US L48 conventional oil peaked in 1970. since that peak, it has declined 80%.

In 1970, crude oil cost just $3.18/barrel. Prices in 1973 were still $3.18, but they soared to reach $34/barrel by 1981. This was due to two oil shocks: the Arab oil embargo in 1973 and the Iranian revolution in 1979.

In 1973, President Nixon announced Project Independence. The American rig count jumped from 302 in 1970 to 993 in 1973 to 4500 in 1981. Oil production during that time fell 34% from 9.6 MMBD (1970) to 9.2 MMBD (1973) to 6.3 MMBD (1981). American Lower 48 production fell despite massively increased drilling.

I think this is the fate of the Permian and the other shales.

Mike can probably explain why the oil production fell better than I can, but I think it was due to declining pressure.