On the Fundamental Influence of Drilling Noise on the Acoustic Communication Channel Through the Drill String

Abstract

Advances in well drilling technology are increasing the need for real-time geophysical data on the drilling process. It is obvious that the most promising channel of data transmission from the bottom of the well to the surface is the acoustic communication channel through structural elements of the drill string. Currently available estimates predict that the data transmission rate through the acoustic communication channel can reach several hundred bits per second. When designing an acoustic communication channel and calculating its capacity, it is generally assumed that the noise associated with the drilling process is an additive random Gaussian process. However, direct measurements of drilling noise over a wide range of frequencies show that this assumption is incorrect. There is a high probability for the occurrence of high-amplitude spikes, and the average vibration level varies greatly over short periods of time. This paper is devoted to the study of the influence of real drilling noise on the acoustic communication channel. A digital model was developed for this purpose. The model takes into account experimentally obtained data on drilling noise that has been recorded over a long period of time in natural experiments. The results of modeling the bit error probability under different approaches to noise-tolerant coding are presented and a comparison with a Gaussian channel is made. It is shown that deviations of noise that accompanies drilling from the normal random process have a fundamental effect on the quality of communication in the acoustic data transmission channel.