Didnt get the question? I suppose you are talking about osmotic pressure which is different for sea water and well water because of the difference in TDS. Sea water has a huge amount of TDS  and hence needs around 60 bar pressure for efficient recovery in Ro membranes whereas well water has very less amount of TDS and hence needs around 20 bar. One can use the same membrane for both, but pressure for them varies according to TDS.

My question is that, Sea water membrane can tolerate 60 bar pressure & well water can tolerate only 20 bar pressure. well water membrane can be damage on more than 20 kg pressure but sea water membrane not.
So what is the material quality difference between both membrane.