Saudi Arabia has made up for much of the export declines from Iran since the sanctions were put in place. In the event that Iran can replace its lost barrels, it is unlikely to drive global prices much lower, as the Saudis certainly can respond by lowering their own crude production to keep prices in check.
All in all, this is a long term unfolding situation with little immediate impact on global oil supplies. Politically it is a very charged issue and will continue to be regardless of how it is resolved, but it is unlikely that oil prices will trend downwards for any sustained period as a result of developments in Iran. Indeed, reaching a final agreement that satisfies all parties adequately, reduces nuclear risk and reduces Middle East tension (and the associated fear premium) is remote at best.
When you cut through the noise we believe there are simple truths that remain intact. Demand for oil continues to rise, but it is becoming harder and more expensive to maintain or increase global oil production. The barrels produced today cost more to get out of the ground and thus necessitate higher prices. Prices in turn seem to find a floor at the marginal cost of a barrel of production. We believe all of these factors are supportive of higher oil prices, and thus this most recent accord does nothing to change our investment thesis or commitment to the oil industry.