Here is the IEA on possible production shortfalls from Iran and Venezuela:
“The issue of exports from Venezuela and Iran is likely to dominate the agenda when leading producers meet in Vienna later this month. For our part, we have looked at a scenario, not a forecast, showing that by the end of next year output from these two countries could be 1.5 mb/d lower than it is today. In Iran’s case, we assume a loss of exports close to that seen in the last round of sanctions, recognising that this remains uncertain and a broader range of outcomes is possible. No judgement was made as to which countries will cut back purchases. For Venezuela, we assume no respite in the production collapse that has taken 1 mb/d off the market in the past two years.
To make up for the losses, we estimate that Middle East OPEC countries could increase production in fairly short order by about 1.1 mb/d and there could be more output from Russia on top of the increase already built into our 2019 non-OPEC supply numbers. However, even if the Iran/Venezuela supply gap is plugged, the market will be finely balanced next year, and vulnerable to prices rising higher in the event of further disruption. It is possible that the very small number of countries with spare capacity beyond what can be activated quickly will have to go the extra mile.”