The block is Vermilion 380. I think the 398 is Mariner’s internal name for the platform.
Vermilion 398, another block entirely, doesn’t have Mariner involved in it.
I am looking at the map right now. Vermillion South Block 380 and 398 are adjacent to one another. Dynamic, Forest, and McMoran also have active platforms in the area. Water depth is between 340 and 380’.