@adam yes. Don't get them on the trunk (it can burn the bark) and spread about the size of the root ball. Olive roots go wide rather than deep. On a mature tree the root ball will be about the same width as the canopy.
@adam got pics? I'll send you some #OlivePorn in return, we are on with pruning at the moment. We have a new set of trees to deal with that haven't been properly done for about a decade or so.