Upstream (Exploration & Production) – An E&P company is known to be in a specific sector within the oil and gas industry. Companies involved in the high-risk/high-reward area of exploration and production focus on finding, augmenting, producing and merchandising different types of oil and gas.

Midstream – Term used to describe one of the three major stages of oil and gas industry operations. Midstream activities include the processing, storing, transporting and marketing of oil, natural gas and natural gas liquids.

Downstream – The oil and gas operations that take place after the production phase, through to the point of sale. Downstream operations can include refining crude oil and distributing the by-products down to the retail level. By-products can include gasoline, natural gas liquids, diesel and a variety of other energy sources.

Integrated – A business entity that engages in the exploration, production, refinement and distribution of oil and gas. Given the high entry costs relating to many oil and gas industry operations, many of the world’s largest oil and gas companies, like Chevron Corporation and Exxon Mobile, are integrated. Typically, integrated companies divide their various operations into categories: upstream, which includes all exploration and production endeavors, and downstream, which is confined to refinement and marketing activities.

Drilling – Drilling companies physically drill and pump oil out of the ground. The drilling industry has always been classified as highly skilled. The people with the skills and expertise to operate drilling equipment are in high demand, which means that for an oil company to have these people on staff all the time can cost a lot. For this reason, most drilling companies are simply contractors who are hired by oil and gas producers for a specified period of time.

Oilfield Services – Oilfield service companies assist the drilling companies in setting up oil and gas wells. In general these companies manufacture, repair and maintain equipment used in oil extraction and transport.