"When it comes to U.S. shale, it is still very much a case of the only way is up." The first clause was perfectly fine to me, but the second one got me good. Could anyone help me understand the whole sentence in an understandable way? Thank you.
The phrase 'the only way is up' is commonly used to mean 'only improvement (or increase) can be expected'. Whatever is being discussed is in a good place and it is surely going to get even better. Reference to the origin of the sentence quoted in the question makes clear that this is the meaning - the only way for earnings from US shale to go is upwards.
... industry analysts point out the U.S. shale boom is perhaps the most notable supply consideration not currently receiving the attention it deserves.
Packages may have text on them indicating which way something should be shipped:
It's an instruction to shippers that they should only be carrying it in a single way—otherwise they risk damaging the contents.
In a similar vein, we also hear the phrase:
The only way is (up/down/left/right/through/forward).
In other words, there is only one way to correctly navigate something.
To paraphrase your example sentence:
When it comes to U.S. shale, it is still very much a case of only being able to handle it in one way.
Further context would be needed to understand what can only be done in one way—so, handle may not actually be appropriate.
Update: I see actual content for the question has been provided in another answer. With it, my analysis, while still correct, reaches an odd conclusion.
It's now apparent that it's not talking about only one way but only one result: given the market, shale prices can only rise.