3 replies to this topic

[Light]

Hello everyone. I have a few questions regarding cross-country piping.

What are the different challenges associated with the transportation of natural gas and natural gas liquids through pipelines between two countries? What are the factors considered for the feasibility of a cross-country NG pipeline? What type of material of construction is used for the same and what is the pressure of the gas at the pumping station? Is it a two-phase flow? How is the corrossion of the pipes prevented here because it is ought to be done so since replacement of the pipes after corrossion would be a difficult task for such piping systems?

[PingPong]

I am not an expert on designing natural gas pipelines over enormous distances, so below are some educated guesses:

 

Pressure could be anything up to 250 barg, depends on what is agreed between supplier and customer. Depending on the distance, there can be multiple compression stations along the pipeline to increase the pressure every now and then to compensate for frictional pressure loss.

As far as I know those pipelines are made of (high quality) carbon steel, with an adequate corrosion allowance (extra wall thickness) to last the intended life of the pipeline.

Corrosion can be prevented/minimised by using an outside coating of epoxy or polyethylene, in combination with cathodic protection. Maybe in some cases also corrosion inhibitors are used, I am not sure, probably depends on content of H2O, CO2 and H2S.

It depends on the ambient temperature (ground temperature in case of underground pipeline) and composition of the natural gas whether water condensation, or even hydrate formation is possible, requiring injection of hydrate inhibitors as well.

Accurate metering of the natural gas is required at every border crossing and at every take-off point, obviously.

Edited by PingPong, 03 August 2014 - 05:33 AM.

[Light]

PingPong, 

Thanks for solving my queries.

Is there any method for detecting any leakage occuring in the line?

Is anything done to protect the pipeline from say terrorist groups or enemy nations that can steal the oil or gas from the pipeline?

Are the costs of laying the pipeline beared only by the customer (i.e. the country importing the crude)?

What is the expected life generally for any cross-country pipeline?

[PingPong]

Periodical inspection, by driving along the route of the pipeline, can show signs of leakage. Underground gas leakage can suppress (or kill) plant growth. Using a mobile gas detector one can check for gas leak.

Oil leak is easier to spot when inspecting the route of the pipeline.

Underwater pipelines are more difficult to inspect, but a leak is easier to spot, especially when it is gas.

If a leak is big it can be detected by difference in flow measurements along the route.

 

Protecting a pipeline against terrorism is impossible. Same applies to stealing of gas or oil by rogue nations through which the pipe runs. In Western Europe we have this problem with Ukraine. From the CNN propaganda you may have the impression that only saints live in that country (except in th east), but in reality they import gas from Russia for which they have not paid for years. Problem is however that a lot of gas for Western Europe also runs via the same pipeline through Ukraine. When Russia decided in the past to cut their export to Ukaine that country simple took what they needed from the supply to Europe, so Russia had to increase export again due to Europe blaming Russia instead of Ukraine. As a result of that behavior new pipelines between Russia and Western Europe are now built around rogue states like Ukraine: the Nord Stream and the South Stream pipelines.

 

Pipelines between nations are expensive projects that are built and operated by joint ventures in which companies of varies companies participate. This can also be companies from countries outside the route of the pipeline.

 

Lifetime? Don't know, but I would expect that a pipeline is designed to last for 50 years.

Edited by PingPong, 03 August 2014 - 07:07 AM.