The midstream operations are often taken to include some elements of the upstream and downstream sectors. For example, the midstream sector may include natural gas processing plants which purify the raw natural gas as well as removing and producing elemental sulfur and natural gas liquids (NGL) as finished  end-products.
The midstream sector is often seen as a bridge between upstream (oil and gas extraction) and downstream (refining, transportation, and distribution) segments of the energy industry. It involves activities like natural gas processing plants that refine raw natural gas into usable products such as sulfur and NGLs.