Through-water wireless means subsea data can be easily gathered and transmitted to manned or unmanned vessels, writes Sonardyne International’s Stephen Auld
During field appraisal operations, frequent downhole pressure and temperature readings need to be logged using wellbore gauges over periods ranging from a few days to many months. In late life, field monitoring and data gathering are essential for maintaining the integrity and productivity of subsea wells, helping to inform drilling or injection decisions to enhance or increase production.
At the end of field life, suspended wells are monitored, to inform re-entry operations, and, following abandonment, wells may need monitoring for integrity containment purposes.
But, operators don’t always have the infrastructure in place to retrieve this data. During field appraisal, umbilical systems and subsea control modules (SCM) might not yet be available to power the wellbore gauges and retrieve pressure and temperature data. The same applies to surveillance wells where an operator might want to assess the impact of water injection or production from a nearby well but may have no way to access the information generated.
Then, as infrastructure ages, communications lines in umbilicals can and do fail, as do SCMs, which could lead to early abandonment of an otherwise economic well. Finally, when fields are shut-in, and production facilities removed, ahead of full abandonment, there’s quite simply no infrastructure left to support transmission of well monitoring operations.
There is another option. It doesn’t require power for the downhole gauges, as it powers them. And it doesn’t need hardwired communications infrastructure to the host facility. Using through-water wireless communications, the subsea acoustic Data Logger can collect large amounts of data from downhole gauges, well heads and capping stacks and rapidly and accurately transmit it to a surface vessel or subsea vehicle, wirelessly.
Using acoustic signal technology, a variety of data collection platforms could be used, from remote operated vehicles, manned vessels, unmanned surface vehicles, autonomous underwater vehicles or via subsea communication networks.
The Data Logger can interface with all industry standard downhole gauges, enabling short and long-term, multi-year data logging from wells in up to 3,000 m water depth. The current generation includes Sonardyne’s Wideband 3 acoustic signalling technology, enabling large volumes of logged data to be rapidly and accurately retrieved.
OEM variants of the Data Loggers are also available, so that service companies can incorporate it into their own subsea monitoring systems.
For data retrieval to shore, vessel mounted transceivers are typically deployed from a small crane or another over-the-side deployment scheme, or permanently mounted on a vessel through a gate valve and deployment machine, to acoustically retrieve the logged data.
The transceivers can also be mounted on unmanned surface vehicles, including wave and buoyancy propelled vehicles. These are low-powered devices, which can stay at sea for long periods, harvesting and then transmitting data via satellite to shore.
All of this can be remotely controlled by a standard laptop communicating with the vehicle’s control system via satellite.
Having the ability to gather timely data from subsea wells, from appraisal through to abandonment, gives operators valuable information about the status of their wells.
The information gathered aids decision making, helping to ensure cost efficiencies, prolong field life, maximise economic recovery and inform end of life and plugging and abandonment operations.