• Crude Petroleum and Natural Gas
    – sic code 1311 / 186 companies
  • Drilling Oil and Gas Wells
    – sic code 1381 / 130 companies
  • Natural Gas Liquids
    – sic code 1321 / 15 companies
  • Oil and Gas Field Exploration Services
    – sic code 1382 / 198 companies
  • Oil and Gas Field Services, NEC
    – sic code 1389 / 394 companies