When you take into account all the wells drilled in mature and...

When you take into account all the wells drilled in mature and emerging basins, and with improved 3D seismic data and better drilling and logging techniques, the global average
success rate for all exploration wells is actually close to 40%. And for appraisal wells, where a company has already made a discovery(e.g block 120 I added this bit in) and is looking to firm up the size or extent of the field or find the oil-water contact for example, that rate rises to between 80-90%.

http://www.investorschronicle.co.uk/r/FT%20Publications/IC/Assets/PDF/SmallCapResourcesSeminar_MatthewAllan_220413.pdf