A Seismic‐Frequency Laboratory Study of Solid Substitution in Bentheim Sandstone

Mikhaltsevitch, Vassili; Lebedev, Maxim; Gurevich, Boris; Sun, Yongyang; Glubokovskikh, Stanislav

doi:10.1029/2018jb016960

Cited by 6 publications

(7 citation statements)

References 33 publications

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“…The calculated elastic rock properties of the initial microstructure based on the calibrated bulk and shear moduli for the grain phase are in good agreement with published laboratory data for the Bentheim sandstone [68][69][70][71][72]78,79] as demonstrated in Figure 8a. The growth of minerals within the pore space generally leads to a stiffening of the rock, what depends on the elastic properties of the precipitated phase, which is calcite in the present study.…”

Section: Elastic Rock Propertiessupporting

confidence: 86%

“… ( a ) Absolute and percentual increases in bulk and shear moduli due to preferential precipitation at high flow velocity magnitudes (HFV, red), low flow velocity magnitudes (LFV, blue) and uniform alterations, independent of the fluid flow (black). Calculated elastic properties are in good agreement with published laboratory data [ 68 , 69 , 70 , 71 , 72 , 78 , 79 ]. ( b ) Stress distribution within the initial microstructure compared to the uniform and LFV alteration patterns.…”

Section: Figuresupporting

confidence: 85%

“…In the present study, the quartz moduli are reduced according to the workflow of Saenger et al [ 71 ] to avoid a significant overestimation of the initial elastic rock properties. For that purpose, five published datasets of laboratory measurements on the Bentheim sandstone [ 68 , 69 , 70 , 71 , 72 ] are used to perform a non-linear regression of the wave velocities to the empirical relation of Eberhart-Phillips et al [ 73 ] (Equation ( 6 ); see Figure 4 ).

where v represents the P- or S-wave velocity, P is the confining pressure and a , k , b , d are fitting coefficients.…”

Section: Methodsmentioning

confidence: 99%

“… Pressure-dependent laboratory measurements [ 68 , 69 , 70 , 71 , 72 ] of dynamic elastic properties (dots) and the non-linear regression using the empirical relation of Eberhart-Phillips et al [ 73 ] (lines) indicate an exponential increase with rising confining pressures for the Bentheim sandstone until the soft porosity features are closed. The initial mineral moduli of the grain phase are calibrated according to the workflow of Saenger et al [ 71 ], assuming that the effect of the soft porosity features becomes negligible at 20 MPa.…”

Section: Figurementioning

confidence: 99%

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Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

2020

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Geochemical processes change the microstructure of rocks and thereby affect their physical behaviour at the macro scale. A micro-computer tomography (micro-CT) scan of a typical reservoir sandstone is used to numerically examine the impact of three spatial alteration patterns on pore morphology, permeability and elastic moduli by correlating precipitation with the local flow velocity magnitude. The results demonstrate that the location of mineral growth strongly affects the permeability decrease with variations by up to four orders in magnitude. Precipitation in regions of high flow velocities is characterised by a predominant clogging of pore throats and a drastic permeability reduction, which can be roughly described by the power law relation with an exponent of 20. A continuous alteration of the pore structure by uniform mineral growth reduces the permeability comparable to the power law with an exponent of four or the Kozeny–Carman relation. Preferential precipitation in regions of low flow velocities predominantly affects smaller throats and pores with a minor impact on the flow regime, where the permeability decrease is considerably below that calculated by the power law with an exponent of two. Despite their complete distinctive impact on hydraulics, the spatial precipitation patterns only slightly affect the increase in elastic rock properties with differences by up to 6.3% between the investigated scenarios. Hence, an adequate characterisation of the spatial precipitation pattern is crucial to quantify changes in hydraulic rock properties, whereas the present study shows that its impact on elastic rock parameters is limited. The calculated relations between porosity and permeability, as well as elastic moduli can be applied for upscaling micro-scale findings to reservoir-scale models to improve their predictive capabilities, what is of paramount importance for a sustainable utilisation of the geological subsurface.

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Section: Elastic Rock Propertiessupporting

confidence: 86%

Section: Figuresupporting

confidence: 85%

where v represents the P- or S-wave velocity, P is the confining pressure and a , k , b , d are fitting coefficients.…”

Section: Methodsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

2020

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“…Though the proposed model has been derived for fluid‐saturated rocks, the pressure relaxation model of Glubokovskikh et al (2016) is more general and can also incorporate solid and viscoelastic pore fill (Mikhaltsevitch et al, 2019; Sun et al, 2018; Sun et al, 2019). Thus, the present model can be easily extended to also incorporate these rheologies.…”

Section: Discussionmentioning

confidence: 99%

Modeling the Effect of Pressure on the Moduli Dispersion in Fluid‐Saturated Rocks

Sun

Gurevich

2020

JGR Solid Earth

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Laboratory experiments of ultrasonic velocities of fluid‐saturated rocks are often much higher than the predictions of the Gassmann theory. This difference is usually attributed to the velocity dispersion caused by fluid pressure relaxation between pores of different shapes and orientation. This paper proposes a simple model to characterize pressure and frequency effects on the elastic moduli of fluid‐saturated rocks in a broad frequency range. The proposed model incorporates micromechanics of wave‐induced fluid pressure relaxation at grain contacts (between crack‐like contacts and stiff pores) into pressure dependency of elastic moduli. Previously, the pressure dependency of the velocities or elastic moduli was ascribed to the progressive closure of cracks with the increasing effective pressure and expressed as an integral of crack compliance over the range of aspect ratios. For isolated cracks, this compliance is a function of crack geometry only. For cracks hydraulically connected to stiff pores, this crack compliance can be replaced by a frequency‐dependent solution of the micromechanical problem of fluid pressure relaxation between a single crack and surrounding pores. The resulting equation expresses the bulk and shear moduli of the fluid‐saturated rock as functions of both pressure and frequency. Furthermore, if pressure‐dependent moduli of both dry and fluid‐saturated moduli are known, the aspect ratio distribution can be obtained from the pressure dependency of the dry moduli, and then the saturated moduli can be computed with no adjustable parameters. The model predictions show reasonable agreement with laboratory data measured using ultrasonic and forced oscillation techniques.

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Experimental investigation of pore-filling substitution effect on frequency-dependent elastic moduli of Berea sandstone

He,

Wang,

Tang

et al. 2024

Geophysical Journal International

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Summary Based on both forced oscillation and ultrasonic pulse transmission methods, we investigated solid pore infill influences on rock elastic moduli in a broad frequency range $[ {1 - 3000,\ {{10}}^6} ]$ Hz for different differential pressures. For a Berea sandstone sample, filled sequentially by solid (${22}^{\rm{o}}{\rm{C}}$), quasi-solid (${26}^{\rm{o}}{\rm{C}}$) and liquid (${34}^{\rm{o}}{\rm{C}}$) octadecane, a frequency-dependence was found for the Poisson's ratio, Young's modulus and bulk modulus, nevertheless, these elastic parameters were strongly suppressed by increasing pressures. Experimental measurements showed that shear wave velocity and modulus of solid-octadecane-filled samples are significantly larger than those of the dry and liquid-octadecane-filled ones, implying the potential stiffening effects related to solid infill in compliant pores. A three porosity structure model, which describes the solid stiffening effects related to equant, compliant and the intermediate pores with aspect ratios larger than those of compliant pores but much less than those of stiff pores, was used to compare against the experimentally measured elastic properties for octadecane pore infill, together with several other fluid/solid substitution theories. The agreement between experimental measurements and theoretical predictions is reasonably good for the sandstone tested, providing that the three porosity model can be applied for pressure- and frequency-dependent elastic moduli estimations for a viscoelastic pore-infill-saturated sandstone. Evaluating the combined squirt flow mechanism responsible for the observed moduli dispersion and attenuation is of great importance to reduce potential errors in seismic AVO inversion and 4D seismic monitoring of gas-hydrate or bitumen-saturated reservoir, especially for reservoir rocks with complex microstructures and heterogeneous pore types.

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A Seismic‐Frequency Laboratory Study of Solid Substitution in Bentheim Sandstone

Cited by 6 publications

References 33 publications

Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

Modeling the Effect of Pressure on the Moduli Dispersion in Fluid‐Saturated Rocks

Experimental investigation of pore-filling substitution effect on frequency-dependent elastic moduli of Berea sandstone

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