5,000 energy-related firms numerous oil and gas corporations numerous oil and gas corporations second most popular place for Fortune 500 companies oil rigs numerous oil and gas corporations List of Houston Employers on Wikipedia numerous oil and gas corporations Houston’s corporate HQs second most popular place for Fortune 500 companies second most popular place for Fortune 500 companies serves as home base second most popular place for Fortune 500 companies second most popular place for Fortune 500 companies numerous oil and gas corporations extractive numerous oil and gas corporations second most popular place for Fortune 500 companies numerous oil and gas corporations http://en.wikipedia.org/wiki/List_of_companies_in_Houston