Effect of carbonate pore structure on dynamic shear moduli

Verwer, Klaas; Eberli, Gregor P.; Baechle, Gregor; Weger, Ralf J.

doi:10.1190/1.3280225

Cited by 47 publications

(30 citation statements)

References 20 publications

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“…As a consequence, the identification of pore type and diagenetic overprints from elastic properties is a major challenge for rock physics and for seismic inversion in carbonate reservoirs. Various studies have focused on the relationship between pore type, pore geometry and acoustic velocity Eberli, 1993, 1999;Eberli et al, 2003;Baechle et al, 2008;Weger et al, 2009;Verwer et al, 2010), but few papers have described predictive tools for detecting pore type or diagenetic patterns from elastic properties. A few authors have attempted to establish qualitative velocity-porosity relationships for different diagenetic transformations: Anselmetti and Eberli (2001) for Miocene to Pleistocene carbonates from the Great Bahamas Bank; Brigaud et al (2010) for the Middle Jurassic of the Paris Basin; Borgomano (2009) andFournier et al (2011) for Cretaceous microporous limestones from SE France.…”

Section: Equivalent Pore Aspect Ratio As a Tool For Linking Velocity-mentioning

confidence: 99%

Depositional Facies, Pore Types and Elastic Properties of Deep‐water Gravity Flow Carbonates

Hairabian

Fournier

Borgomano

et al. 2014

Journal of Petroleum Geology

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Quantitative petrographic analyses of deep-water resedimented carbonates from the Gargano Peninsula (SE Italy) were integrated with petrophysical laboratory measurements (porosity, Pand S-wave velocities) to assess the impact of sedimentary fabrics and pore space architecture on velocity-porosity transforms. Samples of Upper Cretaceous carbonate came from the Monte Sant'Angelo, Nevarra and Caramanica Formations and can be classified into four depositional facies associations: F1, lithoclastic breccias; F2, bioclastic packtones to grainstones; F3, interbedded grainstones-packstones and wackestones; and F4, (hemi-) pelagic mudstones. Five pore type classes were distinguished: I and II, dominant intercrystalline microporosity; IIIa, dominant intergranular macroporosity; IIIb, dominant mouldic macroporosity; and IIIc, mixed intergranular and mouldic macroporosity. Pore type was found to strongly control velocity-porosity transforms, unlike depositional facies associations.The equivalent pore aspect ratio (EPAR), derived from differential effective medium models, is proposed to identify pore types from elastic properties. The EPAR originates from the bulk modulus or shear modulus of the samples (K-and μ-EPAR, respectively). Regardless of porosity values and depositional facies, microporous samples (type I) and samples with dominant intergranular porosity (type IIIa) are characterized by low values of K-and μ-EPAR (<0.22) and by K-EPAR > μ-EPAR. By contrast, samples with dominant mouldic porosity (type IIIb) display high values of K-and μ-EPAR (>0.25 and 0.4 respectively) and K-EPAR < μ-EPAR.High permeability limestones with dominant intergranular porosity cannot be discriminated from low permeability microporous carbonates. The petrophysical classes derived from elastic properties are shown to be distinct from reservoir property-driven rock types. In the present case, a seismic-based poro-elastic model does not match the reservoir property model. Hence, a sedimentary facies model for the studied carbonates cannot accurately represent the petrophysical properties, which are determined by pores types and pore network architecture.

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Section: Equivalent Pore Aspect Ratio As a Tool For Linking Velocity-mentioning

confidence: 99%

Depositional Facies, Pore Types and Elastic Properties of Deep‐water Gravity Flow Carbonates

Hairabian

Fournier

Borgomano

et al. 2014

Journal of Petroleum Geology

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“…Their elastic properties are affected by the pore network and the mineralogy, which can be modified through diagenetic processes [Fournier and Borgomano, 2009]. Several studies have attempted to understand the relationship between seismic wave velocity and porosity [e.g., Anselmetti and Eberli, 1993;Verwer et al, 2010] or to verify the applicability of Biot-Gassmann's fluid substitution theory [e.g., Baechle et al, 2009;Fabricius et al, 2010]. Very few studies aimed at characterizing the dispersion and the attenuation at seismic frequencies in carbonate rocks, due to the interplay between microstructure and fluid flow [e.g., Adam et al, 2006Adam et al, , 2009Mikhaltsevitch et al, 2016a].…”

Section: Introductionmentioning

confidence: 99%

Dispersion and attenuation measurements of the elastic moduli of a dual‐porosity limestone

et al. 2017

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The dispersion and the attenuation of the elastic moduli of a Lavoux limestone have been measured over a large frequency range: 10−3 Hz to 101 Hz and 1 MHz. The studied sample comes from a Dogger outcrop of Paris Basin and has the particularity to have a bimodal porosity distribution, with an equal proportion of intragranular microporosity and intergranular macroporosity. In addition to ultrasonic measurements, two different stress‐strain methods have been used in a triaxial cell to derive all the elastic moduli at various differential pressures. The first method consists of hydrostatic stress oscillations (f∈[0.004;0.4] Hz), using the confining pressure pump, from which the bulk modulus was deduced. The second method consists of axial oscillations (f∈[0.01;10] Hz), using a piezoelectric oscillator on top of the sample, from which Young's modulus and Poisson's ratio were deduced. With the assumption of an isotropic medium, the bulk modulus (K) and the shear modulus (G) can also be computed from the axial oscillations. The sample was studied under dry, glycerin‐ and water‐saturated conditions, in order to scale frequency by the viscosity of the fluid. Results show a dispersion at around 200 Hz for water‐saturated conditions, affecting all the moduli except the shear modulus. This dispersion is related to the drained/undrained transition, and the bulk modulus deduced from the axial and hydrostatic oscillations are consistent with each other and with Biot‐Gassmann's equations. No dispersion has been detected beyond that frequency. This was interpreted as the absence of squirt flow or local diffusion between the microporous oolites and the macropores.

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“…(), Vega, Prajapat and Al Mazrooei (), Verwer et al . (), Regnet et al . () and Gegenhuber (), and for sandstone samples by Khazanehdari and Sothcott (), Bhuiyan and Holt (), Li et al .…”

Section: Introductionmentioning

confidence: 94%

“…Several authors, who reported the shear softening effect for saturated rocks argued that it was extremely difficult to achieve full saturation of rock sample, especially if the rock sample is tight (e.g. Murphy 1984;Verwer et al 2010;Li et al 2017). Even after applying different advanced saturation techniques, there might be some pores that are not completely saturated, containing entrapped oil or gas bubbles.…”

Section: A P P L I C a T I O N O F T H E M O D E L T O R E S E R V Omentioning

confidence: 99%

“…Shear softening at ultrasonic frequencies for carbonate rocks were reported by Assefa, McCann and Sothcott (2003), Japsen et al (2002), Røgen et al (2005) and Sharma et al (2013). Both shear softening and shear stiffening at ultrasonic frequencies for carbonate rocks were reported by Baechle et al (2005Baechle et al ( , 2009), Verwer, Braaksma and Kenter (2008), Fabricius et al (2010), Vega, Prajapat and Al Mazrooei (2010), Verwer et al (2010), Regnet et al (2015) and Gegenhuber (2015), and for sandstone samples by Khazanehdari and Sothcott (2003), Bhuiyan and Holt (2016), Li et al (2017Li et al ( , 2018.…”

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confidence: 91%

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Effects of pore fluids on quasi‐static shear modulus caused by pore‐scale interfacial phenomena

Rozhko

2019

Geophysical Prospecting

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It is evident from the laboratory experiments that shear moduli of different porous isotropic rocks may show softening behaviour upon saturation. The shear softening means that the shear modulus of dry samples is higher than of saturated samples. Shear softening was observed both at low (seismic) frequencies and high (ultrasonic) frequencies. Shear softening is stronger at seismic frequencies than at ultrasonic frequencies, where the softening is compensated by hardening due to unrelaxed squirt flow. It contradicts to Gassmann's theory suggesting that the relaxed shear modulus of isotropic rock should not depend upon fluid saturation, provided that no chemical reaction between the solid frame and the pore fluid. Several researchers demonstrated that the shear softening effect is reversible during re‐saturation of rock samples, suggesting no permanent chemical reaction between the solid frame and the pore fluid. Therefore, it is extremely difficult to explain this fluid–rock interaction mechanism theoretically, because it does not contradict to the assumptions of Gassmann's theory, but contradicts to its conclusions. We argue that the observed shear softening of partially saturated rocks by different pore fluids is related to pore‐scale interfacial phenomena effects, typically neglected by the rock physics models. These interface phenomena effects are dependent on surface tension between immiscible fluids, rock wettability, aperture distribution of microcracks, compressibility of microcracks, porosity of microcracks, elastic properties of rock mineral, fluid saturation, effective stress and wave amplitude. Derived equations allow to estimate effects of pore fluids and saturation on the shear modulus and mechanical strength of rocks.

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Effect of carbonate pore structure on dynamic shear moduli

Cited by 47 publications

References 20 publications

Depositional Facies, Pore Types and Elastic Properties of Deep‐water Gravity Flow Carbonates

Depositional Facies, Pore Types and Elastic Properties of Deep‐water Gravity Flow Carbonates

Dispersion and attenuation measurements of the elastic moduli of a dual‐porosity limestone

Effects of pore fluids on quasi‐static shear modulus caused by pore‐scale interfacial phenomena

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