RE:RE:OCMHi again, Blinded by the word "ascertain", I might have missed the gist of your message...
Probably the more relevant answer you are looking for is that one:
An exploration well encountering (several) hydrocarbon bearing formations with flow potential (but regardless of commercial quantities being in place) would take, as a general indication, longer to drill than the very same well going through layers of the same hardness etc that would not hold hydrocarbons in place, due to many points related to pressure management, gas levels management, potentially wellbore stability issues, loss/kick issues etc. It is not to say that none of these issues exist in dryholes, they do exist but as a general rule HC-bearing formations will give you more (and a combination) of these points and as a consequence you will be slowed down.
GLTA,