There are two general types of energy pipelines -petroleum oil pipelines and natural gas pipelines.

Within the oil petroleum pipeline network there are crude oil lines, refined product lines, highly volatile liquids (HVL) lines, and carbon dioxide lines (CO2). 

Crude oil pipeline is also subdivided in to Gathering Lines and Transmission Lines

Gathering line,A pipeline usually within an oilfield which gathers produced oil to bring it to a more common point for further transmission.

Gas gathering pipelines are very small pipelines usually from 2 to 8 inches in diameter in the areas of the country where crude oil is found 

deep within the earth.

The larger cross-country crude oil transmission pipelines bring crude oil from producing areas to refineries. Natural gas is transported through 

the transmission pipeline system, which is composed of large diameter steel pipe.

The industrial standards for oil and gas pipelines usually are API 5L Psl1 /Psl2 with material Gr. A, B, X42, X46, X52, X56, X60, X65, X70, X80.