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RDC conference: Pipeline technology much improved over 25 years With higher strength steel, stronger compressors, pressure can be great enough to allow some liquids to move with the natural gas Kristen Nelson PNA News Editor
It was mix and match time for proposals to commercialize Alaska North Slope natural gas at the Resource Development Council's 21st annual conference in Anchorage Nov. 16 and 17: pipelines with or without liquefied natural gas plants in either Valdez or Kenai; pipelines across the Beaufort Sea to the Mackenzie Delta or down the trans-Alaska pipeline right-of-way to Fairbanks and then south; gas-to-liquids projects on the Kenai or on the North Slope; gas to Interior Alaska from a pipeline or trucked in as propane; gas to Southcentral from a Kenai pipeline or by spur from Glennallen or Delta Junction.
All the projects had in common a plan to commercialize North Slope natural gas. Almost all involved a pipeline.
And pipeline technology has changed a lot in the years since a pipeline was last built in Alaska, Robert Sluder, vice president of operations for Williams Gas Pipelines West, told the conference. A unit of Williams, then Northwest Energy, was certificated to build the Alaska segment of the Alaska Natural Gas Transportation System in 1977, Sluder said, and the company stayed active in the effort until 1994, investing nearly $100 million.
Williams moves gas coast to coast in the Lower 48, Sluder said, and “we have seen it time and again, that when the market finally aligns with the supply, some project will go. We believe that's what's happening up here, as well.”
To move gas to Chicago, he said, at tariffs and fees in the range of $1.60 and a price in Chicago of $3, “you are still left with a netback to the producers of somewhere between $1 and $1.50 and that has never been the situation in the past. That has usually been a negative number.” Technology driving costs down “Knowledge and technology have driven down the cost of installation of the kinds of facilities that are necessary to move gas out of the Arctic to the marketplace” over the past 25 years, Sluder said.
And both knowledge and Arctic construction experience have increased.
“We have learned a lot about how to deal with the Arctic environment… what we can do during what times of the year,” he said.
Environmental knowledge is better and the Federal Energy Regulatory Commission has been streamlining some of the permitting process, although Sluder said that hasn't gone far enough. Dense-phase flow carries heavy ends When the trans-Alaska oil pipeline was built, directional drilling was not available for stream crossings and that technology, Sluder said, means that buried stream crossings can be done better and for significantly less cost.
Ice road and winter construction are viewed differently today, he said. “Twenty-five years ago it was thought to be something you might kind of shy away from unless you were at Prudhoe Bay where it was always winter construction.
“But today, that is the way many pipelines get built, in the winter.”
Dense-phase flow has changed the level of processing needed on a gas pipeline system because it allows the pipeline system to carry heavy ends like hexane, pentanes and butanes — which used to have to be removed before the gas entered the line and shipped separately because they would precipitate out of the gas stream. The Alliance pipeline, which began operation in November, carries 1,180 BTU gas, compared to the 950 to 1,050 BTU rate on non dense-phase flow lines.
A dense-phase line can carry heavy ends in the gas stream by maintaining extremely high pressure, Sluder said.
“That's new technology. So when you look at how that works, they move the equivalent of the two products, the liquids and the gas, all at one time: deminimus difference in the frictional characteristics of that gas stream or the compression required to move it, but a tremendous advantage by the time it gets to Chicago and their … plant, to strip those liquids out and have them at the market at the same place that they have the gaseous market.”
With a high-pressure pipeline you need high-strength steel. State-of-the-art pipeline strength was X70 steel when the trans-Alaska pipeline was built — today you can get X80 and people will manufacture X120 if you really want it, he said.
The higher strength steel “has a greater resistance to the strains and stress imposed on a pipeline by the environment,” Sluder said, so the new pipe can better resist stresses like frost heave.
Compressor units — coupled with higher strength steel and greater pressures — allow pipelines to operate at more pounds of pressure per square inch, resulting in “a lot greater efficiency in the compression aspect of moving the natural gas.”
“Many times,” Sluder said, “you're able to put larger units at fewer stations, spread your stations out, overcome the frictional losses, and end up impacting less land and investing less in the major infrastructure necessary to support a compressor station.” Construction more efficient Mechanized welding is now being accepted by unions, was used in North American for the first time on a large scale on the Alliance pipeline and was, Sluder said, “very successful, very high quality, very high production.”
Trenching equipment has evolved over the years and is more powerful and efficient, and should be capable of handling frozen gravel that had to be blasted during construction of the trans-Alaska pipeline.
Gravel also had to be brought in to go under the pipeline in the trench, but today, there is “equipment that will take the spoil pile and segregate it” allowing what comes out of the trench to be graded and used for bed and to pad the pipeline, minimizing the need to permit and develop gravel pits and truck in materials.
Ultrasonic weld testing is now done immediately, eliminating the time needed to develop X-rays. It was used for the first time on the Alliance pipeline, Sluder said. “And it was very successful. … the welder can stand there and see exactly what if any defects are in the weld, where they're at, what the nature of them is, immediately make the repair and check it again immediately.”
Geometry pigs and smart pigs are used right after construction, particularly geometry pigs, he said. “We want to run a geometry pig through a pipe to make sure we don't have any construction damage in the form of a dent or a gouge, a place where the pipe may have been set on a hard spot and flattened itself.”
The pig runs establish a baseline and also mean that any needed repairs can be done while the crew is still there.
Project management tools have also improved, Sluder said, from flow modeling to estimating software and financial models.
There is also a different relationship between the owner and the contractor on major projects. “We're finding better ways to share the risk and share the reward. And you've got to do both. In the past it was kind of share the risk and keep the reward. Today the most successful projects are the ones where they do them under a partnering kind of arrangement.”
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