This is from memory, from almost 30 years ago, so I may be a little off on specifics, but....
The fuel tanks I believe you are referring to are these:
View attachment 708979
In the early 1990s new tanks were installed at Groom Lake. There had been smaller tanks there previously (the old tanks are visible on 1988 satellite imagery). They were again changed in the early 2000s (the configuration shown above).
There was speculation that these may be cryogenic tanks supporting the Aurora program. At the time we had very, very limited information about them. Few photos, though at the time there were accessible viewpoints that allowed these to be seen.
Since then there have been better photos from the ground, from satellites, etc. There is no evidence to support the hypothesis that these are cryogenic tanks. There is considerable evidence to refute it. There is no evidence of any of the infrastructure needed to support the storage of cryogenic methane or hydrogen. These tanks appear to be be conventional POL storage for aviation fuel.
Further, back when these rumors and speculation were happening I looked deeply into liquid methane. At the time the total production capacity of liquid methane in the US was.... tiny. Not even enough to fill the tanks of an "Aurora", much less support a flight test program. And there is no evidence of methane or hydrogen production facilities at Groom Lake (not then, not now).