E~~\ LINEAR SIGNA~~~~ROCESSIN6 1 a n d A~~1//9~ J Approved I or public releaa.; A number of implementati ons of transversal filters employing a variety of delay line types are described and some aspects of transduction and wave propagation in bounded media arc presented in relation to these implementations.Ac_czszjolI 1w MTI~
A new approach to acoustic communication along the drill string employing zero-order torsional acoustic waves is presented. This new approach is introduced because the presented. This new approach is introduced because the extensional acoustic waves presently used by the petroleum industry in drill string acoustic telemetry are fundamentally limited to short communication distances along the string, except for extremely low data rates. This limitation occurs because extensional waves are inherently severely attenuated in propagating along the string. The physical mechanism propagating along the string. The physical mechanism responsible for this attenuation is described. Analysis is presented that provides estimates of this attenuation and presented that provides estimates of this attenuation and indicates a very large value for extensional waves in typical drill-string acoustic telemetry applications. Conversely, the analysis indicates a very small attenuation for zero-order torsional acoustic waves. Therefore, the communication distance along the string should be significantly increased by he use of zero-order torsional waves. Two new types of drill string acoustic communication system that are made feasible by the low attenuation of zero-order torsional waves are mentioned. Both of these systems have major advantages relative to conventional drill string acoustic telemetry systems. A series of field experiments measuring zero-order torsional acoustic wave propagation on drill strings in wells has been completed and another series is in progress, to verify the analytical predictions for these waves. These experiments are described and preliminary results are presented. Introduction In drilling a well, the usual method employed by the petroleum industry to obtain down-hole drilling data consists of petroleum industry to obtain down-hole drilling data consists of lowering an instrument package down the inside of the drill string on a wire line. As presently used, this method requires the interruption of the drilling process and the opening of the drill string in order to lower the instrument package into the well. In a deep well, the time required for this operation can amount to an hour or more. Moreover, in directional drilling applications the interruption of drilling to obtain steering data often introduces errors, due to the absence of torque on the drill string during the measurements. A similar situation exists in open-hole logging, where the drill string must be removed from the bore hole before the open-hole logging instrument package can be lowered into the well. In a deep well, the time consumed during this logging operation may be several hours. A wireless system for telemetering data from down hole to the surface would not require opening the drill string and interrupting the drilling process for long periods of time and would have immense operational and economic advantages over the methods presently used for obtaining down-hole drilling and logging data. Such a system could be used to provide virtually continuous information on drilling parameters, such as bore-hole direction and pressure, and on formation parameters, such as conductivity and density. In addition, a system that could function while directional drilling is actually in progress would eliminate the errors in directional steering data caused in present systems by the drill-string torque differences between drilling and data measurement conditions. Because of the potential advantages of a wireless telemetry system, during the past thirty or more years there have been many attempts to communicate down-hole data to the surface by means of acoustic waves propagating along the drill string. The success of these attempts has been severely limited, since communication has been achieved only over short lengths of drill string, except when the data rate has been restricted to extremely low values. This limitation in performance is a direct consequence of the very large acoustic attenuation associated with the type of acoustic wave - the extensional wave - that has been used for previous attempts at drill string communications. previous attempts at drill string communications. An extensional wave on a drill string consists of propagating regions of longitudinal compressive and extensive strain propagating regions of longitudinal compressive and extensive strain in the drill pipe and tool joints. Because these waves consist of regions of longitudinal strain, they have sometimes been called longitudinal waves. Strictly speaking, however, the term "longitudinal" is applied only to waves in extended solids, such as seismic "P" waves in the earth. In an extensional wave, at each region of compression the pipe is bulged and at each region of extension the pipe is necked down, the magnitude of bulging or necking being related by Poisson's ratio to the magnitude of the strain in the longitudinal direction. Because of this interaction between longitudinal and radial strain, as extensional waves propagate along the drill string they are accompanied by radial propagate along the drill string they are accompanied by radial waves that radiate acoustic power into the surrounding drilling fluid and formation. It is this radiation loss that accounts for the very large attenuation associated with these waves.
Various acoustic systems will be described briefly that have been studied and developed by one or both of the authors for use in well logging. Most of these systems have been developed with the goal of operating at extreme temperature (in some cases as high as 200 °C). A few of them have been developed with the additional goal of operating at extreme pressure (in some cases as high as 20 000 psi). A list of the systems to be discussed follows: a wireless telemetry system to transmit data from the bottom of the well to the surface, utilizing the drill pipe as an acoustic wave guide with zero-order torsional waves on the drill pipe as the data carrier; an oil and gas well passive listening device or an acoustisonde (a stethoscope or, as called by the petroleum industry, a noise tool); a wireless telemetry system to transmit data from the bottom of the well to the surface, utilizing the drill pipe as an acoustic wave guide with acoustic pulses in the drilling fluid (drilling mud) inside the drill pipe as the data carrier, with a data rate greater than existing mud pulse systems; an acoustic borehole televiewer technology with an order of magnitude finer resolution than existing systems; and advanced pressure release materials for use in acoustic transducers at extreme temperature and pressure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.