There is no "season" for OVAs : Contrary to a TV 
serie, there can be any number of OVAs.

For Tenchi Muyo, the first serie of OVAs is made
of episodes 1 to 6. The 7th is a special but 
usualy counted as part of the second serie of 
OVAs.

Both series of OVAs were produced before the first 
TV serie and the movies.

AIC is currently working on a 3rd series of OVAs 
but it will be only CG.

Cheers,
Yann Stettler