Ok, to answer myself: I created my blockchain wallet in Q2/2016. Today, that is regarded as "legacy" wallets, and no longer really supported.
The recovery passphrase for legacy wallets was called "mnemonic", and there is still a page where this 17-word long mnemonic can be used to recover a lost access to these legacy wallets:
https://blockchain.info/wallet/forgot-password?guid=

Thanks a lot guys & good luck with finding your solution.

Apologies to "hijack" the thread a bit, but I'm in a similar situation like the OP, with the exception that I have those passphrase words written down onto a piece of paper.
My problem is that I have 17 words, not 12, and they do not work. Anybody seen this and/or knows if e.g. the pasphrases changed?

Thanks a lot.

Hello everyone,

I have logged around a year ago to my blockchain.info wallet.
I have also recorded the resovery passphrase words (I have 17 of them).

Now, I cannot log in (my password does not work) but also if I try to recover using my passphrase, the site saiz I need to use my "12 worded passphrase".

This is weird, because I have 17 words written down . (I tried to use them too, but with no luck).

Anybody has the same issue?

Thanks a lot in advance for your help.