Influence of Fittings of Drill Pipe Ultrasonic Signal Dampening in a Well

The telemetry transfer from the bottom to the wellhead is an urgent problem that does not have a general-purpose solution. The paper presents studies aimed at the effect of drill locks and foreign conductive objects on the ultrasonic signal attenuation. Ultrasonic receiver and transmitter based on TR60-10H0Z-01 piezoelectric elements were used for measurements. The frequency of the transmitted signal is 60 kHz. The measurements were carried out on an experimental setup representing a six-meter-long pipe, in which the transmitter moved freely. Regression analysis follows a nonlinear attenuation model in a pipe filled with water, with a drill lock, and filled with air. It was found that one drill lock in the pipe reduces the signal level by 18 %. At the same time, the attenuation model without the linear component remains the same. Modeling of the attenuation level over a longer distance when using drill locks in pipes of 8.3 m showed that a decrease of the signal amplitude to the noise level would occur to 400 m. For comparison, a damping model was obtained for an ultrasonic signal in an empty waveguide.