Crude oil pipelines transport both crude oil and refined crude oil products (such as gasoline, heating oil, and diesel). Therefore crude oil pipelines are laid near the original source of the crude oil (wells and offshore drilling rigs). Because the drilling sites are usually in remote areas, pipelines have to be constructed over mountains, through deserts and frozen tundra, under the ocean floor, and across rivers. Pumping stations have to be constructed every 20 – 100 miles in order to provide the power that keeps the crude oil moving at a rate of about five miles per hour to the refineries where the oil is heated in distillation chambers and distributed as refined petroleum products, such as gasoline, kerosene, heating oil, JP-1 jet and aviation fuel, and diesel.
When one considers transporting millions of barrels of crude from remote locations, we usually think of oil tankers – titanic ocean-going vessels moving massive amounts of crude to major ports all across the globe. While it’s true that transporting oil overseas for long distances is predominantly done by tankers, it is pipelines that dominate areas closer to shore and inland. Although the initial investment for building a tanker is far less than that of building a pipeline, over the long term the pipeline is clearly the wiser investment because of fuel, crew, and maintenance cost of the tanker. To give some perspective to the cost of building a large scale crude oil pipeline, the Trans Alaska Pipeline System cost $8 billion in the mid-1970s and required over 25,000 workers.
Crude oil pipelines along the ocean floor are far less expensive to make than most above-ground pipelines. They require little welding (if at all) and the pipeline is wound onto enormous spools placed on barges that head out to sea and lay the pipeline for miles.
Crude oil pipelines come in two categories: Gathering Lines and Trunk Lines.
Gathering lines are very small pipelines between 2 to 8 inches in diameter that are located where oil is drawn from deep underground, both onshore and offshore. These small lines gather the crude oil from the source well or offshore rig and connect up to larger lines, known as trunk lines. The United States has about 40,000 miles of these small gathering lines located predominantly in Louisiana, Texas, Oklahoma, and Wyoming.
Trunk Lines can range anywhere from 8 to 24 inches in diameter. However, trunk lines can also include very large pipelines with a diameter of 48 inches, such as the Trans-Alaska Pipeline System. These large lines typically stretch across the country and bring crude oil from the gathering lines near the source of the oil to refineries. There about 55,000 trunk lines in the United States.