Now is the big test. When the pipeline is finished, it is filled with water and pumped to a high pressure. Then the workers look for leaks, and fix them. Finally, the water is pumped out, and the gas or oil can be transported. Natural gas pipelines cost more to build than oil pipelines, but they are cheaper to run afterwards.
Oil pipelines cost less to build, but cost more to run.
According to the Guiness Book of World Records, the world's longest petroleum pipeline is the Interprovincial Pipeline. The Trans-Alaska Pipeline is another famous one. It runs for 1300 km, and more than half is build above ground on stilts. This prevents the heat of the oil from thawing the permafrost, and lets the caribou walk underneath. Oil used to be sold in barrels, which were transported by horse-drawn carts, and later by trucks.