* Two biggest oil firms have finished major projects
* Exxon, Shell able to cut 2015 spending
* All oil majors face 2015 negative cashflow
* Set to increase borrowing easily to cover shortfalls
By Ron Bousso and Dmitry Zhdannikov
LONDON, March 10 (Reuters) – The world’s two biggest oil firms, Exxon Mobil Corp and Royal Dutch Shell, may withstand the oil price collapse better than their rivals because they are closer to finishing expensive investment projects while others must keep spending.