Multiple-scale facies and reservoir quality variations within a dolomite body – Outcrop analog study from the Middle Triassic, SW German Basin

Koehrer, Bastian; Heymann, Christian; Prousa, Frank; Aigner, Thomas

doi:10.1016/j.marpetgeo.2009.09.009

Cited by 55 publications

(35 citation statements)

References 17 publications

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“…Koehrer et al . () expanded on the above‐mentioned studies by adding a telogenetic stage, which leached out much of the late‐stage saddle dolomites. Turpin et al .…”

Section: Introductionmentioning

confidence: 99%

Dolomitization by hypersaline reflux into dense groundwaters as revealed by vertical trends in strontium and oxygen isotopes: Upper Muschelkalk, Switzerland

2018

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The Trigonodus Dolomit is the dolomitized portion of the homoclinal ramp sediments of the Middle Triassic Upper Muschelkalk in the south‐east Central European Basin. Various dolomitizing mechanisms, followed by recrystallization, have been previously invoked to explain the low δ18O, high 87Sr/86Sr, extensive spatial distribution and early nature of the replacive matrix dolomites. This study re‐evaluates the origin, timing and characteristics of the dolomitizing fluids by examining petrographic and isotopic trends in the Trigonodus Dolomit at 11 boreholes in northern Switzerland. In each borehole the ca 30 m thick unit displays the same vertical trends with increasing depth: crystal size increase, change from anhedral to euhedral textures, ultraviolet‐fluorescence decrease, δ18OVPDB decrease from −1·0‰ at the top to −6·7‰ at the base and an 87Sr/86Sr increase from 0·7080 at the top to 0·7117 at the base. Thus, dolomites at the top of the unit record isotopic values similar to Middle Triassic seawater (δ18OVSMOW = 0‰; 87Sr/86Sr = 0·70775) while dolomites at the base record values similar to meteoric groundwaters from the nearby Vindelician High (δ18OVSMOW = −4·0‰; 87Sr/86Sr = >0·712). According to water–rock interaction modelling, a single dolomitizing or recrystallizing fluid cannot have produced the observed isotopic trends. Instead, the combined isotopic, geochemical and petrographic data can be explained by dolomitization via seepage‐reflux of hypersaline brines into dense, horizontally‐advecting groundwaters that already had negative δ18O and high 87Sr/86Sr values. Evidence for the early groundwaters is found in meteoric calcite cements that preceded dolomitization and in fully recrystallized dolomites with isotopic characteristics identical to the groundwaters following matrix dolomitization. This study demonstrates that early groundwaters can play a decisive role in the formation and recrystallization of massive dolomites and that the isotopic and textural signatures of pre‐existing groundwaters can be preserved during seepage‐reflux dolomitization in low‐angle carbonate ramps.

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“…Koehrer et al . () expanded on the above‐mentioned studies by adding a telogenetic stage, which leached out much of the late‐stage saddle dolomites. Turpin et al .…”

Section: Introductionmentioning

confidence: 99%

Dolomitization by hypersaline reflux into dense groundwaters as revealed by vertical trends in strontium and oxygen isotopes: Upper Muschelkalk, Switzerland

2018

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“…Koehrer et al . ). Here, image analyses of a large number of thin sections allow quantification in 2D and the creation of field maps.…”

Section: Discussionmentioning

confidence: 97%

Quantification of diagenesis impact on the reservoir properties of the Jurassic Arab D and C members (Offshore, U.A.E.)

et al. 2013

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An increasing need exists to quantify the impact of diagenesis on complex and heterogeneous geological reservoirs and to predict the related field‐scale porosity‐permeability distribution. Development of approaches to quantify diagenetic events is an important step towards the construction of integrated numerical reservoir models predicting the impact of successive diagenetic events on petrophysical properties at various scales. This article describes two distinct approaches, which allow capturing, quantifying and explaining reservoir heterogeneities of the Jurassic Arab Formation (offshore oilfield in Abu Dhabi, U.A.E.) at the field and plug scale. Based on a classical diagenesis study, whereby the major diagenetic phases were characterized, distribution patterns were highlighted to further explain reservoir heterogeneities through a set of 2D interpolation diagenesis maps across the field. The best reservoir properties are encountered in the central‐northern (grainstones with syntaxial calcite overgrowth cement – typical of Arab D) and south‐western (dolostones – typical of Arab C) parts of the oilfield. Following another independent approach at the scale of the plug, quantification of rock components and description of the pore space connectivity and geometry are obtained by 2D and 3D image analyses, μ‐CT and pore network modelling. This latter approach resulted in a better understanding of the effect of anhydrite dissolution on the pore structure of the investigated dolostone. The overall, presented workflow provides valuable constraints for assessing reservoir heterogeneities in statistical field‐scale models.

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“…Some studies calculate the statistical description of geobody geometry in terms of parameters such as length, width, and height (Qi et al, 2007;FabuelPerez et al, 2009) or implement predefined geometries (Mikes and Geel, 2006). However, only a few studies deal with dolomite bodies, stratabound (Koehrer et al, 2010) or fault-controlled (Lapponi et al, 2011;Dewit et al, 2012). Because dolomitization of the Latemar platform is not limited to lateral or stratigraphical variation or geometrically well-defined geo-bodies, none of the approaches listed previously can be directly applied.…”

Section: Discussionmentioning

confidence: 99%

Multi-scale three-dimensional distribution of fracture- and igneous intrusion- controlled hydrothermal dolomite from digital outcrop model, Latemar platform, Dolomites, northern Italy

Jacquemyn¹,

Huysmans²,

Hunt³

et al. 2015

Bulletin

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A B S T R A C TIn recent years, fracture-controlled (hydrothermal) dolomitization in association with igneous activity has gained interest in hydrocarbon exploration. The geometry and distribution of dolomite bodies in this setting are of major importance for these new plays. The Latemar platform presents a spectacularly exposed outcrop analogue for carbonate reservoirs affected by igneous activity and dolomitization.Light detection and ranging (LIDAR) scanning and digital outcrop models (DOMs) of outcrops offer a great opportunity to derive geometrical information. Only a few analysis methods exist to quantitatively assess huge amounts of georeferenced threedimensional lithology data. This study presents a novel quantitative approach to describe three-dimensional spatial variation of lithology derived from DOMs. This approach is applied to the Latemar platform to determine dolomite body geometry and distribution in relation to crosscutting dikes.A high-resolution photorealistic DOM of the Latemar platform allows description of dolomite occurrences in three dimensions, with high precision at platform scale. This results in a unique lithology dataset of limestone, dolomite, and dike positions. This dataset is analyzed by true three-dimensional variography for the geospatial description of dolomite distribution. In most

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Multiple-scale facies and reservoir quality variations within a dolomite body – Outcrop analog study from the Middle Triassic, SW German Basin

Cited by 55 publications

References 17 publications

Dolomitization by hypersaline reflux into dense groundwaters as revealed by vertical trends in strontium and oxygen isotopes: Upper Muschelkalk, Switzerland

Dolomitization by hypersaline reflux into dense groundwaters as revealed by vertical trends in strontium and oxygen isotopes: Upper Muschelkalk, Switzerland

Quantification of diagenesis impact on the reservoir properties of the Jurassic Arab D and C members (Offshore, U.A.E.)

Multi-scale three-dimensional distribution of fracture- and igneous intrusion- controlled hydrothermal dolomite from digital outcrop model, Latemar platform, Dolomites, northern Italy

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