The standard method involves percussion drilling in which a drill is alternatively raised and dropped in the descending borehole. It is suited to the drilling of wells in any material from soft clay to the hardest rock.
[pdf] Bospi is the Swiss manufacturer of drilling equipment and tools for applications in general construction and geothermal wells. Drilling companies in Switzerland and abroad rely on the quality of our products since more than 40 years. There are hardly two drill strings which look the same.
[pdf] The first offshore mobile drilling platform was the Breton Rig 20, first operated in 1949. This rig had evolved from the inland drilling barges which were used to drill in marshes and protected waters in up to 10 feet of water. The Breton Rig 20 was 160 feet by 85 feet, and could work in 20 feet water depth.
[pdf] 
