Design and Experiment for a Quadrupole Acoustic LWD Tool

Because the monopole acoustic logging while drilling (LWD) tool cannot measure the velocity of shear waves in soft formations while drilling, a quadrupole acoustic LWD tool (QUAST) was designed. This logging tool is composed of LWD System Drilog^®, a receiving circuit, centralizer, receiving acoustic system, isolator, transmitting acoustic system, and the transmitting circuit. This paper introduces in detail the design method of the key technologies of the logging tool, such as the transmitting transducer, isolator and receiving acoustic system and verified their functions through experiment and simulation. The logging tool was tested in Well KS3-B1Sa in Luntai, Xinjiang, and high-quality signals of monopole full waves and quadrupole shear waves were detected. In hard formations, the time slowness in the shear waves of monopole full waves was consistent with that in quadrupole shear waves. The field test showed that the function of quadrupole acoustic LWD tool could meet the design requirements, and so as to measure the velocity of shear waves in the formation while drilling, and provide logging data for accurate formation evaluation.