By Kelli Ainsworth, Associate Editor
As operators drill more wells in deeper waters and harsher offshore environments, loop currents and the vortex-induced vibrations (VIV) that they create are becoming more of a concern for drilling contractors. Trelleborg has introduced the Helical Buoyancy drilling riser technology in order to mitigate VIV in these deepwater drilling environments, Alan McBride, Vice President Drilling and Syntactic Products for Trelleborg, told Drilling Contractor on 1 May at the 2017 OTC in Houston. The company also recently launched the FireNuts passive fire protection solution for bolted connections. This technology is currently being installed on a platform for Statoil.
The Helical Buoyancy riser technology builds on some of Trelleborg’s existing riser technologies, Mr McBride said. The company has been making syntactic foam attachments to reduce the weight of drilling risers since the 1970s. Syntactic foam can reduce the weight of a drilling riser by as much as 95%, making it much easier to run. In addition, its Helical Strength solution has previously been used to reduce VIV on production risers. “This is a raised fin on a polyurethane product that’s formed in a helical. It disrupts the flow of the water around the pipe so you cannot lock in the frequency and it can’t vibrate,” Mr McBride said.
Because drilling risers are larger than production risers, the external fins would create too much drag, he added. “We took that same concept and made some recess grooves in the buoyancy. We mold them into the product that creates a helical shape.” When water flows around the drilling riser, the grooves disrupt the flow of water and prevent VIV. Trelleborg has already deployed this technology for a Diamond Offshore’s Ocean BlackRhino drillship in the Gulf of Mexico. Two more strings, which will also be deployed for Diamond Offshore, are being assembled.
Along with the Helical Buoyancy design, Trelleborg is also developing sensors that can be run on the drilling riser. The development of the sensors was spurred by the company’s desire to evaluate how effectively the Helical Buoyancy was able to reduce VIV. The sensors can measure temperature, riser depth and deflection, among other variables. At this point, the data collected by the sensors can be accessed once the riser is pulled, but Trelleborg is working to make the data available sooner. “What we’re working on ultimately is real-time monitoring,” Mr McBride said. “That’s what everybody wants. They want instant information.”
Trelleborg also recently launched its FireNuts technology, which is used to provide fire protection for bolts where flanges are connected on offshore drilling rigs and platforms. The bolts are the weakest point in a connection, Doug Marti, Trelleborg Market Development Manager, explained. “If a flange is in a fire on a rig, the bolts will elongate under the temperature. Once they elongate, they will break the face of the flange so that high-pressure gases can now escape,” he said.
Statoil approached Trelleborg, with whom they have a master service agreement, asking for a solution that would better protect the bolts and increase the time before they succumbed to failure during a fire. “In their operating procedure, they need six minutes to offload any high-pressure gases and remove any hydrocarbons from the pipes themselves,” Mr Marti said. “They were getting about three minutes on smaller bolts, and maybe four to five minutes on some of the larger ones. With the FireNuts, we’re able to actually double that time and, in some cases, in the larger ones, we tripled the amount of time it takes for those bolts to elongate and break the seal on the flanges.”
The protection provided by the technology was confirmed on Trelleborg’s ISO-rated fire rig. Testing qualified the FireNuts for a jet fire, in which temperatures can reach 1,400°C nearly instantaneously. Statoil plans to deploy the technology on a platform that is being built in South Korea.
The nuts, which are made of rubber, contain a wire mesh that provides insulation in the event of a fire. At this time, company is developing a version of the FireNuts that can provide the same protection without the wire mesh. Removing the wire mesh would allow the material to be injection molded and extruded directly onto pipes, allowing the material to provide passive fire protection in more places on the rig or platform. “The purpose of it all is to save people and to increase the amount of time it gives them to evacuate, should it get too bad,” Mr Marti said.