While the pipeline to Valdez is a little under 800 miles, there are over 16,000 miles of pipelines within Prudhoe Bay itself. Pipes come from various wells and carry Oil, Gas, and different Oil/Water mixes from different well owners. These are sent to various distribution centers within the area and sorted and measured so each company gets credit for what they send.
Note: the dark area at the top is due to a reflection in the shuttle window.