Trelleborg unveils new buoyancy system

HOUSTON—Trelleborg A.B.'s Offshore and Construction business is offering a landing string buoyancy system that company officials said is safer and more cost-effective than traditional deep water oil and gas drilling systems.

Working under an agreement with Landing String Solutions L.L.C., the developer of the technology, Trelleborg qualified the necessary landing string buoyancy materials and successfully manufactured the first Landing String Solutions' patented system.

Initially, it was successfully deployed in the Gulf of Mexico in April 2016, "proving the robust nature of the design and delivering the anticipated results," said Antony Croston, business group director of Trelleborg Offshore and Construction in the U.S., which is based in Houston.

Development of the technology, however, "took several years due to the harsh environment in which the product must operate," he said.

Deep water applications

Croston said the primary application of the system is in deeper well formulations where rig installation capacity becomes a limiting factor in well design. It reduces the weight of the landing string/hook load while running heavy casing strings in deep water.

"The result of this is to effectively increase the hook capacity of the vessel, which allows more casing to be installed on a single run," he said. When the system was used in the Gulf of Mexico, it simplified the well casing program and removed significant time and risk from that operation.

He noted that Madisonville, La.-based Landing String's buoyancy "knowledge comes from a deep understanding of operations, engineering, technology, best practices and confidence in people who have extensive industry experience."

In December 2017, Trelleborg and Landing String, which had worked together in the past, signed an agreement under which Trelleborg manufactures products for Landing String's system that features 100 percent composite materials. The companies' aim is to market the system to a wider customer base globally.

Croston said at the time the new pact was signed that the agreement "builds on an existing relationship where Trelleborg augmented Landing String's vision and qualified a range of nonmetallic materials to operate in drilling fluids through a range of pressures in combination with high temperatures experienced in drilling operations. This included clamp components as well as protected buoyancy elements."

Trelleborg's product modules are made of a high grade syntactic foam that is encapsulated by a polyurethane shell. Clamps used to secure the modules in place are made out of what a spokeswoman said is essentially a high-strength, fiberglass epoxy composite material.

The system's core technology is built around the syntactic foam, which "has been in use for well over 40 years over the full range of ocean depths. With this application, the fluid in which we were required to operate was drilling mud as opposed to sea water.

"There are many types of drilling mud that can be used in well construction operations, and almost all of them are chemically incompatible with traditional syntactic foam. The challenge, therefore, was to understand which components within our systems were affected by the different fluids, and what alternatives would be used to replace them."

Croston said that involved an extended test program aimed at redesigning the company's systems from the ground up while still relying on Trelleborg's established manufacturing processes and engineering know-how.

Trelleborg successfully overcame the challenge of providing buoyancy while drilling in mud. "Failure could result in significant rectification costs to recover the well," he said, "so we had to be sure that the qualification testing covered all the possible scenarios and left a good margin of safety."

Continuous upgrades

Following its first use, several modifications were identified which improved the functionality and efficiency of the first product, he said. Landing String and Trelleborg are now working together to develop the next generation landing string buoyancy solution.

In fact, Landing String has applied for a number of patents to cover some of the concepts. The firm's U.S. patents have been approved and the global patents are still pending approval.

However, Croston said, "we intend to gather more data from subsequent uses before embarking on a second-generation product."

By removing complete steps from the construction operation, "large sums of money can be saved by reducing rig time," he said. That improves the economics of drilling operations, he added, and compounded over time can potentially allow contracted rigs to drill more wells within a fixed period of time.

"Offsetting the weight of the landing string is beneficial in simply reducing the load on the rig to increase the margin of safety," Croston said. "This gives more capacity for the rig to tolerate the dynamic loads caused by wave motions on the vessel offshore—meaning that the rig can undertake installation operations in a wider environmental window."

In addition to Trelleborg's work with Landing String on the buoyancy system, Trelleborg has ties with a Landing String sister company, ExPert Riser Solutions. After working together in the past, ExPert Riser has become an authorized repair center for Trelleborg's offshore operation.

When ExPert Riser was brought on board, Croston said, it expanded and improved Trelleborg's Drill Riser Buoyancy Module repair offering. Through a license agreement with ExPert Riser, Trelleborg has upgraded its capability as the sole DRBM supplier offering certified third-party repair services with in-house production standards, he added.