Midstream Is the Conduit Between the Producer and the Interstate Pipeline System
The Midstream sector provides the essential link between the upstream (wellhead) and downstream (interstate pipeline and distribution) sectors. Without sufficient midstream infrastructure, consumers would not be able to get natural gas delivered to their homes and businesses.
Midstream activities include the processing, storing, transportation and marketing of oil, natural gas and natural gas liquids. For natural gas, Midstream describes the activities that take place from the wellhead, where the gas is produced, to the national gas transmission pipeline system.
Natural gas coming out of the ground is composed mostly of methane, but may also contain natural gas liquids (NGLs) which comprise ethane, propane, butane, and pentane. This gas is considered “wet” gas. The natural gas that flows into the gas transmission pipeline system in the United States must meet specific quality specifications so it can be transported and delivered to the final consumers. As a result, natural gas produced at the wellhead must be processed, before it can be safely delivered to the high-pressure, long-distance transmission pipelines that, in turn, deliver it to natural gas distribution systems and final consumers.
Non-pipeline-quality gas production is gathered by a midstream pipeline system and transported to a natural gas processing facility where water vapor and NGLs are extracted. Cryogenic processes are often used to extract NGLs from natural gas. This process drops the temperature of the gas stream to around -120 degrees Fahrenheit. The rapid temperature drop used in cryogenic processing condenses the NGLs in the gas stream while maintaining methane in gaseous form.
Once the gas is processed at the processing facility, the pipeline quality production, or dry gas, is delivered to the transmission system by way of a lateral pipeline. This is the gas that is eventually delivered via a distribution pipeline system to the consumer. NGLs removed at the processing facility (which are valuable themselves) are delivered by pipelines and trucks to a natural gas fractionation plant where they are further separated into the individual components to be delivered to market.