heavily affected all of the lithofacies and presence of mottled burrows as well as Devonian fauna indicate that oxic to dysoxic conditions prevailed during deposition. The deposition of this organic-rich mudstone succession through dynamic processes in an overall oxic to dysoxic environment is different from conventional anoxic depositional models interpreted for most of the organic rich black shales worldwide. Total organic content (TOC) varies from top to bottom in the succession and is highest in BCM facies. The brittleness index, calculated on the basis of mineralogy, allowed classification of the lithofacies into three distinct zones, i.e., a brittle zone, a less brittle zone, and a ductile zone with a general proximal to distal decrease in the brittle behavior due to a decrease in the size of the sediments.
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Small, C. A., and N. R. Morgenstern. "Performance of a highwall in soft rock, Highvale mine, Alberta." Canadian Geotechnical Journal 29, no. 3 (June 1, 1992): 353–63. http://dx.doi.org/10.1139/t92-041.
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The Highvale mine, west of Edmonton, Alta., is a strip-mining operation with Upper Cretaceous soft sandstone and mudstone overlying the coal deposit. Highwalls cut in the soft rock experienced numerous failures from 1983 to 1985 that disrupted stripping and mining operations and posed a threat to safety. The performance of a 20–23 m highwall at Highvale was studied in 1987 and 1988 to gain insight to the mechanisms of failure. The study utilized surveying, slope indicators, and piezometers to determine the deformation and seepage pattern behind the highwall as it rebounded into the pit upon excavation. Translational movements were found to extend over 250 m behind the highwall along weak, probably presheared bentonitic mudstones. The sandstone and mudstone overburden was observed to extend toward the open pit. This affected the pore-pressure regime and led to a reduction in the mass strength of the sandstone and mudstone. The findings of this study contributed to a better understanding of the mechanisms of highwall failure in soft sedimentary rocks. Key words : highwall, deformations, failure, seepage, loosening, softening.
11
Su, Siyu, Yongqiang Zhao, Renhai Pu, Shuo Chen, Tianyu Ji, and Wei Yao. "Growth and Distribution of Coal-Measure Source Rocks in Mixed Platform: A Case Study of Carboniferous in Bamai Area, Southwest Tarim Basin, China." Energies 15, no. 15 (August 5, 2022): 5712. http://dx.doi.org/10.3390/en15155712.
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Coal-measure source rocks are generally developed in marsh facies under a humid climate and are rarely reported in a carbonate platform or a mixed platform. Carboniferous seawater intruded from west to east in the Tarim Basin, and mixed platform deposits of interbedded mudstone and carbonate developed in the southwest of the basin. In recent years, with the deepening of the exploration, nearly 20 m coal seams and carbonaceous mudstone source rocks have been found in the Carboniferous lagoon’s tidal-flat background. The hydrocarbon generation potential, development, and distribution of these coal-measure source rocks have become an important issue for oil and gas exploration. Coal seams and carbonaceous mudstones were found in the Carboniferous formation of wells BT5, BT10, and Lx2. The hydrocarbon prospect, development, and distribution characteristics of these coal formations have become an important research topic. The authors conducted organic geochemical tests and analyses of core and samples drill cuttings from multiple wells in the study area, combined with research focused on the identification and distribution of coal seams, dark mudstones, and depositional facies via logging cross plots of different lithology and 3D seismic inversion. The results show that coal-measure source rocks in the BT5 well are related to the set of delta-lagoon sedimentary systems widely developed in the Carboniferous Karashayi Formation. The maximum cumulative thickness of coal-measure source rocks is about 20 m, with total organic carbon (TOC) contents of 0.15–60%, kerogen types II2-III, and vitrinite reflectance (Ro) values of 0.78–1.65%. The rocks have generally low maturity in the northwestern area and high maturity in the southeastern area, and the maturity changes as the burial depth changes. The effective hydrocarbon source rocks such as coal, carbonaceous mudstone, and dark mudstone all show acoustic time (AC) greater than 300 µs/m, and density (DEN) less than 2.3 g/cm3, but possess different gamma ray (GR) values. The GR value is less than 75 API for coal, between 75–100 API for carbonaceous mudstone, and greater than 100 API for dark mudstones. The distribution of source rocks can be identified in the area between the wells according to a 3D seismic inversion impedance (IMP) of less than 7333 m/s·g/cm3. The development and controlled factors of coal-measure source rocks of delta facies in the mixed platform have a significant role for oil and gas exploration of Upper Paleozoic in this area. The coal measure and sandstones of delta in the Carboniferous are expected to form self-generation and self-storage pools in this area.
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Boulesteix, Kévin, Miquel Poyatos-Moré, David M. Hodgson, Stephen S. Flint, and Kevin G. Taylor. "Fringe or background: Characterizing deep-water mudstones beyond the basin-floor fan sandstone pinchout." Journal of Sedimentary Research 90, no. 12 (December 31, 2020): 1678–705. http://dx.doi.org/10.2110/jsr.2020.048.
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ABSTRACT Mud dominates volumetrically the fraction of sediment delivered and deposited in deep-water environments, and mudstone is a major component of basin-floor successions. However, studies of basin-floor deposits have mainly focused on their proximal sandstone-prone part. A consequent bias therefore remains in the understanding of depositional processes and stratigraphic architecture in mudstone-prone distal settings beyond the sandstone pinchouts of basin-floor fans. This study uses macroscopic and microscopic descriptions of over 500 m of continuous cores from research boreholes from the Permian Skoorsteenberg Formation of the Karoo Basin, South Africa, to document the sedimentology, stratigraphy, and ichnology of a distal mudstone-prone basin-floor succession. Very thin- to thin-bedded mudstones, deposited by low-density turbidity currents, stack to form bedsets bounded by thin packages (< 0.7 m thick) of background mudstones. Genetically related bedsets stack to form bedset packages, which are bounded by thicker (> 0.7 m thick) background mudstones. Stratigraphic correlation between cores suggests that bedsets represent the distal fringes of submarine fan lobe elements and/or lobes, and bedset packages represent the distal fringes of lobe complexes and/or lobe complex sets. The internal stacking pattern of bedsets and bedset packages is highly variable vertically and laterally, which records dominantly autogenic processes (e.g., compensational stacking, avulsion of feeder channels). The background mudstones are characterized by remnant tractional structures and outsize particles, and are interpreted as deposited from low-density turbidity currents and debris flows before intense biogenic reworking. These observations challenge the idea that mud accumulates only from hemipelagic suspension fallout in distal basin-floor environments. Thin background mudstones separating bedsets (< 0.7 m thick) are interpreted to mainly represent autogenically driven lobe abandonment due to up-dip channel avulsion. The thicker background mudstones separating bedset packages (> 0.7 m thick) are interpreted to dominantly mark allogenically driven regional decrease of sand supply to the basin floor. The recognition of sandstone-prone basin-floor fans passing into genetically linked distal fringe mudstones suggests that submarine lobes are at least ∼ 20 km longer than previously estimated. This study provides sedimentological, stratigraphic, and ichnological criteria to differentiate mudstones deposited in different sub-environments in distal deep-water basin-floor settings, with implications for the accurate characterization of basin-floor fan architecture, and their use as archives of paleoenvironmental change.
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Huang, Kai, Chunsheng Shen, Kai Kang, Libing Wang, Zhongbo Xu, and Lin Li. "Characteristics of Mudstone in Complex Fluvial Sedimentary System in Bohai L Oilfield." Earth Science Research 7, no. 2 (July 8, 2018): 79. http://dx.doi.org/10.5539/esr.v7n2p79.
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Bohai L oilfield develops a complex fluvial sedimentary system, which includes many types of fluvial sedimentary facies. Based on the coring well of oil field, the distribution characteristics of mudstone are analyzed, it is shown that the mudstone has similar internal structure and can be classified into four types according to its color: gray to grayish, variegated, brown to gray-brown and khaki, the assemblage has a large gray to grayish mudstone section, large gray to grayish mudstone intercalated thin layer sandstone, gray to grayish mudstone associated with variegated (brown) mudstone, grayish mudstone associated with lacustrine sand grain bedding sandstone, concomitant generation of large staggered bedding sandstone and grayish mudstone, mixed (gray-brown) mudstone associated with large staggered bedding sandstone, interaction between different colors of mudstone and sandstone and large interlaced sandstone intercalated with thin layer mudstone. The mudstone color is mainly gray and grayish, and very few oxidized mudstone is developed alone, which indicates that fluvial mudstone may be formed in the reductive environment in humid climate, and the fluvial mudstone in this area may be formed in the oxidizing environment, which is different from the general understanding of fluvial facies, the oxidation color is the result of the later transformation.
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Zhang, Tongwei, Xiangzeng Wang, Jianfeng Zhang, Xun Sun, Kitty L. Milliken, Stephen C. Ruppel, and Daniel Enriquez. "Geochemical evidence for oil and gas expulsion in Triassic lacustrine organic-rich mudstone, Ordos Basin, China." Interpretation 5, no. 2 (May 31, 2017): SF41—SF61. http://dx.doi.org/10.1190/int-2016-0104.1.
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Forty-six core samples were collected from a deep well that penetrated organic-rich layers of the Chang 7, 8, and 9 members of the Yanchang Formation (Fm) in the Ordos Basin. Tests for total organic content (TOC), Rock-Eval pyrolysis, X-ray diffraction (XRD) mineralogy, and molecular composition of gases released from rock crushing were conducted. Analytical results indicate that TOC and clay contents are elevated. The organic matter (OM)-rich mudstone in the Triassic Yanchang Fm suggests good-to-excellent source potential for oil generation. Its thermal maturity is in the oil window. Strong petroleum expulsion occurred from the upper part of the approximately 13 m (42.6 ft) thick Chang 7 member, and for the Chang 8 and Chang 9 members, resulting in low free oil and low methane ([Formula: see text]) concentration in these OM-rich intervals. A combination of sandstone and thin organic-rich mudstone layers is a perfect hybrid lithology stacking pattern for petroleum expulsion. The thickness for effective source rock, approximately 10–12 m (32.8–39.3 ft), varied with sandstone/mudstone lithology stacking pattern. In contrast, limited or no oil expulsion occurred in the lower part of Chang 7 member, a 25 m (82 ft) thick organic-rich interval, which is indicated by high free oil and high [Formula: see text] concentration. A [Formula: see text]-TOC plot can be used to differentiate generated gas, retained gas in OM-rich mudstones, and migrated gas in permeable sandstone beds. We have developed a conceptual model for petroleum expulsion from OM-rich thin versus OM-rich thick layers. Compaction and thermal volume expansion of oil generated from OM may play an important role in petroleum expulsion in OM-rich mudstones. The estimated petroleum expulsion efficiency is approximately 70% and 35% for thin and thick OM-rich mudstone layers, respectively. The redistributed OM in clay-dominated rock assemblage likely forms the preferred migration path to petroleum expulsion.
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Wang, Min, Shuangfang Lu, Wenbiao Huang, and Wei Liu. "Pore characteristics of lacustrine mudstones from the Cretaceous Qingshankou Formation, Songliao Basin." Interpretation 5, no. 3 (August 31, 2017): T373—T386. http://dx.doi.org/10.1190/int-2017-0010.1.
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Cretaceous Qingshankou ([Formula: see text]) mudstone of lacustrine origin is the major source rock for conventional hydrocarbon currently being produced in the Daqing and Jilin oilfields of the Songliao Basin, which is one of the largest continental basins in the world. Therefore, elucidating the geochemical and petrological characteristics of the [Formula: see text] mudstone is important to help determine its quality as an economically viable source for shale oil production. In our study, eight dark mudstone core samples from the [Formula: see text] formation were subjected to total organic carbon (TOC), Rock-Eval pyrolysis, X-ray diffraction, scanning electron microscopy (SEM), field emission SEM (FE-SEM), and low-pressure [Formula: see text] gas adsorption (LPGA-[Formula: see text]) experiments. Geochemical and petrological analysis results indicated the presence of a high TOC content, which originated mainly from alginate and some plant-derived organic matter, whereas bitumen was frequently present in mudstones with thermal maturity in the oil-generation stage. The [Formula: see text] mudstones were comprised mainly of clay minerals, followed by quartz, feldspar, and carbonates. The LPGA-[Formula: see text] experiments revealed the presence of nanoscale slit-shaped pores, and the contribution from mesopores to the total pore volume was the highest in most of the samples. The average pore diameters (APDs) of the mudstone samples were all smaller than 20 nm (4.36–17.79 nm). We determined that there was a clear positive correlation between the APD and the free oil content; however, there were no clear correlations between the APDs and the quartz, carbonate, and TOC contents. FEM studies revealed the presence of intergranular pores with widths of approximately 10 μm, micron-level autogenetic organic matter pores within spores, organic matter pores caused by the hydrocarbon generation effect within organic matter or clay-organic complexes, and intraparticle pores within clays or pyrite framboids. The microlevel intergranular pores might play an important role in shale oil accumulation from source rock of lacustrine origin.
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WILLIAMS, MARK, JEREMY R. DAVIES, RICHARD A. WATERS, ADRIAN W. A. RUSHTON, and PHILIP R. WILBY. "Stratigraphical and palaeoecological importance of Caradoc (Upper Ordovician) graptolites from the Cardigan area, southwest Wales." Geological Magazine 140, no. 5 (September 2003): 549–71. http://dx.doi.org/10.1017/s0016756803008057.
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Graptolites from more than 60 horizons in the basinal Caradoc succession of southwest Wales, between Fishguard and Cardigan, allow recognition of the multidens, clingani and linearis biozones. The biostratigraphy permits recognition of major differences in the sedimentary rock-sequence north and south of structures associated with the Fishguard–Cardigan Fault Belt. The Penyraber Mudstone Formation, disconformably overlying the Fishguard Volcanic Group (Llanvirn), is partly of multidens Biozone age. It is succeeded south of the Newport Sands Fault by the Cwm yr Eglwys Mudstone Formation of clingani to linearis biozones age. North of the fault the Cwm yr Eglwys Mudstone Formation is replaced laterally by the northwards-thickening, sandstone turbidite-dominated Dinas Island Formation (clingani and linearis biozones). Graptolite stratigraphical distribution indicates that Dicranograptus clingani occurs only rarely within the caudatus Subzone of the clingani Biozone and that Climacograptus antiquuss.l. also does not range above the lower part of the clingani Biozone. The first occurrence of Dicellograptus morrisi, within the upper clingani Biozone, confirms its value as a marker for the morrisi Subzone, and is associated with the first occurrences of Diplacanthograptus dorotheus and Normalograptus minimus. Dicellograptus flexuosus, used to indicate the morrisi Subzone elsewhere, occurs throughout the clingani Biozone in the Cardigan area. The linearis Biozone is recognized by Climacograptus tubuliferus. Oxic bottom conditions in early and early mid-Caradoc times largely precluded the influx of, or preservation of, graptolite faunas in the Penyraber Mudstone Formation. Anoxic mudstones of the Cwm yr Eglwys Mudstone and Dinas Island formations preserve graptolite assemblages of 21 and 26 species, signalling strong open marine influences which persisted in this area until late Caradoc times. This contrasts with the shelfal faunas in the Whitland area (south Pembrokeshire), where the late Caradoc is dominated by low-diversity Normalograptus-dominated assemblages.
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Hu, Ankui, Shuai Zhou, Mengkun Wu, Xiaohui Liu, and Rui Zhao. "Modified Rheological Model for Deep-Buried Silty Mudstone and Support Time Analysis Application." Mathematical Problems in Engineering 2023 (February 11, 2023): 1–16. http://dx.doi.org/10.1155/2023/3124359.
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The rheological properties of soft rocks should be considered in the long-term design and maintenance of deep-buried tunnels using uniaxial single-stage loading and graded incremental cyclic-loading methods. In this article, creep tests were performed on deep-buried silty mudstone from a specific water conveyance tunnel in China, with a buried depth in the range of 1650–2320 m and subjected to high in situ stress. The creep curves of silty mudstone under different loading stresses were obtained, showing evident rheological mechanical behavior under complicated external environmental conditions. Based on the classic Burgers rheological model, a new nonlinear creep model was established based on the creep properties of deep-buried silty mudstone in the project area. Typically, the designated rheological models for certain projects are unsuitable or inadequate. A nonlinear dashpot was calculated using the Levenberg–Marquardt (L–M) method coupled with origin to account for the deterioration trend in the strength of the silty mudstone over time. With the determined parameters, the modified Burgers model exhibited good qualitative consistency with field monitoring data. The user-defined material mechanical behavior (UMAT) subroutine of the modified Burgers model was successfully achieved after it was implemented in the numerical code ABAQUS. Based on the full-rheological effect, the proper supporting time of a deep-buried tunnel was studied, and it was proposed that a second lining should be cast in situ approximately 150 days after the excavation of the tunnel. The outcomes of the proposed modified rheological model can accurately represent the creep behavior of deep-buried silty mudstones in a specific engineering instance. The research results can provide a basis for the rheological behavior and supporting time of deep-buried silty mudstone.
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Denommee, Kathryn C., Dario Harazim, Samuel J. Bentley, James H. Macquaker, Stefanie Lode, and Babatunde John Olanipekun. "Mud deposition and diagenesis within an Early Palaeozoic clinothem: Power Steps Formation, Newfoundland, Canada." Geological Magazine 157, no. 2 (May 28, 2019): 134–48. http://dx.doi.org/10.1017/s0016756819000402.
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AbstractThe early Ordovician (∼385 Ma) Power Steps Formation, Newfoundland, Canada, exposes a well-preserved mudstone-dominated clinothem that serves as an excellent archive for understanding how mud has been produced, transported and converted into mudstone prior to the evolution of globally widespread, deep soil horizons. Sedimentological analysis of four sandstone and five mudstone facies, along the Ochre Cove clinothem, reveal that mud and sand were delivered by unidirectional currents and experienced episodic reworking by storm waves. Petrographic examination and X-ray diffraction from described mudstone facies reveal significant variability in the distribution of illite versus chlorite between the lower and upper part of the Ochre Cove clinothem. This research highlights that in the present-day clay mineral fraction, illite is often detrital whereas chlorite originated via the alteration of silt-sized, highly unstable, mafic (volcanoclastic?) grains. Throughout all sedimentologic facies, albeit in different proportions, these mafic lithic grains were diagenetically altered via in situ weathering before significant compaction occurred, resulting in the precipitation of significant volumes of pore-bridging, silica- and iron-rich chlorite cement. Compositional, diagenetic and textural attributes across the Ochre Cove mud clinothem vary as a function of starting composition, hydrodynamic sorting and grain density. Given that a significant proportion of clay minerals has been generated via in situ transformation of a mafic, non-stable precursor assemblage, we recommend future studies to incorporate detailed petrographic description along with X-ray diffraction analyses when aiming to employ trends in whole-rock clay mineral data as a proxy in provenance and palaeoclimate studies of very old (pre-Devonian) mudstones and sandstones.
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Yang, Wan Qin, Yan Yin, and De Yan Zhu. "Sedimentary Sequence of Different Salinization Stages Lower Es3-Upper Es4 in Jiyang Depression." Advanced Materials Research 1073-1076 (December 2014): 2042–45. http://dx.doi.org/10.4028/www.scientific.net/amr.1073-1076.2042.
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This paper establishes the lithological sequence of different salinization stage through the corresponding relation between the salinity and salt minerals. It develops salt gypsum rock-glauber's salt-gypsiferous mudstone-dolomitein in brine stage, and stratiform limestone-lamina argillaceous limestone/ lime mudstone-stratiform argillaceous limestone in salt water stage and stratiform argillaceous limestone/ lime mudstone-massive lime mudstone/ massive mudstone in brackish water stage. The shale sedimentary evolution model is established, with climate changing from the hot dry to wet, and water from shallow to deep, and salinity from high to low, lithological sequence is gypsum-carbonate-argillaceous limestone - lime mudstone and mudstone.
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Chao, Li, Luo Xiaorong, Zhang Likuan, Lei Yuhong, Chen Ming, and Yu Lan. "Chemical compaction of deep buried mudstone and its influence on pressure prediction." IOP Conference Series: Earth and Environmental Science 600, no. 1 (November 1, 2020): 012012. http://dx.doi.org/10.1088/1755-1315/600/1/012012.
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Abstract The chemical compaction of mudstones which is dominated by the transformation of clay minerals leads to significant changes in the mineral composition and microstructure of mudstone during process of deep burial. In particular, the transformation of smectite to illite in mudstones results in noticeable impact on the pore pressure formation and the overpressure logging responses. At present, the study about the pressurization mechanism of chemical compaction and the impact on overpressure logging responses is really weak, which made it hard to pore pressure identification and pressure prediction for deep buried formations. Taking the Paleogene Shahejie Formation in the Dongying depression of the Bohai Bay Basin in eastern China as typical case, this paper analyses the characteristics of clay mineral transformation of the Shahejie Formation in the Dongying depression, the logging responses of overpressures, and the influence of chemical compaction on the prediction of pore pressure. The results showed that the chemical compaction of mudstones changes the relationship between the petrophysical properties of mudstone and vertical effective stress and the logging responses of overpressure. The typical characteristic of chemical compaction manifested as density increase continuous with the depth. The normal compaction trends of the different compaction stages are the basis for overpressure mechanisms identification and pore pressure prediction. The depth of the rapid transformation of clay minerals has a good consistency with the top of overpressure zone (2000–2800 m) in Dongying depression, which indicates that the overpressure and its logging responses may be related to the chemical compaction of mudstones. The measured pressure in intervals deeper than 3000 m is closer to the predicted pressure based on the normal compaction trend of chemical compaction.
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Li, S. N., Z. H. Huang, Q. Liang, J. Liu, S. L. Luo, and W. Q. Zhou. "Evolution Mechanism of Mesocrack and Macrocrack Propagation in Carbonaceous Mudstone under the Action of Dry-Wet Cycles." Geofluids 2022 (July 19, 2022): 1–8. http://dx.doi.org/10.1155/2022/6768370.
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The crack propagation evolution of carbonaceous mudstone under the action of dry-wet cycles is an important cause of the unstable failure of this type of slope. This paper attempts to reveal the evolution mechanism of mesocrack and macrocrack propagation in carbonaceous mudstone under the action of dry-wet cycles from chemical, physical, and mechanical perspectives. Firstly, the soaking solution of carbonaceous mudstone during the dry-wet cycles was extracted for an ion concentration test to analyze the chemical reactions of carbonaceous mudstone. Then, CT scans were performed on the carbonaceous mudstone samples to study the changing pattern of mesostructure of carbonaceous mudstone during the dry-wet cycles. In the end, the mechanical properties and failure characteristics of carbonaceous mudstone after dry-wet cycles were studied by triaxial compression tests. The results showed that chemical reactions such as calcite dissolution, potassium feldspar hydrolysis, and sodium feldspar hydrolysis occurred during the dry-wet cycle of carbonaceous mudstone. Affected by the dry-wet cycles, the mesostructure of the carbonaceous mudstone gradually changed from face-face contact and edge-face contact to edge-corner contact and corner-corner contact, and the interlayer flake structure was opened and was locally curled and fractured. With the increase in the number of dry-wet cycles, the failure characteristic of carbonaceous mudstone transformed from tensile failure to shear failure, the failure surface of carbonaceous mudstone was deflected from 90° to 60°, and the crack propagation path of carbonaceous mudstone became more complicated. The chemical reaction of carbonaceous mudstone minerals during the dry-wet cycle is an important reason for the initiation and development of pores. The dry-wet cycle aggregates the propagation of mesocracks and structural disorder, transforming the uniform stress state of the rock mesostructure to the concentrated stress state, which is the important reason for the macrocrack propagation evolution of carbonaceous mudstone.
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Li, Chao, Xiaorong Luo, Likuan Zhang, Bing Wang, Xiaoyan Guan, Hongmei Luo, and Yuhong Lei. "Overpressure Generation Mechanisms and Its Distribution in the Paleocene Shahejie Formation in the Linnan Sag, Huimin Depression, Eastern China." Energies 12, no. 16 (August 20, 2019): 3183. http://dx.doi.org/10.3390/en12163183.
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The Linnan Sag is one of the main oil-producing units in the Huimin Depression, Eastern China, and the pore pressure gradients obtained from drill stem tests (DSTs) range from 9.0 to 16.0 MPa/km. Uncertainty about the origin and distribution of abnormally high pressures in the Linnan Sag has led to different interpretations of hydrocarbon accumulation and resource assessments, and it interferes with safe drilling. In the Linnan Sag, mudstone compaction curves are substantially affected by several non-compaction factors, and the normal trend of the compaction curve is difficult to determine. The determination of the origin and distribution of overpressure in the Linnan Sag is a challenge. In this study, the factors that may affect mudstone compaction—such as the shale volume, higher calcareous, and organic matter content—were carefully examined and processed. The pressures in the mudstones were estimated by the corrected mudstone compaction curves, which were compiled from acoustic, density, and neutron logs, and calibrated using DST and mud weight data. The log response–vertical effective stress and acoustic velocity-density crossplots were used to identify the mechanisms that generate overpressure. The comprehensive compaction curve shows that the mudstones in the overpressured layer exhibit clear disequilibrium compaction characteristics. The logging response crossplots demonstrate that those overpressured points were consistent with the loading curve. The findings suggest that, the fundamental mechanism resulting in overpressures is the disequilibrium compaction of thick Paleocene mudstones. Hydrocarbon generation and vertical transfer of overpressure may be the main unloading mechanisms, which corresponds to the overpressure points that deviate from the loading curves. Since organic matter cracking may occur in formations at depths greater than 4000 m (Ro > 1.0%), the contribution of hydrocarbon generation to overpressuring is expected to be limited. The transfer of overpressure through opening faults is therefore considered to be the main cause of higher overpressure in local sandstones. The overpressures in the mudstones are characterized by a gradual decrease from the center to the margin in the Linnan Sag. The pressure in the isolated sand bodies are generally similar to that in the surrounding mudstones, whereas it can be lower or higher when the overpressure in the sand bodies are vertically transferred by faults to other pressure systems. The results of this analysis provide an indication of the magnitude, mechanism, and distribution of overpressure in the Linnan Sag. This insight can be used to guide further exploration of the Linnan Sag and similar geological basins.
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Baiyegunhi, Christopher, and Kuiwu Liu. "Sedimentary facies, stratigraphy, and depositional environments of the Ecca Group, Karoo Supergroup in the Eastern Cape Province of South Africa." Open Geosciences 13, no. 1 (January 1, 2021): 748–81. http://dx.doi.org/10.1515/geo-2020-0256.
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Abstract The stratigraphy of the Ecca Group has been subdivided into the Prince Albert, Whitehill, Collingham, Ripon, and Fort Brown Formations in the Eastern Cape Province, South Africa. In this article, we present detailed stratigraphic and facies analyses of borehole data and road-cut exposures of the Ecca Group along regional roads R67 (Ecca Pass), R344 (Grahamstown-Adelaide), R350 (Kirkwood-Somerset East), and national roads N2 (Grahamstown-Peddie) and N10 (Paterson-Cookhouse). Facies analysis of the Ecca Group in the study area was performed to deduce their depositional environments. Based on the lithological and facies characteristics, the stratigraphy of the Prince Albert, Whitehill, Collingham, and Fort Brown Formations is now subdivided into two informal members each, while the Ripon Formation is subdivided into three members. A total of twelve lithofacies were identified in the Ecca Group and were further grouped into seven distinct facies associations (FAs), namely: Laminated to thin-bedded black-greyish shale and mudstones (FA 1); Laminated black-greyish shale and interbedded chert (FA 2); Mudstone rhythmite and thin beds of tuff alternation (FA 3); Thin to thick-bedded sandstone and mudstone intercalation (FA 4); Medium to thick-bedded dark-grey shale (FA 5); Alternated thin to medium-bedded sandstone and mudstone (FA 6); and Varved mudstone rhythmite and sandstone intercalation (FA 7). The FAs revealed gradually change of sea-level from deep marine (FA 1, FA 2, FA 3 and FA 4, FA 5, and FA 6) to prodelta environment (FA 7). This implies that the main Karoo Basin was gradually filling up with Ecca sediments, resulting in the gradual shallowing up of the water depth of the depositional basin.
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Chen, Feng, Xiaoming Sun, and Hao Lu. "Influence of Water Content on the Mechanical Characteristics of Mudstone with High Smectite Content." Geofluids 2022 (March 17, 2022): 1–10. http://dx.doi.org/10.1155/2022/9855213.
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Water content plays an important role in strength of mudstone; many works pay more attention to the strength of dry and saturated rocks. In this study, the water absorption characteristics of mudstone were obtained by a computer-automated WA (water absorption) equipment system experiments. The complete stress–strain curves and UCS (unconfined compress strength) and E (Young’s modulus) of mudstone samples under different water contents were achieved by using the WEP-600 microcomputer-control screen universal testing machine. SEM (scanning electron microscope) test were carried out to study the microstructure characteristics of mudstone samples under different water contents. The results showed that the water absorption process of mudstone consists of three stages. The UCS and E of the mudstone samples markedly decrease with water content increasing. Based on the experimental results and analysis, a porous medium mechanical model of the mudstone was established and a deeper understanding of water-induced strength damage mechanism of the mudstone was achieved.
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Wang, Chengxiang, Huailiang Kou, and Wei Han. "Mechanical Properties and Failure Mechanism of Sandstone with Mudstone Interlayer." E3S Web of Conferences 136 (2019): 04048. http://dx.doi.org/10.1051/e3sconf/201913604048.
Full textAbstract:
In order to study the strength and failure characteristics of sandstone with mudstone interlayer. According to mudstone interlayer dip and distribution form, it can be divided into three kinds of sandstone: sandstone with horizontal mudstone interlayer is Class I; sandstone with inclined mudstone interlayer is Class II; sandstone with irregular distribution mudstone is Class III. The three kinds of sandstone uniaxial test were carried out and combined with the theory of layered rock mass failure, it revealed mechanical properties and failure mechanism of sandstone with mudstone interlayer. The results show that: crack generated from interface in Class I and II and crack generated from irregular distribution mudstone interlayer in Class III; The sandstone with higher strength is destroyed before the mudstone interlayer; sandstone at unbonded interface is failure before sandstone at bonded interface; Three kinds of sandstone vary in compressive strength, Class II is greater than Class III while Class III is greater than Class I.
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Song, Kanglei, Bolong Liu, and Haiqing Yang. "Experimental Study on the Evolution of Argillization of Mudstone and Cutter Wear during the TBM Tunnelling." Shock and Vibration 2021 (October 22, 2021): 1–14. http://dx.doi.org/10.1155/2021/7227194.
Full textAbstract:
Argillization is a process in which clay-bearing rocks disintegrate into the clay under the action of high temperature, pressure, and water. When tunnel boring machines (TBMs) excavate in the mudstone, argillization takes place, causing the clogging of the TBM cutterhead. As a result, the penetration rate drops gradually. Abnormal wear might occur. To investigate the evolution of argillization of mudstone and cutter wear during the TBM tunnelling, a series of rotary indentation tests were carried out on the self-designed experimental bench for different loading times. During the test, the temperature and penetration depth of disc cutters were measured in real time. After loading, microstructures of cutting grooves, slacking mudstone, and worn cutter ring were observed by stereomicroscope. Consequently, the evolution of argillization in mudstone and cutter wear were investigated. Experimental results indicate that the argillization process of mudstone by disc cutter can be divided into three stages: mechanical cutting stage, deterioration of mudstone and the formation of slacking mudstone stage, and adherence of slacking mudstone stage. Specifically, at mechanical cutting stage, the rock was cut by cutter directly, causing high frictional heat. Then the microstructure of mudstone was deteriorated due to the water-weakening mechanisms, temperature effect, and mechanical activation effect. Finally, the slacking mudstone was adhered to the disc cutter. Correspondingly, due to the argillization of mudstone, the disc cutter wear goes through the mechanical wear stage, argillization wear stage, and secondary wear stage in sequence. This investigation reveals the rock cutting mechanism of TBM considering the argillization of mudstone. Furthermore, it provides some references for design and operation of the TBM.
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Rizal, Yan, and Aji Rahmat Gumilar. "The Architectural Element Distribution of Cinambo Formation in Jatigede Area, Sumedang District, West Java - Indonesia." Modern Applied Science 13, no. 7 (June 30, 2019): 94. http://dx.doi.org/10.5539/mas.v13n7p94.
Full textAbstract:
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.
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Corbeanu, Rucsandra M., George A. McMechan, Robert B. Szerbiak, and Kristian Soegaard. "Prediction of 3‐D fluid permeability and mudstone distributions from ground‐penetrating radar (GPR) attributes: Example from the Cretaceous Ferron Sandstone Member, east‐central Utah." GEOPHYSICS 67, no. 5 (September 2002): 1495–504. http://dx.doi.org/10.1190/1.1512794.
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A 3‐D fluid permeability distribution is estimated inside a channel sandstone reservoir analog in the Cretaceous Ferron Sandstone fluvio‐deltaic complex in east‐central Utah from ground‐penetrating radar (GPR) attributes. Fluid permeability measurements at 5 cm spacing along four boreholes and one pseudohole section at the adjacent cliff face are used together with instantaneous amplitude and frequency attributes of GPR data to predict fluid permeabilities away from the measured vertical transects and to delineate the distribution and geometry of mudstone layers inside the reservoir analog. Statistically significant relationships are determined between the well data (fluid permeability and mudstone content) and the GPR attributes. These calibrations are applied to the entire GPR volume to estimate the 3‐D fluid permeability variation and the lateral development of mudstone units. Measured and predicted fluid permeabilities range from 0.1 to 290 md. One of the five units considered contained no mudstone layers; cores from the other four units contained 18–42% mudstone and mudstone intraclast conglomerate. The mudstone content is estimated to be 8% by volume in these four units. Variograms show that the mudstone bodies fall into two main categories; most are 2.3–3.5 m in extent in the maximum correlation direction, with anisotropies of 0.4 to 0.7. A few ribbonlike mudstone bodies are also present, with 20‐ to 30‐m extents in the maximum correlation direction and with anisotropies of ∼0.1.
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He, Shijie, Xianglu Tang, Zeyu Shao, Zhenxue Jiang, Bo Wang, Xiaoxue Liu, Yuchao Wang, and Mingli Xu. "Pore Structure Characteristics, Genesis, and Its Controlling Effect on Gas Migration of Quaternary Mudstone Reservoir in Qaidam Basin." Geofluids 2022 (July 15, 2022): 1–27. http://dx.doi.org/10.1155/2022/7098109.
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The Sanhu Depression in Qaidam Basin is the largest Quaternary biogenic gas exploration area with the shallowest burial depth in the world. The shallow high abundance of gas reservoirs and high-quality pure methane have become the main production areas. The development characteristics of loose mudstone reservoirs are restricted by extreme heterogeneity. Therefore, the Quaternary Qigequan Formation mudstone in Qaidam Basin is selected as the research object. Based on the study of the sedimentary background, petrological characteristics, and pore structure characteristics, by comparing the characteristics of different mudstone reservoirs, the controlling factors of the development of different mudstone reservoirs and the control of gas migration are clarified. Research shows the following: (1) The mudstone reservoirs of the Qigequan Formation mainly develop intergranular pores, clay mineral pores, and intragranular pores. The pore size distribution varies from nanometers to micrometers, and mesopores mainly contribute to the specific surface area. (2) Rigid minerals and clay minerals are the main controlling factors for the pore structure of mudstone reservoirs. The increase in the content of rigid minerals is conducive to the development of macropores or larger micropores, while the increase in the content of clay minerals is conducive to the development of mesopores and provides an important specific surface area for gas adsorption. (3) The gas migration form of pure mudstone is mainly dominated by Fick diffusion and slippage flow, which has the characteristics of self-sealing accumulation. The gas migration form of silty mudstone is the coexistence of Fick diffusion, slippage flow, and Darcy flow, which has the features of self-sealing and Darcy flow accumulation. The gas migration form of sandy mudstone is mainly Darcy flow, only with Darcy flow accumulation characteristics. The flow form of gas creates different accumulation modes of mudstone biogas. The Quaternary mudstone reservoir shows different particularity under different material components, and the exploration targets should be treated differently according to specific mudstone types.
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Hu, Hai Yan, and Hui Wang. "Characteristics of the Overpressure Resulted from Hydrocarbon Generation." Applied Mechanics and Materials 295-298 (February 2013): 2707–10. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.2707.
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Overpressure is often encountered in the Jurassic tight sandstones in the central Junggar Basin. In this studt, a new mechanism of overpressure formation related to gas generation is proposed. Organic-rich mudstones have sonic velocity well-line reserves but their densities continue to increase in the over-compacted mudstone system resulting in the overpressure development during the conversion of the organic matter to oil and gas. The top of the overpressure zone correlates with the depth required for a large quantity of gas generation in which the vitrinite reflectance (Ro) is about 0.7%, showing that the overpressure in organic-rich mudstones is closely associated with gas generation.
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Ji, Ming, and Nong Zhang. "Constitutive Equation of Expansion Rock under Humidity Field." Advanced Materials Research 261-263 (May 2011): 1705–8. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1705.
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The weight and length, width and height of three directions of cuboids’ type calcareous mudstone after infiltrated with water in different period of time were measured by using electronic balance and vernier caliper. The results show that the calcareous mudstone expansion strain is proportional to volume and mass water content. Mchanical properties of calcareous mudstone were studied by uniaxial compression experiments of calcareous mudstone with different water content which carried out by using microcomputer controlled electro-hydraulic servo compression testing machine control system of YAW series. It is concluded from experiment result that calcareous mudstone is brittleness with low water content but when water content reaches saturation, calcareous mudstone presents plastic features. Based on the results above, the constitutive equation of rock considering humidity field is derived which provides important guiding significance to engineering practice.
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Ma, Fu Rong, Xin Gui Zhang, and Nian Ping Yi. "Analysis of Influence Factors on Strength of Mudstone with Soft-Hard Alternant Strata in Nanning Basin." Advanced Materials Research 204-210 (February 2011): 891–94. http://dx.doi.org/10.4028/www.scientific.net/amr.204-210.891.
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The mudstone is formed under the special environment with soft-hard alternant strata in Nanning Basin . The composition,engineering and mechanical properties have a certain complexity and specificity,so the parameters of the mudstone are discrete and variable by which the strength characteristics are influenced. According to the problem of the strength of mudstone,the influence factor is analysed on the strength of mudstone with soft-hard alternant strata in Nanning Basin through the composition, stress history, geological environment, water-rock interaction and disturbance, etc.. The analysis shows that in the final analysis the reduction of the mechanical properties of mudstone is due to structural damage, stress weakening and energy weakening.And the measures of improving the bearing capacity of mudstone are discussed from the test methods, construction control measures, in situ testing and engineering design.
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Wei, Jing Ping, Fan Chen, and Zhi Hao Ding. "Deformation Characteristics and Load-Bearing Capacity of NO.21 Coal Seam’s Mudstone Floor in Western Henan." Advanced Materials Research 644 (January 2013): 175–78. http://dx.doi.org/10.4028/www.scientific.net/amr.644.175.
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Through the floor specific pressure test, the floor specific pressure was obtained. The rock mass of mudstone, under the loading perpendicular to the weak plane, was in brittle-plastic failure state, and the bearing capacity of mudstone was equal to the Ⅲa grade floor. The brittle-plastic transition mechanism of the mudstone was revealed: Firstly, the more size, the more heterogeneity. The mudstone body was bigger than its rock samples, so there were more planes of weakness, which caused the macroscopic plastic deformation. Secondly, the directions of the load and the weak plane influenced the strength of the mudstone floor. During the plastic deformation, the compressive failure occurred layer by layer under the loading perpendicular to the weak planes, and the post peak load-bearing capacity of mudstone floor was decided by the layer’s strength.
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Xin, Tianyu, Yashengnan Sun, Junguang Wang, and Weiji Sun. "Influence of Unloading Conditions of Confining Pressure on the Compressive Strength and Permeability of Deep Mudstone." Advances in Civil Engineering 2021 (March 8, 2021): 1–10. http://dx.doi.org/10.1155/2021/6611377.
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To investigate the compressive strength and permeability of deep mudstone under stress disturbance, a triaxial rheometer is used to conduct seepage experiments on mudstone specimens with different buried depths under triaxial compression and unloading conditions. The experimental results show that the compressive strength of mudstone specimen with a depth of 1000 m is much lower than that of specimen with a depth of 200 m, and the compressive strength of mudstone increases with the increase in confining pressure. Under constant axial pressure and unloading of the confining pressure, the mudstone with a depth of 200 m exhibits brittle failure, and the strain fluctuates in a pointwise manner with the increase in axial stress. In this case, the mudstone with a depth of 1000 m exhibits a transition from brittle failure to ductile failure, and the strain fluctuates linearly with the axial stress. Further, when the volumetric strain change reaches 0.01, it shows an oblique “Z” fluctuation. During the initial stage of unloading of confining pressure, the permeabilities of both the mudstone specimens (with depths of 200 and 1000 m) decrease gradually. As the confining pressure is unloaded, the permeability of mudstone with a depth of 1000 m increases. Until the specimen is completely destroyed, the permeability of mudstone increases rapidly. Overall, this study can serve as a useful reference for analyzing the engineering disasters associated with deep rock mass, tunnel ventilation, and gas storage.
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Zhou, Ruihe, Hua Cheng, Haibing Cai, Xiaojian Wang, Longhui Guo, and Xianwen Huang. "Dynamic Characteristics and Damage Constitutive Model of Mudstone under Impact Loading." Materials 15, no. 3 (January 31, 2022): 1128. http://dx.doi.org/10.3390/ma15031128.
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The mechanical response characteristics of mudstone from the ingate roadway of the west ventilation shaft in Yuandian No. 2 coal mine, Huaibei City, Anhui Province, China to dynamic loads were quantified in single- and cyclic-impact compression tests, using the split-Hopkinson pressure bar test device. The dynamic stress–strain relationships and the failure characteristics of mudstone samples under different impact loads were analyzed systematically. Considering the “rate effect” of the mudstone dynamic strength, the dynamic strength criterion of mudstone was proposed, and the dynamic damage constitutive model of mudstone was established, based on the statistical damage theory. In response to single-impact loads, with increasing impact pressure, the mudstone peak stress and strain gradually increased, and the peak stress and average strain rate increased nonlinearly. In response to cyclic-impact loads, with an increasing number of impacts, the mudstone peak stress first increased and then decreased, and the peak strain increased gradually. With increasing impact pressure, the number of impacts to the samples’ failure decreased gradually. By parameter identification and comparative analysis of the test results, the proposed dynamic damage constitutive model of mudstone was validated. The model can be used for stability analysis of roadway-surrounding rock under dynamic loads.
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Liu, Xinxi, Yu Li, Shengnan Li, and Yanming Zhou. "Research on the Disintegration Characteristics of Carbonaceous Mudstone and Properties of Modified Materials." Advances in Civil Engineering 2019 (December 9, 2019): 1–10. http://dx.doi.org/10.1155/2019/4382054.
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This work presents the results of an experimental investigation aimed to study the disintegration of carbonaceous mudstone and properties of modified materials. The mineralogical composition of carbonaceous mudstone was determined with X-ray diffraction. The microscopic characteristics of carbonaceous mudstone disintegration were determined with scanning electron microscopy. The surface modification effect of carbonaceous mudstone was researched by comparative tests on coatings’ hydrophobic property, fastness, and waterproof before and after modification, and the modification mechanism of polymer-cement composite modified carbonaceous mudstone was analyzed. The results show that the mineral composition of carbonaceous mudstone mainly contains illite, quartz, and kaolinite. It is found that the disintegration of carbonaceous mudstone can be divided into external factors and internal factors. External factors are water and temperature difference, and internal factors are the swelling of the kaolinite and illite mineral particles. There are differences in the modification effects under different cement dosage. When the cement dosage is 30%, the modification effect is the best. The results may provide a reference for the prevention and control of soft rock slopes.
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He, Zhongming, Panpan Wang, and Weidi Gong. "Dynamic response of pre-disintegrated carbonaceous mudstone embankment under multi-lane vehicle load." PLOS ONE 17, no. 7 (July 7, 2022): e0270937. http://dx.doi.org/10.1371/journal.pone.0270937.
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The purpose of this study is to reveal the response of multi Lane pre disintegrated carbonaceous mudstone embankment under vehicle dynamic load. In this paper, the pre-disintegrated carbonaceous mudstone samples whose fractal dimension meets the requirements are obtained through the indoor disintegration test of carbonaceous mudstone. Geotechnical basic tests such as particle analysis experiments, compaction tests, and direct shear tests were carried out on the pre-disintegrated carbonaceous mudstone samples, and the physical and mechanical parameters of the pre-disintegrated carbonaceous mudstone were obtained. On this basis, a two-way 4-lane pre-disintegration carbonaceous mudstone embankment model of the expressway was established by ABAQUS numerical software. Three different working conditions are set up to study the dynamic response of multi-lane pre-disintegrated carbonaceous mudstone embankment under vehicle load. The results show that the stress change trend on the surface of the pre-disintegrated carbonaceous mudstone embankment without vehicles is the same as that on the side with vehicles. Under this condition, the vertical displacement of the pre-disintegrated carbonaceous mudstone embankment surface can be as high as 4.33mm, and the vertical displacement change of the embankment in the 0–0.6s phase is basically the same as the stress amplitude distribution. When a traffic jam occurs on one side, the maximum increase in vertical stress on the surface of the embankment on the normal driving side is about 170 kPa compared to condition one, and the vertical displacement at each depth of the embankment has been significantly increased. When a traffic jam occurs on one side, it can significantly increase the vertical stress on the surface of the pre-disintegrated carbonaceous mudstone embankment in this lane. The middle part of the stress time curve of monitoring points 3 and 4 in working condition three is more stable and significant than in working condition one, and the maximum vertical displacement is increased by about 1.70mm. The research results can reference the stability analysis of carbonaceous mudstone embankments and engineering practice.
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Yu, Haijun, Honglin Liu, Yinjian Hang, Jinhu Liu, and Shuqi Ma. "Deformation and Failure Mechanism of Weakly Cemented Mudstone under Tri-Axial Compression: From Laboratory Tests to Numerical Simulation." Minerals 12, no. 2 (January 26, 2022): 153. http://dx.doi.org/10.3390/min12020153.
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The success of the water-preserved mining technology is closely related to the stability of the aquiclude and the aquifer, in particular, which is made of weakly cemented rock mas. This paper starts with the tri-axial compression tests on the mudstone specimens obtained from the Ili mining area, followed by the systematic numerical simulation via the Particle Flow Code (PFC) program, aiming at obtaining an in-depth understanding of the response of weakly cemented mudstone under tri-axial compression loading state. The main outcomes obtained from this research indicated that: (1) the behavior of weakly cemented mudstone is closely sensitive to the confining pressure. As the confining pressure increases, both the peak strength and plastic deformation capacity of weakly cemented mudstone will be enhanced; (2) the main feature of weakly cemented mudstone after tests is its centrosymmetric “Z” shape, mainly attributed to the progressive separation of the particle element of mudstone; (3) the behavior of weakly cemented mudstone either in terms of the axial stress-axial strain or the failure mode is sensitive to the confining pressure. If the applied confining pressure is lower than 5 MPa, the micro-cracks are in the form of the single shear band, whereas the tested specimens will tend from brittle shear to plastic shear associated with the “X” shear when the confining pressure is higher than 5 MPa; and (4) The failure of weakly cemented mudstone is mainly attributed to the continuous expansion and penetration of internal microcracks under compression. The brittle failure mode of weakly cemented mudstone tends to ductile failure with the increase of confining pressure. The main contribution of this research is believed to be beneficial in deepening the understanding of the mechanics of weakly cemented mudstone under tri-axial compression and providing the meaningful reference to the practical application of water-preserved mining in the Ili mining area.
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Jia, Jinglong, Fenghai Yu, Yunliang Tan, and Xuepeng Gao. "Experimental Investigations on Rheological Properties of Mudstone in Kilometer-Deep Mine." Advances in Civil Engineering 2021 (January 23, 2021): 1–12. http://dx.doi.org/10.1155/2021/6615379.
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The soft rock roadway in deep high-stress environment has the problems of strong rheology and large deformation. Based on the analysis of the stress distribution of the surrounding rock of the roadway in a kilometer-deep mine, rheological tests under different stress paths are carried out for mudstone in a kilometer-deep mine. The rheological deformation curve, damage characteristics, and change rule of the main mechanical parameters of mudstone under different stress conditions are studied. The results show the following: (1) the peak strength of the triaxial compression of mudstone is closely related to confining pressure, and, with increasing confining pressure, the confining pressure effect decreases gradually; (2) the strain increases slowly under uniaxial loading, and, with increasing axial pressure, the velocity of rheological deformation increases nonlinearly, and the amount of mudstone deformation increases with time; (3) under the condition of unloading confining pressure with constant axial pressure, with decreasing confining pressure, the instantaneous axial and radial strains of mudstone specimen increase nonlinearly, the rheological strain and velocity of mudstone increase gradually, and the lateral rheological strain is close to the axial rheological strain; and, (4) in the unloading confining pressure with axial compression triaxial test, with increasing deviating stress, the axial and radial instantaneous strain increments of mudstone decrease gradually, the lateral strain and rheological velocity of mudstone increase gradually, and the lateral strain is approximately 2.05 times the axial strain. These conclusions reveal the rheological characteristics of the mudstone under different surrounding rock conditions and provide a theoretical basis for the excavation deformation and support control of roadways.
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Ma, Fu Rong, and Shou Mei Yang. "Research on the Bearing Mechanism of Mudstone with Soft-Hard Alternant Strata." Applied Mechanics and Materials 368-370 (August 2013): 1718–21. http://dx.doi.org/10.4028/www.scientific.net/amm.368-370.1718.
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In order to analyse the bearing mechanism of mudstone with soft-hard alternant strata, the mudstone layer is choosed, and the interbedded mudstone models were built. The standard penetration test and shallow plate loading test have been studied. The results of test show that the relationship between standard penetration number and depth of burial is exponential relationship. The characteristic value of bearing capacity of interbedded mudstone is linearly related to the logarithm of standard penetration number. The bearing characteristic of interbedded mudstone is vulnerable to the unloading, disturbance and water content. Model formula of the relationship between the characteristic value of bearing capacity and the logarithm of blow count was verified with high reliability.
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Rahim, Yasin, Qiugen Li, Umar Farooq Jadoon, Wasiq Lutfi, Junaid Khan, and Shamim Akhtar. "MICROFACIES ANALYSIS OF LATE JURASSIC SAMANA SUK FORMATION, HAZARA BASIN LESSER HIMALAYA NORTH PAKISTAN." Earth Science Malaysia 4, no. 2 (June 9, 2020): 102–7. http://dx.doi.org/10.26480/esmy.02.2020.102.107.
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The detailed petrological investigation of Samana Suk Formation from Hazara Basin, Pakistan was carried out to elaborate its microfacies. The Samana Suk Formation is mostly composed of fine to coarse-grained, limestone with dolomite in parts developed as a secondary diagenetic fabric. Twenty-five samples were studied from Thandiani Section, and five microfacies with seven sub microfacies were identified. The identified microfacies include Peloidal Foraminiferal Mudstone, Ooidal Peloidal Mudstone, Bioclastic Planktonic Mudstone as Submicrofacies, Peloidal Wackstone, Ooidal Wackstone, Intraclastic Wackstone as Sub Microfacies, Peloidal-Packstone Microfacies, Ooidal Mud-Wack Microfacies and Peloidal-Ooidal Wack-Pack Submicrofacies. Diagenetic features, such as Stylolites, Calcite Veins, Fractures, Dolomitization, Cementation, Compaction and Micritization have been observed in the petrographic study of the samples. The environment of deposition as depicted from the microfacies is Outer ramp for Mudstone, Peloidal Foraminiferal Mudstone, Ooidal to Peloidal Mudstone and Bioclastic Mudstone; Middle ramp for Peloidal Wackstone; Inner ramp for Ooidal Wackstone, Intraclastic Wackstone Peloidal Packstone and Peloidal-Ooidal Wack-Packstone; Inner-Middle ramp for Ooidal-Mud-Wackstone. Based on the microfacies analysis the Samana Suk Formation was interpreted to be deposited in a shallow shelf environment.
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Li, Wenshuai, Bangyou Jiang, and Shitan Gu. "Effect of Water on Mechanical Properties of Coal Measures Mudstone Using Nanoindentation." Geofluids 2022 (May 9, 2022): 1–16. http://dx.doi.org/10.1155/2022/9032572.
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Mudstone rich in clay minerals exhibits an obvious water-induced weakening effect, and the mechanical properties of mudstone are significantly affected by the groundwater. To investigate the effect of water on mechanical characteristics of mudstone at microscale, a series of uniaxial compression and nanoindentation tests were conducted on mudstone specimens at different moisture contents. Microscale measurements are upscaled to estimate the corresponding magnitudes at the macroscale using the Mori-Tanaka method. The results showed that the indentation modulus varied significantly, from as low as 0.2 GPa to a quite high value of 125 GPa, indicating a strongly heterogeneous distribution of mudstone. The water illustrated a significant effect on the microscale mechanical properties of water-sensitivity minerals like clay minerals. The water-sensitivity minerals occupied the highest proportion of the mudstone and were believed to play an important role in the mechanical properties of mudstone. For water-bearing specimens, the comparison with elastic modulus data obtained from common method indicated similar values as those predicted by homogenization method. The results of this study indicated that nanoindentation technique is a feasible experimental technique to assess the macroscale mechanical properties of rock materials.
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YAMAGUCHI, Hareyuki, Koutarou YOSHIDA, Ichirou KUROSHIMA, and Makoto FUKUDA. "Slaking properties of mudstone." Doboku Gakkai Ronbunshu, no. 406 (1989): 17–26. http://dx.doi.org/10.2208/jscej.1989.406_17.
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Schieber, Juergen, David Bish, Max Coleman, Mark Reed, Elisabeth M. Hausrath, John Cosgrove, Sanjeev Gupta, Michelle E. Minitti, Kenneth S. Edgett, and Mike Malin. "Encounters with an unearthly mudstone: Understanding the first mudstone found on Mars." Sedimentology 64, no. 2 (November 30, 2016): 311–58. http://dx.doi.org/10.1111/sed.12318.
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Zhong, Guang Jian, Da Meng Liu, and Guang Hong Tu. "Petroleum Exploration Potential of Xisha Trough Basin in SCS." Advanced Materials Research 734-737 (August 2013): 1230–34. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.1230.
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Nowadays oil-gas exploration make a great contribution to the world oil-gas reserve increase. A series of deepwater passive continental margin basins are found in Northern Continental Slope of South China Sea. These basins consisted of thick Mesozoic and Cenozoic sedimentary strata with the characteristics of the major world deepwater oil-gas basins. As one of Cenozoic sedimentary basins in deepwater area of Northern Slope of South China Sea, Xisha Trough Basin developed 1500-8000m thick sedimentary strata, which are north-south zoning characteristics of thicker in the center and thinner both in the north and south sides of basin. In its evolutionary history there are two stages: One is Paleocene-Oligocene Rift with Continental River-Lake Facies sedimentary and the other is Miocene-Quaternary Depression with shallow sea-hemiplegic sedimentary. It has good petroleum geological conditions that source rocks consist of lacustrine mudstones, paralic mudstone, and marine mudstone, Tertiary high porosity and permeability deepwater fan reservoirs are the main reservoir, and structural traps and lithologic traps developed. In a word, it has good oil-gas exploration potential.
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Xu, Qiang, Fengyin Xu, Bo Jiang, Yue Zhao, Xin Zhao, Rong Ding, and Jianxin Wang. "Geology and transitional shale gas resource potentials in the Ningwu Basin, China." Energy Exploration & Exploitation 36, no. 6 (April 27, 2018): 1482–97. http://dx.doi.org/10.1177/0144598718772316.
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We analyzed the tectonic evolution characteristics, sedimentary environment, geochemical characteristics, petrological characteristics, and gas-bearing properties of three mudstone sections of the Lower Paleozoic in Ningwu Basin, NE China, and determined the geologic characteristics and resource potential of the transitional facies shale gas. Geochemical analysis of the organic carbon content, kerogen macerals, and vitrinite reflectance of the shale samples showed that the total organic content was generally over 2.0%, the main organic type was type III, and the vitrinite reflectance values (Ro) were between 1.20 and 1.90%. Thus, the mudstones are good shale gas source rocks. The thickness of the three mudstone sections was approximately 30–70 m, and the average porosity was 3.10%. The pore types were diverse with good reservoir capacity. The shale gas resources of the Carboniferous-Permian transitional facies estimated by the volumetric method were approximately 2798.97 × 108–4643.09 × 108 m3. Through a comparison with shales in SW China, where shale gas has been successfully exploited, we determined the preferred criteria for favorable shale gas areas, as well as favorable areas for shale gas enrichment.
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Zhang, Yamei, Fengjiao Wang, Xiaoyu Bai, Nan Yan, Songkui Sang, Liang Kong, Mingyi Zhang, and Yufeng Wei. "Numerical Simulation of Bearing Characteristics of Bored Piles in Mudstone Based on Zoning Assignment of Soil around Piles." Buildings 12, no. 11 (November 4, 2022): 1877. http://dx.doi.org/10.3390/buildings12111877.
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This study conducts a field indoor simulation test, SEM observation, and penetration test to determine the bearing capacity of the dynamic driving pile in the mudstone foundation. It comprehensively analyzes the variation laws of structure and strength of mudstone around piles after piling. Indeed, the strength of mudstone structure is significantly reduced from outside to inside. Therefore, the numerical simulation of piles in mudstone should consider the actual characteristics of soil damage around piles. The strength of mudstone after pile driving damage is measured, and the scatter diagram depicting the relationship between mudstone strength and pile side distance is produced. Then, the best-fitting curve of the relationship between the strength ratio and the distance ratio of the simulated pile driving test is established by the nonlinear fitting of multiple curves. A numerical simulation method is proposed to consider the damaged area and parameters surrounding the pile. The range of soil damage caused by pile driving in the mudstone foundation is determined to be two times that of the pile diameter. The disturbance area is divided into four parts on average, and the width of each part is 0.5d. The simulation results are compared to the conventional approach of uniform parameter assignment to prove the rationality of the method.
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Gomez-Veroiza, Carolina A., and Ronald J. Steel. "Source to sink sandstone-mudstone proportion and facies distribution across a third-order clastic wedge, Cretaceous Western Interior Seaway." Interpretation 5, no. 4 (November 30, 2017): ST11—ST34. http://dx.doi.org/10.1190/int-2017-0019.1.
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The Iles Clastic Wedge is a 500 m thick, 3 My duration, third-order sequence that built out eastward in the Cretaceous Western Interior Seaway. The wedge also contains high-frequency regressive-to-transgressive sequences that are irregularly stacked in a basinward-stepping pattern (lower limb) and in a landward-stepping pattern (upper limb). The entire wedge and the component cycles were analyzed in terms of vertically monitored sandstone-mudstone proportion, thickness, and facies distribution. The measured profiles through the Iles Clastic Wedge form a 300 km long, source-to-sink transect from southeast Rock Springs uplift, Wyoming to Kremmling, Colorado. The sandstone proportion in the entire wedge (and also in the basinward-stepping half of the wedge) attains a maximum in the proximal reaches (fluvial and tidal-fluvial/estuarine channels) of the study transect and decreases unsteadily toward the medial and distal zone. A slight secondary increase in sand proportion also appears irregularly in the medial shoreline zone. On the other hand, the sandstone proportion in the landward-stepping half of the wedge reaches a maximum in the medial (tidal-fluvial and estuarine channels and delta-front) to distal zone (basinal regressive delta) of the wedge and decreases slightly sourceward. Along individual fourth-order sequences, the sandstones and mudstones indicate a more nuanced partitioning, with three marked sandstone maxima (proximal, medial, and distal zones), separated by zones with abundant mudstone. These sandstone peaks are produced by the presence of fluvial and tidal-fluvial/estuarine channel sandstones in the most proximal zone, delta front/shoreface in the medial reaches, and basinal regressive delta front in the distal zone. The mudstone peaks represent the muddy, coal-bearing coastal plain and the prodelta area. This accentuated sandstone and mudstone partitioning at shorter time scales (few 100 Ky) becomes blurred at the longer time scale (3 My) because of the progressive basinward, then landward, offset of successive high-frequency sequences that form the larger clastic wedge.
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Hu, Bin, Aneng Cui, Kai Cui, Yang Liu, and Jing Li. "A novel nonlinear creep model based on damage characteristics of mudstone strength parameters." PLOS ONE 16, no. 6 (June 24, 2021): e0253711. http://dx.doi.org/10.1371/journal.pone.0253711.
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Mudstone interlayer is a weak layer in rock engineering. When it is subjected to continuous stress higher than its damage threshold, due to the dislocation of particles in mudstone crystals and the expansion of cracks, mudstone strength is gradually damaged and deteriorated and the strain gradually increases, thus accelerating the phenomenon of creep damage. In order to describe the characteristics of the whole process of mudstone aging deformation, based on the damage evolution of strength parameters (cohesion and internal friction coefficient) with stress and time in mudstone creep tests, a novel damage nonlinear viscoelastoplastic body (D-NVPB) is proposed through improving traditional plastic element. D-NVPB describes the nonlinear characteristics of the accelerated creep stage of mudstone. With the element combination method, D-NVPB is connected with the Burgers model in series to form a new nonlinear damage creep model (D-NVEP model). The analysis results of creep characteristics theoretically verified the rationality of the model in describing the instantaneous elasticity, viscoelasticity, and nonlinear viscoplastic characteristics of the complete creep curve of mudstone. With the data obtained in the uniaxial compression creep test of mudstone under the action of a stress level of 14 MPa, based on the Levenberg-Marquardt nonlinear least squares method, the fitting calculation was performed through piecewise fitting and overall fitting. The correlation coefficient was 0.9909, which verified the applicability of the model. The obtained model parameters by the identification were used to predict the mudstone creep curve under the stress levels of 13 MPa and 15 MPa. The good prediction results further verified the feasibility of the model. Compared with the traditional creep model, the D-NVEP model can better describe the nonlinear characteristics of the accelerated creep stage and quantitatively display the strength damage evolution process of rock in the creep failure process.
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Landing, ED, and Richard A. Fortey. "Tremadocian (Lower Ordovician) sea-level changes and biotas on the Avalon microcontinent." Journal of Paleontology 85, no. 4 (July 2011): 678–94. http://dx.doi.org/10.1666/10-076.1.
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The Chesley Drive Group, an Upper Cambrian-Lower Ordovician mudstone-dominated unit, is part of the Ediacaran–Ordovician cover sequence on the North American part of the Avalon microcontinent. The upper Chesley Drive Group on McLeod Brook, Cape Breton Island (previously “McLeod Brook Formation”), has two lithofacies-specific Tremadocian biotas. An older low-diversity benthic assemblage (shallow burrowers, Bathysiphon, phosphatic brachiopods, asaphid trilobites) is in lower upper Tremadocian green-gray mudstone. This wave-influenced, slightly dysoxic facies has Bathysiphon–brachiopod shell lags in ripple troughs. The upper fauna (ca. 483 +/- 1 Ma) is in dysoxic-anoxic (d-a), unburrowed, dark gray-black, upper upper (but not uppermost) Tremadocian mudstone with a “mass kill” of the olenid Peltocare rotundifrons (Matthew)—a provincial trilobite in Avalonian North America that likely tolerated low oxygen bottom waters. Scandodus avalonensis Landing n. sp. and Lagenochitina aff. conifundus (Poumot), probable nektic elements and the first upper Tremadocian conodont and chitinozoan reported from Avalon, occur in diagenetic calcareous nodules in the dark gray-black mudstone. An upper Tremadocian transition from lower greenish to upper black mudstone is not exposed on McLeod Brook, but is comparable to a coeval green-black mudstone transition in Avalonian England. The successions suggest that late late Tremadocian (probable Baltic Hunnebergian Age) sea level was higher in Avalon than is suggested from successions on other paleocontinents. The Tremadocian sea-level history of Avalon was a shoaling-deepening-shoaling sequence from d-a black mudstone (lower Tremadocian), to dysoxic green mudstone (lower upper Tremadocian), and back to black mudstone (upper upper Tremadocian).Scandodus Lindström is emended, with the early species S. avalonensis Landing n. sp. assigned to the emended Family Protopanderodontidae. Triangulodus Van Wamel is considered a junior synonym of Scandodus. Peltocare rotundifrons is emended on the basis of complete specimens.