Defining Terms: Wildcat, Development, Extension

A reader is wondering about the difference among: wildcat, development, and extension wells.

This was my unedited, quick answer:

That's a very, very good question.

Wildcat is probably the easiest to explain: there's much more to it, but two factors -- drilling in an area that has not yet been designated a field, and a "six-mile" rule. I could be way wrong on this, but it appears that even if a company drills inside a designated field, if there is no other activity within six miles, it is deemed a wildcat. I have seen some wells that are designated "wildcats" in the Bakken and they are literally sitting in a sweet spot, but because there is no other local activity, they are considered wildcats. For me, the designation of "wildcat" in the Bakken has lost a lot of its historical meaning.

"Development" and "extension" are a bit more difficult for me to understand. Perhaps just a continuum. Regardless, "development" wells are additional wells in the same section or, I suppose, adjacent sections, where there are already producing wells.

But it's a fine line. I will post this as a stand-alone and see if a roughneck has time to set me straight.

A much better answer:

This is probably the best source: at this google book link.

Wildcats: as noted above
Development: as noted above
Extension: wells that will be drilled at the perimeter of where known reservoirs are.

I've learned something. I never paid attention to the "extension" designation before.