Advanced Acoustic Telemetry System Provides Real-time Data Acquisition that Increases Efficiency in Well Testing Operations
Authors: Harper George , Almanza Edgar , Fosså Arild , Finley Doug , Strang Gerry 
Published: October 2008

This paper discusses an innovative SRO system that takes advantage of state-of-the-art developments in acoustic technologies, wireline, and wireless transmission to acquire real-time, bottomhole SRO (surface read-out) data. In the past, in order to obtain this type of data, either a downhole latching system or a download probe in close proximity to the transmitting device had to be used. This acoustic dataacquisition system provides access to real-time bottomhole data using either a wireline-deployed probe or wireless acoustic signals sent through the production tubing. If the probe is used, this does not have to be close to the transmitting device in order to transfer the data to surface. Since the system offers the option of transmitting via wireline or via the wall of the testing pipe, the need for a probe or latching device along with the inherent problems that sometimes occur because the probe becomes stuck in the latch or mechanically fails can be eliminated. Finally, the additional rig time required for preparation and running of the probe to move the acoustic telemetry system (ATS) transmitter up to proper depth is saved, reducing operational costs. The system is compatible with tools conventionally used during drill stem test operations.

Background

Early SRO systems required a mechanical downhole latch mechanism that required wireline in the hole for communication of the information from the downhole probe to the surface. For low-rate, low-pressure wells without any H2S or CO2, use of this type of system posed few potential problems. However, as the industry pursued testing of deeper, higher-capacity wells with greater concentrations of impurities in the well effluent, several safety issues were experienced with the use of wireline in the hole. In the late 1980's and early 1990's, various intermediate SRO systems usedelectromagnetic proximity probes to alleviate some of the safety issues and to improve the operational reliability of the SRO systems. However, these systems did not address the fundamental problem of using wireline-deployed signal pickup probes.

The realization of the advantages that a reliable wirelessmethod of communicating downhole data to surface could provide is not new, and the oil industry began searching for a wireless method of communicating downhole data to the surface over 50 years ago. One of the first documented field tests was performed in 1948 to study the response at the surface of a downhole hammer. The results were not encouraging, and the project was dropped. As technology evolved, interest in wireless telemetry rekindled. Several companies revisited acoustic telemetry and developed research projects to address transmission of acoustic signals through tubing. Significant work by Barnes and Kirkwood in 19721 and, by Douglas Drumheller in 19882,3 helped the industry to understand how the acoustic waves responded to the tubing at various frequencies. Based on the principles laid by the earlier work, several companies now offer short-hop acoustic devices.