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.