This will explore the feasibility of extracting shale oil from the site, and has been the subject of a campaign against the fracking process which injects water into the ground under high pressure to fracture shale rocks and release oil or gases trapped inside.
There is a 78 feet high rig in place and will implement a 3,000 foot exploratory well.
In a statement Cuadrilla said: “Cuadrilla can confirm that it has commenced test drilling at the Balcombe site. We have full planning and regulatory approval for this work from the Department for Energy and Climate Change, West Sussex County Council, the Environment Agency and the Health and Safety Executive.
“The first stage involves drilling a 3,000ft vertical well. We will provide further updates as test drilling proceeds.”
Over 20 of the protesters have been arrested at the site. They are concerned that the drilling will cause earth tremors and the potential of environmental damage.