Experimental Study on the Simulation Prototype of Acoustic Nipples for Logging-While-Drilling (LWD)

In order to solve transducer and assembly process-related issues in acoustic logging-while-drilling (LWD), a simulation prototype of acoustic nipples was developed for acoustic LWD. The performance of acoustic nipple and its components was evaluated on the basis of three indexes (directivity, receiving response, and monopole measuring function. The process showed that the acoustic field generated by outward radiation of the transmitter acoustic system based on monopole excitation could be, to some extent, characterized by circumferential uniformity and its directivity pattern was close to a circle, so a monopole acoustic radiator can be developed. The average receiving sensitivity of the receivers was around-208.0 dB with deviation less than 2.0 dB. The receiving response characteristics of receivers were reasonably consistent, so the monopole acoustic wave could be received by adding the output of the receivers. During the integral debugging testing in a well by using the monopole measuring function, wave train in cased borehole was recorded. The extracted propagation velocity of casing wave was 5245.6 m/s with relative error below 3.0%. It demonstrated that the acoustic nipples of acoustic LWD could be used to simulate acoustic LWD for its measuring function for monopole transmission and reception, and it could provide experimental data in the development of acoustic LWD units.