Observation and theoretical calibration of the fluid flow mechanism of artificial porous rocks with various size fractures

Ding, Pinbo; Wei, Jianxin; Di, Bangrang; Li, Xiangyang; Zeng, Lianbo

doi:10.1111/1365-2478.13083

Cited by 6 publications

(4 citation statements)

References 58 publications

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“…Laboratory experiments typically use synthetic samples with controlled and known rock physical properties and fracture parameters. A number of experimental studies have been conducted to observe elastic wave velocity and anisotropy in fractured rocks [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. These studies have investigated how parameters, such as fracture density, scale, and aspect ratio, can influence elastic wave velocity and anisotropy, providing significant insights into the physical mechanisms of elastic wave propagation in fractured rocks.…”

Section: Introductionmentioning

confidence: 99%

Effects of Background Porosity on Seismic Anisotropy in Fractured Rocks: An Experimental Study

Zhang

Gao

et al. 2023

Applied Sciences

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Fractures are widely distributed in the subsurface and are crucial for hydrocarbon, CCS, offshore infrastructure (windfarms), and geothermal seismic surveys. Seismic anisotropy has been widely used to characterize fractures and has been shown to be sensitive to background matrix porosities in theoretical studies. An understanding of the effects of background porosity on seismic anisotropy could improve seismic characterization in different fractured reservoirs. Based on synthetic rocks with controlled fractures, we conducted laboratory experiments to investigate the influence that background porosity has on P-wave anisotropy and shear wave splitting. A set of rocks containing the same fracture density (0.06) with varying porosities of 15.3%, 22.1%, 26.1% and 30.8% were constructed. The P- and S-wave velocities were measured at 0.5 MHz as the rocks were water saturated. The results show that when porosity increased from 15.3% to 22.1%, P-wave anisotropy and shear wave splitting exhibited slight fluctuations. However, when porosity continued to increase to 30.8%, P-wave anisotropy declined sharply, whereas shear wave splitting stayed nearly constant. The measured results were compared with predictions from equivalent medium theories. Qualitative agreements were found between the theoretical predictions and the measured results. In the Eshelby–Cheng model, an increase in porosity reduces fracture-induced perturbation in the normal direction of the fracture, resulting in lower P-wave anisotropy. In the Gurevich model, an increase in porosity can reduce the compressional stiffness in parallel directions to a larger extent than that in perpendicular directions, thus leading to lower P-wave anisotropy.

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Section: Introductionmentioning

confidence: 99%

Effects of Background Porosity on Seismic Anisotropy in Fractured Rocks: An Experimental Study

Zhang

Gao

et al. 2023

Applied Sciences

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“…Validation of these theoretical models through well-designed laboratory experiments is desirable [17][18][19][20][21]. Unfortunately, the fractures are unknown and cannot be quantitatively controlled in natural rocks.…”

Section: Introductionmentioning

confidence: 99%

Experimental Validation and Calibration of the Galvin Model with Artificial Tight Sandstones with Controlled Fractures

Zhang

2023

Applied Sciences

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The study of fractures in the subsurface is very important in unconventional reservoirs since they are the main conduits for hydrocarbon flow. For this reason, a variety of equivalent medium theories have been proposed for the estimation of fracture and fluid properties within reservoir rocks. Recently, the Galvin model has been put forward to model the frequency-dependent elastic moduli in fractured porous rocks and has been widely used to research seismic wave propagation in fractured rocks. We experimentally investigated the feasibility of applying the Galvin model in fractured tight stones. For this proposal, three artificial fractured tight sandstone samples with the same background porosity (11.7% ± 1.2%) but different fracture densities of 0.00, 0.0312, and 0.0624 were manufactured. The fracture thickness was 0.06 mm and the fracture diameter was 3 mm in all the fractured samples. Ultrasonic P- and S-wave velocities were measured at 0.5 MHz in a laboratory setting in dry and water-saturated conditions in directions at 0°, 45°, and 90° to the fracture normal. The results were compared with theoretical predictions of the Galvin model. The comparison showed that model predictions significantly underestimated P- and S- wave velocities as well as P-wave anisotropy in water-saturated conditions, but overestimated P-wave anisotropy in dry conditions. By analyzing the differences between the measured results and theoretical predictions, we modified the Galvin model by adding the squirt flow mechanism to it and used the Thomsen model to obtain the elastic moduli in high- and low-frequency limits. The modified model predictions showed good fits with the measured results. To the best of our knowledge, this is the first study to validate and calibrate the frequency-dependent equivalent medium theories in tight fractured rocks experimentally.

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“…Seismic waves attenuation also, has a great potential for investigating physical properties of fractures as well (Bouchaala et al, 2019) because of its closure to petrophysical properties of reservoirs, such as fluid type and saturation (e.g., Bouchaala and Guennou, 2012;Matsushima et al, 2017). Scattering and waveinduced fluid flow, which are the main seismic attenuation mechanisms, cause a scale-dependence of seismic anisotropy in fractured media (Ding et al, 2020(Ding et al, , 2021. However, a lack of well-established methods makes the estimate of seismic attenuation difficult.…”

Section: Introductionmentioning

confidence: 99%

Investigation of fractured carbonate reservoirs by applying shear-wave splitting concept

Diaz-Acosta

Bouchaala

Kishida

et al. 2022

Adv. Geo-Energy Res.

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In this study, fracture orientations in carbonate reservoirs were determined using a multicomponent velocity analysis based on shear wave splitting. The analysis is based on the estimated velocities of large seismic events with different polarizations. In a fractured zone with a dominant orientation, weak amplitude split shear events, including shear noise, result in shear waves that are polarized toward the symmetry and anisotropy axes and propagate with a common fast and slow velocity, respectively. Thus, a velocity stack should show high coherency anomalies in directions parallel and orthogonal to the fracture strike. Furthermore, because the analysis is applied locally at a specific depth range, it is less susceptible to the effects of overburden anisotropy and noise. The dominant fracture orientations from carbonate reservoirs of four oilfields were compared to those interpreted from fullbore microimager and core data. Fractures in two offshore reservoirs strike NNE-SSW and NW-SE, which are related to Zagros stress. Fractures in two onshore reservoir strikes NE-SW, while in deeper onshore reservoir fractures are aligned with N-S direction. The findings of this study are promising, particularly for the fractured reservoirs especially those located in Abu Dhabi, which are characterized by high heterogeneity and complex fracture network related to complex tectonic history. In order to obtain geometrical parameters of fractures at seismic scale, it is recommended to implement the analysis adapted in this study after acquiring three component zero-offset vertical seismic profiling.

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Observation and theoretical calibration of the fluid flow mechanism of artificial porous rocks with various size fractures

Cited by 6 publications

References 58 publications

Effects of Background Porosity on Seismic Anisotropy in Fractured Rocks: An Experimental Study

Effects of Background Porosity on Seismic Anisotropy in Fractured Rocks: An Experimental Study

Experimental Validation and Calibration of the Galvin Model with Artificial Tight Sandstones with Controlled Fractures

Investigation of fractured carbonate reservoirs by applying shear-wave splitting concept

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