Petrographic criteria for the recognition of marine, syntaxial overgrowths, and their distribution in geologic time

Walker, Kenneth R.; Jernigan, D. Gregory; Weber, L. James

doi:10.1007/bf03174845

Cited by 32 publications

(19 citation statements)

References 10 publications

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“…on Fig. 9B) is still controversial (Walker et al, 1988;Frank et al, 1995). According to Sonnenfeld (1996), this cement would have crystallized in a meteroic phreatic realm during the subaerial exposition of the platform at the end of Visean times.…”

Section: The Syndepositional Diagenetic Phasesmentioning

confidence: 96%

Nature and distribution of diagenetic phases and petrophysical properties of carbonates: The Mississippian Madison Formation (Bighorn Basin, Wyoming, USA)

Barbier

Floquet

Hamon

et al. 2015

Marine and Petroleum Geology

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Section: The Syndepositional Diagenetic Phasesmentioning

confidence: 96%

Nature and distribution of diagenetic phases and petrophysical properties of carbonates: The Mississippian Madison Formation (Bighorn Basin, Wyoming, USA)

Barbier

Floquet

Hamon

et al. 2015

Marine and Petroleum Geology

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“…Minor amounts of the inclusionrich fibrous cement occurs as coatings on mollusk skeletons, especially in protected locations inside chambered shells (Fig. 12C, D), and on some crinoid ossicles (Walker et al 1990). …”

Section: Diagenetic Componentsmentioning

confidence: 96%

Diagenetic Evolution of Selected Parasequences Across A Carbonate Platform: Late Paleozoic, Tengiz Reservoir, Kazakhstan

Dickson¹,

Kenter²

2014

Journal of Sedimentary Research

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Predicting the diagenetic modification of reservoir quality in carbonate fields is poorly understood but of paramount importance to reservoir characterization. The diagenetic processes and current pore system are reported for two parasequences from the platform center to the margin of the Tengiz reservoir (, 16 km); the late Visean (Lvis13 cbs 900) and Bashkirian (Bash2.5 MSF 350) parasequences are separated by 8 million years.Syndepositional fibrous cement (. 10% rock volume) and aragonite skeletal molds developed in both parasequences. On subaerial exposure, brown soil-related calcite, and meniscus and pendant cements were emplaced in both parasequences.The application of CL petrography to these rocks for the first time has revealed the depositional components and early marine components are altered developing a mottled pattern implying that their original chemistry is not preserved. The principal calcite cement shows a complex growth pattern by CL that is unreported from any other calcite cement. CL is also used to divide the main cement into stage 1, nonluminescent, and stage 2, orange to brown luminescent, calcite. Stage 1 calcite shows vadose meniscus and pendant fabrics followed by uniform phreatic euhedral terminations. Stage 1 cement is patchily distributed at a millimeter scale; 28% to 40% in the Visean and 0.5% to 22% in Bashkirian grainstones. Stage 1 cement is more abundant at the center of the platform in the late Visean than at its margin. Abundant stage 1 calcite creates a framework that prevents later compaction preserving a high porosity at the center of the platform. This sweet spot is reinforced by the deposition of late-stage bitumen cement that occupies 8% rock volume at the margin of the platform but is almost absent at its center. Stage 1 d 13 C values (22.4% to +1.7%) are derived by dissolution of host rock, and their d 18 O values (26.3% to 23.7%) are compatible with precipitation from meteoric or mixed marine-meteoric water.Depositional micrite and micritic grains are transformed by dissolution-precipitation processes into porous microrhombic calcite not by Ostwald ripening. Microrhombic calcite is ubiquitous in the Tengiz icehouse, dispelling the myth that this fabric is restricted to greenhouse epochs.At , 300 million years before significant burial the study grainstones were patchily cemented and dissolved to reach peak porosity; their transformed texture set up flow paths that controlled the distribution of later diagenetic products. Reservoir compartmentalization did not occur through extensive hardground formation at this time as occurs in some greenhouse sequences, but ash bands at parasequence boundaries were turned into tonsteins and wackestones were compacted perhaps sufficiently to influence vertical flow.CL examination of stage 2 calcite that adds 0.5% to 16% to rock volume reveals that its precipitation was episodic and switched sites as the pore network became blocked through precipitation and compaction and was opened by new fractures. A change from acute to equant habit ...

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“…Calcareous remains of echinoderms rarely constitute more than 10% of modern sediment grains [14]. But in the past (especially in the Palaeozoic) they had much greater quantitative significance, in some cases even dominating the allochems [15].…”

Section: Crystallinity Of Carbonate Grains and Early Calcite Cement Tmentioning

confidence: 99%

“…Syntaxial overgrowth is associated exclusively with grains that can be treated as monocrystalline, while isopachous cement occurrs around polycrystalline grains [15,10,16,17,18]. Early marine cementation occurs rapidly before significant compaction takes place.…”

Section: Crystallinity Of Carbonate Grains and Early Calcite Cement Tmentioning

confidence: 99%

Quantifying the impact of early calcite cementation on the reservoir quality of carbonate rocks: A 3D process-based model

Hosa

Wood

2017

Advances in Water Resources

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Quantifying the impact of early calcite cementation on the reservoir quality of carbonate rocks: a comparison of 2D and 3D process-based models Citation for published version: Hosa, OA & Wood, R 2017, 'Quantifying the impact of early calcite cementation on the reservoir quality of carbonate rocks: a comparison of 2D and 3D process-based models' Advances in Water Resources, vol. 104, General rightsCopyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policyThe University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact openaccess@ed.ac.uk providing details, and we will remove access to the work immediately and investigate your claim. AbstractThe reservoir properties of carbonates are controlled both by deposition and diagenesis, and the latter includes early calcite cementation which can exert a strong control on the evolution of subsequent diagenetic pathways. Here we investigate early cement growth in grainstones to quantify the impact on evolving pore space and partially to examine trends in the relationships between cementation and permeability. We compare process-based models of early cementation in 2D (Calcite2D) and 3D (Calcite3D). Both models assume polycrystalline and monocrystalline grain types, upon which grow isopachous and syntaxial calcite cement types, respectively. We also model two common rhombohedral calcite forms: the blocky form 0112 and elongated form 4041.Results demonstrate the effect of cement competition: an increasing proportion of monocrystalline grains creates stronger competition and a reduction in the impact of individual grains on the early calcite cement volume and porosity.Isopachous cement is effective in closing pore throats and limiting permeability, especially in the 2D model. We also show that the impact of syntaxial cement on porosity occlusion and therefore flow is highly dependent on monocrystalline grain location and direction of the grain crystal axis. This can lead to very different permeabilities in samples of the same porosity in both the 2D and 3D * Hosa, AleksandraEmail address: ola.hosa@ed.ac.uk (Hosa, Aleksandra) These results illustrate that subtle differences in early carbonate diagenesis, such as the exact location and orientation of the crystal axes of the monocrystalline grains, can have significant impact on the properties of cemented rocks. Preprint submitted to Advances in Water ResourcesWe also highlight the importance of 3D, rather than 2D, digital rock modelling and flow simulation to obtain reliable rock properties predictions.

show abstract

Petrographic criteria for the recognition of marine, syntaxial overgrowths, and their distribution in geologic time

Cited by 32 publications

References 10 publications

Nature and distribution of diagenetic phases and petrophysical properties of carbonates: The Mississippian Madison Formation (Bighorn Basin, Wyoming, USA)

Nature and distribution of diagenetic phases and petrophysical properties of carbonates: The Mississippian Madison Formation (Bighorn Basin, Wyoming, USA)

Diagenetic Evolution of Selected Parasequences Across A Carbonate Platform: Late Paleozoic, Tengiz Reservoir, Kazakhstan

Quantifying the impact of early calcite cementation on the reservoir quality of carbonate rocks: A 3D process-based model

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