Integrated oil companies. These companies are involved either directly or through their subsidiaries and affiliates in all three segments of oil & gas industry (upstream, midstream, and downstream). However, in the last several years, some of these companies have spun off their downstream businesses and are focusing on E&P. Although E&P activities are more capital intensive, they can also be more profitable.

National oil companies. These companies are owned in whole or in part by a national government (for example, Saudi Arabian Oil Company (Saudi Aramco) and Petróleos Mexicanos (PEMEX)).

Independent exploration and production companies. These companies range from small family companies with a few rigs that operate in one shale play to publicly traded companies that own hundreds of thousands of acres of reserves in different onshore or offshore plays. There are thousands of these companies in the US and they produce the vast majority of US oil & gas.

Oilfield service companies. These companies provide a range of services, equipment, and products to E&P companies for their core activities.