Pipelines play a key role in transporting petroleum products across continents in an efficient and economical way. They are a vital link in the transportation value chain and they help add value to the products. For example, they transport crude oil from upstream oil storage tanks to refineries for further processing where more refined consumable products such as gasoline, gasoil, kerosene, etc., are produced. Feedstocks for petrochemical plants are usually transported from refineries through pipelines. Hence, pipelines create economic value for the world.
An Interesting and Compelling History
Pipelines have quite a fascinating history. During the first periods of oil production in the 1800s, pipes were mainly used to drill oil wells to extract the product from the earth. When black oil, which had significant economic and consumable value was discovered, the challenge was how to transport this black gold to refining processing facilities. Wooden pipes were initially used to route the crude oil to nearby refineries. However, as the scale of operations increased, the emergence of pipelines to efficiently transport petroleum products was inevitable.
Pipelines have become an integral part of the oil and gas industry, and they are considered national assets. For example, the United States depends on a network of more than 185,000 miles (297,700 km) of liquid petroleum pipelines, nearly 320,000 miles (515,000 km) of gas transmission pipelines and more than 2 million miles (3,219,000 km) of gas distribution pipelines. These pipelines safely and efficiently move energy and raw materials to fuel the nation's economic engine. The pipelines serve as a national network that moves the energy resources from production areas or ports of entry throughout North America to consumers, airports, military bases, population centers and industry on a daily basis.
Pipeline Complexity and Variety
Oil and gas pipelines run through various terrains in very complex and crisscrossing ways. Designing a pipeline requires astute technical expertise that takes into consideration various factors such as the nature of the products, the sloppy or plain terrain, and pressure requirements.
The terrain has special significance regarding complexity. For example, when a massive cross country pipeline is constructed across a river or a road, it may entail a special design at that particular segment. Hence, meticulous planning and design capability is essential when laying the pipelines.
Oil and gas pipelines are of two types: liquid pipelines for transporting crude oil and petroleum products, and gaseous pipelines for transporting natural gas and other petroleum gas products such as liquefied petroleum gas (LPG). (Related reading: The Challenges of Shipping and Distributing Liquefied Natural Gas.)
Crude oil pipelines are further classified as gathering pipelines, transmission pipelines and distribution pipelines. Gathering pipelines gather crude oil from the oil well to upstream storage. Transmission pipelines are used to transport the crude oil to refineries or vessels. Their capacities vary depending on the requirements; for example, a gathering pipeline is usually about 8 inches (20 cm) in diameter while cross country pipelines are up to 48 inches (122 cm) in diameter. They are massive and run long distances, hence achieving economies of scale in operations.
There is another set of pipelines called distribution pipelines that are a composition of several interconnected pipelines with small diameters. These pipelines transport the crude oil to the end consumer. Distribution pipelines include feeder lines that distribute gas to homes and businesses downstream, and pipelines at terminals that distribute products to tanks and storage facilities. (Learn more about distribution in the article Oil & Gas Retailing Secondary Distribution Processes.)
Composition of a Pipeline Network
A pipeline network consists of various parts that work in perfect synchronization while transporting the products or crude through them. The starting point of a pipeline delivery network is the initial injection station. This is where the product is fed into the pipeline system, which has comprehensive facilities attached to the storage tanks of the plant. A partial delivery station allows the operator the flexibility of diverting the product according to the contractual arrangements. It is also a kind of secondary initial injection point for routing the products per commercial requirements.
The flow of products throughout the pipeline is regulated so that safe product supplies are ensured.
A smooth product flow is maintained by the compressor and pump stations. The main impediment to free flowing products is the underlying friction. The products cause friction while flowing due to their characteristics such as viscosity and stickiness. Another factor that necessitates compressors and pumps is gravity, because the long-distance routes that pipelines travel through often contain uneven terrain. The pump facilities are stationed at regular intervals along the network based on factors like terrain topography, nature of the products and other operational requirements.
Block valve stations are necessary to protect and maintain the pipelines. With these valves, the operator can isolate any segment of the pipeline for maintenance work (e.g., to isolate a rupture or leak).
Although it is not a part of design stipulation, liquid pipeline block valve stations are usually located every 20 to 30 miles (30 to 50 km). The location of these stations depends on the nature of the product being transported, the trajectory of the pipeline and the operational conditions. A special type of valve station is a regulator station, where the operator can release some of the pressure from the line. They are usually located at the downhill side of a peak.
Finally, the destination of the pipeline network is called a terminal or outlet station, which is either the customer’s storage point or the operator's own storage tanks.
Pipeline Management Systems
There have been notable advancements in managing the entire pipeline network. The Supervisory Control and Data Acquisition (SCADA) system efficiently manages the network through their remote monitoring capability. It is also possible through SCADA to detect leaks in the pipeline and perform maintenance operations without much delay. They provide opportunities to control the quantity of products delivered per any commercial contracts and help to ascertain the pipeline stock for month-end closing.