When to SellIf you are long then you should hold your position. Big money is not inclined to short oil until after the OPEC meeting at the end of the month. In fact short interst has been declining since the middle of Oct and is almost at 5 years lows. Here's a link to the net short position of managed money.
https://ycharts.com/indicators/nymex_light_sweet_crude_oil_futures_managed_money_short_positions
The Saudis are essentially OPEC and what they want will happen. At the OPEC meeting next week look to them extending the cut agreement until later into 2018 as the world wide oil inventory levels are still above the 5 year average plus they intend a saudi aramco IPO in 2018. This will spike WTI oil to the low $60's over the next few weeks.
Once the OPEC euphoria runs out in a few weeks then the big shorts will start to build a position. In the $60 range NA producers will lock into the fuures curve, rig counts will jump and so will NA production.
As a general rule when at extremes expect to see a reversal like the short interest at 5 year lows. Also net long positions will want to take profit. Even slight bear news after the OPEC meeting will trigger a sellnig downtrend as net longs exit and shorts pile in. The bottom line is right now shorts are scared of OPEC so won't step infront of longs until that decision is made public.
If OPEC doesn't extend cuts then this will trigger corrrection. It's a virtural cerantity that OPEC will extend the cuts though so no worries for the bulls until after Nov 30.