Shall I tell you why Putin wants the Ukraine?
1) Grain and other agricultural products.
In 2010-2011 Russia and the Ukraine had a bit of a drought. Their exports of things like grain and wheat dropped massively.
What happened? The Arab Spring happened.
Imagine if you could control oil countries by controlling their food.
www.fao.org
You can see here, 2010-2011 about 4 million tons for Ukraine, down from 12 million the previous year. Russia down to 11 million tons of exports compared to 16 million the previous year.