Abstract: With the development of underground space, more and more attention has been paid to the special areas on borehole wall. In order to overcome the low resolution of traditional ultrasonic borehole imaging technology, a new borehole imaging method based on ultrasonic synthetic aperture technology is proposed to improve the resolution and image quality. Firstly, high resolution synthetic aperture focusing technique(SAFT) is used to synthetically process a large number of cross-section scanning echo signals, so as to enhance the reflection signal and suppress the interference signal, which makes the echo of the corresponding typical area at the rock wall more prominent. Then the sound amplitude and sound time parameters of the scanned cross-section echo signals are extracted. The principle of ultrasonic drilling image reconstruction based on correlation is proposed based on the synthesized characteristics of sound amplitude and sound velocity parameters. After superimposing the detection data of different depths, the borehole reconstruction image with more obvious focus area is formed. Finally, the method is applied in practical engineering, and its feasibility and accuracy has been verified.

Key words: borehole imaging, synthetic aperture focusing technique(SAFT), ultrasound imaging, geological drilling