Those sanctions pushed Russia to sign a $400 billion deal with China last year and these oil executives (who wanted to but could not invest in Siberia and Sakhalin, where they have big stakes, like Shell's $20 billion giant gas plant and BP's 20% in Rosnet), want to make sure that they do ot miss out again.
These western oil executives have been influenced by a recent BP report that stated that Russia's oil and gas reserves have jumped to 103 billion barrels (from 93 billion in 2013).
Their visit to Putin's hometown will definitely give him a boost, especially as they will meeting with him.
Europe needs Russian oil and gas and Russia needs the money, and this will play well with the Russian people, with whom Putin enjoy an above 80% popularity. A recent lull in the fighting in Ukraine gave these executives the excuse to make sure they maintain good relations with Moscow and to further their oil ad gas investments for the future when political leaders in the West (eg. Obama) will no longer be in power.