Pipelines play a key role in the transportation of petroleum products across continents in a more efficient and economical way. They are a vital link in the transportation value chain and they help in adding value to the products. For example, they help in the transportation of crude oil from upstream oil storage to refineries for further processing where more refined consumable products like gasoline, gasoil, kerosene, etc., are produced. Feedstocks for petrochemical plants are usually transported from refineries through pipelines. Hence, pipelines aid in economic value creation for the world.
Pipelines have quite a fascinating history. During the first periods of oil invention in the 1800s, pipes were mainly used to drill oil wells to extract the product from the earth. When black oil was discovered which had significant economic and consumable value, the challenge was how to transport this black gold to refining processing facilities. Wooden pipes were used initially for routing the crude oil to nearby refineries. However, as the scale of operations went up, pipelines emergence in the industry was inevitable for transportation of petroleum products efficiently.
Pipelines have become an integral part of the oil and gas industry and they are considered as national assets. For example, the United States depends on a network of more than 185,000 miles of liquid petroleum pipelines, nearly 320,000 miles of gas transmission pipelines and more than 2 million miles 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 to move 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.
Complexity and variety
Oil and gas pipelines run through various terrains in very complex and crisscross ways. Designing of pipelines requires astute technical expertise taking into consideration various factors such as nature of products transported, the sloppy or plain terrain and pressure requirements. The terrain has special significance of complexity. For example, when a massive cross country pipeline is constructed across a river or a road crossing, it may entail special design in that particular segment. Hence, meticulous planning and design capability is essential while laying the pipelines. That brings us to understand what the broad types of pipelines are.
Oil and gas pipelines are of two types, i.e., 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. Crude pipelines are further classified as gathering pipelines and transmission 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. Depending on the requirements their capacities vary, for example, a gathering pipeline is usually of about 8 inches in diameter while cross country pipelines are up to 48 inches in diameter. They are massive and run long distances hence achieve economies of scale in operations. There is another set of pipelines called distribution pipelines which are a composition of several interconnected pipelines with small diameters. These pipelines are used to transport the crude oil to the final consumer. Distribution pipelines include feeder lines which distribute gas to homes and businesses downstream, and pipelines at terminals which distribute products to tanks and storage facilities.
Composition of a pipeline network
Pipeline network consists of various parts that work in perfect sync 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 as per the contractual arrangements. It is also kind of secondary initial injection point for routing the products as per commercial requirements.
The flow of products throughout the pipeline has to be regulated so that safe product supplies are ensured. This smooth flow is maintained by the compressor and pump stations. Main deterrent in free flowing products through pipeline is the underlying friction. The products by themselves cause friction while flowing due the nature of petroleum products such as viscosity, stickiness etc. Another factor which necessitates compressors and pumps in the pipeline delivery process is the gravity. Since long distance cross continental pipelines travel through very different uneven terrain, regulation of gravitational pull plays a great role in ensuring smooth efficient flow of products that is facilitated by the pump stations. These facilities are stationed at regular intervals through the network based on factors like topography of the terrain, nature of products transported and other operational requirements.
Block valve station consisting of valves is necessary for the protection and maintenance of pipelines. With these valves, the operator can isolate any segment of the line for maintenance work, e.g., 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. The location of these stations depends on the nature of the product being transported, the trajectory of the pipeline and the operational conditions of the line. 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. It is either customer’s storage point or operators own storage tanks.
Pipeline management system
There have been notable advancements in managing the entire pipeline network effectively. SCADA (Supervisory Control and Data Acquisition) system provides an efficient management of the network through their remote monitoring capability that enables control of operations in a better way. It is also possible to detect leaks in the pipeline through SCADA and perform maintenance operations without much delay. They provide opportunities to control quantity of products delivered as per commercial contracts and help in ascertaining the pipeline stock for month end closing.