Published in SEG 2014 DAILIES
Modern seismic recording instruments fall into two camps — cabled and cable-free. Cabled systems have long been the default system of choice, recording the data in real time and allowing operators to continuously gauge and control the condition of the spread.
This choice comes at a price: the cables that enable the instant data transmission are cumbersome to move around and need to be in perfect condition to function. The difficulties in transmitting high-bandwidth data through miles of cables and thousands of connectors can result in significant downtime while troubleshooters check the spread for problems and make repairs. This downtime reduces the working day and crew productivity.
The advent and adoption of autonomous cable-free systems in recent years has circumvented many of the cable systems’ problems. These “autonomous nodal systems” tend to be lower in weight and volume than cable systems. Operators simply deploy them in the field and leave them to acquire data, trusting that data are being recorded and that the spread remains within specification (e.g., noise levels, quality of geophone coupling, etc.). As the electronics of these systems are reliable, this choice is often a safe bet. Contractors don’t have to wait on the recording system status to start shooting, so productivity is limited by the energy source, not by the recording system.
As autonomous nodes are blind, the user has no idea if they are recording or are still in place. They have no real-time QC, making it impossible to monitor the state of the spread. Data have to be harvested from the nodes by bringing them back to the camp or by harvesting the data in situ using complex field terminals. The contractor has to invest in and mobilize large transcription trailers to house the expensive computers needed to carry out this work. The customer has to wait for days or weeks to see the data produced by skilled technicians in the field, which often leads to delays in making informed decision on the ongoing survey parameters.
Up to 20% extra units are needed in the field with some nodal systems, since they need to be taken off the line for harvesting and battery recharging. At the end of the survey, all of the nodes are brought back to camp, resulting in a huge backlog as they wait to be harvested.
Wireless Seismic’s RT System 2 is an alternative system offering the best of both worlds. The system architecture is best imagined as a cable system, where the cables are replaced by high-bandwidth radios that transmit data wirelessly, in real time, between Wireless Remote Units (WRUs). RT System 2 works by digitizing the analog input data from the geophones and storing them in the WRU’s memory. The data are then streamed through the telemetry system to the Central recording system. As the transmission distance between WRUs is small, the system is not subject to the limitations of other radio architectures. RT System 2 is free from the drawbacks of cabled systems and offers the benefits of autonomous nodes, without the drawbacks — truly the best of both worlds.
RT System 2 now features a robust Hybrid Radio Telemetry system, so that if a WRU loses radio connectivity, its internal GPS turns on and continues to record seamlessly, storing data into its large flash memory. When radio connectivity is restored, the buffered data are transmitted wirelessly to the Central recorder, as telemetry bandwidth permits, and the internal GPS switches off to extend battery life.
With the RT System 2 Hybrid Radio Telemetry capability, you can be confident knowing that your seismic data is safely recorded and stored and that your crew can continue to operate at its maximum efficiency. Real-time RF data return systems are now a reality for large channel count and demanding terrain. To learn more about the system, visit www.wirelessseismic.com.