Mica Alteration Reactions in Jurassic Reservoir Sandstones from the Haltenbanken Area, Offshore Norway

Diagenetic modifications that occur after deposition at near-surface conditions (i.e. low T, P and surface-related fluids) and before significant burial (e.g. < 2 km; Morad et al., 2000) are referred to here as eodiagenesis, whereas modifications occurring after significant burial (e.g. > 2 km; Morad et al., 2000), under the influence of increasing P and T, and by modified diagenetic fluids, are referred to as mesodiagenesis ABSTRACTModal petrographic analysis, textural criteria and petrophysical data were used to unravel the origin and timing of kaolinite formation and its impact on reservoir properties of Triassic sandstones of the Lunde Formation, Snorre Field, northern North Sea. Kaolinite formation occurred by the replacement of detrital feldspar, mica, rock fragments, mud intraclasts and pseudomatrix. Some of the kaolinitization occurred shortly after deposition, but most occurred during the Early Cretaceous regional uplift and formation of the late Cimmerian Unconformity. Kaolinite stable isotopic data (δ 18 O SMOW = +13.9‰ to +18.5‰, and δD SMOW = −83‰ to −69‰) support kaolinite formation from Early Cretaceous meteoric waters. Kaolinite content in the sandstones increases from less than 5 to up to 20 vol.% within the first 200 m below the unconformity and average total porosity was enhanced by about 5%. Where mudstones were present between the unconformity and the Triassic sandstones, meteoric water flushing and, hence, kaolinite formation, were limited. However, in some cases, kaolinitization in sandstones buried under thick mudstones was aided by major normal faults that were hydraulically connected to the unconformity surface. The lack of a negative correlation between kaolinite and feldspar content is attributed to: (i) the presence of kaolinite sources other than feldspar (pseudomatrix, mica, mud intraclast and rock fragments), (ii) the strong variations in the initial detrital mineralogical composition of the sandstones, and (iii) to mass transfer of Si and Al ions on scales greater than that of the thin-section.

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“…† Structural formula from Morad et al (1990). ‡ Structural formula from Morad (1990). § Structural formula from Kerr et al (1950).…”

Section: Reservoir Heterogeneity and Reservoirquality Evolution Belowmentioning

confidence: 99%

The Role of the Cimmerian Unconformity (Early Cretaceous) in the Kaolinitization and related Reservoir‐Quality Evolution in Triassic Sandstones of the Snorre Field, North Sea

Ketzer

Morad

Nystuen

et al. 1999

Clay Mineral Cements in Sandstones

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“…Chlorite is the commonest and the most abundant secondary mineral of heated seawater-basic rocks as a result of substantive changes in the Ca/Mg ratio of the reacting fluid. Chlorites have been extensively studied in metamorphic, igneous rocks [34,35], sedimentary rocks [36,37], and in geothermal systems as well as hydrothermal ore deposits [38][39][40]. The presence of chlorite in aggregates is known to have a critical effect on the freeze-thaw durability of concrete.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Secondary Phyllosilicate Minerals on the Engineering Properties of Various Igneous Aggregates from Greece

et al. 2018

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This paper investigates the effect of alteration on the physicomechanical properties of igneous rocks used as aggregates, from various areas from Greece. The studied lithologies include serpentinized dunites, serpentinized harzburgites, serpentinized lherzolites, metamorphic gabbros, diabases, dacites and andesites. Quantitative petrographic analysis shows that the tested samples display various percentages of secondary phyllosilicate minerals. Mineral quantification of the studied rock samples was performed by using the Rietveld method on X-ray diffraction patterns. The samples were also tested to assign moisture content (w (%)), total porosity (n t (%)), uniaxial compressive strength (UCS (MPa)) and Los Angeles abrasion test (LA (%)). The influence of secondary phyllosilicate minerals on the physicomechanical behavior of the tested samples was determined using regression analysis and their derived equations. Regression analysis shows a positive relationship between the percentage of the phyllosilicate minerals of the rocks and the moisture content as well as with the total porosity values. In mafic and ultramafic rock samples, the relationships between the secondary phyllosilicate minerals and their physicomechanical properties have shown that the total amount of the secondary phyllosilicate minerals results negatively on their physicomechanical properties. On the other hand, the low percentage of phyllosilicate minerals in volcanic rocks can't be able to define their engineering properties.

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“…In those laboratory experiments biotite altered to vermiculite and/or mixed-layer clay minerals. Natural weathering of biotite may also produce kaolinite, halloysite, illite, smectite, chlorite and sesquioxides (Stoch and Sikora 1976;Gilkes and Suddhiprakarn 1979;Craw et al 1982;White et al 1985;A1Dahan and Morad 1986;Morad 1990;Robertson and Eggleton 1991). In contrast to the abundant data on synthetic and natural physico-chemical weathering of micaceous minerals, the involvement of biological alteration processes is not as well understood.…”

Section: Introductionmentioning

confidence: 99%

Morphological and Chemical Features of Bioweathered Granitic Biotite Induced by Lichen Activity

Wierzchoś

1996

Clays and clay miner.

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Abstract--to study the physico-chemical activity of lichens on micaceous components of granitic rocks, samples covered by thalli of Parmelia conspersa (Ehrht) Ach. and Aspicilia intermutans (Nyl.) Arn. were collected and examined with Scanning Electron Microscopy (SEM) equipped with a Back Scattered Electron (BSE) detector and an Energy Dispersive Spectroscopy (EDS) microanalytical system. The biophysical activity of both lichen species leads to a deep alteration of biotite, which results in detachment, separation and exfoliation of biotite plates. Chemically, the bioweathering process of biotite in the lichenmineral contact zone involves considerable depletion of potassium (K) from interlayer positions in biotite and removal of several elements, corresponding to a 9.7% loss in matter. The sequence of the loss of elements is: K § >> Fe wt > Ti 4+ ~ Mg 2 § There are also some gains in the order: Ca ~ § > Na § >> AP + > Si 4 § attributed to dissolution of co-existing Ca and Na rich minerals. Geochemical mass balance results suggest the transformation of K-rich biotite to scarcely altered biotite interstratified with a biotite-vermiculite intermediate phase in the lichen bioweathered contact zones.

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Mica Alteration Reactions in Jurassic Reservoir Sandstones from the Haltenbanken Area, Offshore Norway

Cited by 44 publications

References 21 publications

The Role of the Cimmerian Unconformity (Early Cretaceous) in the Kaolinitization and related Reservoir‐Quality Evolution in Triassic Sandstones of the Snorre Field, North Sea

The Role of the Cimmerian Unconformity (Early Cretaceous) in the Kaolinitization and related Reservoir‐Quality Evolution in Triassic Sandstones of the Snorre Field, North Sea

The Impact of Secondary Phyllosilicate Minerals on the Engineering Properties of Various Igneous Aggregates from Greece

Morphological and Chemical Features of Bioweathered Granitic Biotite Induced by Lichen Activity

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