I recall a game update that was made to fix gasses being multiplied near steam vents, but it appears that the bug is back again. But it does not seem to be limited to steam vents can happen anywhere steam is generated. The attached screenshots and save file are of water dripping into the oil biome. Both the steam and CO2 have multiplied to an extreme level. There was originally only 2-3 tiles of water (so, appox 2500 kg) but now I have far more than that. The CO2 has also run away and is flooding my base.
There are also some related bug posts, most related mine from April 5
Create/condense steam in a confined area; most commonly seen near cool steam vents.