Unique Acoustic Telemetry Network with Distributed Pressure Measurement Nodes Enables Accurate Real-Time Analysis of Sweep Effectiveness
Authors: Reeves Michael , Smith Douglas , Groves Duncan , Brehm Andy , Rovira Scott , Armagost Ken 
Published: June 2014

Abstract
Sweeps are a commonly employed hole cleaning protocol during drilling operations. Typically consisting of elevated density and/or elevated viscosity fluids, they are circulated with the intent of facilitating the transport of cuttings to surface.
Traditionally, sweep effectiveness has been judged qualitatively via visual appraisal of cuttings flow at the surface shakers. While modestly useful, this limited analysis has not resulted in optimization of sweep programs and most operators still design sweep frequencies, volumes and types based on subjective observations. Real-time transmission of downhole pressure from a single location at the bottom of the drill string can be utilized to confirm the presence of a sweep in the borehole; however, such data reveals very little detail of sweep effectiveness. Continued use of ineffective sweeps may eventually lead to lost time events or opportunity time, including, lost circulation, stuck pipe, reduced drilling penetration rate, or the inability to run casing. These risks are elevated as the well's geometric complexity increases.
A unique acoustic telemetry network has demonstrated the ability to help in the design and management of hole cleaning operations. This network, comprised of nodes spaced periodically along the string, enables real-time visibility of string ID and annular pressure from multiple locations along the wellbore. This capability allows real-time analysis of many downhole pressure based events, including accurate measurement of sweep location, dilution and the volume of carried solids. Such visibility enables timely adjustments to sweep size and/or recipe to ensure the well bore is optimally cleaned.
The acoustic telemetry network utilizes a high-voltage broad-band amplifier coupled with a piezoelectric stack to generate modulated compression waves which propagate within the steel of the drill pipe. Multiple nodes, spaced periodically along the string, repeat this acoustic signal to the surface while introducing information from each location into the data stream. The acoustic telemetry functions regardless of fluid type or flow rate. Each acoustic node is packaged to provide a large, unobstructive through bore while still providing mechanical strength similar to that of the drill string within which it is positioned. The resulting network communication infrastructure can be deployed with minimal complexity and is virtually transparent to all rig operations.
This manuscript documents the field use of acoustic telemetry network technology in a horizontal drilling campaign, during which string ID and annular pressure and temperature data was acquired, recorded and transmitted to surface from five different locations along the length of the drill string. It describes, from service supplier and operator perspectives, the technology's well-site implementation, downhole performance and data capture capabilities.
For the first time, data collected along the drill string is used to deliver a quantitative analysis and interpretation of actual sweep behavior and downhole performance. Included are lessons learned and resultant changes in the operator's sweep program to optimize performance based on this unique information.