Fracking blow-out prevention system. Control system for blow-out prevention at a fracking drilling operation. Valves prevent blow outs by relieving the high pressures used in this technique. Fracking or hydraulic fracturing is a drilling technique used to extract gas from shale deposits. A mixture of sand, chemicals and water is pumped under high pressure from the surface to underground horizontal wells. The pressure forms fissures (fractures) in the shale. The sand keeps the fissures open, allowing gas to flow into the well and rise to the surface. This drill rig is part of exploratory drilling being carried out to assess the potential of the Fayetteville Shale in Arkansas, USA.