Definition - What does Gathering Line mean?
A gathering line is defined as a pipeline with a nominal outside diameter (OD) 219.1 mm or less that transports petroleum from a production site or one that transports natural gas from a natural gas site to a transmission line.
These pipelines operate at relatively low flow and pressure than transmission lines and basically transport natural gas or crude oil from the wellhead to a collection point for refining or to transmission lines.
Trenchlesspedia explains Gathering Line
The product produced at well sites are moved in gathering lines to collection points such as processing facilities or connect with larger pipelines known as transmission lines.
Crude oil and gas move through pipelines specially designed for them and are always separated for transportation, i.e. they are not sent in the same pipeline. This separation happens at the well site. The pipeline network including gathering lines, transmission lines and distribution lines are regulated by The Pipeline and Hazardous Materials Safety Administration (PHMSA) in the United States.