Difference, Russian gov't is screwing Shell and Exxon.
COP is buying (and has been for a "long" time now) into a russian company. If Russian gov't wants to screw COP, they have to screw LUK and even a 20% COP ownership, LUK is 80% Russian.
Now COULD Russia (gov't) or Putin, find a way to screw COP on the LUK deal. Yep, sure could. But fallout for doing that would be much greater than from the RD/XOM issue.
A simplistic (and not completely accurate but good enough) way to look at is this. Putin feels that XOM/RD are taking from Russia due to the good deals they extracted in the past when they held the upper negotiating hand. COP otoh, is investing in Russia via LUK not taking from them.