Bimodal Porosity in Oolitic Reservoir--Effect on Productivity and Log Response, Rodessa Limestone (Lower Cretaceous), East Texas Basin

Keith, Brian D.; Pittman, Edward D.

doi:10.1306/03b5ba2e-16d1-11d7-8645000102c1865d

Cited by 9 publications

(1 citation statement)

References 10 publications

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“…The bimodal characteristics of carbonate porosity can sometimes be inferred from mercury injection measurements [ Keith and Pittman , 1983]. To interpret the capillary pressure data of such measurements, one typically considers a conceptual model of pore space that is made up of pores (that occupy most of the volume) connected by throats (that are of negligible volume but control the percolation and fluid transport), with the implication that the mercury injection capillary pressure is inversely proportional to throat size according to the Young‐Laplace equation [ Dullien , 1992].…”

Section: Dual Porosity and Stress‐induced Damage In Limestonementioning

confidence: 99%

Micromechanics of cataclastic pore collapse in limestone

2010

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[1] The analysis of compactant failure in carbonate formations hinges upon a fundamental understanding of the mechanics of inelastic compaction. Microstructural observations indicate that pore collapse in a limestone initiates at the larger pores, and microcracking dominates the deformation in the periphery of a collapsed pore. To capture these micromechanical processes, we developed a model treating the limestone as a dual porosity medium, with the total porosity partitioned between macroporosity and microporosity. The representative volume element is made up of a large pore which is surrounded by an effective medium containing the microporosity. Cataclastic yielding of this effective medium obeys the Mohr-Coulomb or Drucker-Prager criterion, with failure parameters dependent on porosity and pore size. An analytic approximation was derived for the unconfined compressive strength associated with failure due to the propagation and coalescence of pore-emanated cracks. For hydrostatic loading, identical theoretical results for the pore collapse pressure were obtained using the Mohr-Coulomb or Drucker-Prager criterion. For nonhydrostatic loading, the stress state at the onset of shear-enhanced compaction was predicted to fall on a linear cap according to the Mohr-Coulomb criterion. In contrast, nonlinear caps in qualitative agreement with laboratory data were predicted using the Drucker-Prager criterion. Our micromechanical model implies that the effective medium is significantly stronger and relatively pressureinsensitive in comparison to the bulk sample.

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Section: Dual Porosity and Stress‐induced Damage In Limestonementioning

confidence: 99%

Micromechanics of cataclastic pore collapse in limestone

2010

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Determining fractal dimension from nuclear magnetic resonance data in rocks with internal magnetic field gradients

2014

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Pore size distributions in rocks may be represented by fractal scaling, and fractal descriptions of pore systems may be used for prediction of petrophysical properties such as permeability, tortuosity, diffusivity, and electrical conductivity. Transverse relaxation time ([Formula: see text]) distributions determined by nuclear magnetic resonance (NMR) measurements may be used to determine the fractal scaling of the pore system, but the analysis is complicated when internal magnetic field gradients at the pore scale are sufficiently large. Through computations in ideal porous media and laboratory measurements of glass beads and sediment samples, we found that the effect of internal magnetic field gradients was most pronounced in rocks with larger pores and a high magnetic susceptibility contrast between the pore fluid and mineral grains. We quantified this behavior in terms of pore size and Carr-Purcell-Meiboom-Gill (CPMG) half-echo spacing through scaling arguments. We additionally found that the effects of internal field gradients may be mitigated in the laboratory by performing [Formula: see text] measurements with different CPMG half-echo spacings and fitting the apparent fractal dimensions determined by the NMR measurements with a model to determine the true pore system fractal dimension.

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Pore system characterization in diagenetically complex Mississippian-aged carbonate reservoirs (Kansas, USA)

et al. 2022

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Advanced petrophysical methods and detailed statistical analysis help to quantitatively and qualitatively characterize pore structure variations in carbonate rocks. Utilizing a core from the Mississippian limestone play in south-central Kansas, we investigated geological constraints on reservoir properties using observations of the variability in pore architecture and measured petrophysical properties, i.e., porosity, permeability, and nuclear magnetic resonance (NMR) response. The sample-set includes facies that retain their original depositional texture and rocks that have been subject to dolomitization, silicification, and dissolution to varying extents. Dominant macropore types include intercrystalline, moldic, and dissolution-enhanced vuggy porosity, whereas the dominant microporosity types are micritic and dolomitic intercrystalline micropores and nano-intercrystalline within silicified samples. The porosity-permeability relationships and T2 modal distribution of the carbonates we investigated correlate with dominant pore types depending on the extent and type of diagenetic modification. The fractal nature of pore systems in dolograinstones is not apparent in partially dolomitized samples, and pore complexity significantly decreases with increasing dolomitization. T2cutoff and bound fluid volume (BFV) estimates indicate that independent of geologic origin, small and intricate pore systems with microporosity are likely to host higher amounts of capillary-bound fluids. This relationship holds, especially among samples with nano-intercrystalline porosity. Correlation coefficients from predicting NMR-derived parameters with porosity improved from 0.1 to 0.78 by including pore architecture data and pore types in the multiple linear regression model. The results and observations presented here improve the current understanding and predictability of petrophysical parameters in carbonate rocks with complex pore systems.

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Bimodal Porosity in Oolitic Reservoir--Effect on Productivity and Log Response, Rodessa Limestone (Lower Cretaceous), East Texas Basin

Cited by 9 publications

References 10 publications

Micromechanics of cataclastic pore collapse in limestone

Micromechanics of cataclastic pore collapse in limestone

Determining fractal dimension from nuclear magnetic resonance data in rocks with internal magnetic field gradients

Pore system characterization in diagenetically complex Mississippian-aged carbonate reservoirs (Kansas, USA)

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