Maintaining US shale oil production depends entirely on drilling new wells. Average decline rates y/y are around 70%, so without a continual supply of new wells being drilled, shale production will drop off dramatically.
The Haynesville shale play was the first shale play to experience a rig decline. You can get a sense of how production will drop nationwide by looking at how production responded to the dropping rig count in Haynesville. So first look at the total rigs in operation compared to the rigs required to keep production at the break-even point (i.e. no increase, but no decline). Then look at what happens when the rig count drops precipitously, as it did in Haynesville.