The first time I saw the Ruined Portal, I tried rebuilding it so would need only a few obsidian blocks to finish. This is far a way from my house, a few hundred blocks away. I then made a portal near my house to save time travelling to and from the rebuilt ruined portal. I destroyed the rebuilt ruined portal and used the portal I made near my home. After I got in the nether and went back, the game made another portal in the overworld near the ruined portal and returned me there rather than returning me at the original portal I came in through.

This is the portal I have from home.
Whenever I'd destroy the portal, and go back in the nether. I'd return to the Overworld with a new portal generated near the ruined portal.