Developing tracking and signalling pigs to work at extreme depths creates new challenges.

Pre-commissioning pigs pass along subsea pipelines and may be pre-installed into launchers months and sometimes a year, in advance of flooding, cleaning, gauging, and testing operations.

Subsea pigging provider Online Electronics says that pressure rating, battery life, and delayed-activation techniques are examples of the parameters that need to be met to ensure the integrity of pigging equipment matches the intended purpose.

Deep water pigging in Brazil

In 2009, Petrobras developed the Hybrido gas field, offshore Brazil. The field development involved the installation of 141 km of flexible and rigid lines in four different fields in the Santos, Espirito Santos and Campos basins. Subsea 7 was contracted to install and commission the pipelines. This field involved water depths of more than 2,000 m, over 100 km from shore.

Online Electronics supplied pig-tracking, signalling, and data-logging equipment that enabled proof of launch, proof of receipt, and a means of tracking pigs. All products delivered met the battery-life requirement by incorporating pressure-switch activation where appropriate, while also complying with the necessary pressure rating.

Petrobras’ safety standards require that any subsea pipeline is fully tested to one-and-a-half times its operating pressure. Online Electronic’s temperature and pressure subsea data-logging system was used to monitor, record and report pressure and temperature data for each pipeline hydrotest. Its function is to secure the data while freeing up the support vessel to continue to the next phase of operations.

Online Electronics said that the technology supplied had to confirm that various events had taken place in the interests of optimum operational efficiency and optimal vessel utilisation.

Providing solutions with depth

To best contribute to the success of operations, such as those at the Hybrido field, Online Electronics said that it has to understand, from information supplied by its clients, the logistics of each project. A method statement or pipeline pig monitoring and testing philosophy statement is then prepared and the appropriate equipment can be offered, for example acoustic, electromagnetic (EM), magnetic or ultrasonic solutions to best suit the demands of the project.

Different systems work better in different areas. EM technology operates well in gas-filled, buried pipelines and in pipe-in-pipe installations. Acoustic systems have a greater detection range. Magnets can be used where there is inadequate space to house transmitters or pingers. Ultrasound is a very effective method for pig signalling in topside applications.

Online Electronics said that its 4000SD unit can be strapped to a receiver prior to deployment or attached to a receiver by a remotely operated vehicle, which can then interrogate the unit after all the pigs have arrived. An acoustic modem or high-power beacons can be added to enable confirmation of events to remote locations up to 8 km away.

In addition, the company said that its gauging-run integrity data system transmits data through a pipe wall, giving confirmation of the condition of a gauging plate with the time of an event if the plate has been damaged. This enables the client to continue with the hydrotest immediately after the completion of the gauging pig run, avoiding the need to recover the pigs to manually inspect the plate, saving a lot of vessel time.