The natgas pipeline theory has floated for a while.
Note, however, that MOST presentations of that theory have Quatar and Saudi Arabia on the same side - with BOTH supporting anti-Assad (ie. ISIS) fighters.
Here is a much better tie-in than the whatdoes russky source:
http://www.news.com.au/world/middle-east/is-the-fight-over-a-gas-pipeline-fuelling-the-worlds-bloodiest-conflict/news-story/74efcba9554c10bd35e280b63a9afb74

Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...