Keeping Jakarta afloat
In 2013, pipeline equipment and services specialist T.D. Williamson had to mobilise quicker than ever before. The job: isolate gas pipelines offshore Indonesia to keep gas flowing to Jakarta while urgent work was being carried out under the Lima Subsidence Remediation Project. T.D. Williamson’s offshore market development director George Lim recalls the project and the challenges it threw up for the team.
The phone rang one morning in the spring of 2013. After Syamsu Alam, Pertamina EP’s president director, hung up the phone, he knew he would have to make a quick and difficult decision that could affect employee safety, the citizens of West Java, and energy supply.
The Lima Flow Station, located off the coast of Jakarta in the Northwest Java Sea, was at risk of structural failure. The flow station, acquired by Pertamina EP in 2009 when they purchased BP West Java, was starting to sink into the seabed.
Seabed subsidence in a fixed offshore platform isn’t uncommon – especially in a flow station like Lima, which has been around since 1973. The sinking is caused by a release in pressure in the reservoir’s porous rock after years of oil production. This pressure reduction causes the rock to compact, which lowers the seabed, taking the platform along with it.
Now, the Lima Flow Station wasn’t going to disappear overnight, but the seabed subsidence was beginning to bring the platform too close to the water. Offshore platforms are built to stand high above the ocean, protecting the structure, equipment, and workers from potentially destructive wave force. The space between the average wave height and the platform – called an air gap – must allow a sufficient separation between the water and the station. Allowing Lima’s air gap to fall below that distance could seriously compromise the safety of the flow station’s production platform, compression platform, living quarters platform and bridges – especially if a strong storm caused significant waves.
Lima will be retired in 2026, but Alam knew that Pertamina EP couldn’t wait that long to fix the problem. He consulted with Jamsaton Nababan, vice president of surface facilities. After some deliberation, Alam and Nababan came up with a solution to the problem: raise Lima Flow Station by four meters.
Pertamina EP hired its main contractor and a project management firm to carry out what became known as the Lima Subsidence Remediation Project. The two companies got started right away and, for a moment, it seemed that the sinking station problem would be fixed without issue.
Shortly after the project got underway, Alam was presented with an even more difficult challenge: To safely lift the flow station’s most critical platforms and facilities, they would have to shut down several pipelines connected to it, severely limiting the gas supply for approximately three months.
This was the last thing that Alam wanted to hear. Pertamina EP is the main supplier of gas to West Java, including the big city of Jakarta. It supplies gas to Kujang’s fertilizer plant, a refinery in Balongan, and several power stations. The Lima field also supplies natural gas to millions of residential consumers, with many depending on it for their electricity. Disrupting the gas supply for a mere three days would be a problem. Three months would be a disaster.
To further complicate matters, Pertamina EP is a government-owned company. Any accidents or disruption in gas supply would have political implications. And, of course, shutting down the flow of product would cause them to lose profit.
In other words, the pipelines had to keep running no matter what.
Forming a solution
Rakhmat Sani, a sales engineer at T.D. Williamson (TDW), got the call from Pertamina EP. They explained that the project needed TDW’s expertise in a pipeline isolation project, specifically the installation of several lines to bypass the 14-inch and 20-inch main gasline pipelines (MGL) that extend from the TLA and TLD platforms to the L-PRO platform, as well as the 24-inch MGL pipeline that extends between the L-PRO and a port onshore. Pertamina EP wanted to isolate the affected lines while the bypass lines were installed – keeping gas flowing to Jakarta.
TDW specialises in isolating pipelines using hot tapping and plugging. Hot tapping involves connecting a piece of equipment to the pipeline, then making an opening in the pipeline so that the plug can be inserted. The company’s STOPPLE plugging system is used for hot tapping and plugging. It helps isolate sections of pipeline, then allows the rerouting of the product through a temporary bypass so that the isolated section of pipeline can undergo maintenance. This procedure allows the operator to keep the oil or natural gas supply flowing while repairs are made.
After the pipeline is repaired, a diving team comes in and plugs the openings created for bypass. Sani assured Pertamina EP that the line intervention and temporary isolation project wouldn’t be an issue – but then Pertamina EP revealed that TDW needed to get their part of the project done in just four months to avoid the gas shutdown – an unprecedentedly short timeline
Planning for success
TDW project manager Mohamad Ameen came on board to manage Pertamina EP’s isolation and rerouting project. Ameen knew he would have to go to extreme lengths to meet the client’s tight deadline.
“Typically, a subsea hot tap and STOPPLE isolation takes several months – but TDW was asked to plan, research, and execute in less than four,” explains Ameen. “We had never completed a project of this type so quickly. In fact, I don’t think anyone in the industry has completed such a big project in such a short time.”
Ameen and Edmund Ang, a TDW operations manager, didn’t waste a second. They, along with others at TDW, came up with a unique plan: To safely bypass the pipelines and keep gas flowing, they would need to perform nine hot taps, then execute STOPPLE isolations in six different locations. In order to complete the project in the four month timeline, the team would have to execute all nine hot taps simultaneously, followed by performing, concurrently, all six STOPPLE plugging operations.
Not only did TDW need to get the project done quickly, they needed a lot of equipment and personnel to complete it. Usually, the company uses equipment from its nearest location and builds more if necessary.
“Because our timeframe was so short, we opted to mobilise equipment from other locations around the world,” says Ameen. “That way we were able to get it all to Singapore to do a final assessment test before going offshore.”
“Such complex operations typically take several months to plan,” explains Ang.
All hands on deck
TDW, Pertamina EP and the contractors all met to plan every detail of execution. First, various pieces of hot tap and plugging equipment from North America, Europe, and Asia Pacific were gathered in Singapore, along with a team of expert technicians. Once they completed system integration testing and a mock-up simulation of 14-, 20- and 24-inch hot tap and STOPPLE plugging, the team was ready to mobilize to the offshore jobsite.
In hot tapping and plugging, the entire execution is performed by subsea divers. The underwater operation takes a great deal of skill to avoid human error. For example, if the plug setting is not completed, the pipe contents can escape, causing a potential safety hazard and wasting valuable product.
A diving contractor was brought on to support the project with divers and dive support vessels (DSVs). Working in five-member teams at depths of 131 feet below the surface, the divers deployed a 1200 XL and a SubSea 1000 XL Hydraulic Operated Tapping machine. They took field measurements on the subsea mechanical clamps to calculate the cutting distance, then mounted the tapping equipment and completed the hot taps to cut into the pipeline.
Saving time with simultaneous isolations
With all nine hot taps completed, it was time to carry out the task of installing six STOPPLE plugging heads onto the mechanical fittings and setting them into position, so that gas could continue flowing through the bypass lines while maintenance was performed on the main pipelines. In order to get this done within Pertamina EP’s timeline, the STOPPLE plugging operation had to be performed in six locations at once.
At this critical juncture, the offshore technicians ran into a problem that almost delayed them. “We discovered that a piece of equipment had been damaged during execution,” recalls Ameen. “We had actually never had a piece of equipment damaged like that before, and we didn’t anticipate it.” The project manager quickly procured a replacement and the project was able to move forward.
“When subsea, just one hot tap can take several weeks, including planning,” Ameen explains. In just 23 days, the team completed all hot tapping, plugging and isolation of all lines – a feat that kept Pertamina EP’s project perfectly on schedule.
With STOPPLE plugging equipment in place, the pipelines remained safely isolated while the bypass lines were commissioned and the L-PRO platform was raised. The entire operation took only 63 days, keeping safely within Pertamina EP’s timeline.
How was the team able to pull off the tapping and plugging operation in such an unprecedented amount of time? Edmund Ang credits use of the latest plugging technology.
A seal that snaps into place
Plugging the openings where the bypass occurred is the last phase in a hot tap and plugging operation. Murky waters, such as those at the Lima flow station, can complicate an operation, because it’s difficult for divers to determine exactly when the plug has been set. With divers struggling with traditional, unwieldy equipment, each plug setting can take several hours.
To save time, the team decided to try something previously performed only onshore: Installation of LOCK-O-RING Plus completion plugs.
This completion plug technology was patented in early 2011, and has been successfully used to complete multiple onshore STOPPLE isolation jobs. The technology had been thoroughly tested for subsea, but had not yet been used on a subsea job.
Each STOPPLE fitting has a flange with no side openings, which reduces any potential leak paths. This flange helps with the attachment of the bypass system. Once the bypass is removed, the flange can also assist with the attachment of the LOCK-O-RING Plus completion plug.
A feature of the completion plug that made it the right tool for Pertamina EP’s project is that its interlock system indicates when the leaves are fully extended, which lets divers know, with certainty, when it is positively set in the flange. Plus, the plug setting machine used to set the plug transfers pressure from the pipeline to the inside of the plug setter, balancing the pressure by counteracting the force pushing against the machine. Altogether, this system provided divers and engineers with a quicker and safer way to complete their work underwater.
Pertamina EP’s customers continue to cook
The Lima project was a distinguished introduction of the LOCK-O-RING Plus completion plug to its new subsea application. Now that the technology has proven to be effective underwater, the door has been opened to using the technology in similar projects following the shared experiences and lessons learned by Pertamina EP, the contractors and TDW’s project managers.
Most importantly, Pertamina EP was able to raise Lima Flow Station without any incidents or disruptions to the gas supply. Jakarta and the rest of West Java had gas for cooking and power, and Pertamina EP didn’t lose profits from a shutdown. “We asked our team to make the impossible possible, and they did it,” says Nababan.
Source: Offshore Technology