The Nigerian Government must be feeling the heat now. When they made a budget for 2015, they didn't think the oil price would fall to as low as $59 a barrel (price as of 16/12/14). Saying that Nigeria's economy is wholly dependent on oil revenues would be an understatement, despite the nation having many other natural resources, politicians over the years have instead been drawn to the insane revenues that can be made from oil at the detriment of other sectors of the economy.
The revenues from the oil should have been used as a catalyst for expanding the other sectors of the economy (agriculture, finance, fishing (yes), instead, it has been squandered on corruption and out-of-this-world salaries and expenses of the federal and state government officials.
That Nigeria's external foreign reserves has been plummeting is no surprise to anyone, years of neglect of the other sectors of the economy not related to crude oil by successive governments have led the current government scrambling to find much needed funds in the wake of the still plummeting oil price.