We might be out in those fields, but check your math. 4.5% decline the first year, 96.5%. 4.5% the second year (of the 96.5%) is less, so the depletion curve has a tendency to flatten out.
Of course, this assumes no new discoveries will occur, and we are finding new reserves (maybe not as spectacular, but new reserves) all the time. As those come on line, their production replaces the production 'lost' to depletion in reservoirs which were developed earlier.
New technology, especially horizontal drilling, has opened up entire fields which were previously not considered possible to produce.
I live in a part of the US where oil wells are very common. I have never been able to understand why most oil wells will be pumping merrily away until there is talk of an energy shortage. For some reason, the pumps seem to quit running. When the price of gas increases the pumps start again.