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 often involves activities from both upstream and downstream segments of the energy industry.  For example, it might encompass natural gas processing plants that refine raw natural gas, remove sulfur, and produce NGLs for use as finished products.