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This is inspired by the discussion and controversy surrounding the Keystone Pipeline.

The main part of the Keystone Pipeline system is about 3,400 kilometers long, stretching across a large portion of the United States. The Keystone XL extension would add another long section to it. Altogether, the length of all the segments would be . . . oh, something very big, I imagine (though I acknowledge that none of the oil will travel through all sections).

What is the practical limit for how long an oil pipeline can be?

In the interest of narrowing this down, I'd like to focus on two sub-questions:

  • Is the structural integrity of the pipeline at risk the longer it gets?
  • Is there any possibility of adverse effects on the oil over longer spans?
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  • $\begingroup$ I think your question about adverse effects on oil over longer spans is a different one with a different kind of expertise. (Most undergrad mechEs/chemEs learn roughly how to design long pipelines. Industry specialists know about the effects that handling has on different grades of oil.) $\endgroup$ – dcorking Feb 16 '15 at 14:51
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The total length of the pipeline has little to do with the length that oil can be pumped in a pipe. This is because a pipeline is broken into many smaller segments between pumping stations. Stations are conveniently located either where required (see discussion below) or where another pipeline joins in.

Pipelines are rarely one single pipe between point A and point B. They have lots of smaller pipelines connecting into them. Each of these pipeline will have their own pump stations. These stations also help to divide the pipeline into segments. With segments, you can ensure that different oil is sent to specific locations.

You can think about the system from a logistics point of view. Any long pipeline is almost guaranteed to pass close to another location that either produces or consumes oil. It only makes sense to connect to these locations as the pipeline goes past.

Factors that affect the length that oil can be pumped in a single pipe

This is a large topic. Everything that affects regular pipe design also effects pipelines.

  • Length of pipe
  • Smoothness of pipe
  • Temperature of the oil - Oil in pipeline is usually heated because warmer oil has a lower viscosity and is easier to pump
  • Elevation changes
  • Number and degree of turns
  • Pressure capacity of pipe
  • Diameter of pipe
  • Allowable pressure drop between ends
  • A lot more...

Structural Integrity of Pipe

The length of the pipe does not influence the strength of the pipe. All pipe lengths in a pipeline will be welded and tested to the same requirements.

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  • $\begingroup$ Also, pipelines need to be correctly supported at intervals calculated to economic & minimize stresses & bending moments in the pipeline. $\endgroup$ – Fred Feb 15 '15 at 0:45
  • $\begingroup$ Long distance pumping takes a lot of electricity. Implied in hazzey's answer is the economic tradeoffs between the running costs of pumps, and the capital cost of the pumping station and pipe. This in turn depends on the rate of return the investors want from their pipeline. $\endgroup$ – dcorking Feb 16 '15 at 15:08
  • $\begingroup$ Thermal expansion comes into it somewhere... As the pipe gets longer you need to accommodate changes in length with temperature. $\endgroup$ – Floris Feb 17 '15 at 3:13
  • $\begingroup$ @Floris: Of course, and the "somewhere" is merely a couple hundred meters at most. $\endgroup$ – SF. Feb 19 '15 at 2:13
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    $\begingroup$ As for "Structural Integrity of Pipe" - the longer the distance between pumping stations the higher pressure needed (to overcome viscosity of the liquid over longer distance) and as result, higher pipeline structural requirements. $\endgroup$ – SF. Feb 19 '15 at 2:16
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Same as gas or water,etc, pipelines ; As long as someone is willing to pay for the construction. Presumably because they can profit by delivering the oil/gas/products to a destination. Other comments refer to the "nuts and bolts" of design and construction.

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