Rear wheel deep abrasion on carbon chain stay - safe to ride?

I've got similar on my old road bike - pothole buckled the wheel and I didn't notice until I got home.

All I did with mine was put a patch of thick frame tape over the scuff to both seal it and protect it - and then did the same on my other bikes to prevent the same happening on them.

I concur with Jerome. You can readily fill that with epoxy and be on your way. There's no evidence of carbon fibres involved, filling with an off the shelf epoxy will provide some protection if your wheel should rub again. Nor would I be too concerned about dire predictions of "failing suddenly and catastrophically" I've ridden with 2 guys whose chainstays have ruptured (both while trying to bunnyhop railway lines) and they both continued safely at speed after the incident. 

Not a single fiber has been severed. The chainstay is as structurally sound as new. Just check it from time to time.

Is that chainstay likely to be hollow? If so you might be able to reinforce from the inside?

A quick search doesn't look promising for CF repair in HK, however if you strip all the parts off and can spring for shipping to Singapore, The Rebound Centre (http://thereboundcentre1995.blogspot.com/p/service-specialities.html) seems to have a good reputation.

At least it won't involve intercontinental shipping...

There's a carbon repair workshop in Dorking that will fix this for a few hundred quid.

how deep is it difficult to tell.  I would imagine as others have said a carbon repair shop would be the best place to get some advice.  

I'd be more worried that your entire wheel appears to be missing.

I concure with Canyon48, ask a carbon repair shop. They can tell you if it's OK as it sits, or needs repairing.

That looks like barely anything - just the top coat, resin and possibly the outer wrap of fibre (which isn't usually a structural element as such).

That said, I recommend getting it checked by someone who knows what they are doing (like carbonbikerepair).

I've seen far worst come off operational aircraft that have operated in the desert in my job as a carbon fibre design engineer!

It doesn't look deep, but no-one can really tell you much definitively without a proper frame scan.  I wouldn't ride it untill you have one performed, carbon fibre is liable to fail with little warning.

Get in touch with these guys https://carbonbikerepair.co.uk/ who can help properly, scan it and price up a repair.  Best case you get a safe bike for less than a frame, worst case you're out the cost of a scan.

Your LBS can't scan or repair carbon bikes so the default will always be to replace rather than repair.

I've got the same on my bike and have been riding it for years without any issues.  Yours looks ever so slightly deeper than mine but I wouldn't worry too much about it.