The effects of gas saturation on the acoustic velocity of carbonate rock

He-hua, Zhu; Tan, Yanhu; Qiao, Chen; Wang, Lisha; Yao, Gongcheng; Cao, H.

doi:10.1016/j.jngse.2015.06.013

Cited by 9 publications

(3 citation statements)

References 5 publications

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“…Theoretical analysis shows that the P-wave velocity decreases when there is a small amount of gas in a stratum, whereas the S-wave velocity is almost invariant, which makes the Vp/Vs ratio more sensitive to types of fluids; the Vp/Vs ratios of rocks containing water are higher than those of rocks containing gas (Shi Xingjue, 1995) [5]. From these figures, we notice that some difference exist between the P-wave and S-wave velocities.…”

Section: Experimental Analysis Of the Vp/vs Ratio And Water Saturationmentioning

confidence: 99%

“…They discovered that a basket of gas in rock may decelerate the acoustic velocity in a short period; the P-wave velocity remains almost unchanged when the water saturation is greater than 90%, and the acoustic velocity increases drastically when the water saturation is less than 90%. Chardac et al (2003) adopted a cross plot of the P-and S-wave velocity ratio (Vp/Vs) vs. the P-wave offset time to identify the characteristics of strata that contains oil and gas [4,5]. This differs from the previous methods, although they have essentially made use of Vp/Vs.…”

Section: Introductionmentioning

confidence: 99%

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An Experimental Study of Velocity-Saturation Relationships in Volcanic Rocks

Liu¹,

Zhao²

2015

TOPEJ

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Abstract:In this paper, experiments are carried out under different pressures and water saturations using core samples of volcanic rocks from the Junggar Basin in China to understand how water saturation affects P-and S-wave velocities. The results show that water saturated rocks exhibit significantly higher P-and S-wave velocities than gas saturated rocks. In addition, the P-and S-wave velocity ratio declines with increasing water saturation. Furthermore, a P-and S-wave velocity ratio vs. resistivity cross plot is created to identify gas reservoirs in the volcanic rocks in the Junggar Basin.

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Section: Experimental Analysis Of the Vp/vs Ratio And Water Saturationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Experimental Study of Velocity-Saturation Relationships in Volcanic Rocks

Liu¹,

Zhao²

2015

TOPEJ

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“…and Zhu et al25 conducted research on acoustic velocity and mechanical property with variable water content. Yan et al26 and Li et al 27 combined acoustic test and uniaxial test to acquire acoustic velocity in the loading, which can be used to reflect stress damage evolution in uniaxial test.…”

mentioning

confidence: 99%

Hydration index and hydrated constitutive model of clay shale using acoustic frequency spectrum

Liu

Ding

Ranjith

et al. 2019

Energy Science & Engineering

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Clay shale is frequently encountered in drilling. With strong hydration capacity, when clay shale contacts with drilling fluid, rock structural and mechanical property will be affected, causing wellbore instability. Acoustic frequency spectrum is a significant parameter in geophysical logging. The influence of hydration on clay shale can be reflected in acoustic logging. Therefore, in order to identify hydration damage and have precise evaluation for hydration damage, a novel hydration damage index has been built on the basis of acoustic frequency spectrum. Meanwhile, considering the influence of hydration, hydrated constitutive model has been proposed using this new index. Results demonstrate that acoustic frequency spectrum has clear modification due to hydration damage. In the hydration evolutionary process, fracture initiation and propagation happen, decreasing acoustic amplitude and dominant frequency. The whole hydration evolutionary process exhibits S curve with clear three stages. In the initial stage, changing ranges of acoustic amplitude and frequency are small. In the middle stage, clear fracture propagation can be noticed and fracture network is formed, boosting the change of acoustic frequency spectrum. Finally, acoustic frequency spectrum becomes stable, meaning hydration damage has reached its limitation. Hydration damage degree is variable with different conditions, but the tendency still remains typical S curve. Stress‐strain curves simulated from hydrated constitutive model are in good agreement with results of uniaxial compressive test, indicating this model can be used to express shale mechanical property in hydration evolutionary process. Findings of this paper can offer theoretical reference for evaluating hydration damage and are advantageous for drilling operation in clay shale formation.

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