New evidence for the origin of distinctive quartz overgrowth textures in the Raisby Formation (Zechstein carbonate), north-east England

Benzagouta, M. S.; Lee, Martin

doi:10.1144/pygs.48.4.409

Cited by 4 publications

(1 citation statement)

References 8 publications

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“…However, kaolinite filling calcium sulphate dissolution pores has been described by Benzagouta & Lee (1991) from the Raisby Formation and by Scholle et al (1992) from Upper Permian carbonates of the Capitan Reef Complex in Texas and New Mexico, USA. Conventional models for kaolinite formation during meteoric diagenesis require the breakdown of aluminosilicate minerals such as feldspars.…”

Section: Pore-filling Kaolinitementioning

confidence: 99%

Emplacement and diagenesis of gypsum and anhydrite in the late Permian Raisby Formation, north-east England

Lee

1994

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Cavities, pores and crystal pseudomorphs which are lined or filled by calcite are ubiquitous in Raisby Formation dolostones at outcrop in north-east England. Their distribution in most exposures is random on a metre scale. On a smaller scale, cavities, pores and crystal pseudomorphs are most numerous in bioclastic and resedimented beds. Deep borehole cores of the Raisby Formation contain nodules and euhedral crystals of gypsum and anhydrite of very similar size and shape to the cavities and pseudomorphs. This indicates that calcium sulphates were once abundant in the Raisby Formation at outcrop, but almost all have been removed subsequently.Calcium sulphate minerals were formed early in the diagenetic history of the Raisby Formation, predominantly by selective replacement of carbonate rocks. Gypsum was precipitated first, probably as a by-product of dolomitization, by brines refluxing basinwards through the Raisby Formation from the hypersaline Zechstein Sea during deposition of the Edlington Formation and the Hartlepool Anhydrite Formation. Later, replacive anhydrite formed following both pressure-solution and dehydration of the gypsum. During further burial, some anhydrite was replaced by barite, dolomite and sphalerite. Upon uplift of the Raisby Formation during the Tertiary, anhydrite rehydrated to porphyroblastic gypsum and this was then dissolved by meteoric groundwaters. The resultant pores were lined or filled by two generations of calcite and also, locally, by kaolinite. The earlier calcite generation is luminescent and was precipitated partly as a passive cement and partly by replacement of surviving gypsum and anhydrite, a reaction thought to have been mediated by sulphate-reducing bacteria. The later calcite generation is predominantly non-luminescent and was precipitated from near-surface meteoric groundwaters.

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Section: Pore-filling Kaolinitementioning

confidence: 99%

Emplacement and diagenesis of gypsum and anhydrite in the late Permian Raisby Formation, north-east England

Lee

1994

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Reservoir compartmentalization and fluid property determination using a modular dynamic tester (MDT): case study of an Algerian oil field

Belhouchet

Benzagouta

Dobbi

et al. 2021

Euro-Mediterr J Environ Integr

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Reservoir compartmentalization identification and initial properties determination are key factors for any development of oil field aspects. These characteristics are largely serving for outlining the type and the number of reservoir fluids setting. They are expected to state initial reservoir pressure and reservoir potential. Assessing the potential fluid presence and its range, for each respective zone, comes to be essential. For the case study, the associated reservoirs consist of different respective borehole potentially effective zones where fluid limits remain ambiguous. The applied method in these commitments consists of exploiting recorded pressure using Modular Formation Dynamics Tester tools (MDT) to analyze the pressure gradients and variation. This device is intended to make real-time discrimination and split up between formation fluids. Objectives in that concern are also to define reservoir compartments based on the analytical analysis of pressure gradients, taking into account the reservoir fluid type. Aims in this investigation are conducted towards the identification of the reservoir initial conditions and the setting of the Free Water Level (F.W.L.) for each interesting zone. Thus, in that context, approach on reservoir heterogeneity can be a key factor.Conducted analysis is related to an oilfield consisting of an anticlinal structure, located in the Saharan platform (South -Eastern of Algeria). This oilfield is part of Hassi Berkine basin. From a sedimentological point of view, the depositional environment has been found as fluvial-continental deposits. Some erosional impacts of the Hercynian discordance were present affecting essentially the top of the Frasnian clays. The main hydrocarbon reservoir consists of the Lower Shaly -Triassic Sandstone Formation (TAG-I): Current designation for the Sahara plateforem Triasic reservoir in the investigated area. This TAGI has been subdivided into three sub-levels: Upper TAGI (TAGI-U), Middle (TAGI-M) and the Lower (TAGI-L).Obtained outcomes revealed several pressure gradients versus depth. According to obtained graphs, and statistically, these gradients elucidate, for the same considered borehole section, significant trends. Important to mention that a substantial difference in pressure was observed between the oilfield boreholes e.g. TAGI-U+M and TAGI-L. The equivalent density of these gradients displays a fluid deposit succession as; oil (TAGI-U+M), water (TAGI-M), and oil (TAGI-L). Lithologically, a stratigraphic barrier between TAGI U+M and TAGI-L has been identified. With a superimposed pressure gradients observed in the two wells (1 and 2), two reservoir compartments have been deduced. Furthermore, using pressure evolution versus depth as well as density record, for each reservoir communicated level; two free water levels (F.W.L.), in addition to the initial pressure, were identified.

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Formation and diagenesis of slope limestones within the Upper Permian (Zechstein) Raisby Formation, north-east England

Lee

1993

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SUMMARY Isolated bodies of bedded limestone, metres in thickness, occur within dolostones of the Zechstein Raisby Formation in north-east England. Carbonate sedimentary rocks, which comprise the Raisby Formation, were deposited as pelagic and hemipelagic mudstones and wackestones on a carbonate slope during cycle 1 of the English Zechstein sequence. A characteristic of the slope environment, especially during its early evolution, was extensive submarine cementation. The intensity of early cementation at any place and time was a function of an interplay between sedimentation rate, the degree of bioturbation, and agitation of the sediment by currents. Early cementation was a significant factor in inhibiting later dolomitisation of some slope sediments by restricting the intergranular movement of dolomitising brines. Dolomitisation of Raisby Formation slope carbonates was additionally influenced by distance from the shelf area of the cycle 1 carbonate wedge, which is inferred to have been the source of dolomitising fluids, and local stratigraphic variations in porosity and permeability.

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New evidence for the origin of distinctive quartz overgrowth textures in the Raisby Formation (Zechstein carbonate), north-east England

Cited by 4 publications

References 8 publications

Emplacement and diagenesis of gypsum and anhydrite in the late Permian Raisby Formation, north-east England

Emplacement and diagenesis of gypsum and anhydrite in the late Permian Raisby Formation, north-east England

Reservoir compartmentalization and fluid property determination using a modular dynamic tester (MDT): case study of an Algerian oil field

Formation and diagenesis of slope limestones within the Upper Permian (Zechstein) Raisby Formation, north-east England

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