Interesting post, as I was one of those who held off building oil wells for quite sometime, and was happy with just the refinery. But, finally, I bit the bullet and went with building and upgrading the oil wells.
What you're saying might have been true quite some time ago, but, things have changed with the game, and with the recent changes, it's worthwhile to build and upgrade the oil wells. The recent 40% boost to production, and the Moctezuma researches at the University to increase storage capacity of oil wells have made oil wells quite compelling now, if not already.
The key to minimizing oil losses from attacks is to design the base as follows:
1. Do not place the refinery and the oil wells together in a single or adjacent compartments.
2. Let the oil refinery be at or near the center of your resource protecting layout, but, distribute the placement of oil wells around the base, preferably inside the walls. Try making one of the compartments slightly larger, and place an oil well or two, along with other defensive buildings. Let this not be in the obvious path to breaking walls and getting to your refinery.
If you design your base as described above, the only reason you would lose oil would be to overpowered attackers who might 5 star your base, but, will be able to discourage raiding attacks.
If you get a good and a long peace treaty, and if you don't expect to play for quite a while (say, shortly after you've finished your gaming session for the day, and sometime later, you discover you've been attacked), you might want to consider activating an oil blessing, and try collecting from the wells as much as possible.
Hope this helps!
Cheers and happy gaming!
