Porosity–permeability relationships in Miocene carbonate platforms and slopes seaward of the Great Barrier Reef, Australia (ODP Leg 194, Marion Plateau)

Ehrenberg, S. N.; Eberli, Gregor P.; Baechle, Gregor

doi:10.1111/j.1365-3091.2006.00817.x

Cited by 60 publications

(32 citation statements)

References 49 publications

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“…This redistribution of porosity increased tortuosity and established the pathways available for subsequent fluid flow. High porosity values similar to those established in the Tengiz study rocks before burial are found today in Pleistocene grainstones in the Unda core, from the Bahamas (average neutron porosity values of 52% and plug porosity at , 40%; Melim et al 2001) and from the South Marion Platform off the Great Barrier Reef (porosity values between 15% and 50%; Ehrenberg et al 2006).…”

Section: The History Of the Late Visean Parasequencementioning

confidence: 60%

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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Section: The History Of the Late Visean Parasequencementioning

confidence: 60%

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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“…Image analysis of all thin sections was conducted at the University of Miami. The entire thin section was photographed in plane light and crossed nicols, and the volume and shape of macroporosity described by macropore volume, dominant pore size and perimeter over area (PoA; Ehrenburg et al, 2006). Microporosity was calculated from both modal analysis and image analysis data by: Microporosity (%) ¼ Helium porosity (%) À macroporosity Water-oil capillary pressure was measured by centrifuge on 56 samples and steady state relative permeability measurements were made on 30 samples, from which residual oil saturation (Sor) were determined.…”

Section: Databasementioning

confidence: 99%

Pore system characterisation in heterogeneous carbonates: An alternative approach to widely-used rock-typing methodologies

Hollis

Vahrenkamp

Tull³

et al. 2010

Marine and Petroleum Geology

165

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“…These cores are characterized by strong petrophysical heterogeneities over short vertical depth intervals, reflecting varying influence of both depositional textures and diagenesis (Ehrenberg et al, 2006b). Details regarding the units sampled and the separation of the samples into different textural classes are provided by Isern et al (2002); Ehrenberg et al (2006a). Fifteen horizontally oriented, 25 mm core-plugs were selected among the samples analysed by Ehrenberg et al (2003) (Figs.…”

Section: Samplesmentioning

confidence: 99%

Petrophysical properties of bioclastic platform carbonates: implications for porosity controls during burial

Croizé

Ehrenberg

Bjørlykke

et al. 2010

Marine and Petroleum Geology

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International audienceThis study is based on rock mechanical tests of samples from platform carbonate strata to document their petrophysical properties and determine their potential for porosity loss by mechanical compaction. Sixteen core-plug samples, including eleven limestones and five dolostones, from Miocene carbonate platforms on the Marion Plateau, offshore northeast Australia, were tested at vertical effective stress, View the MathML source, of 0–70 MPa, as lateral strain was kept equal to zero. The samples were deposited as bioclastic facies in platform-top settings having paleo-water depths of <10–90 m. They were variably cemented with low-Mg calcite and five of the samples were dolomitized before burial to present depths of 39–635 m below sea floor with porosities of 8–46%. Ten samples tested under dry conditions had up to 0.22% strain at View the MathML source, whereas six samples tested saturated with brine, under drained conditions, had up to 0.33% strain. The yield strength was reached in five of the plugs. The measured strains show an overall positive correlation with porosity. Vp ranges from 3640 to 5660 m/s and Vs from 1840 to 3530 m/s. Poisson coefficient is 0.20–0.33 and Young's modulus at 30 MPa ranged between 5 and 40 GPa. Water saturated samples had lower shear moduli and slightly higher P- to S-wave velocity ratios. Creep at constant stress was observed only in samples affected by pore collapse, indicating propagation of microcracks. Although deposited as loose carbonate sand and mud, the studied carbonates acquired reef-like petrophysical properties by early calcite and dolomite cementation. The small strains observed experimentally at 50 MPa indicate that little mechanical compaction would occur at deeper burial. However, as these rocks are unlikely to preserve their present high porosities to 4–5 km depth, further porosity loss would proceed mainly by chemical compaction and cementation

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Porosity–permeability relationships in Miocene carbonate platforms and slopes seaward of the Great Barrier Reef, Australia (ODP Leg 194, Marion Plateau)

Cited by 60 publications

References 49 publications

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

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

Pore system characterisation in heterogeneous carbonates: An alternative approach to widely-used rock-typing methodologies

Petrophysical properties of bioclastic platform carbonates: implications for porosity controls during burial

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