Actually, the Russians apparently have oil & gas shale potential that makes US resources look modest, but while that may make them self-sufficient it may not provide the type of income needed to arrest the decline of their military.
I wonder how much Russia’s oil and gas sales contribute to their economy. I’ve read that Iran needs oil around $80/bbl to fund their programs. In future years, it looks like unless it’s convenient we won’t be importing anywhere near the 12%, IIRC, of the world’s production like we do now.
There really won’t be a drop in demand. There will be an oil surplus. Russia will see their earnings drop along with all oil exporters.