What happens to long otm oex puts if you exercise them?

Given this is an exchange traded option, the exchange contract specification should state exactly what would or could happen.

http://www.cboe.com/products/stock-index-options-spx-rut-msci-ftse/s-p-100-index-options-oex-xeo/oex-specifications

It doesn't seem to state that out of the money exercise is prohibited, so perhaps you can do it and pay the loss into your margin account - more detailed procedures are probably detailed elsewhere. However, I can't see why anyone would want to do this. I suspect that your clearer would probably try to stop you or at least ask if you know what you are doing!