Seismic acquisition in swamps, marshes and shallow-water transition zones poses a particularly vexing challenge for contractors tied to conventional cabled recording systems. Traditional crews spend an inordinate amount of time troubleshooting leakage issues caused by inevitably damaged cables and, at water depths of 60-plus m (197-plus ft), contractors are limited in their ability to conduct surveys at all. These marine challenges waste time and impede productivity at the very least; at worst, they put workers at much greater risk with every maintenance issue that requires attention.

Understandably, seismic contractors and oil companies alike for quite some time have been on the hunt for a low-cost shallow marine system that not only improves a crew’s operational performance but also allows crews to work more safely. Using the technology of its Z700 nodal acquisition system, FairfieldNodal developed the Z100 nodal acquisition system, which is designed to meet the challenges of seismic acquisition in transition zones and shallow water.

Recent field trials in the Gulf of Mexico proved that the Z100 system provides the same advantages of the Z700 and Z3000 marine nodes, yet the Z100 nodes’ reduced size and lighter weight allow smaller boats to handle them without the need for a sophisticated node-handling system. The Z100 autonomous node systems operate with near 0% technical downtime and no troubleshooting required. Production rates are increased while HSE exposure for companies and crew members is reduced.

Weighing 26 lb, the Z100 node is lightweight and man-portable and can acquire multicomponent/4-C data from onshore out to a water depth of 300 m (984 ft). Because the Z100 nodal system shares the same data management system as FairfieldNodal’s ZLand system, seismic contractors can operate a single crew with a combination of ZLand nodes and Z100 nodes to overcome water obstacles such as lakes and rivers found in traditional land surveys.

Each Z100 node contains a highly accurate chip-scale atomic clock to provide acquisition-corrected timing of plus or minus 0.1 ms when deployed for 30 days. Typically, crews deploy the Z100 nodes by boat via a rope system or place them in the water individually with an anchor and float assembly for easy retrieval. Dual-tilt sensors and an internal digital compass make it possible to correctly reorient the data received from each of the three orthogonal omnidirectional velocity sensors. The Z100 nodes’ circular shape and specific gravity allow excellent vector fidelity and coupling along the seafloor compared to rectangular or box-shaped nodes.

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