StatoilHydro Uses HART Communication to Deliver Natural Gas from Under the SeaPROJECT OBJECTIVES
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SOLUTION
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RESULTS
- HART technology helped the plant meet a commissioning schedule
- Diagnostic data enhance compliance with the company's Total Reliability Initiative for higher efficiency, asset availability and safety
- A full-time connection between HART-enabled devices and the control system’s asset optimization package allows real-time tracking, troubleshooting and fault diagnosis
By designing in the advanced communication and self-diagnostics capabilities of HART technology, Norway’s StatoilHydro and its partners started efficiently delivering natural gas to the U.K.
When winter strikes, you need heat to beat back the cold. It would be best if the fuel were reliable, plentiful, and relatively clean burning. Now consumers in the U.K. have a new source for that heat, natural gas and condensate pumped across the ocean from Norway’s subsea Ormen Lange gas field. They’ll warm water for tea, cook food, heat homes, generate power and otherwise use the fuel for years to come.
StatoilHydro Offshore Plant – Ormen Lange
They’re able to do so, in part, because of HART technology. Erling Ramberg is an automation lead engineer at the Norwegian oil company StatoilHydro. The firm designed the onshore processing facility that produces the natural gas and condensate shipped to the U.K. He notes that the goal was to be as efficient as possible and that HART-capable transmitters and valves were chosen for this and other factors.
“It has to do with size of the plant, of course, and the location out on the island. Also, we do not want to bring in more people than required,” he says.
Up from the Cold, Dark Sea
Discovered a decade ago by one of StatoilHydro’s parent companies, Ormen Lange is a natural gas field off the Norwegian coast. It’s large in more ways than one. It measures 40 kilometers long and eight wide. It also has proven gas reserves total nearly 400 billion cubic meters, an amount projected to be able to supply up to 20 percent of the natural gas needs of the U.K. for the next forty years.
But Ormen Lange is not easy to exploit. The gas field itself lies roughly 3000 meters below sea level, buried beneath an uneven seabed and sitting under 800 to 1100 meters of water. Situated 120 km off the coast of Norway, the site experiences some extreme natural conditions. There are subzero temperatures, whether measured in Fahrenheit or Centigrade, most of the year. The seas are stormy, with strong underwater currents.
Subsea wells in seabed templates
The project that brought this fuel up from the bottom of the sea and into British homes consists of a 24 subsea wells in four seabed templates. The output of the wells is sent in pipes 120 km to Nyhamna on the island of Aukra on the west coast of Norway. There the fuel is processed and readied for shipment to the U.K. via a 1200 km long undersea pipeline.
Ramberg notes that direct pumping of the fuel to shore-based processing won’t be problematic because special steps are taken to prevent pipe-clogging due to freezing of the liquid. That’s done with an on-shore monoethylene glycol (MEG) plant. “We pump the MEG liquid out to the wells, inject it in the pipelines and transport it with the gas to shore to prevent freezing.”
Meeting the Challenge for Less
Once onshore, the MEG is removed and reused. The fuel then has to be processed and readied for shipment to the U.K.
When designing the plant, StatoilHydro faced several constraints. One was the remote location, another was the sometimes harsh weather, and a third was the size of the facility. As finally built, the on-shore plant is one square km, with a main control room and 10 substations. “This plant is quite large,” says Ramberg.
An overriding concern in the design was the need for absolutely reliable operation. No one, after all, wanted a consumer in the U.K. to turn on a burner and get nothing out because of a problem with a plant across the sea. The company, quite naturally, also wanted to accomplish all of its goals as efficiently and with as little onsite manpower as possible.
Ormen Lange Onshore facility
Ramberg recalls the technology selection process. Given the constraints, the ability to do predictive diagnostics was particularly important. With that capability, the health of a valve or other component could be gauged and maintenance could be done as needed. Valves wouldn’t be changed out too soon, which would waste money. They also wouldn’t be changed out too late, which could potentially jeopardize operations.
There were other benefits to having a wealth of diagnostic information. With the right data, it should be possible to identify the root cause of a problem. It might then be possible to correct the issue remotely, meaning fewer personnel would be exposed to harsh weather and possibly dangerous conditions. What’s more the collection of data could, over time, lead to the elimination of some problems as root causes were identified and fixes implemented.
Because of the advantages of a communication rich approach, the company selected HART Communication technology to deliver the device diagnostic information they were seeking. The finished plant has about 1400 separate HART-enabled field devices connected on-line—full time. Of these, about 350 are valve positioners, with most of the rest transmitters. A handful of traditional 4-20 mA anti-surge valves are connected to HART multiplexers so that their data can be converted for communication.
Control is handled by a DCS with secondary controllers in the substations handling the interface between local devices and the plant-wide controller. As might be expected given the need for reliability, there are redundancies and intelligent approaches built into the setup. Some of these aren’t those typically thought of or used. For example, there’s a robust video conferencing capability so that experts from around the world can meet virtually to help diagnose problems and propose solutions.
After processing at the plant, the fuel begins a trek to the U.K., traveling 1200 km before arriving at a terminal at Easington at the other end. “It is a very long pipeline. I think it is the longest subsea pipeline so far,” says Ramberg.
Operations Begin
He notes that startup of the operation was an activity that took some time, with an eye toward full production over a span of months. “The startup was an activity going on for weeks, but the actual startup was when they opened the valve to the well,” he says.
Ramberg adds that HART technology helped the plant meet its commissioning schedule. However, in some sense, his job is done. Starting in December, operation of the plant was taken over by project partner A/S Norske Shell, the Norwegian member of the Shell family.
Graham Baird, a condition monitoring engineer for A/S Norske Shell, will be one of those responsible for monitoring of the plant’s day-to-day operations and health. He’s had input in the design phase, particularly with regard to what’s needed for operational monitoring of intelligent field equipment condition.
While there hasn’t been a lot of operational data so far, what the HART-enabled technology has delivered is promising. Baird cites the control system’s asset optimizing package and device manager. “Early indications are that these will give us a lot of useful actionable data, as they are online systems scanning the HART-enabled instrumentation continuously,” he says.
With alert reporting activated, work can be prioritized, scheduled, and tracked. Baird notes that so far fault diagnosis has been made very quickly, thereby enabling corrective action to be taken in a controlled manner. Often, this has allowed fixes to be made directly to the root cause of the problem.
There also can be synergies with other non-HART condition monitoring systems. For example, compressor performance can be influenced by surge valve conditions, instrumentation calibrations, and so on. With more diagnostics data available, it’s possible to cross reference between systems to establish why equipment may not appear to be performing according to design.
“All in all we get a much better overall view of the plant asset condition right now” sums up Baird.
He explains that the use of HART technology and the wealth of diagnostic information it provides aligns with Shell’s Total Reliability Initiative. Getting that more informative picture also helps plant operators rest easier at night, Baird says.
“Having a large number of instruments and valves connected to the HART-based systems for diagnostics can help us achieve a high availability for safety related instruments, critical process instruments and control valves. This gives plant operators the confidence that they have properly operating control equipment.”
Thus, an intelligent application of HART technology helps keep the U.K warm. With the predictive diagnostic capabilities built into the system, the Ormen Lange plant should be able to do so in a cost-effective manner for years to come.