Limits on Data Communication Along the Drillstring Using Acoustic Waves (2005)

Limits on Data Communication Along the Drillstring Using Acoustic Waves Gao Li; Gao Li Halliburton Energy Services Group Search for other works by this author on: This Site Google Scholar Wallace R. Gardner; Wallace R. Gardner Halliburton Energy Services Group Search for other works by this author on: This Site Google Scholar Carl Robbins; Carl Robbins Halliburton Energy services Search for other works by this author on: This Site Google Scholar Don H. Johnson; Don H. Johnson Rice University Search for other works by this author on: This Site Google Scholar Mahsa Memarzadeh Mahsa Memarzadeh Rice University Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2005. Paper Number: SPE-95490-MS https://doi.org/10.2118/95490-MS Published: October 09 2005 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Li, Gao, Gardner, Wallace R., Robbins, Carl, Johnson, Don H., and Mahsa Memarzadeh. "Limits on Data Communication Along the Drillstring Using Acoustic Waves." Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2005. doi: https://doi.org/10.2118/95490-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractThe first commercial acoustic telemetry system was successfully introduced in 2000 as part of a drillstem testing system. However, duplicating the success of the acoustic telemetry to environmentally challenging LWD applications at high data throughput remains a formidable task. The primary limitation arises from normal drilling operations that produce in-band acoustic noise at multiple sources at intensities comparable to the transmitter output. This noise, together with the signal attenuation along the drill string, adversely affects the data throughput. To determine the communication capacity of the drill string channel using acoustic waves, we examined the impact of channel characteristics, signal attenuation and noise in detail. Based on a communication model which incorporates the effects of both drill string acoustic channel and noise, we extensively studied the capacity of the system using the waterfilling method. For this analysis, realistic downhole transmitter power output, experimentally measured noise at the surface, and measured attenuation of acoustic waves in the drill string were used as input parameters. The results show that a typical drill string channel has a potential capacity of up to several hundred bits per second under noisy drilling conditions.Implications of the channel capacity on acoustic telemetry system designs are discussed.A communication technique that comes close to realizing a high-rate telemetry system is introduced. Methods to optimize various aspects of the system such that maximum channel utilization can be realized under drilling conditions are also discussed. Potential enhancement to data rates through application of error control coding is briefly covered.IntroductionLogging-While-Drilling (LWD) plays crucial roles in the exploration of hydrocarbons. LWD is used to gain understanding of the earth formations in real time. This knowledge is not only useful for hydrocarbon reservoir characterization, it is also important in geosteering. To transmit LWD data to the surface, the current standard technology in the industry is mud pulse telemetry in which pressure pulses are generated downhole and propagate to the surface where they are detected and decoded. Unfortunately, the throughput of the mud pulse system is only a few bits per second. On the other hand, with the ever increasing complexity of LWD sensors, more data are required to be transmitted to the surface than ever before. Clearly, faster data rate wireless telemetry systems are needed. In fact, the industry has been searching for such systems for a long time. As early as 1948 [1], the transmission of data via acoustic stress waves propagating along the drill pipe was identified as a potential method for high speed communication. Theoretical studies were carried out by Barnes and Kirkwood [2] as well as by Drumheller [3] in an attempt to analyze acoustic wave propagation in drill strings. Work by Lee [4] and Ramarao [5] on wave propagation in fluid-laden drill strings further advanced understanding of the attenuation processes of acoustic attenuation.In the 90s, Halliburton launched an effort to develop a wireless telemetry system for non-drilling applications. As a result, Acoustic Telemetry System TM (ATS) was commercialized in 2000, demonstrating the value of acoustic telemetry in non-drilling applications such as drill stem testing. Since then, effort has been extended into research of an LWD acoustic telemetry system that is operable under drilling conditions [6].To the authors' knowledge, our work represents the first systematic study on the communication channel capacity of drill string under drilling conditions. After a brief discussion of the motivation, the channel characteristics of the drill string are examined. This is followed by an introduction to the general channel capacity theory. The theory is then applied to 3,000, 5,000 and 6,000 ft long drill strings to derive their capacities, respectively. Implications of the capacity result and potential means to achieve maximum data rate are investigated. Keywords: upstream oil & gas, data rate, signal power, artificial intelligence, communication, transfer function, noise, data communication, drill string, drilling equipment Subjects: Drillstring Design, Drilling Equipment, Drilling Measurement, Data Acquisition and Automation, Information Management and Systems, Logging while drilling This content is only available via PDF. 2005. Society of Petroleum Engineers You can access this article if you purchase or spend a download.