Given the immense untapped shale resources in Europe and the US, it seems extraordinarily unlikely that these powers would risk fucking nuclear war over a bit of gas. If it's about Chevron's 10 billion, the Pentagon has suffered sneezes significantly more expensive than 10 billion. If the US administration should be so inclined, it would be so much simpler and cheaper just to reimburse Chevron for their loss.

However much we want to pretend that stuff ended in 1989, we need to wake up to the fact that it didn't. Russia has invaded a sovereign country as it tried to exercise it's sovereignty to align with the western values. However much we're busy hating ourselves (legitimately) over Iraq, Guantanamo and NSA, our values are infinitely better than Putin's.

EDIT: Oh, and as the linked articles explain, Europe is deeply dependent on Russian gas and the business and political interest is squarely towards appeasement. See former German Chancellor Gerhard Schröder for reference. If there should be a rational gas/Russia conspiracy, it would be leveraging the conflict to squash opposition to fracking. If that's actually going on, it's the weakest conspiracy yet this century.

The idea that you can represent a government, let alone an entire country or collection of countries, as having a single intent is faulty. I'm sure some individuals are motivated by economic interests, while others are desperate to have a worthy object of their Cold War chauvinistic sentiments, while others dislike Russia because of domestic homophobic and racist policies, while others like the face that the new government of Ukraine flattered their cultures and countries, while others just listened to Russophobic Western media, while others really dislike the idea of one country invading another and being sprayed with bullshit propaganda.

The search for intent and motivation as causal mechanisms in international relations is pretty dangerous.

There is no need to drag shale gas into this. Ukraine is a big country, even if very poor (for now). The economic part of the association agreement was especially damaging to the economic relationship between Russia and Ukraine. The EU played zero-sum game here, hoping (and not without reason) that the government will be forced to sign it anyway. It's just the whole thing escalated well beyond anyone would expect. Apparently, it was a mistake to impose such dividing agreements on an already deeply divided nation, the lesson the EU learned too late.

Seems to me the pressing interest of the us and European governments is keeping Putin's power and influence in the region in check. He's very clearly shown his willingness to use whatever means he likes including military force and assassination to expand his power in the region. Everyone remembers the impacts of the USSR doing the same. A success here could embolden him further so its in their interest to push back.

No doubt economic concerns are part of the equation but IMO its a bit tinfoil hattish to suggest its purely about some particular shale gas deal.

Perhaps some businesses care (I haven't heard this), but from a political point of view, many Americans would have opposed it anyway and politicians would do the same.