含水饱和度对致密砂岩声波特性的影响研究

以四川盆地须家河致密砂岩为研究对象,研究了含水饱和度对致密砂岩声学特性的影响,以及致密砂岩的各向异性。采用透射法对干燥和饱和水的致密砂岩岩样进行声波测试,分别对干燥和饱和水岩样的声波传播规律进行研究。研究结果表明:对声波信号进行3层Db6小波分解后发现,岩石内部孔隙明显;致密砂岩岩样饱和水状态主频的能量较干燥条件下呈现不同程度的衰减,其中高频区域的能量衰减程度较大,低频区域信号能量所占比例增加,较高频率段纵波信号能量所占比例降低;随着含水饱和度增加,不同方向的岩样的声波速度和衰减系数变化趋势一致,但增加幅度不一致,即含水饱和度对致密砂岩岩样各向异性存在较大的影响。

Study on the influence of water saturation on acoustic characteristics of low-porosity sandstone

Taking the low-porosity sandstone of Xujiahe in Sichuan basin as the research object, the influence of water saturation on the acoustic characteristics of low-porosity sandstone and the anisotropy of low-porosity sandstone are researched. The dry and saturated rock samples were taken the acoustic testing by acoustic transmission method and some information of rock sound waves is obtained by Fourier transform, then researched the sound wave propagation law of rock samples under dry and saturated conditions. After the 3 layer of the Daubechies 6 wavelet decomposition, it is found that the internal porosities of the rock are obvious.The energy of the dominant frequency of the low-porosity sandstone sample is different from which under the dry condition, and the energy attenuation in the high frequency region is larger.The proportion of signal energy in the low frequency region increases, the proportion of the energy of the longitudinal wave signal in the higher frequency segment decreases with the increase of water saturation,variation trend of acoustic wave velocity and attenuation coefficient of rock samples in different directions is consistent,but the increase amplitude is not consisteng,that is,water saturation has a great influence on the anisotropy of tight sandstone rock samples.