at VoxEU: Plummeting oil prices, depreciating oil currencies? Not so simple

VoxEU features a post [voxeu.org] by Sascha Bützer, Maurizio Michael Habib and Livio Stracca on the effect of oil price changes on currencies, finding some unexpected results:

The large dip in oil prices reverberated across asset markets, contributing to the depreciation of the Russian rouble. This column argues that the recent fall of the rouble may be more an exception than the norm. Oil shocks have only a limited impact on global exchange rate configurations, since oil exporters tend to lean against exchange rate pressures by running down or accumulating foreign exchange reserves.

There is a paper underlying it, here [europa.eu].