The horizontal technology has been around a while too, although constantly being refined I'm sure. All of the Northern Alaska fields were drilled horizontal. We were doing that 25-30 years ago. Usually around 20 wells on one work pad. Drill a hole, move over 40 or so feet and rill another one. I was long gone from the oil rigs when they perfecter the coil a decade ago. Also those holes weren't as deep as the williston basin oil.
My guess is the $130 a barrel prices had more to do with the field coming on line that the advance of the technology.