Academic literature on the topic 'Quartz grain diagenesis'
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Journal articles on the topic "Quartz grain diagenesis"
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Shoukat, Noureen, Numair Ahmed Siddiqui, M. Suhaili B. Ismail, and Syed Haroon Ali. "Depositional environment and diagenesis of early Miocene Nyalau Formation, Sarawak, Malaysia." IOP Conference Series: Earth and Environmental Science 1003, no. 1 (April 1, 2022): 012044. http://dx.doi.org/10.1088/1755-1315/1003/1/012044.
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Abstract Diagenetic understandings tied to depositional sequences that developed over the past decades help to predict the reservoir quality in oil and gas exploration. Understanding the lithologic characteristics and diagenetic alterations is key to decipher the various complex controls on its porosity and permeability. This diagenetic heterogeneity is a product of a complex history of diagenetic modifications, however, there are not many studies addressing this problem. The results show that the exposed sections around Bintulu town comprise of massive sandstones intervals, laminated clays, and brackish-shales and lignite. Five main types of lithologies are identified in the stratigraphic sections: sandstones, shales, coal, siltstones, and mudstones. These rock types are further sub-divided into fifteen lithofacies based on sedimentary structures and other characteristics. Petrographic studies revealed that the sandstones are well-sorted quartz arenite, with fine to medium grained sand. The diagenetic processes recognized include compaction, dissolution and cementation. The early, middle, and late diagenetic stages are present in the lithostratigraphy. Bioturbation marks the start of post-depositional changes, and allowed rapid exchange of pore waters with overlying depositional water. Iron oxide occurred in early diagenesis rapidly after the sediments were buried. However, later grain dissolution provided the secondary porosity and permeability. Compaction rates were high in muddy sediments. Sandstone samples with high mud content have less diagenetic signatures. Later, quartz and calcite cement stabilizes the grains and decreases porosity generated by early dissolution. Middle stages of diagenesis involved the growth of chlorite perpendicular to quartz grains. The late diagenetic changes involved the growth of pyrite crystals associated with chemical composition of deep burial pore fluids. The cement types that have been observed in this formation include clay, calcite, quartz overgrowth and iron oxides whereas, the later phases destroyed the early generated porosity. The calcite cement in the early stage of diagenesis, though, resisted the compaction of sediments and aids to preserve the porosity. Dominant porosity is interparticle porosity that is present depositionally and later enhanced by secondary grain dissolution.
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Milliken, Kitty L., Ying Shen, Lucy T. Ko, and Quansheng Liang. "Grain composition and diagenesis of organic-rich lacustrine tarls, Triassic Yanchang Formation, Ordos Basin, China." Interpretation 5, no. 2 (May 31, 2017): SF189—SF210. http://dx.doi.org/10.1190/int-2016-0092.1.
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The role of the primary detrital grain assemblage as a control on diagenetic pathways is reasonably well-understood in sandstones and limestones, but less so in mudrocks. We have documented diagenesis in mudstones from the Triassic Yanchang Formation that are dominated ([Formula: see text] by volume) by grains derived from outside the basin of deposition (terrigenous-argillaceous mudstones or tarls). Major extrabasinal grains are K-rich clay, quartz, plagioclase, K-feldspar, lithic fragments, and micas. In terms of the quartz-feldspar-lithic grain compositions, the silt fraction in these samples is classified as arkose. Grains of intrabasinal derivation include particulate organic matter, phosphatic debris, and rare carbonate allochems. The principal chemical diagenetic components in these mudrocks have strongly localized spatial distributions at micrometer to centimeter scales. Chemical diagenetic components include cone-in-cone structures, replacements of detrital feldspar, pore-filling precipitates within anomalously large pores, pore-filling solid hydrocarbon, and very minor quartz overgrowths associated with local packing flaws around silt-size detrital quartz grains. Matrix-dispersed intergranular cementation, as observed in well-known organic-rich marine mudstones, such as the Barnett Shale and the Eagle Ford Formation, is not observed in Yanchang Formation lacustrine mudstones. The authigenic features present are consistent with the thermal maturity of the units ([Formula: see text]) and are broadly similar to features observed in other mudstones that contain grain assemblages dominated by particles of extrabasinal derivation. The low porosity and the absence of significant amounts of intergranular cement indicate that compactional porosity loss and in-filling by migrated solid hydrocarbon were the major causes of porosity decline during diagenesis of Yanchang Formation mudrocks. Although the mudstones of the Yanchang Formation have a relatively high content of organic carbon and serve as source rocks in the Ordos Basin, the depositional grain assemblage is not conducive to creation of porosity, permeability, and mechanical properties that would make these mudrocks effective unconventional reservoirs.
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Spark, I. S. C., and N. H. Trewin. "Facies-related diagenesis in the Main Claymore Oilfield sandstones." Clay Minerals 21, no. 4 (October 1986): 479–96. http://dx.doi.org/10.1180/claymin.1986.021.4.05.
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AbstractFour major sedimentary sequences of the Triassic and Upper Jurassic of the Main Claymore Oilfield of the North Sea each contain a characteristic suite of diagenetic minerals and fabrics. (1) Triassic Skagerrak Formation fluvial sandstones contain early authigenic pore-lining smectite, together with kaolinite and chlorite which form grain replacements and pore fills. Quartz and feldspar overgrowths are minor. Ferroan dolomite forms a late diagenetic patchy poikilotopic cement. Smectite is converted to illite-smectite in a 5 m thick zone beneath the sub-Jurassic unconformity. Smectite formed early in diagenesis prior to oil migration and destroyed permeability. Thus oil is not found in these sandstones although they occur in the oilzone. (2) The Piper Formation (late Oxfordian/early Kimmeridgian) paralic deposits mainly contain authigenic, pore-lining illite-smectite, vermicular kaolinite grain replacements and pore fills. Quartz overgrowths are generally well developed. (3) The Kimmeridge Clay Formation (early Kimmeridgian/early Volgian) comprises thin marine sandstone turbidites, contained within a thick siltstone/shale sequence. In the sandstones (the ‘Ten Foot Sandstone’) discrete double-ended quartz crystals (1–20 µm) developed prior to quartz, K- and Na-feldspar overgrowths. Only minor kaolinite and lllite-smectite are present. Late diagenetic dolomitic occurs as a patchy poikilotopic cement and as clusters of pore-filling rhombs. (4) The Claymore Sandstone Member (early to middle Volgian) thick marine sandstone turbidites are interbedded with thin siltstones/shales. Sandstones have well-developed quartz, K and Na-feldspar overgrowths, and kaolinite and illite-smectite occur as grain replacements and rarely as pore fills. Late-diagenetic dolomite and ferroan dolomite form poikilotopic cement and clusters of pore-filling rhombs. The major factors which control diagenetic features are depositional environment and associated porewater together with original mineralogy. Burial history and textural features of the sandstones also have important influences. Reservoir quality is controlled by a complex interplay of these features.
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Qi, Yukai, Huixi Lin, Fushun Zhang, Xiuxiang Zhu, Hanwen Hu, Bo Zhou, and Qing Wei. "The Relationship between Diagenetic Evolution and Hydrocarbon Charge in Deep Tight Reservoirs: A Case Study from Kepingtage Formation of S9 Well Block in Tarim Basin." Geofluids 2021 (April 8, 2021): 1–18. http://dx.doi.org/10.1155/2021/6665237.
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The Silurian Kepingtage Formation of Tarim Basin is an important deep clastic reservoir. Exploration practice shows that the reservoirs are generally characterized by extremely low porosity and permeability, exhibiting strong mineral composition and physical property heterogeneities. The study of heterogeneity and its effect on oil charge is of great significance to the understanding of oil migration and accumulation in such reservoirs and thus is crucial to oil exploration. Therefore, based on identification and quantitative statistics of thin sections, SEM, and homogenization temperature measurements, this study was designed to examine the relationship between diagenetic evolution and oil emplacement in the Silurian Kepingtage Formation in S9 Block in Tarim Basin. The control of differential diagenesis and physical property evolution on oil charge process are discussed. It is found that the sandstones with fine grain size and high content of ductile grains (>20%) have experienced strong mechanical compaction, the porosity decreases rapidly in the early stage of burial. The densification process has been completed before the first period of oil charge so that no oil was found in the reservoir. In contrast, sandstones with relatively coarse grain size and low ductile grain content have better porosity and permeability properties, which are generally oil-bearing. This kind of sandstone generally experienced two periods of oil charge. Apart from moderate compaction, multiple diagenesis events were also observed, including quartz cementation, calcite cementation, and dissolution. Before the early period of oil charge, the diagenesis events are dominated by moderate compaction, chlorite cementation, and dissolution, and the reservoir property is still high. It seems that the time of late period oil charge is relatively long. With the growth of multiple types of authigenic minerals such as quartz, calcite, and illite after or sometimes synchronously occurred with the late period oil charge, the porosity gradually decreases.
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Chima, Priscilla, Christopher Baiyegunhi, Kuiwu Liu, and Oswald Gwavava. "Diagenesis and rock properties of sandstones from the Stormberg Group, Karoo Supergroup in the Eastern Cape Province of South Africa." Open Geosciences 10, no. 1 (December 13, 2018): 740–71. http://dx.doi.org/10.1515/geo-2018-0059.
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Abstract Diagenesis is one of the factors that affect reservoir quality in sandstones. Knowledge of diagenetic transformation and how it impacts the development of porosity in reservoirs rocks is thus key to successful mineral exploration. To date, little is known about the diagenesis of the uranium-hosted sandstones of the Stormberg Group, Karoo Basin, South Africa. Petrographic study, scanning electron microscopy (SEM) aided with energy dispersive X-ray (EDX), and X-ray diffraction (XRD) analyses were employed for the diagenetic study of the sandstones. This study aims to provide an account of the diagenesis of these rock units and how it impacts their reservoir quality. The diagenetic processes that have affected the sandstones are cementation, compaction, recrystallization, replacement, mineral overgrowth and dissolution. These processes have passed through early, late and uplift-related diagenesis. Formation of authigenic minerals and precipitation of the mineral cements occurred during different diagenetic phase but mostly during the early diagenetic stage. This stage was followed by lithification, which resulted in increased in grain packing, loss of pore spaces and thinning of bedding. Quartz and feldspar overgrowths, chloritization, muscovitization, concave-convex contacts, recrystallization, albitization and suture contacts are present in the late diagenetic stage. The uplift-related diagenetic stage was affected by calcitization, grain deformation and fracturing, dissolution and saussuritization. All these diagenetic processes largely affected the porosity and permeability of the sandstones. Primary and secondary porosities were both observed in the sandstones. In general, there is no single diagenetic process that is controlling the pattern of porosity evolution in the sandstones. On the other hand, the presence of fractured and dissolution pores tend to increase the porosity, thus enhancing the reservoir quality. This study shows that diagenesis has significantly altered the original petrologic characteristics of the sandstones which have induced considerable deterioration and heterogeneity in the reservoir quality of the Stormberg Group sandstones in the Main Karoo Basin of South Africa.
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Anis, Dr, Abdullah Khan, Narendra Kumar, and Mujeebul Hasan. "Diagenesis and Porosity Evolution of the Pachmarhi Sandstones (Early Triassic), Satpura Gondwana Basin, Central India." Journal of The Indian Association of Sedimentologists 37, no. 2 (December 31, 2020): 37–48. http://dx.doi.org/10.51710/jias.v37i2.104.
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This study deals with the diagenetic history of the Pachmarhi Sandstones of Satpura Gondwana Basin, Central India. The sandstones are classified as quartz-arenite and sub-arkose type. Monocrystalline quartz grains dominate the detrital mineralogy followed by polycrystalline quartz grains, feldspars (more alkali-feldspar than plagioclase), rock fragments, detrital mica and heavy minerals. The diagenetic signatures observed in the Pachmarhi Sandstones include mechanical compaction, cementation (Fe-oxide, quartz overgrowths, calcite, matrix and clay minerals), replacement and dissolution of feldspar and calcite cement. The most commonly observed type of secondary porosity is dissolution of feldspars. The porosity loss is mainly due to cementation by pore occlusion and by early stage of mechanical compaction. In addition, several clay minerals occurred as pore-filling and pore-lining cements. The nature of various types of grain- to grain contacts suggests early cementation and consequent minor compaction. Among the various cements, calcite is the earliest followed by iron oxide while silica cementation occurred probably at a late stage. The carbonate cement formed during burial by dissolution and re-precipitation represents redistributed calcite which was buried with the sandstone. The iron cement was perhaps derived from weathering and leaching of ferromagnesian minerals of overlying Deccan traps. Silica cement was derived from the corrosion of quartz and feldspar grains. Types of grain contacts, minus-cement porosity and porosity reduction indicate a shallow depth of burial conditions for these sandstones.
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Bello, Abdulwahab Muhammad, Stuart J. Jones, Jon Gluyas, and Khalid Al-Ramadan. "Impact of Grain-Coating Clays on Porosity Preservation in Paleocene Turbidite Channel Sandstones: Nelson Oil Field, UK Central North Sea." Minerals 12, no. 5 (April 29, 2022): 555. http://dx.doi.org/10.3390/min12050555.
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The Forties Sandstone Member is an important deep-water reservoir in the Central North Sea. The role of depositional characteristics, grain-coating clays, and diagenesis in controlling the reservoir quality of the sandstones is poorly understood. The main aim of the study is to understand the role of depositional characteristics, grain-coating and pore-filling clays, and diagenesis in controlling the reservoir quality evolution of turbidite-channel sandstones. The study employed a multi-disciplinary technique involving thin section petrography and scanning electron microscopy (SEM) to investigate the impact of grain size, clay matrix content, mode of occurrence of grain-coating chlorite and illite, and their impact in arresting quartz cementation and overall reservoir quality in the sandstones. Results of our study reveal that porosity evolution in the sandstones has been influenced by both primary depositional characteristics and diagenesis. Sandstones with coarser grain size and lower pore-filling clay content have the best reservoir porosity (up to 28%) compared to those with finer grain size and higher pore-filling clay content. Quartz cement volume decreases with increasing clay-coating coverage. Clay coating coverage of >40% is effective in arresting quartz cementation. Total clay volume of as low as 10% could have a deleterious impact on reservoir quality. The Forties Sandstone Member could potentially be a suitable candidate for physical and mineralogical storage of CO2. However, because of its high proportion (>20%) of chemically unstable minerals (feldspar, carbonates, and clays), their dissolution due to CO2 injection and storage could potentially increase reservoir permeability by an order of magnitude, thereby affecting the geomechanical and tensile strength of the sandstones. Therefore, an experimental study investigating the amount of CO2 to be injected (and at what pressure) is required to maintain and preserve borehole integrity. The findings of our study can be applied in other reservoirs with similar depositional environments to improve their reservoir quality prediction.
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Ramadhani, Hanindya. "DIAGENESYS STAGE ANALYSIS OF SANDSTONE INTERVAL ON WELL DAR-24, GABUS FORMATION, ANOA FIELD, WEST NATUNA BASIN." KURVATEK 2, no. 2 (March 15, 2018): 67–76. http://dx.doi.org/10.33579/krvtk.v2i2.529.
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Stage of diagenesis of a rock will effect the quality of the rock as a reservoir. Hence, it is a necessary to analyze the diagenesis stage of sandstone at Anoa Field, West Natuna Basin, since the diagenesis stage has not been identified properly. The analysis is carried out using thin section method in five different depths. The product of diagenesis is observed for its cementation level, compaction, recrystallization, dissolution, replacement, and type of porosity wich developed in the rock. The appearance of quartz overgrowth cement and pore filling and pore lining calcite cement show a diagenesis stage which are recrystallization and cementation. The appearance of bent mica mineral and suture grain contact can be a sign of late stage compaction. Dissolution of matrix, cement and grain in the sample show that the rock has come to mesodiagenesis stage. As a result of the observation, the conclusion can be made that the rock has passed the eodiagenesis and mesodigenesis phase. Porosity of the section is both primary porosity (interparticle) and secondary porosity (dissolved) with a range 15%-20% (medium to good). Crossplot depth vs porosity show a linear distribution, which when the depth is increase the porosity will decrease. So it can be concluded that the process of diagenesis is very influential on the quality of reservoir rocks in the study area.Keyword: Gabus Formation, sandstone diagenesis, stage of diagenesis.
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Yu, Zhenghong, Si Chen, Weidong Xie, Shu’e Zhao, Jianghao Ma, and Tianhao Gong. "Implication Linkage among Microfacies, Diagenesis, and Reservoir Properties of Sandstones: A Case Study of Dongying Formation, Nanpu Sag, Bohai Bay Basin." Energies 15, no. 20 (October 20, 2022): 7751. http://dx.doi.org/10.3390/en15207751.
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The reservoir quality of sandstones is significantly impacted and transformed by sedimentation and diagenesis. It is necessary to clarify the internal relationship among them to precisely predict the sweet reservoir. In this study, five types of sedimentary microfacies are recognized through core observation and logging data: submerged distributary channel (fan delta), submerged interdistributary bay, submerged distributary channel (braided delta), distal bar, and turbidite fan. The major diagenetic processes, including compaction, cementation, and dissolution, have been analyzed based on petrography, scanning electron microscopy, and X-Ray diffraction. The dominant diagenetic cement includes calcite, smectite, kaolinite, illite, and I/S mixed-layer minerals, with small quantities of chlorite, pyrite, siderite, feldspar, and quartz cement. The reservoir quality is best in the submerged distributary channel (fan delta) sandstones, followed by submerged distributary channel (braided delta). Submerged interdistributary bay, distal bar, and turbidite fan are of poor reservoir quality. The grain size is the primary reservoir quality controlling factor, highly affected by sedimentary microfacies. Subsequent controls are diagenetic processes such as mechanical compaction, clay minerals formation, grain replacement, and dissolution that collectively influence the porosity and permeability.
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Odedede, O. "Petrographic Characterization of Selected Sidewall Core Samples from NG-1 Well, Niger Delta, Nigeria: Palaeoclimatic Implication." Journal of Scientific Research 11, no. 2 (May 1, 2019): 157–64. http://dx.doi.org/10.3329/jsr.v11i2.37110.
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Petrographic investigation of sandstones from Agbada Formation in NG-1 well was undertaken in order to petrographically characterize the sandstones. Petrographic examination of the sandstone shows that the sandstones are mineralogically mature and poorly to moderately sorted quartz arenite. Compositionally, made up of monocrystalline quartz (90-96%), polycrystalline quartz (7-2%), feldspar (2-5%), rock fragments < 3%, silica, hematite cement and clay matrix. Abundant of monocrystalline quartz with marginal undulose extinction over polycrystalline quartz suggest igneous source derivatives. Presence of close packing, point and concavo – convex contacts, weathered plagioclase feldspar, grain dissolution, and fabric imprints indicates intermediate diagenesis. Consideration of petrographic attributes and paleoclimatic discrimination plot inferred semi-humid to humid palaeoclimates.
Dissertations / Theses on the topic "Quartz grain diagenesis"
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Williams, Randolph T. "A Combined Experimental and Numerical Approach to Understanding Quartz Cementation in Sandstones." Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1339354653.
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Fraser, S. A. "Nanoscale imaging of the Woodford Shale, Oklahoma, USA: Organic matter preservation as clay-organic nanocomposites." Thesis, 2012. http://hdl.handle.net/2440/92218.
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This item is only available electronically.Regional and within well variability in hydrocarbon production from organic carbon rich shales has demonstrated that these unconventional reservoirs are complex and require an in-depth understanding of geological factors to make successful predictions. Variability is apparent in porosity and permeability, mechanical properties governing fracture susceptibility for enhanced hydrocarbon release, and concentrations of organic carbon (OC). The economically successful, though variable Woodford Shale, Oklahoma, USA, shows a R2 = 0.72 correlation between mineral surface area (MSA) and total organic carbon (TOC) consistent with a mineral surface preservative effect on OC extending across a range of samples from multiple cores and with TOC values of <0.5% to 18%. The TOC and MSA data illustrates the systematic stratigraphic covariant relationship between TOC and MSA showing steps of up to 15% TOC that are matched by similar shifts in MSA. Transmission electron microscope (TEM) imaging performed on ~80 nanometre thick ultramicrotomed thin sections independently confirms quantitative geochemical clay-OC associations at the nanoscopic scale of interaction. Energy Dispersive Spectrometry (EDS) spot analyses reveal that organic carbon is entirely constrained to nanoscale clay laminae within the sample. Grey zones encapsulated by clay aggregates appear homogeneous at low magnifications and are similar to discrete organic matter particles commonly interpreted in recent studies. However, high resolution inspection resolves these zones in to laminated clay particles occurring at tens of nanometres. TEM micrographs of later stage submicron-scale quartz grain growth may also explain how the opposing mechanisms of hydrocarbon leaching and entrapment can co-exist for over 300 million years and provide an insight into shale brittleness, known to increase fracture susceptibility. Determining key modes of how OC is preserved during deposition and early diagenesis in proven gas-shales, such as the Woodford Shale encompasses a more holistic approach to enhancing the prediction of prospective hydrocarbon resources in frontier basins.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012
Book chapters on the topic "Quartz grain diagenesis"
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Wang, Zizheng, Xin-Sheng Jiang, Bang-Guo Zhou, and Sheng-Lin Lu. "Sedimentary Characteristics of the Member 1 of the Middle Devonian Suotoushan Formation and Its Ore-Bearing Potential in Northeastern Yunnan." In Mineralogy. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103826.
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Super-large quartz sandstone deposit has been discovered in Northeastern Yunnan and the major ore-bearing bed is occurred in the Member 1 of the Middle Devonian Suotoushan Formation. Systematic study on the sedimentary characteristics of the Suotoushan Formation in Yiliang region, northeastern Yunnan Province has been conducted, Profile surveying, drilling and trenching show that, microscopic identification, the thickness of the Suotoushan Formation is 62.8 m ∼ 222.7 m and principally composed of gray-white thick-bedded medium-grained quartz sandstone with well developed parallel bedding, swash bedding, oscillation cross-bedding and wave ripple, showing remarkable wave action features. Thin section observation shows that quartz sandstone in the Member 1 of the Suotoushan Formation is grain supported, siliceous cemented, concave-convex and line contact and the pressure solution and secondary overgrowth of quartz sand grains are obvious. Grain size analysis shows that the grain size is concentrated between 1.5Φ and 3.5Φ with saltation population up to 99% which is composed by tow sub populations and lacking of traction and suspension populations, showing a typical foreshore grain size distribution. Chemical analysis shows SiO2 chemical purity of the quartz sandstone is 99.05 ∼ 99.39 with weighted average 98.99 (N = 11) which has exceeded the industry standard for first-grade raw material of plate glass. Based our studies above, it can be concluded that the quartz sandstone in Member 1 of Suotoushan Formation is high energy coastal foreshore sediments with high texture and mineral maturity, and has been further purified by diagenesis, and both the grain-size characteristic and chemical purity have reached the standard of high-purity quartz sandstone, which can be expected raw material for high-purity quartz. The results in this article can provide accurate prospecting target to enlarge the resources potential of high-purity quartz deposits in northeastern Yunnan.
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Bethke, Craig M. "Sediment Diagenesis." In Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0023.
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Diagenesis is the set of processes by which sediments evolve after they are deposited and begin to be buried. Diagenesis includes physical effects such as compaction and the deformation of grains in the sediment (or sedimentary rock), as well as chemical reactions such as the dissolution of grains and the precipitation of minerals to form cements in the sediment's pore space. The chemical aspects of diagenesis are of special interest here. Formerly, geologists considered chemical diagenesis to be a process by which the minerals and pore fluid in a sediment reacted with each other in response to changes in temperature, pressure, and stress. As early as the 1960s and especially since the 1970s, however, geologists have recognized that many diagenetic reactions occur in systems open to groundwater flow and mass transfer. The reactions proceed in response to a supply of reactants introduced into the sediments by flowing groundwater, which also serves to remove reaction products. Hay (1963, 1966), in studies of the origin of diagenetic zeolite, was perhaps the first to emphasize the effects of mass transport on sediment diagenesis. He showed that sediments open to groundwater flow followed reaction pathways different from those observed in sediments through which flow was restricted. Sibley and Blatt (1976) used cathodoluminescence microscopy to observe the Tuscarora orthoquartzite of the Appalachian basin. The almost nonporous Tuscarora had previously been taken as a classic example of pressure welding, but the microscopy demonstrated that the rock is not especially well compacted but, instead, tightly cemented. The rock consists of as much as 40% quartz (SiO2) cement that was apparently deposited by advecting groundwater. By the end of the decade, Hayes (1979) and Surdam and Boles (1979) argued forcefully that the extent to which diagenesis has altered sediments in sedimentary basins can be explained only by recognition of the role of groundwater flow in transporting dissolved mass. This view has become largely accepted among geoscientists, although it is clear that the scale of groundwater flow might range from the regional (e.g., Bethke and Marshak, 1990) to circulation cells perhaps as small as tens of meters (e.g., Bjorlykke and Egeberg, 1993; Aplin and Warren, 1994).
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Cox, Morgan A., Aaron J. Cavosie, Michael Poelchau, Thomas Kenkmann, Phil A. Bland, and Katarina Miljković. "Shock deformation microstructures in xenotime from the Spider impact structure, Western Australia." In Large Meteorite Impacts and Planetary Evolution VI. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2550(19).
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ABSTRACT The rare earth element–bearing phosphate xenotime (YPO4) is isostructural with zircon, and therefore it has been predicted that xenotime forms similar shock deformation microstructures. However, systematic characterization of the range of micro structures that form in xenotime has not been conducted previously. Here, we report a study of 25 xenotime grains from 10 shatter cones in silicified sandstone from the Spider impact structure in Western Australia. We used electron backscatter diffrac tion (EBSD) in order to characterize deformation and microstructures within xenotime. The studied grains preserve multiple sets of planar fractures, lamellar {112} deformation twins, high-angle planar deformation bands (PDBs), partially recrystallized domains, and pre-impact polycrystalline grains. Pressure estimates from micro structures in coexisting minerals (quartz and zircon) allow some broad empirical constraints on formation conditions of ~10–20 GPa to be placed on the observed microstructures in xenotime; at present, more precise formation conditions are unavailable due to the absence of experimental constraints. Results from this study indicate that the most promising microstructures in xenotime for recording shock deformation are lamellar {112} twins, polycrystalline grains, and high-angle PDBs. The {112} deformation twins in xenotime are likely to be a diagnostic shock indicator, but they may require a different stress regime than that of {112} twinning in zircon. Likewise, polycrystalline grains are suggestive of impact-induced thermal recrystallization; however, in contrast to zircon, the impact-generated polycrystalline xenotime grains here appear to have formed in the solid state, and, in some cases, they may be difficult to distinguish from diagenetic xenotime with broadly similar textures.
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Doveton, John H. "Porosity Volumetrics and Pore Typing." In Principles of Mathematical Petrophysics. Oxford University Press, 2014. http://dx.doi.org/10.1093/oso/9780199978045.003.0007.
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The primary objective of porosity estimations based on measurements made either from petrophysical logs or core is the volume of pore space within the rock, given simply by the equation: . . . Φ = Vp/Vb . . . The Greek letter, phi, is the standard symbol for porosity and is expressed in this equation as the ratio of the volume of void space (Vp) to the bulk volume of the rock (Vb). The simplest concepts of porosity are generally explained in terms of the packing of spheres as the sum of the pore volume of the space between the spheres. There are five basic arrangements of uniform-sized spheres that can be constructed: simple cubic, orthorhombic, double-nested, face-centered cubic, and rhombohedral packing (Hook, 2003). Each has a geometrically defined pore volume that represents an upper limit for granular rocks whose constituent grains have a variety of sizes and shapes and whose pore volumes have been reduced by compaction and diagenetic cements. This intergranular model is a useful starting point for the characterization of pores in clastic rocks and will be considered first, before reviewing the additional complexities of pore geometry introduced by dissolution in carbonate rocks. The solid framework of a sandstone consists of a nonconductive “matrix” dominated by quartz, but commonly with accessory nonconductive minerals, and conductive clay minerals, whose electrical properties are caused by cation exchange with ions in saline formation water. It is important to distinguish between connected and unconnected pores, as well as larger pores that sustain fluid movement in contrast to smaller pores filled with capillary-bound water. A graphic presentation of these components is widely used in the petrophysical literature as a reference basis to disentangle terminology that can be confusing and contradictory. In particular, the term “effective porosity” has different meanings that vary from one technical discipline to another. In their review of porosity terms, Wu and Berg (2003) concluded that many core analysts considered all porosity to be effective, log analysts excluded clay-bound water, while petroleum engineers excluded both clay-bound and capillary-bound from porosity consideration, thereby restricting effective porosity to pores occupied by mobile fluids.
Conference papers on the topic "Quartz grain diagenesis"
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Kasim, Fadzlin Hasani, Budi Priyatna Kantaatmadja, Wan Nur Wan M Zainudin, Amita Ali, Hasnol Hady Ismail, and Numair Ahmed Siddiqui. "Factors Controlling Porosity Permeability Relationship for Reservoir Quality Prediction: A Case Study of Malay Basin Reservoir, Malaysia." In International Petroleum Technology Conference. IPTC, 2021. http://dx.doi.org/10.2523/iptc-21386-ms.
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Abstract Predicting the spatial distribution of rock properties is the key to a successful reservoir evaluation for hydrocarbon potential. However, a reservoir with a complex environmental setting (e.g. shallow marine) becomes more challenging to be characterized due to variations of clay, grain size, compaction, cementation, and other diagenetic effects. The assumption of increasing permeability value with an increase of porosity may not be always the case in such an environment. This study aims to investigate factors controlling the porosity and permeability relationships at Lower J Reservoir of J20, J25, and J30, Malay Basin. Porosity permeability values from routine core analysis were plotted accordingly in four different sets which are: lithofacies based, stratigraphic members based, quartz volume-based, and grain-sized based, to investigate the trend in relating porosity and permeability distribution. Based on petrographical studies, the effect of grain sorting, mineral type, and diagenetic event on reservoir properties was investigated and characterized. The clay type and its morphology were analyzed using X-ray Diffractometer (XRD) and Spectral electron microscopy. Results from porosity and permeability cross-plot show that lithofacies type play a significant control on reservoir quality. It shows that most of the S1 and S2 located at top of the plot while lower grade lithofacies of S41, S42, and S43 distributed at the middle and lower zone of the plot. However, there are certain points of best and lower quality lithofacies not located in the theoretical area. The detailed analysis of petrographic studies shows that the diagenetic effect of cementation and clay coating destroys porosity while mineral dissolution improved porosity. A porosity permeability plot based on stratigraphic members showed that J20 points located at the top indicating less compaction effect to reservoir properties. J25 and J30 points were observed randomly distributed located at the middle and bottom zone suggesting that compaction has less effect on both J25 and J30 sands. Lithofacies description that was done by visual analysis through cores only may not correlate-able with rock properties. This is possibly due to the diagenetic effect which controls porosity and permeability cannot visually be seen at the core. By incorporating petrographical analysis results, the relationship between porosity, permeability, and lithofacies can be further improved for better reservoir characterization. The study might change the conventional concept that lower quality lithofacies does not have economic hydrocarbon potential and unlock more hydrocarbon-bearing reserves especially in these types of environmental settings.
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Ning, Chaozhong, Xili Deng, Xuan Liao, Youjing Wang, Guangya Zhu, Haiying Han, Jing Yang, et al. "Development Mechanism of Ultra-Low Permeability Limestone Reservoirs: A Case Study of the Cretaceous S-Reservoir in H Oilfield, Iraq." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211591-ms.
Full textAbstract:
Abstract Ultra-low permeability limestone reservoirs in the Middle East have huge untapped reserves. In Iraq, Field H has nearly one quarter of reserves in the S-Reservoir with permeabilities of (0.02-0.4 mD). It is difficult to identify optimal drilling locations, or sweet spots, that maximize recovery factors due to poor understanding of reservoir characteristics. Using the S-limestone reservoir, this study aims to clarify the environment of deposition, diagenetic evolution, reveal the development mechanism of ultra-low permeability, and predict the distribution of more favorable areas. Whole core, thin sections, scanning electron microscope (SEM), mercury injection (MICP), well logs, and seismic data were utilized for the analysis. Through core and thin section observation, lithology, biostratigraphic sequences, pore type, and sedimentary structures were determined. Through these observations the environment of deposition of the S-Formation is interpreted as mid to outer carbonate ramp. The lithology is mainly wackestone to packstone deposited in a low energy environment below fair weather wave base. Primary fossils are planktonic foraminifera tests as grains and coccolith microfossils in the matrix. Thin sections and MICP analysis helped delineate the porosity classes and diagenetic history. The pore throat size, determined by MICP data, was 0.03 - 0.1 μm. Primary porosity is around 10-25% and is driven by intragranular voids in foraminifera tests, followed by intergranular, and intercrystalline microporosity of the matrix. Foraminifera tests are generally intact and float in the mud matrix. As a result, large intragranular pores are well developed but not connected, causing overall medium-high porosity but ultra-low permeability. Early marine calcite cement is the primary diagenetic process which destroyed porosity and permeability. Little to no evidence of secondary dissolution was observed.