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High-speed oil-free intelligent motor to make North Slope debut Smaller size makes truckable modules possible for equipment which will produce miscible injectant for enhanced oil recovery Kristen Nelson PNA News Editor
What’s small enough to go up the haul road, requires no lubrication and runs on electricity rather than diesel?
The high-speed oil-free intelligent motor which will drive the compressors ARCO Alaska Inc. will use to make miscible injectant for the Point McIntyre field.
It’s a first for the North Slope. In fact, this one-of-a-kind compressor motor will be only the second of its type in the world.
Raymond Eastlack, an ARCO Alaska engineer who is Point McIntyre EOR project leader for Shared Services Engineering, told PNA in early May that rotors in the compressor cases and in the motor are levitated on magnetic bearings.
Normal technology, said Kris Fuhr, ARCO Alaska operations superintendent for the Greater Point McIntyre area, uses roller or wall bearings and a film of oil for lubrication. But, Fuhr said, there’s no oil here. No metal-to-metal contact “There’s no metal-to-metal contact. No oil,” said Eastlack. The bearings levitate in a magnetic field, with the position of all the rotors monitored constantly. If a rotor drifts out of position, he said, a signal is sent back to the control panel and the control panel changes the field around the rotor to move it.
Since the system needs no lubricating oil, he said, “all the attention it needs is electronic.” A normal compressor requires a lot of mechanical attention — looking after lubricating oil system and “a lot of moving parts that touch each other and therefore wear out. But this thing doesn’t have any parts that touch each other and it’s more electronic than mechanical as compared to previous installations,” Eastlack said. System small The motor rotates at 14,000 RPMs, Eastlack said.
“Compared to a conventional motor it’s very small,” he said, “because the horsepower is derived from speed more than torque. … And because it is driving at the speed that the compressors need, you don’t need a speed-increasing gearbox between the motor and the compressors.” And that, he said, was a heavy item. A conventional format motor with speed-increasing gearboxes for each compressor and an oil lubrication and oil seal system would have meant a 90-ton skid. The skid for this system, he said, weighs 30 tons.
Because the system is smaller than a conventional motor and compressors, Fuhr said, it could be done with truckable modules versus sealift modules.
“It opened up a whole economic case for us as well as linking it to the ability to fabricate the stuff here in the state.” VECO Engineering is doing the site engineering — and also introduced the concept of the high-speed oil-free intelligent motor. VECO Construction is building the truckable module which will house the compressor section and other equipment such as scrubbers, piping and fans, Fuhr said. Another truckable module has some of the electrical gear.
The small size, he said, “allowed us to package it here, truck it up the haul road and install it, versus sea lifting it…”
International project The assembly is being done by Sulzer in Switzerland, Eastlack said. But it’s an international project. The motor was fabricated in Belgium; the bearings in the motor and compressor cases were built in France; the seals in the compressors were built in England.
This is the second combination of these technologies, Fuhr said. But it’s a one-of-a-kind machine designed for the application needed on the North Slope, he said, and is about three times the size of the existing application, which is in a gas storage application in Germany.
Once fabrication and testing are complete in Switzerland, it will be shipped to Anchorage, installed in the module and put on flatbed trucks for shipment to the Lisburne production center. Eastlack said the modules will go up by truck at the end of August and it will take about a month to get everything tied in and started up. The module will be split, Eastlack said, because it weighs about 150 tons, and 100 tons is the limit for road shipment.
Testing next In a June schedule update, Fuhr and Eastlack told PNA that Sulzer is working on a misalignment problem between casing and rotor, and hasn’t yet begun testing. Shipment of from Switzerland is now scheduled for mid-October. The rest of the modules will go up in September, Eastlack said, be put on piles and tied in. The last module will be held for the motor and compressors.
Fuhr said that 1999 is still the target for Point McIntyre EOR start-up.
Fuhr said that this could serve large or small fields. “One concept of using these is instead of having turbine-driven equipment all over the field, have one large power plant somewhere…” The high-power oil-free intelligent motors would be feed to power cables. Turbines, he said, are expensive to run and expensive to maintain. This, on the other hand, appears to be pretty economic.
“You put this thing on remote sites,” Fuhr said. “You don’t need to run fuel gas to it. All you need to run is a power cable to it and it can run itself. If it were to go down, you don’t have lube oil that’s going to spill on the ground, you don’t have seal oil that’s going to spill on the ground. And this is very attuned to being operated remotely.”
Eastlack said that the one in Germany, which has been running for a couple of years now, is started up and shut down remotely from two or three miles away.
Eastlack said that the unit needs about 60 cubic feet per minute of nitrogen and a lot of natural gas to cool the seals — with the seal system selected for the project — about 4 million cubic feet a day. At Lisburne they can’t use gas discharge to cool the seals because the miscible injectant could liquefy and damage the seals. But at Lisburne, Fuhr said, “we’ve got a bunch of residue gas that we can’t make MI out of — that’s what we’re going to use.” The seals, he said, require high pressure gas to keep the product from getting out. Electrical power for the project will come from one of four turbine-driven generators at Lisburne. With all four generators on line on a cool day, about 38 to 40 megawatts is generated, Fuhr said. This project will take nine megawatts.
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