Advanced components, reliable performance
ZLand nodal systems are comprised of two major parts:
- Handheld terminal
- Source controller
- Data download and charging
- Data recorder
ZLand nodes are field units used to detect and store seismic events; each node is generally laid at a related receiver station. Nodes are completely autonomous during acquisition. ZLand nodes are extremely rugged, environmentally friendly and exceptionally reliable.
Each node’s geophone, electronic circuitry and battery are safely contained in a single high-impact, rugged case. Due to their outstanding reliability, nodes need no troubleshooting after layout, thus enabling jobs to be completed on or even ahead of schedule. Nodes are very environmentally friendly because of their small footprint and an absence of troubleshooting.
Nodes detect and store seismic data continuously for more than two weeks. Nodes employ extremely accurate internal clocks to maintain precise timing. Each clock is also periodically checked against GPS time (UTC) and adjusted as necessary. Nodes employ special GPS timing receivers, which can operate with a minimum of one satellite when the node position is already known.
If the seismic operation is somewhat less than 24 hours per day, nodes can be programmed prior to deployment to operate only during actual production hours. During nonproduction hours, nodes will go into a low power mode, allowing nodes to operate for almost double the number of days. Nodes may also be programmed to start acquisition at a preset day and time in the future. This is useful during layout of very large spreads where production may not start for several days.
Nodes can record seismic data generated from all types of energy sources and using all types of source techniques.
Handheld Terminal (HHT)
Handheld terminals (HHT) are used to aid in the layout and the pickup of nodes. Handheld terminals comprise high-quality, survey-grade programmable GPS positioning devices, each utilizing FairfieldNodal’s proprietary software. When connected to nodes, the HHT downloads precise positional information to nodes, initiates nodal acquisition and can also test the nodes’ performance.
Nodes respond to the HHT with their serial numbers and report the status of internal tests. All this information is logged in the internal memory of the HHT, and this log is later transferred to the data recorder to provide inventory management and spread deployment status information.
A source controller is used to synchronize source activation, log source locations and log the source times from GPS (Universal Time Coordinate or UTC) for every epoch event. This log information is later used by the data recorder to aid in the segmentation of the continuously recorded seismic data from each node into short seismic trace records.
Data Download and Charging
After nodes are picked up from the spread, their data need to be downloaded and their batteries recharged. Nodes are plugged into data collection and charging racks (DCCRs) for this purpose. One or more data collection and charging rack is mounted in a suitable facility, typically located at the crew base.
Node data are downloaded from the data collection and charging racks into a redundant array of independent disks (RAID) system for temporary storage. RAIDs are controlled by a server-based data recorder. Shot information from the source controller is also supplied to the data recorder so that the long streams of node data from the RAID can be segmented according to each shot epoch event.
Segmented data from the data recorder are output for storage on suitable media such as tape, removable hard drives, flash drives or other devices for later processing at an appropriate processing center.