Technology and portfolio high grading enables U.S. shale to defy early predictions This happy circumstance is largely due to a couple of things primarily. The first is technology making the extraction of more oil per unit of interval than even just a few years ago. And, operator high grading of their portfolios to focus almost solely on Tier I acreage. Tier I acreage, as we have discussed in the past is the low cost, high return play that works particularly well in the Permian with its stacked reservoirs. Shale drillers have simply been making some prodigious wells in the last couple of years, and this increase in the Productivity Index-PI has made itself known. As an example I would cite Devon Energy's, (NYSE:DVN) recent performance in its core Delaware basin area.