Communicating in real time or near real time, between drill rig and bottom hole, is something of a holy grail for the digital oilfield. At the low end of the downhole digital spectrum, conventional logging while drilling uses mud pulses to achieve bit per second bandwidth. Other applications record data to a memory chip downhole for later retrieval—offering high data volumes but no real time or control loop functionality.
Digital oilfield promoters have cited high bandwidth downhole communications as contributing to the ‘data deluge,’ so we thought it would be a good idea to take a rain check on current downhole bandwidth via some recent presentations and publications.
A paper in the Autum 2014 issue of Schlumberger’s Oilfield Review describes an alternative approach to downhole telemetry. Schlumberger’s Muzic ‘wireless,’ but not radio, system is used for well testing. Muzic uses a string of acoustic repeaters clamped onto the tubing string to provide bidirectional communications between the test unit and the surface. Data rates are lower than memory devices but the ability to control gauges and valves during testing is a plus.
At the Amsterdam SPE ATCE earlier this year, National Oilwell Varco presented a field ‘premiere’ of along-string dynamic measurements for drilling optimization in the Eagle Ford shale. The system uses real time downhole data streaming from the bottom hole assembly via the IntelliPipe wired drill string. This offers a 57,600 bps bandwidth used to monitor and mitigate drilling dysfunctions such as stick/slip and bit bounce.
In a follow-up presentation, NOV teamed with Halliburton and ConocoPhillips Norge to show similar successes in a North Sea wired drillpipe deployment. Here the bi-directional data network was used for early pack-off detection and to mitigate drill string vibration. ‘Memory quality’ LWD measurement was transmitted uphole in real time and the downlink allowed for control of downhole tools. The system also produces high quality image logs, used for geosteering through fault zones.
So is the data deluge living up to its name? Well if 57kbps was acquired continuously that would make for around 622 MB/day. Say 10 GB for a 20 day well. That is quite a lot of data but not nearly as much as the terabytes of a seismic survey. Nor indeed as much as all the Scada/DCS systems at the rig itself.
Those interested in learning more about digits and drilling might like to attend the LBCG well site automation for unconventionals conference in Houston next month. We’ll be there. More from the SPE ATCE on page 6 of this issue.
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