Fracking for shale gas has begun for the first time in the UK since 2011.
Energy firm Cuadrilla confirmed the controversial process had started at its site in Little Plumpton, Lancashire after a legal challenge failed on Friday.
Protester Ginette Evans said there was a “mood of disappointment” but insisted the fight was “not over”.
Cuadrilla insisted the process was safe and would be of “enormous” benefit.
The company’s chief executive Francis Egan said: “These are the first exploration wells that will be tested… we have high hopes for them but we have to wait and see what comes out.”
If successful, he said it would “lead to tens of thousands of jobs and could be a very significant contributor to the exchequer and… could also reduce emissions because it will be better than importing gas from far afield”.
The energy firm confirmed in a statement at 13:15 BST that it would spend at least three months fracking two horizontal wells, and then it would test to see if the gas flow was commercially viable.