Inversion Of Borehole Azimuthal Acoustic Reflection Imaging Logging Data With Beamforming

Acoustic reflection imaging logging,also called remote acoustic imaging logging,is used to determine the presence of reflector,increasing the conventional investigation range from one meter to dozens of meters.P-wave imaging can only measure the distance of reflector from the borehole,which is based on the symmetrical vibration modes of the transmitter and receiver.Because of the directivity of the borehole dipole source vibration mode,the strike of reflector can be obtained by S-wave imaging,but its azimuth cannot be determined.In recent years,borehole azimuthal acoustic reflection imaging logging that can directly records P-waves in different directions and measures the azimuth and distance of reflector from the borehole have gradually attracted researchers' interests.This dissertation introduces the numerical simulation,physical simulation and field application cases related to borehole azimuthal acoustic reflection imaging logging,and applies the beamforming method to the acoustic data inversion.Numerical simulations of borehole azimuthal acoustic reflection imaging logging are carried out.The array of azimuthal receiver stations can be regarded as an acoustic phased array,and then the individual-reception waves of receiver sensors are stacked regularly to obtain the scanning-reception waves using beamforming method.Azimuthal and vertical angle of the reflected waves can be accurately determined by distribution curve of scanning-reception wave amplitudes in the horizontal and vertical plane,respectively.In addition,the involved experimental simulations of eight-sensor receiver station are designed to verify the effectiveness of scanning-reception method.A newly developed borehole azimuthal acoustic reflection logging tool consists of a linear phased array transmitter and 10 eight-sensor receiver stations,a total of 80 sensors.To evaluate its capability,underwater experimental simulations are carried out in a deep lake for detecting the single refletor with different distances and double reflectors distributed with respective azimuths.The results show that the azimuth and distance of reflector can be easily obtained,whether there is a single reflector or double reflectors with a distribution pattern in different directions.In addition,not only the measuring accuracy but also the reflection energy is significantly improved from scanning-reception reflections,compared with individual-reception reflections.The consistency between the measured and actual values reveals the reliability and stability of this method.Finally,some field applications are illustrated and the position of nearby reflector such as a fracture or an adjacent borehole is acquired from data inversion successfully.When the size of the reflector is significantly larger than the length of P-waves in the formation,the reflected P-waves can accurately image the reflector;both two are at the same order of magnitude,the distribution of reflector can be obtained by scattered Pwaves.Moreover,the reflector information from the inversion is consistent with that of other geological data,which verifies the reliability of the inversion results and provides reference cases for the field applications of the borehole azimuthal acoustic reflection imaging logging.