I am sure the oil experts around here will pipe up if I messed up that explanation of why reservoirs in KSA are not likely to flow better from Fracking technology in the future.
You got most of it correct, however, the devil is often in the details. Fracking for many years was mainly used in conventional reservoirs to get past damage zones (the area closest to the well bore that for one reason or another had it's permeability adversely affected). It is still done today although operators tend to be a lot more careful with mud weights when drilling, checking for reservoir compatible fluids etc. So my guess is that Aramco has already fracked a number of wells to clean up damage.
The nature of the reservoirs in Saudi are such that, as you say, there are lots of porous and permeable carbonates and sandstones that are largely responsible for production. That being said, there are areas where those same reservoirs were deposited in a different facies and are tighter. Those zones would be the subject of investigation with fracks at some point in time.
Currently Aramco is ramping up their unconventional gas E&P with a plan to begin fracking tighter reservoirs (mainly tight sandstones and carbonates and to a much lesser extent shales). To date they have fracked a number of wells successfully and are trying out all sorts of new technologies. This is a method by which SA plans to increase its available oil for export given they currently consume large quantities of oil for fuel useage and that can be supplanted with natural gas. I described all of this in the Saudi Arabia thread a couple of weeks ago.