Oil and natural gas are major industries in the energy market and play an influential role in the global economy as the world's primary fuel sources. The processes and systems involved in producing and distributing oil and gas are highly complex, capital-intensive, and require state-of-the-art technology. Historically, natural gas has been linked to oil, mainly because of the production process or upstream side of the business. For much of the history of the industry, natural gas was viewed as a nuisance and even today is flared in large quantities in some parts of the world, including the United States. Natural gas has taken on a more prominent role in the world's energy supply as a consequence of shale gas development in the United States, as mentioned above, and its lower greenhouse gas emissions when combusted when compared to oil and coal.

This guide looks at the business of oil and gas and is intended to serve as a research aid to sources worldwide, with a specific emphasis on the United States. It covers a brief history of the oil and gas industry, an overview of companies and organizations, statistic and pricing resources, and regulations. The industry is often divided into three segments:

• upstream, the business of oil and gas exploration and production;
• midstream, transportation and storage; and
• downstream, which includes refining and marketing.

These three areas are reflected in the organization of the guide. Renewable and alternative energy companies are discussed in our Green Business: Sources of Information Guide. For an overview U.S. energy sources, there have been a number of Congressional Research Service reports on renewable energy topics, including: