Even in deep offshore areas, drilling for oil is far from rare. For Norway 1390 wells greater than 30m and 546 over 200m depth and there are over 9000 wells in water greater than 30m depth and 328 deeper than 200m, some quick GIS wizardry with public data sets shows that for the UK. In the Gulf of Mexico, there are 3800 offshore wells, NOAA said.
Reaching depths up to a maximum of over 3000m, e.g. off India, there are at least hundreds of other deep water wells around the world, although these cover some of the major exploration areas in pretty much every ocean. It create a notable disturbance to life on the seafloor, this is a huge amount of activity. In the late 1960′s, since the pioneering days of offshore oil drilling, regulation has been built up and drilling practices have improved. Written in the 80′s and early 90′s, the earlier papers on drilling impacts, focused on the more highly polluting drilling sites that were then producing oil and were available for study.