International Journal of Coal Geology, Mar 1, 2016
Abstract The diagenesis of clay minerals and organic matter in Posidonia Shale has been typically... more Abstract The diagenesis of clay minerals and organic matter in Posidonia Shale has been typically studied independently of each other. Here, the results of an experimental investigation focused on the mineralogical changes of organic-rich shales are presented to understand the dissolution and precipitation processes of minerals as a function of thermal maturity. Three core samples of Posidonia Shale (Hils Syncline, Germany) with increasing natural thermal maturity (Wickensen (WIC) 0.53% R0, Dohnsen (DOH) 0.73% R0, Haddessen (HAD) 1.45% R0) were reacted in experimental aliquots of 0.3 M KCl solution (rock/fluid ratio 1:5) sealed in gold capsules at 300 °C and 120 bars for 27 days. Following treatment, the calculated maturities (Easy-R0 values) of the two samples with the lowest vitrinite reflectance values indicates thermal enhancement (WIC 1.14% R0, DOH 1.15% R0), whereas the most mature sample remained unchanged (HAD 1.45% R0). The educts and products were analysed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). In all experiments kaolinite and carbonates were extensively dissolved whereas quartz underwent partial dissolution. Reaction products consisted of lath shaped Mg2+ rich 1Md illite together with K-feldspar in the form of sanidine. Trioctahedral saponite precipitated only in the oil producing sample (WIC), along with less sanidine and 1Md illite. The unexpected formation of metastable 1Md illite at 300 °C instead of stable 2M1 illite is attributed to low K+ reactivity due to either depletion of this element by the early formation of sanidine and/or the chemical effects of organic acids that shift the stable phase into the K-poor stability field. The precipitation of saponite and the limited sanidine and 1Md illite formation in sample DOH is attributed to high dolomite content and hence Mg2+ availability, along with the more extensive release of hydrocarbon compounds and further reduction of K+ reactivity in this sample. It is concluded that the neoformation of metastable phases (1Md illite and trioctahedral smectite) observed in short-term, higher-temperature experiments may differ significantly from prolonged mineral transformations occurring under natural conditions.
Diagenetic illite growth in porous sandstones leads to significant modifications of the initial p... more Diagenetic illite growth in porous sandstones leads to significant modifications of the initial pore system which result in tight reservoirs. Understanding and quantifying these changes provides insight into the porosity-permeability history of the reservoir and improves predictions on petrophysical behavior. To characterize the various stages of diagenetic alteration, a focused ion beam – scanning electron microscopy (FIB-SEM) study was undertaken on aeolian sandstones from the Bebertal outcrop of the Parchim Formation (Early Permian Upper Rotliegend group). Based on 3D microscopic reconstructions, three different textural types of illite crystals occur, common to many tight Rotliegend sandstones, namely (1) feldspar grain alterations and associated illite meshworks, (2) tangential grain coats, and (3) pore-filling laths and fibers. Reaction textures, pore structure quantifications, and numerical simulations of fluid transport have revealed that different generations of nano-porosi...
The paper describes the performance of a concrete intended for sealing deep boreholes in the host... more The paper describes the performance of a concrete intended for sealing deep boreholes in the host rock of radioactive repositories. The concrete will form plugs where fracture zones are intersected and be located between very tight seals of smectite clay installed where the surrounding rock is tight. The concrete must be able to carry the clay segments after a couple of days but the bearing capacity does not have to be very high since the clay soon adheres to the rock and carries itself. The concrete contains talc as superplasticizer since ordinary organic additives for reaching high fluidity at casting are unwanted. It has a low cement content for maintaining its low porosity after dissolution in a long time perspective.
Illite was first named in 1937 in Illinois by Ralph Grim, one of the founders of clay mineralogy.... more Illite was first named in 1937 in Illinois by Ralph Grim, one of the founders of clay mineralogy. Illite is the most abundant clay mineral on the earth's surface. However, we know very little about the origin of illite in Illinois. This dissertation focuses on two aspects of illite in the Lower Paleozoic of the Illinois Basin: (1) illite polytype quantification, which explains the anomalies of the distribution of illite and smectite in the Illinois Basin, and (2) the origin and age of diagenetic illite, which is used to link illitization to fluid migration.Illite polytype quantification allows the differentiation of diagenetic and detrital illite. In Paleozoic shales from the Illinois Basin three polytypes 1M$\rm\sb{d},$ 1M, and 2M$\sb1$ are observed. 1M$\rm\sb{d}$ and 1M are of diagenetic origin and 2M$\sb1$ of detrital origin. All three polytypes were quantified by mixing single polytypes and comparing the experimental XRD traces with traces calculated using WILDFIRE$\copyright.$Illite polytype quantification of different size fractions combined with K/Ar dates allows the extrapolation to apparent ages of detrital and diagenetic end-members. The extrapolated age of the diagenetic end-members dates episodes of diagenesis. Results show that the Upper Ordovician Maquoketa Group shales contain diagenetic illite (dominantly 1M$\rm\sb{d}$ with minor 1M) with an age of $\sim$360 Ma, that was not formed solely by burial diagenesis but mainly through either a hydrothermal or K-rich brine event. Ordovician and Cambrian shale partings and sandstones, older than the Maquoketa Group, contain diagenetic illite (1M$\rm\sb{d}$ in shales and 1M in sandstones) having an age of 300 Ma. This late Paleozoic age falls within the span of the Alleghanian orogeny.The conclusion is that the diagenetic illite of the Maquoketa Group and that of the underlying formations formed from different precursors in different hydrologic systems. The diagenetic illite in the Maquoketa Group formed mainly during a hydrothermal or K-rich brine event ($\le$100$\sp\circ$C) from smectite or kaolinite. During the Alleghanian orogeny the Maquoketa Group served as an aquitard to fluids ($\le$140$\sp\circ$C) that precipitated the diagenetic illite in the older and more permeable sandstones and carbonates.U of I OnlyETDs are only available to UIUC Users without author permissio
International Journal of Coal Geology, Mar 1, 2016
Abstract The diagenesis of clay minerals and organic matter in Posidonia Shale has been typically... more Abstract The diagenesis of clay minerals and organic matter in Posidonia Shale has been typically studied independently of each other. Here, the results of an experimental investigation focused on the mineralogical changes of organic-rich shales are presented to understand the dissolution and precipitation processes of minerals as a function of thermal maturity. Three core samples of Posidonia Shale (Hils Syncline, Germany) with increasing natural thermal maturity (Wickensen (WIC) 0.53% R0, Dohnsen (DOH) 0.73% R0, Haddessen (HAD) 1.45% R0) were reacted in experimental aliquots of 0.3 M KCl solution (rock/fluid ratio 1:5) sealed in gold capsules at 300 °C and 120 bars for 27 days. Following treatment, the calculated maturities (Easy-R0 values) of the two samples with the lowest vitrinite reflectance values indicates thermal enhancement (WIC 1.14% R0, DOH 1.15% R0), whereas the most mature sample remained unchanged (HAD 1.45% R0). The educts and products were analysed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). In all experiments kaolinite and carbonates were extensively dissolved whereas quartz underwent partial dissolution. Reaction products consisted of lath shaped Mg2+ rich 1Md illite together with K-feldspar in the form of sanidine. Trioctahedral saponite precipitated only in the oil producing sample (WIC), along with less sanidine and 1Md illite. The unexpected formation of metastable 1Md illite at 300 °C instead of stable 2M1 illite is attributed to low K+ reactivity due to either depletion of this element by the early formation of sanidine and/or the chemical effects of organic acids that shift the stable phase into the K-poor stability field. The precipitation of saponite and the limited sanidine and 1Md illite formation in sample DOH is attributed to high dolomite content and hence Mg2+ availability, along with the more extensive release of hydrocarbon compounds and further reduction of K+ reactivity in this sample. It is concluded that the neoformation of metastable phases (1Md illite and trioctahedral smectite) observed in short-term, higher-temperature experiments may differ significantly from prolonged mineral transformations occurring under natural conditions.
Diagenetic illite growth in porous sandstones leads to significant modifications of the initial p... more Diagenetic illite growth in porous sandstones leads to significant modifications of the initial pore system which result in tight reservoirs. Understanding and quantifying these changes provides insight into the porosity-permeability history of the reservoir and improves predictions on petrophysical behavior. To characterize the various stages of diagenetic alteration, a focused ion beam – scanning electron microscopy (FIB-SEM) study was undertaken on aeolian sandstones from the Bebertal outcrop of the Parchim Formation (Early Permian Upper Rotliegend group). Based on 3D microscopic reconstructions, three different textural types of illite crystals occur, common to many tight Rotliegend sandstones, namely (1) feldspar grain alterations and associated illite meshworks, (2) tangential grain coats, and (3) pore-filling laths and fibers. Reaction textures, pore structure quantifications, and numerical simulations of fluid transport have revealed that different generations of nano-porosi...
The paper describes the performance of a concrete intended for sealing deep boreholes in the host... more The paper describes the performance of a concrete intended for sealing deep boreholes in the host rock of radioactive repositories. The concrete will form plugs where fracture zones are intersected and be located between very tight seals of smectite clay installed where the surrounding rock is tight. The concrete must be able to carry the clay segments after a couple of days but the bearing capacity does not have to be very high since the clay soon adheres to the rock and carries itself. The concrete contains talc as superplasticizer since ordinary organic additives for reaching high fluidity at casting are unwanted. It has a low cement content for maintaining its low porosity after dissolution in a long time perspective.
Illite was first named in 1937 in Illinois by Ralph Grim, one of the founders of clay mineralogy.... more Illite was first named in 1937 in Illinois by Ralph Grim, one of the founders of clay mineralogy. Illite is the most abundant clay mineral on the earth's surface. However, we know very little about the origin of illite in Illinois. This dissertation focuses on two aspects of illite in the Lower Paleozoic of the Illinois Basin: (1) illite polytype quantification, which explains the anomalies of the distribution of illite and smectite in the Illinois Basin, and (2) the origin and age of diagenetic illite, which is used to link illitization to fluid migration.Illite polytype quantification allows the differentiation of diagenetic and detrital illite. In Paleozoic shales from the Illinois Basin three polytypes 1M$\rm\sb{d},$ 1M, and 2M$\sb1$ are observed. 1M$\rm\sb{d}$ and 1M are of diagenetic origin and 2M$\sb1$ of detrital origin. All three polytypes were quantified by mixing single polytypes and comparing the experimental XRD traces with traces calculated using WILDFIRE$\copyright.$Illite polytype quantification of different size fractions combined with K/Ar dates allows the extrapolation to apparent ages of detrital and diagenetic end-members. The extrapolated age of the diagenetic end-members dates episodes of diagenesis. Results show that the Upper Ordovician Maquoketa Group shales contain diagenetic illite (dominantly 1M$\rm\sb{d}$ with minor 1M) with an age of $\sim$360 Ma, that was not formed solely by burial diagenesis but mainly through either a hydrothermal or K-rich brine event. Ordovician and Cambrian shale partings and sandstones, older than the Maquoketa Group, contain diagenetic illite (1M$\rm\sb{d}$ in shales and 1M in sandstones) having an age of 300 Ma. This late Paleozoic age falls within the span of the Alleghanian orogeny.The conclusion is that the diagenetic illite of the Maquoketa Group and that of the underlying formations formed from different precursors in different hydrologic systems. The diagenetic illite in the Maquoketa Group formed mainly during a hydrothermal or K-rich brine event ($\le$100$\sp\circ$C) from smectite or kaolinite. During the Alleghanian orogeny the Maquoketa Group served as an aquitard to fluids ($\le$140$\sp\circ$C) that precipitated the diagenetic illite in the older and more permeable sandstones and carbonates.U of I OnlyETDs are only available to UIUC Users without author permissio
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