[fauigerzigerk]

True, but many of those contractors will themselves be classified as energy companies according to the S&P (GICS) sector classification.

For instance, energy services companies such as Schlumberger or Halliburton belong to the energy sector as well.

But it's true that there will be a ton of low value work that gets outsourced to services companies that are mostly classified as industrials (construction, environmental services, transportation, etc).

[burger_moon]

These contracting companies the OP is referring to aren't like Schlumberger. They are just temp agencies basically. The one I used to work for in the power industry also does contracting jobs in oil and gas, tech, mining, chemical. They don't own equipment or anything like Haliburton, they just provide bodies. Maybe they get classified as employing people in those industries but it seems unlikely.