Clean up old 'open vouchers'

There are 1,500+ open vouchers valued at xx amount from 1998 – 2013 that we want to remove (most or all) from the system.  It's our understanding that if the vouchers are closed or deleted, that a reversing entry will be made that will result in xx amount being put back on the books as a liability needing to be paid which would be incorrect and something we don't want to do.

Can you please let us know us what our options are to clear/kill/remove/eliminate/etc. these 1500+ old open vouchers from the system without impacting the ledgers?