When I worked for Gulf Oil, about 30 years ago, (see related oil reserve post below) an article came out in one of the journals that had everybody buzzing.

Someone made a statistical study of the amount of wells that were strikes as a proportion of the total number of wells drilled. By "wells", I mean new holes drilled in an area where oil was suspected, or where exploration had suggested oil might be found. (Additional wells drilled to boost production in an already known field were not counted).

The result was that the number of producing wells relative to dry holes was more or less constant, ever since systematic drilling began in Pennsylvania in the 19th century. That is, you were just as likely to hit oil in 1870 as in 1970. This is really surprising, because we could drill a lot deeper now, and because all sorts of new exploration techniques were now available for mapping underground
rock formations.

I wonder if that trend still holds?