When the bottom dropped out in the mid-eighties, it was just cheaper to buy from OPEC. Fracing technology was no where near what it is today, or even a decade ago. I remember my Dad being absolutely livid, that the Railroad Commission was forcing operators in the Permian to plug thousands of wells in the Spraberry and Dean formations. He said it would never be economical to drill those formations again. He was right, based on 1980's technology. It wasn't really feasible to spend R&D money until around 2003-2004 when the Barnett Shale, and robust gas prices came along. That is when technology really took off and new drilling rigs, multi-stage fracing, steerable drill bits, and all of the supporting infrastructure really took off.
The Permian is where companies go to have the greatest success rate. There are tens of thousands of well logs, from the 1930's to the present for the geologists, and engineers to work off of. The whole basin is basically mapped for a 100% success rate. That is what you are seeing at the end of that graph. As long as prices support it, that map will continue the same trajectory, or possibly rise even faster.
It is beyond time to build some new refineries to match what can be produced. Ones that can refine WTI.
CHIEF