Marine pipelines

Main article: Submarine pipeline

In places, a pipeline may have to cross water expanses, such as small seas, straits and rivers.^[33] In many instances, they lie entirely on the seabed. These pipelines are referred to as "marine" pipelines (also, "submarine" or "offshore" pipelines). They are used primarily to carry oil or gas, but transportation of water is also important.^[33] In offshore projects, a distinction is made between a "flowline" and a pipeline.^[33][34][35] The former is an intrafield pipeline, in the sense that it is used to connect subsea wellheads, manifolds and the platform within a particular development field. The latter, sometimes referred to as an "export pipeline", is used to bring the resource to shore.^[34] The construction and maintenance of marine pipelines imply logistical challenges that are different from those onland, mainly because of wave and current dynamics, along with other geohazards.

Functions

In general, pipelines can be classified in three categories depending on purpose:

Gathering pipelines

Group of smaller interconnected pipelines forming complex networks with the purpose of bringing crude oil or natural gas from several nearby wells to a treatment plant or processing facility. In this group, pipelines are usually short- a couple hundred metres- and with small diameters. Sub-sea pipelines for collecting product from deep water production platforms are also considered gathering systems.

Transportation pipelines

Mainly long pipes with large diameters, moving products (oil, gas, refined products) between cities, countries and even continents. These transportation networks include several compressor stations in gas lines or pump stations for crude and multi-products pipelines.

Distribution pipelines

Composed of several interconnected pipelines with small diameters, used to take the products to the final consumer. Feeder lines to distribute gas to homes and businesses downstream. Pipelines at terminals for distributing products to tanks and storage facilities are included in this groups.

Development and planning

When a pipeline is built, the construction project not only covers the civil engineering work to lay the pipeline and build the pump/compressor stations, it also has to cover all the work related to the installation of the field devices that will support remote operation.
The pipeline is routed along what is known as a "right of way". Pipelines are generally developed and built using the following stages:

1. Open season to determine market interest: Potential customers are given the chance to sign up for part of the new pipeline's capacity rights.
2. Route (right of way) selection
3. Pipeline design: The pipeline project may take a number of forms, including the construction of a new pipeline, conversion of existing pipeline from one fuel type to another, or improvements to facilities on a current pipeline route.
4. Obtaining approval: Once the design is finalized and the first pipeline customers have purchased their share of capacity, the project must be approved by the relevant regulatory agencies.
5. Surveying the route
6. Clearing the route
7. Trenching - Main Route and Crossings (roads, rail, other pipes, etc.)
8. Installing the pipe
9. Installing valves, intersections, etc.
10. Covering the pipe and trench
11. Testing: Once construction is completed, the new pipeline is subjected to tests to ensure its structural integrity. These may include hydrostatic testing and line packing.^[36]

Russia has "Pipeline Troops" as part of the Rear Services, who are trained to build and repair pipelines. Russia is the only country to have Pipeline Troops.^[37]