This is an unambiguously good update given the context. ie after...

This is an unambiguously good update given the context. ie after the previous announcement mentioning only hydrogen a fortnight after reaching 3300m which rightly made many assume they were much deeper without anything material to announce to the market.

As Eric mentioned, seeing background mud gas rise in what is essentially the bottom of the seal above the target is a good thing. Hard to say whether it's indicative of hydrocarbons being trapped in the bottom of the seal from the prospect itself or lateral migration from a similar source, ie, it might be it's own "layer" of the cake as it were. Regardless it shows hydrocarbons and trapping. It's about as good as you'd hope for in a seal before the main target I suppose.

One thing I have to say is that Buru are obviously working off an updated set of assumptions from previously publicly available data so my input can only go so far. Their Rafael 2D survey in 2015 essentially said there was unlikely to be any Anderson or Laurel formation (after Rafael was considered to perhaps be a Laurel target in '13). You can see this in the way the prospect has flipped from an Ungani to Nullara target and back again over the years - the stratigraphy is generally described with a question mark in the reports... Like: "Clanmeyer?".

So I suppose the biggest possible answer in the update is: If they're casing at the bottom of the Anderson... which is at the top of their interpreted target.. Suddenly it's looking a lot more like a Laurel Ungani Dolomite prospect overlain by the Anderson like they first thought rather than a Nullara prospect overlain by the Clanmeyer....

If true I would guess this is a slight positive purely on the numbers as it is more pervasively and regionally dolotimized. It's possible the prospect might have less risk of charge as it might not have had to migrate too far in that case.

I just can't really say much given the lack of drilling in the area. The full range of options is still currently available from success to failure but I am buoyed by the mudgas. It's the sort of thing you want to see, which is why it was mentioned.
Eric is also probably re-iterating that their overall interpretation of the prospect is solid. The seal might be harder and thicker than anticipated, the formation might be the Anderson, they might go to a deeper total depth, but those are kind of more minor issues when you've cased above the target and found mudgas increases and in general it appears to conform to their interpretation of the structure.

I guess this is my TLDR takeaway: Rafael is still completely in play. It's not at some hail-mary depth checking a secondary target trying to pull victory from the jaws of defeat or lacking hydrocarbons or whatever people were saying last week, it simply took much longer than anticipated to get to the main event. That main event is quite possibly a Laurel Ungani Dolomite target (not that that materially changes things too much, it's just nice to have an answer after so many years) so the pool balls are sitting there racked and ready to break and we'll see whether we get any in the pockets.

Judging by the nice rise, the market seems to realize it was adding too much risk to it (length of time, hydrogen ann), and now it's been spelled out that the game is still on and there are hydrocarbons in a trap there is some repositioning.