I worked in the chemical industry for years. Most of which was associated with flows of various type chemicals/liquids. We would often guess temperatures and flows in a non-technical way. Just looking at the flow, and it being upward, etc., I would guess that what you are seeing in the photo is probably close to 8 - 10 gpm. I have no idea the ratio of water to oil, etc. But, the stream you see spurting out will come close to filling a 10 gal. tub in 60 seconds. Now, that is based on it being "steady", and not intermittent. And it very possible that there will be surging. JMO.