All JV partners will share the loss of equity evenly IMO based...

All JV partners will share the loss of equity evenly IMO based on the % they hold so yes you are right if the split is 20-20-20-40 it would be 2-2-2-4%
That is how its normally done. It will already have been negotiated either in the PEDPA or the PSA and will form part of the JV agreement.
The joint venture agreement or JOA sets out the responsibilities of each of the JV members. There will be a panel formed of the JV partners who will decide, and vote, on the work programme and budget.
Its convoluted but each JV partner has a % of the vote attributed to it based on WI. We need to be very careful that we maintain enough WI to veto any vote that is not in our interests, it would also stop the JV members removing us from being operator, which can be done via a vote.
I would like to see IVZ maintain at least 44% or 40% after ZWF back in at FID.