maybe if one was a modifier (increase by %), and the other was a flat bonus (+X) they could synergize without being the same thing. it would also help from having a lesser and greater scouting spell in the same category (one of which becomes useless when the other is researched). one could also swap the mineral infusion spell for the production spell as that might be a better fit for the two spells.
at the very least it is something to think about.