Alaska untapped oil reserves down 90%, pipeline running into low volume problems

[fallout]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

From my memory of the Trans-Alaska pipeline the flow of oil through the pipeline is facilitated by friction. That is, friction of the oil flowing through the pipeline heats the oil and lowers the viscosity of the oil making it possible to pump the oil through the pipeline in the first place. If flow is halted the oil in the pipeline would 'freeze' up, rendering the pipeline all but useless as a
conduit. There is a minimal flow rate (500,000 barrels per day??) that would still create enough friction to keep the oil viscosity low enough to flow through the pipeline. At lower flow rates, flow would still be possible if external heat is added to the oil. However, the net energy available at the end of the pipeline would be correspondingly decreased. Comments?

Negative. There are a number of pumping stations strung out along the length of the pipeline. At each one, the oil is heated (by siphoning some of it off and burning it in oil burning heaters as "heating oil") to allow it to be liquid enough to be pumped down to the next station. The entire Alaska pipeline has always operated with the oil inside at around 140°F, rather warm! The pipeline sits on insulated legs (with radiator fins and thermal breaks on them) above the snow & permafrost to keep it from melting them, and the pipe itself is insulated to prevent heat loss.
The big problem is that the pipe was sized for a greater volume of oil flow. With less and less oil moving through it, pressurizing the oil enough to flow down to the next station becomes more and more difficult. Either the pipe will need to be lined to be smaller in diameter at some point, to allow the same pressure "head" to be maintained with existing pumping equipment, or it will be abandoned. While it is a paid for asset, it is also in fairly bad shape structurally, corrosion being a major problem along its full length, and the pipeline itself was rather hastily constructed with only a planned for 25 year operational life (which it is now close to reaching).

[Shakespear]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

GRG55 - Barring a massive production technology breakthrough of some sort I am quite confident that Prudhoe Bay will still be producing 50 and more years from now.

Yeh, but at rates that are not going to fill that pipeline to its minimum vol. required. Look at the data because it is not obvious to everyone.

[GRG55]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

Yeh, but at rates that are not going to fill that pipeline to its minimum vol. required. Look at the data because it is not obvious to everyone.

And what do you think is the "minimum volume required"?

Because I can assure you that whatever the damn doomsayers are blathering about today is nowhere near as low as that pipeline will be turned down to operate before it's done. And neither the fields feeding it, or the pipeline itself will be done for decades. That's the history of this industry.

[fallout]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

Beyond pressurization and flow issues (sorry, engineer here), there is a certain volume of oil required in order for the oil to retain its thermal mass. That is, in order for it to stay warm enough to reach the next pumping and heating station and not congeal up enroute. So not only will the pipe need to shrink in diameter to maintain the same pressure head at a sufficiently reduced flow rate, but additional heating stations will have to be built along the way to keep the now less-than-designed for warm mass sufficiently warm and moving. It's simply an engineering issue to be sure, but at some point the required investment will outweigh the return on that investment, since it will basically require rebuilding the entire pipeline on the same route. When that happens, tankers may be an economically viable alternative.

[Shakespear]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

" I can assure you that" Show the data.

From the BP data I am not convinced that the required rates will be maintained for even 10 yrs. Or is the dream West Sak or Kuparek that ARCO was starring at for years and had no ideas. Now BP likewise looks to have no clue.

Official data from BP.

http://www.bp.com/liveassets/bp_internet/globalbp/STAGING/global_assets/downloads/A/abp_wwd_alaska_bp_in_alaska_2009.pdf

The minimum flow rate for TAPS is said to be between 200,000 and 400,000 barrels per day. Good Luck to them.

[GRG55]

Re: Alaska untapped oil reserves down 90%, pipeline running into low volume problems

Beyond pressurization and flow issues (sorry, engineer here), there is a certain volume of oil required in order for the oil to retain its thermal mass. That is, in order for it to stay warm enough to reach the next pumping and heating station and not congeal up enroute. So not only will the pipe need to shrink in diameter to maintain the same pressure head at a sufficiently reduced flow rate, but additional heating stations will have to be built along the way to keep the now less-than-designed for warm mass sufficiently warm and moving. It's simply an engineering issue to be sure, but at some point the required investment will outweigh the return on that investment, since it will basically require rebuilding the entire pipeline on the same route. When that happens, tankers may be an economically viable alternative.

The heat loss issue is always one of the biggest problems at declining flow rates [it's an even bigger problem in gas pipelines]. The other is the slugging issue on lines with significant elevation profile, which this pipeline has. And I imagine that's already requiring them regularly use pigs to sweep the line ahead of rising elevation change sections.

But none of these issues is new to pipelining or unique to Trans-Alaska...although you wouldn't know that from some of the stuff being published on the topic. The "rebuilding" you refer to happens as a number of discrete investments over time. Replacing the line with tankers will require a major investment all at once. Part of my background is in the sour gas processing industry. This stuff [H2S] is both toxic, and when combined with the water vapour that is a product of the processing chemistry, highly corrosive. The standing joke is that we rebuild 10% of the plant every year [new steel to replace the rotted out stuff] and therefore every decade we've "replaced" the whole damn plant. We have plants that were "designed" for a 25 year operating life, and are now more than 60 years old and still runnning. Same thing happens with pipelines. Unless there's a fairly fast payback of the significant capital needed to convert [possible, but not probable] with the so-called "savings" from abandoning a functioning asset, I have never seen it happen. Also, let's remember that the owners of Alyeska will not be allowed to just abandon the pipeline as is. They will have to remove all of the above ground assets and reclaim the right-of-way...not a trivial expense, and one that I am certain they will want to defer for as long as practical.

You made mention in a previous post of widespread corrosion. There is absolutely no excuse for the operator to have allowed that to happen, if indeed that is the case. Corrosion in low sections of the line [such as where the line is buried under a water course] would be expected, especially since the Prudhoe crude is paraffinic and deposits allow corrosion cells to form underneath and insulate the steel from the inhibitors.

Finally, perhaps tankers on the North Slope are more viable now than they were in the 1970s...given that the Arctic is now apparently "ice free"...who said global warming was all bad news...