饱和水与干燥碳酸盐岩声波各向异性研究

Acoustic anisotropy of water-saturated and desiccated carbonate rocks

为了解碳酸盐岩在饱和水和干燥条件下的声波传播规律,通过分别对烘干和饱和水后方形碳酸盐岩岩样进行声波物理实验和频谱数值分析,对碳酸盐岩的声波波形、传播速度和波谱特征进行了研究。结果表明:声波透射岩心后,波形疏松,周期明显增大,且饱和水后周期进一步增大,而最大振幅位置提前;岩样的波速和主频率均具有明显的各向异性特征,裂缝越发育,则波速和主频率的各向异性系数均越大,纵波速度和主频率在垂直裂缝方向均明显降低;干燥岩心的波速和主频率的各向异性系数均可以用来评价岩心的各向异性特征,主频率对岩心各向异性特征更加敏感,岩心饱和水后,各向异性系数大大减小。该研究为正确利用声波测井资料以及认识碳酸盐岩储层的各向异性特征提供了依据。

In order to understand the propagation rules of acoustic wave of carbonate rocks in the condition of desiccated and water-saturated, the desiccated and water-saturated quadrate samples of carbonate rocks were tak- en the acoustic testing and numerical simulation testing, and the acoustic waveform, propagation velocity and spectral features of carbonate rocks were studied. The results show that when the acoustic waves through the sam- ples, the waveform is loose, and the cycle is obviously increased. The period increases further after saturated with water, and the maximum amplitude position moves forward. There are obvious anisotropic characteristics of the wave velocity and dominant frequency of the rock samples. The more the fracture develops, the greater the anisotropy coefficient of wave velocity and dominant frequency is, and the P-wave velocity and dominant fre- quency decreases obviously along the vertical direction of fracture. The anisotropy coefficient of the wave velocity and the dominant frequency of the desiccated samples can be used to evaluate the anisotropic characteristics. The dominant frequency is more sensitive for the anisotropy. The anisotropy coefficient is greatly reduced after satu- rated with water. This study result is helpful for us to use acoustic logging correctly and to recognize the anisotropic characteristics of carbonate reservoir.