Preventing bugs

OE Staff

August 1, 2016

The spotlight now shines on how to better integrate multiple complex software systems during drilling rig construction with beneficial results.

Songa Endurance. Photos from Songa Offshore.

Software drives almost every system we use in the 21st century, from our cars to telephones and even home heating systems.

Yet, when a rig leaves a yard its plethora of interconnected software systems haven’t had the same level of scrutiny as the hardware. Software version changes, which can be frequent, are not traced or checked to anything like the level hardware components are traced, from materials source through manufacturing, delivery and testing.

The result can be lengthy commissioning, as bugs are tracked to their source and ironed out, and even complications during operations.

For the past 10 years, DNV GL has been researching and working towards an integrated software dependent systems (ISDS) standard (DNV-OS-D203) to prevent such glitches. The aim is to enable full tracking of the quality and version control of all integrated software systems, so that the yard and the user knows the status of all systems, the latest updates, if any still require close-out at the yard, at any given time.

OE reported on a pilot project DNV carried out with Seadrill back in 2010 (OE: October 2010), which was one of the first trials of the methodology. Seadrill had applied the technology retrospectively to a then recent newbuild.

ISDS process overview. Image from DNV GL.

Cat-D quartet

Now, ISDS has been put to a bigger test. ISDS has been used on Songa Offshore’s four new sixth generation Cat-D semisubmersible rigs, built to be used by Norwegian oil firm Statoil for work on the Norwegian Continental Shelf. Statoil, when it ordered the rigs, made the requirement that ISDS would be used as part of the newbuild program.

All four units have been delivered, with three, Songa Equinox, Songa Encourage and Songa Endurance, now working offshore Norway, while the fourth unit, the Songa Enabler, was delivered late March and is due to start working, after its voyage from Daewoo Shipbuilding & Marine Engineering’s yard in South Korea, in Q3 this year, on the Snøhvit field.

Although the project experienced delays and overruns at the yard the implementation of ISDS combined with the independent hardware in the loop (HIL) testing performed by Marine Cybernetics has been seen as a success.

The Songa Equinox was the first rig to go into service, in December 2015. “The ISDS and HIL testing done on the Cat-D project has definitely made a positive difference for the reliability of the integrated systems in the scope of ISDS,” says Trond Jan Øglend, E&I Engineer for Songa CAT-D OPS Prep. “Cat-D has very complex software integrated systems and is performing very well; by now we would normally have had to deal with a lot more software integration issues.”

Change management

Songa Equinox

So, why do this? Normally, a rig is commissioned and delivered, and its status at that point sets a base line, whatever state the software systems are in, which is traditionally not part of the yard’s remit. This means every rig’s systems, even if they are part of a newbuild program of multiple sister rigs, can end up being different as changes can be made to one rig, but not another.

“Before, you would receive a rig and there would have been no software control,” says Martin Coward, engineering manager for the Songa Cat-D project. “We have got this version, but has it been tested? With what software was a particular function tested? If something was changed during commission how does anyone know? Normally, someone comes on and picks up the functional description for X to do Y. But if you have changed the software, there is no guarantee that X will do Y. It is very easy to make a small change that could impact on someone else’s systems without knowing.”

Patrick Rossi, DNV GL ISDS project manager for Cat-D comments:

“Tracking tools enabled by ISDS can also be used for decision making and staffing of needed software resources for approval and validation of changes.”

As software is often unfinished when systems are delivered to the yard, interfaces are not always completely engineered or tested, so software interfaces need to be coordinated at the vessel level.

Software updates are also always happening during construction: tuning, bug fixes, changes to software requirements (thousands of changes on hundreds of different programmable logic controllers (PLCs) and computers); so the tracking and timely (successful) testing of integrated software systems is a real challenge.

The original manufacturer of the equipment also sometimes sends updates to their firmware that are not requested by the project and may cause unstable conditions and problems during construction and commissioning, if they are not coordinated and planned.

Furthermore, software is not always properly addressed during design/reliability analysis; ISDS RAMS requirements highlight the need for software focus and track the outcomes of failure modes throughout the project. The list of integrated software systems onboard the Cat-Ds helps illustrate the complexity involved:

“All of the above PLCs and computers also come with manufacturer’s firmware (which is low level manufacturer software), so actually there are more sources of software to be aware of,” Rossi says.


ISDS implementation on the Cat-D rigs was done in such a way that as each new rig was rolled out, learnings from the last rig were transferred to the next rig, and as new learnings were introduced in each new rig, they were in turn rolled out across the previously built rigs.

Initially, the ISDS scope hadn’t included the main engines, but this was brought into the system as it was seen as being a mistake not to include them.

The result is a fleet working on the same version software systems and shorter commissioning time, Coward says. “It has been hard work but it has been worthwhile,” he says.

With ISDS, all the software systems are tracked, during the build, commissioning and post commissioning so that the current as well as any past setup can be seen.

Having the documentation which shows which version of software is being used at any one time means that during the build, if an interface isn’t working, it is easier to tell a particular manufacturer or vendor what version of software they need to comply with in order to make the interface work.

This gave Songa Offshore far greater control over supplied software. Standard supplier software change management procedures were improved, more software faults were identified before their usual discovery phase during operations, and tracking the status of software design documents was much easier.

“It [ISDS] also helps in the future when we come to test anything we can show this is where we were at that point in time and how we got there. If there are any changes, we can go back to the last point we know it was all working,” Coward says.

“Should there be an accident or some equipment damaged, the first thing anyone wants is to go back to a base line that would show everything has been tested and working. In the past, that would be delivery.“If we changed something on the fourth rig, we ensured that we followed through on the third, second and first rigs,” he says. In fact, the system is designed so that any change made, if it’s applicable to previous vessels, needs to be rolled out to the other vessels before the task can be closed out.

This means that you don’t end up with four rigs each with their own systems,” Coward says. “It is a lot of work, without a doubt. With so many vendors interfacing with each other, it was a lot of work and we took it to the nth degree. But it has definitely been a benefit.”

“A tremendous amount of work by an entire dedicated team preparing all of the rigs for Norway was done to ensure a timely acceptance phase; many things can go wrong and having ready, stable, completed software also plays a key role. For CAT-D the acceptance phase was completed in four weeks which is a noticeable achievement for such sophisticated rigs.” says Mark Bessell, Songa COO.