Natural gas is transported via pipelines from individual wells to larger interstate pipelines and then to consumers across the US. As shale development continues in Pennsylvania, West Virginia and Ohio, additional pipeline and compressor infrastructure is needed to deliver the product from well to consumer.
Gathering pipelines deliver the natural gas from the wells to the larger interstate and transmission pipelines. Gathering lines run from 2 to 30 inches in diameter, depending on the volume of gas running through them. These pipelines are generally made of steel and are buried in a permanent right of way. Pressure is required to move the gas from the wells to the larger pipelines. Although natural gas comes out of the ground under pressure, additional pressure may be needed to move the gas to the larger lines, and this pressure is commonly provided by compressor stations. The number, spacing, and size of compressor stations depends on the number of wells, production and distance between stations. There may be one or more compressor engines per station in which the natural gas moves through. These engines can run on natural gas, diesel or electricity, and are normally found in buildings for noise abatement and ease of maintenance in inclement weather. Tanks may be on the site to store water and gas condensate that is removed from the natural gas as it moves through the compressors. In some regions, there may also be a glycol dehydrator that removes excess water from the gas to make it 'dry' enough to travel through the main pipelines. A compressor station may not be manned around the clock, but they are often fenced and lit and have security measures in place.
Meter stations are needed for accurate measurement and accounting of all natural gas delivered to the interstate pipelines. Meter stations can also regulate gas pressure. These stations are normally a small building enclosed by a fence that is visited by an industry representative several times a week.
Valves along the pipeline work like gateways. They are normally open to allow the gas to flow, but may be closed to stop gas flow in a section of pipeline that needs maintenance. Launchers can also be found along pipeline right-of-ways. A launcher is a pipeline access that can be used for inserting a device, tool or vehicle to move through the pipeline interior for inspecting, dimensioning, or cleaning. These tools are commonly referred to as 'pigs' because of the occasional squealing noises made as they pass through the pipeline.
With the need for infrastructure, how are pipelines constructed?
The engineering and planning departments of industry work to come up with the best route for connecting wells to the interstate pipeline. Company right-of-way agents will approach landowners for easements (also called right-of-way agreements). Once landowner approval for the route is secured, it will be surveyed and the centerline of the right-of-way is determined. Environmental permitting is submitted to all necessary agencies, ensuring wetlands and stream crossings are taken into consideration. Only when final permitting approval and regulatory processes have been received and followed will the land be cleared and graded. Trees, shrubs and boulders will be removed. Sections of the pipe, usually 40 to 80 feet long, are laid along the path in a process called 'stringing pipe'. Trenches are dug, as pipeline is usually buried at least 30 inches below the surface.
Pipelines are not straight, so the pipe must be bent and angled to fit the contours of the trench. The pipes are then welded, inspected and then an epoxy coating is applied over the welded sections. It is important that the entire coating is inspected and free of defects. The pipe is lowered into the trench by specialized equipment, making sure the pipe's integrity is not compromised. The trench is backfilled, and a hydrostatic test is conducted. Water is sent through the pipeline at pressures higher than needed for natural gas transportation for 24 hours to ensure the integrity of the welds and the pipe itself.
Once the pipeline has been installed, the area is restored to its original state, or as agreed upon with the landowner.