Mobility Effect on Poroelastic Seismic Signatures in Partially Saturated Rocks With Applications in Time‐Lapse Monitoring of a Heavy Oil Reservoir

Zhao, Luanxiao; Yuan, Hemin; Yang, Jingkang; Han, De‐hua; Geng, Jianhua; Zhou, Rui; Li, Hui; Yao, Qiuliang

doi:10.1002/2017jb014303

Cited by 31 publications

(15 citation statements)

References 68 publications

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“…For partially saturated rocks, the mesoscopic fluid pressure diffusion takes place between the two immiscible fluids (water and air) due to their high compressibility contrast (Johnson, 2001; Pride et al, 2004; White, 1975; Zhao et al, 2017). Given the necessary physical parameters of tight sandstone as listed in Table 1, we employ the classical White model (Dutta & Odé, 1979a, 1979b; White, 1975) to compute the attenuation signatures of tight sandstone at varying levels of water saturation.…”

Section: Discussionmentioning

confidence: 99%

Role of Saturation on Elastic Dispersion and Attenuation of Tight Rocks: An Experimental Study

Wang

Gao

et al. 2020

JGR Solid Earth

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Using the forced-oscillation method, we measure the dispersion of Young's modulus, extensional attenuation, and Poisson's ratio of tight sandstone and carbonate samples at seismic frequencies (1-1000 Hz) under a constant confining pressure of 20 MPa and for a water saturation varying between 0% and 100%. The experimental data suggest that the dispersion of Young's modulus and attenuation of tight rocks is significant in a broad frequency band spanning over 1-1000 Hz. A comparison with the high-porosity and high-permeability sample data shows a contrasting dispersion and attenuation characteristics. For the tight sandstone, Young's modulus reaches a maximum dispersion of 16% at 60% water saturation and a 13% dispersion at 100% saturation. Attenuation is insignificant in dry condition and for water saturation ≤30%. In contrast with the peak attenuation occurring at very high water saturation (e.g., 80-100%) in partially saturated high-porosity rocks, peak attenuation of tight sandstone takes place at a water saturation of 60%. For the tight carbonate, the magnitude of dispersion (~3%) and attenuation are markedly lower for all saturation levels. In the explored frequency range (1-1000 Hz), Young's modulus increases monotonously, and no obvious attenuation peak is observed when saturation levels are greater than 10%. Using well-established theoretical models based on physical properties and microstructure of the tested rocks, we suggest that the observed attenuation characteristics are possibly attributed to the combined physical mechanism of microscopic (squirt) flow, mesoscopic flow in partially saturated rock, and shear dispersion due to viscous flow in grain contacts. Key Points:• Dispersion and attenuation of both tight sandstone and carbonate are distributed across frequency range of 1-1000 Hz • Extensional attenuation in tight sandstone is saturation dependent with a maximum at 60% saturation, which contrasts with that of porous sandstones • The coupled pore fabric and fluid distribution heterogeneity in tight rocks might cause complex dispersion and attenuation characteristics

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Section: Discussionmentioning

confidence: 99%

Role of Saturation on Elastic Dispersion and Attenuation of Tight Rocks: An Experimental Study

Wang

Gao

et al. 2020

JGR Solid Earth

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“…Moreover, the peak frequency for measured attenuation does not show a clear dependent relationship with water saturation. Nevertheless, the modelling peak frequency of attenuation shifts to lower frequency band, which is caused by the increase in the characteristic length of the heterogeneity scale related to saturated water with the highest viscosity (three‐order higher than air) (Dutta and Seriff, 1979; Zhao et al ., 2017b). The discrepancy between modelling and experimental results is possibly due to the coupled effect of microscopic squirt flow and mesoscopic flow between two immiscible fluids in realistically heterogeneous and partially saturated media.…”

Section: Discussionmentioning

confidence: 99%

Experimental study on frequency‐dependent elastic properties of weakly consolidated marine sandstone: effects of partial saturation

Zhao

Han

et al. 2020

Geophysical Prospecting

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Investigating seismic dispersion and attenuation characteristics of loosely compacted marine sandstone is essential in reconciling different geophysical measurements (surface seismic, well logging and ultrasonic) for better characterization of a shallow marine sandstone reservoir. We have experimented with a typical high-porosity and highpermeability sandstone sample, extracted from the Paleogene marine depositional setting in the Gulf of Mexico, at the low-frequency band (2-500 Hz) as well as ultrasonic point (10 6 Hz), to investigate the effects of varying saturation levels on a rock's elasticity. The results suggest that the Young's modulus of the measured sample with adsorbed moisture at laboratory conditions (room temperature, 60%-90% humidity) exhibits dispersive behaviours. The extensional attenuation can be as high as 0.038, and the peak frequency occurs around 60 Hz. The extensional attenuation due to moisture adsorption can be dramatically mitigated with the increase of confining pressure. For partial saturation status, extensional attenuation increases as increasing water saturation by 79% with respect to the measured frequencies. Additionally, the results show that extensional attenuation at the fully water-saturated situation is even smaller than that at adsorbed moisture conditions. The Gassmann-Wood model can overall capture the P-wave velocity-saturation trend of measured data at seismic frequencies, demonstrating that the partially saturated unconsolidated sandstone at the measured seismic frequency range is prone to be in the relaxed status. Nevertheless, the ultrasonic velocities are significantly higher than the Gassmann-Wood predictions, suggesting that the rocks are in the unrelaxed status at the ultrasonic frequency range. The poroelastic modelling results based on the patchy saturation model also indicate that the characteristic frequency of the partially saturated sample is likely beyond the measured seismic frequency range.

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“…It is interesting to note that in addition to many known heterogeneities, such as fluid patches, pore fabric, or rock frame heterogeneity, that generate nonuniform pore pressure (Ba et al, ; Pride et al, ; Sun et al, ; Zhang et al, ; Zhao et al, ), elastic interactions associated with the spatial distribution of ellipsoidal pores might represent another type of mechanism giving rise to heterogeneous pore pressure. Moreover, it is important to emphasize that to be consistent with the physical model to be investigated here, the fluid pressure distribution obtained in Figure is associated with a nonporous background, where only one set of isolated and vertically aligned ellipsoidal pores is included.…”

Section: Numerical Simulation Of Elastic Interactions Effects On Porementioning

confidence: 99%

“…Ba et al, 2016;Pride et al, 2004;Sun et al, 2015;Zhang et al, 2019;Zhao et al, 2017), elastic interactions associated with the spatial…”

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confidence: 99%

Gassmann Consistency for Different Inclusion‐Based Effective Medium Theories: Implications for Elastic Interactions and Poroelasticity

et al. 2020

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By evaluating the consistency of the Gassmann theory with various inclusion‐based effective medium theories, we investigate the impact of elastic interactions between ellipsoidal pores on the poroelasticity. To rule out any factors that can violate the Gassmann condition, other than elastic interactions, we first construct idealized models that contain only a single set of isolated, identical, and vertically aligned ellipsoidal pores. The numerical simulation suggests that the periodic distribution of ellipsoidal pores generate uniform pore pressure distribution, whereas random distribution of ellipsoidal pores generates heterogeneous pore pressure distributions. Then we analyze the precise conditions under which the underlying Gassmann relationship is valid for various inclusion‐based models. The results reveal the following: (1) Noninteracting effective medium theories are always consistent with the Gassmann prediction, simply because the elastic interactions are ignored. (2) The elastic interactions between randomly distributed pores cause heterogeneous pore pressure that violates the essential requirement of the Gassmann theory. The differential effective medium and self‐consistent approximation theories corresponding to this model thus are inconsistent with the Gassmann prediction. (3) The elastic interactions between periodically distributed pores cause uniform pore pressure; therefore, the Gassmann condition is fully satisfied. The T‐matrix approach explicitly takes into account such elastic interactions and thus is consistent with the Gassmann theory. It is interesting to notice that on top of other well‐known common types of heterogeneities, like pore structure or fluid heterogeneities, the distribution of pores and its associated elastic interactions can be a separate source of heterogeneity, and this makes Gassmann equations not valid anymore.

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Mobility Effect on Poroelastic Seismic Signatures in Partially Saturated Rocks With Applications in Time‐Lapse Monitoring of a Heavy Oil Reservoir

Cited by 31 publications

References 68 publications

Role of Saturation on Elastic Dispersion and Attenuation of Tight Rocks: An Experimental Study

Role of Saturation on Elastic Dispersion and Attenuation of Tight Rocks: An Experimental Study

Experimental study on frequency‐dependent elastic properties of weakly consolidated marine sandstone: effects of partial saturation

Gassmann Consistency for Different Inclusion‐Based Effective Medium Theories: Implications for Elastic Interactions and Poroelasticity

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