Ocean Bottom Node System

SPRINT ROV

Seismic Positioning Beacon 1

Compatt 6 with seabed nodes

ROV

What you need to know

Position nodes in up to 3,000 metres
Gives you the repeatability you need
High update rate maximises deployment speed
Based on field proven Ranger 2 USBL technology

Seismic surveys using autonomous Ocean Bottom Nodes (OBNs) are becoming an increasingly popular technique to acquire reservoir imaging data. Sonardyne’s acoustic navigation and data telemetry technology can be used to support all stages of these operations. When deploying and recovering nodes, their position can be accurately determined using Ranger 2. During data collection, Sonardyne’s wireless, high-speed acoustic communications technology uploads status data to the surface enabling operators to check that each node is functioning correctly.

Installed on the surface vessel, the Ranger 2 USBL (Ultra-Short BaseLine) positioning system tracks the position of the ROV deploying each node and also the node basket from where the nodes are withdrawn. As the ROV places each node on the seabed, a highly accurate position fix for the ROV and therefore the node, is recorded.

Ranger 2 builds on the simplicity and reliability of Sonardyne’s popular Ranger 1 system but adds support for the latest sixth generation (6G^®) acoustic instruments and Wideband^®2 signal architecture. 6G systems offer higher precision acoustic ranging, faster data telemetry and hardware that is easier to set-up and operate even in the most challenging subsea operating environments.

Transfer of node quality control (QC) information is performed using a low-power acoustic modem attached to each node. These modems communicate with a local subsea data collection transponder anchored several metres above the seabed. Multiple transponders form an acoustic network that autonomously hops the QC data, and on command, uploads it to a waiting surface vessel located anywhere within the survey area. Once received, the status monitoring software shows each node’s operating status. A ‘traffic light’ display allows operators to check the status of the entire node network and identify problems at a glance.

More about this product

Ocean Bottom Node System Overview

Ranger 2

Ranger 2 allows for multiple subsea targets to be tracked simultaneously from a surface vessel. To allow pre-plotted lines to be run and the active transponder list to be automatically updated without operator intervention, Ranger 2 is interfaced to a dedicated survey management application called HydroPos USBL V2.

Fitted in the vessel instrument room, the Ranger 2 and HydroPos software runs on a Navigation Computer connected to a Navigation Sensor Hub (NSH). The NSH provides the interface between the computer and the subsea transponders via the vessel-mounted HPT transceiver.

The software is easy and intuitive to use, requiring only basic operator training to become familiar with it. Ranger 2 includes an extensive array of tools to allow the user to assess the performance of the system, including real-time acoustic quality indicators, noise analysis and signal travel time displays.

Acoustic positioning operations can be monitored over a vessel network using either HydroPos USBL or Viewpoint which offers the added the functionality of supporting .dwg format backgrounds and geodesy.

Transceiver

HPT is a high performance, vessel-mounted acoustic transceiver that enables the targets being tracked with Ranger 2 to be precisely positioned. The HPT transceiver is also used as a modem with Sonardyne’s acoustic modem and subsea data collection transponders thereby allowing the transfer of short QC data messages between each seismic node and the vessel.

The deployment method of the HPT transceiver is critical to Ranger 2’s positioning and modem performance. It should ideally be rigidly mounted to the vessel well below the keel away from any weather or vessel induced aeration. Sonardyne’s hydraulic through-hull deployment systems are extremely rigid and ideal for permanent vessel installation, whether new-build or retro-fit. For short-term projects on vessels-of-opportunity, a high quality over-the-side deployment system is available that is practical to transport and install on a vessel whilst it is alongside.

ROV and Basket Transponder

Ranger 2 is compatible with a wide range of Sonardyne 6G and previous generation subsea transponders. For ROV operations the small, lightweight Wideband Mini Transponder 6 (WMT 6) is recommended. It is depth rated up to 3,000 metres and can operate as either a transponder or as a responder which offers faster position updates.

HydroPos USBL V2 Software

Survey data can be imported into HydroPos USBL from client supplied OGP P1 pre-plot files, CSV files or entered by the user directly. Final survey coordinates for the deployed and as-pinged nodes can be similarly exported in OGP P1 or CSV format. The raw survey data can also be exported as a OGP P2 file as well as a variety of other proprietary formats supported by many of the independent QC packages.

HydroPos USBL is configured around a graphical screen, providing the user with a clear visual display of the data acquisition process, whilst all raw and processed data is stored in a single log file to allow for easy archiving of the data.

Subsea Inertial Navigation

The addition of Sonardyne’s SPRINT technology allows full integration of Sonardyne’s 6G acoustics with a dedicated subsea inertial navigation sensor. SPRINT allows for the final position of the node to be fixed quicker than solely acoustics, thereby operational time on each node deployment.

Nodal Acoustic Telemetry

Sonardyne’s nodal acoustic telemetry technology allows for the transfer of a short QC status record from each 4C seismic node back to a master vessel, regardless of the position of the master vessel within the survey area. The data uploaded contains information such as the recording status of the node, along with parameters such as remaining data capacity and battery capacity. This data can be tailored to clients’ requirements but will always contain a unique node identifier. The node status record is transmitted via a small unit attached to the side of the node. Acoustic Micro modems have been designed to have minimal impact on the handling of the node, both onboard the vessel and subsea. Depth rated versions up to 3,000 metres are available, allowing for all known current nodal operations. The node status record is received in the water column by a network of subsea data collection transponders deployed across the nodal network. Anchored to the seabed on long strops and supported by subsea flotation devices, the transponders are typically deployed by ROV to ensure complete acoustic coverage of a specific section of the seabed network. This also ensures a transponder is not inadvertently placed directly on top of a node. Each transponder uses Sonardyne’s Wideband 2 signal technology to then transmit the status data packet from each node across the seabed network, acoustically ‘hopping’ from unit to unit until it is received by the transponder that is closest to the surface vessel. Data is then uploaded to the vessel-mounted HPT installed on the survey vessel for analysis. Once the survey is complete, the precision offered by Ranger 2 ensures that the ROV can navigate directly to each node to recover it. This ensures no nodes are left behind on the seabed. The transponders can be efficiently recovered by acoustically commanding them to release their anchor weights so that they float up to the surface.

System Performance

Feature	Specification
Operating Range	>6,000 metres
Operating Depth	3,000 metres
System Accuracy Typical Optimised	0.1% of Slant Range 0.2% of Slant Range
	Depending on the installation quality, system accuracy can vary greatly. Where every effort is made to ensure the rigidity of the deployment pole, an appropriate transceiver has been selected and the vessel’s AHRS is high quality, standard Sonardyne USBL systems have been proven to achieve 0.1% of slant range error. In 1,000 metres, this is equal to 1 metre.
Number of Targets Tracked	1 surface, unlimited subsea
Position Update Rate	1 second, independent of water depth
Output Telegrams	Supports all industry standard survey and DP telegrams, including OGP P1 and P2 formats when using HydroPos USBL software.
Data Rate	Up to 10 K baud
Maximum Number of Nodes	Unlimited