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, João Marcelo Medina; Morad, S.; Nystuen, Johan Petter; Ros, Luiz Fernando De

doi:10.1002/9781444304336.ch16

Cited by 14 publications

(22 citation statements)

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“…The patches of pore‐filling kaolinite normally have a high intercrystalline porosity. These observations clearly indicate an in situ diagenetic origin (Ketzer et al. , 2003).…”

Section: Discussionmentioning

confidence: 65%

Palaeo‐climate controlled diagenesis of the Westphalian C & D fluvial sandstones in the Campine Basin (north‐east Belgium)

Bertier¹,

Swennen

Lagrou³

et al. 2008

Sedimentology

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The Westphalian C and D fluvial sandstones in the Campine Basin (north‐east Belgium) are potential reservoirs for the sequestration of CO2 and interesting analogues of the hydrocarbon reservoirs in the Southern North Sea. Although these sandstones were deposited in a relatively short period of time, their reservoir properties and mineralogical compositions are very different. A petrographic study complemented with stable isotope analyses, fluid inclusion microthermometry and X‐ray diffraction analyses of the clay fractions of the sandstones, which were sampled from deep boreholes (>1000 m) in the Campine Basin, revealed that these differences are related mainly to the climate at the time of deposition. The most important eogenetic processes affecting the Westphalian sandstones were the generation of a pseudomatrix by physical compaction of Al‐silicates and lithic fragments that were strongly altered by extensive meteoric leaching, kaolinitization of unstable silicates and precipitation of siderite. These processes had a detrimental influence on the reservoir properties of Westphalian C sandstones, but their impact on the Westphalian D sandstones was minimal. The difference is assumed to be related to the climate at the time of deposition, which changed from tropical humid in the Westphalian C to semi‐arid/arid during the Late Westphalian D. Both the Westphalian C and D sandstones were affected by similar mesogenetic processes. Mesogenetic quartz cementation resulted from chemical compaction and illitization of kaolinite, K‐feldspar and smectitic clays. Illitization of kaolinite was controlled by the available quantities of co‐existing kaolinite and K‐feldspar and mainly affected the Westphalian D sandstones. Illitization of K‐feldspar was controlled by the K‐feldspar content. It had a much larger impact on the reservoir properties of the Westphalian D as, in these sandstones, K‐feldspar was less affected by eogenetic alteration. The illitization of smectitic clays resulted in illite, quartz and ankerite cementation in both reservoirs. This process had a more important impact on the Westphalian C reservoir, since cementation here also resulted from smectite to illite conversion in the interbedded and underlying shales. The effect of mesogenetic alterations on the reservoir properties was much less drastic than the impact of eodiagenesis. Mesogenetic alterations do exert a significant control on the properties of the Westphalian D. The vast impact of eodiagenesis on the Westphalian C sandstones made them less susceptible to mesogenetic alteration. The effect of telogenetic processes on the porosity and permeability of the Westphalian sandstones was small and restricted to the top reservoir intervals that directly underlie the Cimmerian Unconformity. No significant telogenetic alterations related to the Variscan Unconformity were observed.

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“…The patches of pore‐filling kaolinite normally have a high intercrystalline porosity. These observations clearly indicate an in situ diagenetic origin (Ketzer et al. , 2003).…”

Section: Discussionmentioning

confidence: 65%

Palaeo‐climate controlled diagenesis of the Westphalian C & D fluvial sandstones in the Campine Basin (north‐east Belgium)

Bertier¹,

Swennen

Lagrou³

et al. 2008

Sedimentology

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“…Petro graphic evidences suggest an origin for young kaolinite associated with telodiagenesis by the infl ux of meteoric waters during uplift (i.e. Emery et aL 1990;Ketzer et aL 2003;Worden and Morad 2003). At this stage of kaol inite generation, replacements of micas (already de fonned by mechanical compaction), occurred.…”

Section: T-ii T-i T-i T-ii T-i T-ii T-i T-i T-ii T-ii T-ii T-ii T-ii mentioning

confidence: 99%

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Ochoa

Arribas

2005

Int J Earth Sci (Geol Rundsch)

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Buntsandstein deposits generated in a slowly subsiding basin on the western margin of the Iberian Chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick (conglomerates, sandstones, and shales). Diagenetic processes in sand stones can be grouped as eodiagenetic, mesodiagenetic, and telodiagenetic. Eodiagenesis can be associated with Muschelkalk, Keuper, and probably early Juras sic times. Mesodiagenesis is probably related to Jurassic times. Diagenetic chemical reactions suggest a maximum burial less than 1.5 km and low tempera tures « 120°C). Patterns of porosity reduction by compaction and cementation suggest four diagenetic stages: (1) Loss of primary porosity by early mechanical compaction; (2) early cementation (K feldspar and dolomite); (3) dissolution of cements; and (4) framework collapse by re-compaction. These stages are manifested by the presence of two types of sand stone. Type I sandstones present high intergranular volume (mean, 30%). Type II sandstones are charac terized by high compactional porosity loss and exhibit low values of intergranular volume (mean, 16.9%). Type 11 sandstones are associated with the dissolution of cement and later re-compaction of type I sand stones. An intermediate telodiagenetic phase is de duced and related to the sharp unconformity between Lower Cretaceous sediments and the underlying sedi ments. This suggests that a mechanically unstable framework collapsed during the Cretaceous, generating type II sandstones. The analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins.

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“…Sandstones in the Permo‐Triassic Basin stretching from the North Sea to Poland represent some of the most important hydrocarbon reservoirs in Europe (Bjørkum et al ., ). It is, therefore, economically important to understand the impact of diagenesis on reservoir quality, especially for clay minerals that have a large impact on permeability (Ketzer et al ., ; Morad et al ., ; Taylor et al ., ). Permo‐Triassic lithofacies of the Iberian Range, Spain, show close similarities to Permo‐Triassic Basin of Central Europe (Gaupp et al ., ).…”

Section: Introductionmentioning

confidence: 97%

“…Kantorowitcz, ; Glasmann et al ., ; Giles et al ., ; Haszeldine et al ., ; Marfil et al ., ). Modal petrographic analyses, textural criteria and petrophysical data have been used to unravel the origin and timing of kaolinite formation and its impact on reservoir properties of Triassic sandstones of the northern North Sea (Ketzer et al ., ). For these authors, kaolinitisation occurred shortly after deposition, mostly during Early Cretaceous regional uplift, and, formation of the late Cimmerian Unconformity, when meteoric waters entered the system.…”

Section: Introductionmentioning

confidence: 99%

Clay mineral occurrence and burial transformations: reservoir potential of the Permo‐Triassic sediments of the Iberian Range

et al. 2014

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The diagenetic evolution of Permian (Autunian and Saxonian) and Triassic (Buntsandstein) sandstones and mudrocks have been studied over 1000 m sequence from the Sigüenza 44‐3 drill core in the Iberian Range, Spain. We compare and contrast the diagenetic processes in these different lithologies and the timing of clay mineral formation. Moreover, we establish the relationship between clay mineral diagenesis and reservoir potential. Both the Permian and Triassic successions are characterised by conglomerates, sandstones and interbedded mudstones of fluvial origin that change upwards into distal deposits of a fluvio‐deltaic system. The clay minerals are illite, illite‐smectite mixed layers, kaolinite and dickite. The illite content in all sequences is not related to diminished feldspars; it is owing to the initial detrital mineralogical composition of the Autunian sandstones. The effect of feldspar alteration to kaolin minerals has a strong influence on the lost of porosity‐permeability in the Saxonian facies. In contrast, illite and mixed layers illite‐smectite are the main clay rims preserving porosity in the Buntsandstein sandstones. However, fibrous illite is the dominant pore‐filling in the Permian Autunian facies, closing porosity and permeability. Kaolinite and dickite show opposite trends: dickite increases yet kaolinite decreases from Triassic to Permian sandstones. Dickite replaced kaolinite during burial‐thermal evolution of the succession. The δD and δ18O isotopic signatures from silt and clay fractions indicate a mixture of meteoric and marine waters, and suggest a minimum temperature range between 60 and 150 °C for diagenetic pore fluids. The Permian δD values (−24‰ to −44‰) are relatively similar to Buntsandstein values (−24‰ to −37‰). However, the Permian δ18O values (+7.6 and +15.3, average of +13.3‰) are generally higher by ca. 6.2‰ compared to the Buntsandstein data (4.8–10.1‰, average +7.1‰). Such a variation is interpreted as the result of mesodiagenetic pore fluid changes. The extensive dickitisation of kaolinite is attributed to increased hydrogen ions resulting from maturation of organic matter. The vitrinite reflectance of organic matter and the modelled thermal history suggest a maximum burial of 3400 m, accomplished 70 Ma ago. The Permo‐Triassic reached the gas window shortly before major uplift, at 65 Ma, when further maturation and hydrocarbon expulsion ceased.

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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

Cited by 14 publications

References 50 publications

Palaeo‐climate controlled diagenesis of the Westphalian C & D fluvial sandstones in the Campine Basin (north‐east Belgium)

Palaeo‐climate controlled diagenesis of the Westphalian C & D fluvial sandstones in the Campine Basin (north‐east Belgium)

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Clay mineral occurrence and burial transformations: reservoir potential of the Permo‐Triassic sediments of the Iberian Range

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