Research On The Measurement Resolution Of Phased Array Acoustic Logging

Acoustic logging is a widely used logging method.By using the acoustic signal recorded by acoustic logging,not only formation parameters can be obtained,cementing quality can be evaluated,but also acoustic response of sidewall structure can be obtained,so as to judge the expansion of fracture,karst cave and other reservoirs outside the well.Compared with the traditional monopole transmitting and receiving detection technology and orthogonal dipole transmitting and receiving detection technology,phased array acoustic logging technology can record the circumferential multi azimuth waveform data,so this method has azimuth resolution ability and has gradually become one of the research hotspots.In this paper,the measurement response characteristics of phased array acoustic logging tool under different borehole and formation conditions are studied by physical experiment and numerical simulation.Based on the phased array scanning-reception(beamforming)method,the measurement resolution of phased array acoustic logging tool is improved.This paper introduces a new type of azimuthally acoustic bond tool(AABT),which is composed of monopole transmitter and two arcuate phased array receivers.By means of numerical simulation and physical experiment,the effect of the instrument in determining the azimuth of channeling and improving the measurement resolution is analyzed.The results of numerical simulation show that when there is strip channeling in a certain direction of cased hole,the azimuth of channeling can be determined by counting the head wave amplitude in multiple azimuths received by arcuate phased array acoustic receiver station.Compared with the individual-reception mode,the arcuate phased array acoustic receiver station with scanning-reception mode can not only determine the azimuth of channeling more accurately,but also determine the angle range of channeling.The experimental well data processing results show that AABT can evaluate the cement bonding quality of casing-cement interface(I interface)in circumferential and axial direction,and has high azimuth measurement resolution.Compared with the results of ultrasonic imaging logging tool and well condition information,the advantages of phased array scanning-reception mode in identifying small angle cement channeling are verified.Based on the application effect of azimuthally acoustic bond tool in evaluating the cementing quality of casing-cement interface(interface I),the application of phased array scanning-reception technology in the azimuthal cementing quality evaluation of cement-formation interface(interface II)is discussed.The finite difference algorithm is used to simulate the cement channeling at several angles of the cement-formation interface(interface II).The processing results show that the arcuate phased array scanning-reception method can determine the azimuth and angle range of the cement channeling at interface II,and has high azimuth resolution.The principle of 3D scanning receiving method based on the cylindrical phased array acoustic receiver station is introduced.The finite difference algorithm is used to simulate the response of phased array acoustic logging when there are one or more small-scale geological anomalies(scatterers)in the open hole,and the application effect of phased array scanning-reception method in obtaining the azimuth of geological scatterers in the open hole is analyzed.The results show that the azimuth of a single scatterer can be accurately detected by counting the P-P echo amplitude of different azimuth echo waveforms received by arcuate phased array acoustic receiver station,but the application effect of arcuate phased array scanning-reception method is poor when there are multiple scatterers beside the well.At this time,the 3D scanning-reception method based on the cylindrical phased array can measure the number and azimuth of scatterers more accurately.On this basis,the finite difference algorithm is used to simulate the response of phased array acoustic logging when there are multiple geological scatterers in the same horizontal plane and the same vertical plane,and the azimuth measurement resolution of 3D scanning-reception scheme based on cylindrical phased array in horizontal plane and vertical plane is studied.The research results verify the advantages of high measurement resolution of cylindrical phased array 3D scanning-reception technology,and provide a reference for the popularization and application of phased array acoustic logging.