On-Demand Ocean Bottom Node: A New Era in Deepwater Seismic Monitoring

Shell Brasil, Petrobras, Sonardyne, and SENAI CIMATEC are developing autonomous technology that transforms how Brazil's challenging pre-salt fields are monitored. Now entering a major pilot array phase, the On-Demand Ocean Bottom Node (OD OBN) program promises efficient, cost-effective 4D seismic surveillance, with fewer people and lower environmental impact. This milestone marks a step closer to a fundamental shift in deepwater reservoir management.

The Challenge

Brazil’s pre-salt reservoirs lie in more than 2,000m water depth, plus another 3,000m beneath the seabed, making seismic imaging particularly challenging.

Traditional seismic surveys using ocean bottom nodes (OBNs) provide high-quality seismic data, but are often expensive and logistically complex, involving the repeated deployment and recovery of nodes using remotely operated vehicles (ROVs).

These factors can limit the frequency and economic viability of frequent 4D seismic campaigns, which are essential for understanding reservoir dynamics over time.

This is particularly challenging for monitoring large pre-salt carbonate fields where production by alternating water and gas injection (WAG) generates subtle and complex 4D signals that are difficult to measure.

These signals require on-demand monitoring with sufficient fidelity and repeatability to overcome the high levels of survey noise prevalent in conventional node-based surveys.

On-Demand Ocean Bottom Node 

Launched in 2018, the OD OBN program is a research and development collaboration between partners Shell, Petrobras, SENAI CIMATEC and Sonardyne, supported under the Research Development and Innovation funding clause of the Brazilian National Agency for Petroleum, Natural Gas and Biofuels (ANP). The On-Demand Ocean Bottom Node (OD OBN) program marks a step in addressing these challenges, providing an approach to time-lapse seismic data acquisition.

The program is a new system for acquiring 4D seismic data, which delivers more efficient and cost-effective surveillance of complex pre-salt fields. At its core is a long-term OBN system that can remain on the seabed for several years, capturing seismic data that can be recorded and harvested “on-demand” using autonomous underwater vehicles (AUVs), without the need for repeated deployment and retrieval cycles.

Significant quantities of seismic data are harvested wirelessly using an AUV like Saipem’s ‘Flatfish,’ which implements the through-water optical interface to interrogate the OD OBNs, as developed under a separate ANP program sponsored by Shell.

This AUV data harvesting approach eliminates the need for node recovery, reducing vessel time, operational complexity and associated costs.

Key Sonardyne technologies include wireless acoustic communications, required for long range recording control and node clock time offset measurement, and Sonardyne’s BlueComm extremely high-speed optical communications for short range data harvesting to a nearby AUV or remotely operated vehicle (ROV).

Results

Over 2,000 days of trials of pre-production nodes have been conducted across various pre-salt fields including Sapinhoá, Itapu and Buzios. These have successfully demonstrated acoustic control, high-fidelity data acquisition and optical data harvesting using BlueComm, as well as comparing OD OBN data with that of other commercial nodes.

The final round of tests concluded successfully in 2025, with results presented at the IMAGE ‘25 conference in Houston and SBGf Rio’25 conference in Rio de Janeiro. Ultimately, the team deployed 84 OD OBN units, the data from which will be harvested and used to generate the first 4D image in this field.

Next Steps

A pilot array of 660 pre-production nodes is currently being produced at a new manufacturing facility in Camaçari, near Salvador, Brazil. Hundreds of these nodes will soon be deployed at the Mero field operated by Petrobras for extended testing and performance evaluation.

The long-term vision is to use autonomy and state of the art communications technologies to enable operators to conduct more frequent ‘on demand’ seismic surveys, with higher fidelity data, at a fraction of the cost of conventional seismic survey methods.

This capability will provide clearer insights into fluid movements and pressure changes within the reservoir, helping to optimize production strategies, improve decision making and enhance recovery rates in one of the world’s most challenging offshore provinces.

OD OBN is not just an incremental improvement, but a shift in how the industry approaches deepwater reservoir management.

Multiple OD OBN nodes. Credit: Social media reproduction

The Saipem Flatfish. Credit: Saipem