岩样中孔隙、裂缝声波特征的实验研究

作者采用超声波测量技术,对长庆气田储层岩样孔隙和裂缝情况进行测量和研究。研究中,对穿透岩样的声波中携带的大量关于其内部结构的信息,通过接收声波的运动学(如波速)和动力学(如波形、波谱)特征的综合对比,对岩样内部孔隙、裂缝是否发育及发育程度作出了定性和半定量分析。首先,孔隙、裂缝的存在使岩样波速偏低,其中裂缝对波速的影响较大,尤其是未完全充填的裂缝。其次,孔隙、裂缝发育的岩样的接收波形表现出不同程度的初动弱、振幅低和能量衰减现象,其中孔隙的影响更明显;但完全充填的孔隙和裂缝对波形几乎没有影响。最后,孔隙、裂缝对波谱的影响表现在对波谱中高、中、低频成分滤波作用的差异。此外,在孔隙、裂缝发育的岩样中还存在着较为明显的波速各向异性。

AN EXPERIMENT STUDY ON THE ACOUSTIC CHARACTERISTICS OF PORES AND FRACTURES IN ROCK SAMPLES

To investigate the pores and fractures of rock samples from the reserviors of Changqing gasfield,the P wave ultrasonic data with the samples were measured.Much useful information about the inner structure of the samples can be learned from P waves penetrated them.Based on the synthetic analysis of kinematic (such as wave velocity) and dynamic (such as waveform,spectrum) characteristics,qualitative or semi quantitative information about pores and fractures in samples can be determined.Firstly,the existence of pores and fractures makes wave velocity lower,and it is much more obvious for fractures especially those without being fully filled.Secondly,the waveform of samples with pores and fractures shows certain weak break,low amplitude and acoustic attenuation,but well-filled pores have few infleunce on them.Lastly,the influence of pores and fractures on spetrum can be indicated by different filtration of high,middle and low frequency spectrum.Besides,samples with pores and fractures obviously appear velocity anisotropy.