Geologists are uncertain as to the exact amount of oil that is in the Arctic National Wildlife Refuge. Based on the one seismic survey that was done and the exploration of a few test wells drilled, it is estimated that there may be 16 billion barrels of oil under the tundra of the Arctic National Wildlife Refuge. However, how economical it is to recover the oil is dependent on market prices and shipping costs. When oil was $25 per barrel, the United States Geological Survey estimated only seven billion barrels might be pumped profitably. When the price per barrel soared to over $100 per barrel, it would be profitable to recover many more billions of barrels of oil. Drilling for oil in the Arctic National Wildlife Refuge continues to pose many environmental issues and concerns.