Diagenetic Origins of the Calcite Microcrystals That Host Microporosity In Limestone Reservoirs

Hasiuk, Franciszek; Kaczmarek, Stephen E.; Fullmer, Shawn M.

doi:10.2110/jsr.2016.69

Cited by 44 publications

(38 citation statements)

References 93 publications

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“…Meteoric diagenesis occasionally has been proposed as the cause for micarb precipitation based on: (i) presence of meteoric textures in thin section or SEM (for example, micro-moulds and vugs or micro-pendant cement); (ii) proximity to an exposure surface; (iii) negative d 13 C; and (iv) low traceelement concentrations. Hasiuk et al (2016) proposed to use this last criterion with caution, because LMC is always poor in trace-elements. The Stevns-1 succession indeed underlies an exposure surface but shows no evidence for significant meteoric diagenesis (Rasmussen & Surlyk, 2012;Surlyk et al, 2013) and meteoric carbon influence (Fig.…”

Section: Hypothesis On the Formation Processesmentioning

confidence: 99%

“…The new crystals formed as the result of these processes show increasingly negative d 18 O values with depth, reflecting increasing pore water temperature and isotopic evolution of the fluids (Hasiuk et al, 2016). Hasiuk et al (2016) have compiled data of microcrystals from various Upper Cretaceous chalks ( Fig. 4) and showed that individual datasets often lack an evident correlation between d 18 O and depth, but when several datasets are considered the values form a clear trend.…”

Section: Low-magnesium Calcite Precursormentioning

confidence: 99%

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Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

et al. 2020

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Chalk is usually thought to be a homogeneous sediment with a relatively simple early diagenetic history. Here, clumped isotope analyses of samples from a core of Campanian Maastrichtian chalk are presented, indicating that material smaller than 5 µm has a different origin than the coccolith-dominated coarser fraction. The smallest size fraction (1 to 5 µm) of chalk is dominated by calcite particles without a distinct morphology (micarbs). Clumped isotope data of the micarbs reveals formation temperatures of 14 to 18°C which is 8 to 10°C colder than those derived from coeval coccoliths. The micarbs are interpreted as the product of calcite neoformation, precipitated in the uppermost part of the sediment column (100 metres below sea floor) and linked to early dissolution of aragonitic fossils. These findings prove that early cements can be an abundant component in chalk, and thus challenge the common notion that chalk is always largely composed of calcareous nannofossils, and differs only in terms of minor constituents and degree of lithification.

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Section: Hypothesis On the Formation Processesmentioning

confidence: 99%

Section: Low-magnesium Calcite Precursormentioning

confidence: 99%

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

et al. 2020

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“…Recently Hasiuk et al . 10 presented a large geochemical dataset that is consistent with simple burial diagenesis. Important for the present study is that the flow characteristics are directly related to the textural characteristics and crystal size.…”

Section: Introductionmentioning

confidence: 92%

“…The microporosity of such reservoir rocks has been an area of extensive study for many years. Recent work has summarized findings from that literature and complemented that with a substantial data set taken over a broad range of Phanerozoic age carbonates 8 – 10 . This work has identified key structural characteristics and shown their impacts on permeability and recovery factors for water and gas floods.…”

Section: Introductionmentioning

confidence: 99%

Modeling Oil Recovery for Mixed Macro- and Micro-Pore Carbonate Grainstones

King

2017

Sci Rep

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In general, modeling oil-recovery is a challenging problem involving detailed fluid flow calculations with required structural details that challenge current experimental resolution. Recent laboratory experiments on mixed micro- and macro-pore suggest that there is a systematic relationship between remaining oil saturation (ROS) and the fraction of micro-pores. Working with experimental measurements of the pores obtained from X-ray tomography and mercury intrusion capillary pressure porosimetry, we define a digital rock model exemplifying the key structural elements of these carbonate grainstones. We then test two fluid-flow models: invasion percolation model and effective medium model. Although invasion percolation identifies the important impact of macro-pore percolation on permeability, it does not describe the dependence of ROS on micro-pore percentage. We thus modified the effective medium model by introducing a single-parameter descriptor, reff. Oil from pores r ≥ reff is fully removed, while for the remaining pores with r < reff, their contribution is scaled by (r/reff)2. Applying this straightforward physics to pore size distributions for the mixed-pore grainstones reproduces the experimental ROS dependence.

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“…Even for this relatively low‐porosity chalk, pore size is much larger than what would correspond to micropores in physical chemistry, where micropores have diameter of less than 2 nm as defined from gas adsorption (Rouquerol et al ., 1994). According to a reservoir geological definition, micropores have a size of ca 0.2 μm to ca 10 μm and are supposed to be bypassed during water flooding (Hasiuk et al ., 2016). According to this alternative definition, chalk pore space is largely composed of micropores, although this again is ambiguous, because water flooding passes through these supposed micropores (e.g.…”

Section: Introductionmentioning

confidence: 99%

Porosity in chalk – roles of elastic strain and plastic strain

Fabricius

2020

Sedimentology

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Chalks originate as Cretaceous to Recent pelagic or hemipelagic calcareous ooze, which indurate via burial diagenesis to chalk and limestone. Because they accumulate in pelagic settings with high environmental continuity, chalks may form thick formations and even groups. For this reason, and because chalks have a simple mineralogy (low magnesium calcite, silica and clays), they are ideal for the study of diagenetic processes including the depth-related decrease of porosity. It is the aim of this study to illustrate how the evaluation of in situ elastic strain can help in understanding these processes including the interplay between stress-controlled diagenetic processes and processes furthered by thermal energy. Petrophysical core and well data can be used for analyses of how porosity reduction via pore collapse and pressure dissolution is related to in situ elastic strain. The data in question are: depth, density of overburden, pore pressure, ultrasonic P-wave velocity and dry density/porosity. The analysis reveals that the transition from ooze to chalk is associated with high elastic strain and consequent pressure dissolution at calcite-particle contacts causing contact cementation. The transition from chalk to limestone is also associated with high elastic strain, especially at clay-calcite interphases causing development of stylolites via pressure dissolution, and consequent pore-filling cementation. Following each transformation the elastic strain drops rapidly. The observation of this diagenesis-related pattern in elastic strain of the sedimentary rock is novel and should not only be helpful in understanding the porosity development in sedimentary basins, but also add basic scientific insight.

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Diagenetic Origins of the Calcite Microcrystals That Host Microporosity In Limestone Reservoirs

Cited by 44 publications

References 93 publications

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis

Modeling Oil Recovery for Mixed Macro- and Micro-Pore Carbonate Grainstones

Porosity in chalk – roles of elastic strain and plastic strain

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