I believe the depletion rate is getting better with improved drilling and fracking techniques but unfortunately these numbers may not be too far off!
The Post Carbon Institute’s report argues that the EIA is overstating the potential of U.S. shale, calling the projections “highly to extremely optimistic, and are therefore very unlikely to be realized.”
The report argues that while U.S. oil production has doubled from 2005 levels, and shale gas has also exploded over the same timeframe, there are underlying problems that will always bedevil shale production. For instance, shale wells typically see production deplete by 70 to 90 percent in the first three years, while fields see output drop off by about 20 to 40 percent per year without new drilling.
That means that the industry has to constantly plough more money back into production, just to keep output flat.
Maybe M Barnes can provide some better numbers.