岩石含水饱和度,频率,流体类型对声波振幅影响规律的探讨

本实验以不同类型的砂岩为试样,在常温常压下用超声参数测定仪测量了饱和度、频率和流体类型对多孔隙岩石中声波衰减的影响,得到以下结论:(1)在干燥岩石中,纵波衰减比横波高;在被流体完全或部分饱和的岩石中,纵、横波的衰减均高于在干燥岩石中的衰减,横波的衰减的增加量比纵波大,并以复杂的方式依赖于饱和度。(2)在饱和盐水的岩石中,声波振幅随频率的增高而呈指数衰减。在低频段,声波有较大的衰减变化率;在某一特征频率(600kHz左右)之后,振幅与频率基本无关。(3)对同一块样品,饱和不同类型的流体,声波的振幅随流体的粘度增大而减小。

The Investigation of the Influence of the Degree of Saturation, Frequency and Fluid Type on the Sonic Wave Amplitude in Sandstones

This paper uses different representative sand-stones as experimental samples, and core-wave velocity meter. Influence of the degree of saturation, frequency and fluid type on sonic wave attenuation in porous rocks is studied. Under room temperature and common pressure, it is found that:(1) attenuation of compressional wave is higher than that of shear wave in the dry rocks. Attenuation of both P-wave and S-wave in fully brine-saturated rocks is higher than that in the dry rocks. Increment of S-wave attenuation depends on the degree of saturation in complicated way.(2) Amplitude has exponential decrease with increasing frequency in brine-saturated rocks. At low frequency, sonic wave has greater rate of attenuation. After certain characteristic frequency (about 600kHz), amplitude is independent of frequency.(3) For differently fluid-saturated rock, amplitude of sonic wave decreases with increasing viscosity of fluid.To sum up, we can get more fundamental information from attenuation measurement. These laboratory observational results may be helpful in in-situ identification of lithology, and can be used to serve for the development of oil fields.