10/27/2014 09:38 EDT | Updated 12/27/2014 05:59 EST

Oil price will fall to $70 a barrel in 2015, Goldman Sachs says

One of the world's leading investment banks says the benchmark price of North American oil is going to fall even further, to $70 US a barrel by next spring.

Investment bank Goldman Sachs slashed its forecast late Sunday night for both West Texas Intermediate and Brent crude — the two most common types of oil used and sold in North America and Europe.

Goldman Sachs says WTI will go for $75 a barrel in the first three months of 2015. Brent, meanwhile, will change hands at $85 a barrel. Both forecasts are down $15 from what the bank was last expecting. And both are forecast to slip even lower in the second quarter — historically a seasonally low time for oil prices — before rebounding a little in the summer of 2015.

If the prediction on WTI proves correct, it will be the lowest price for North American oil since 2010, when crude was on its way higher after cratering during the recession of 2008 and 2009.

Currently, WTI is trading at about $80. That's down from more than $100 a barrel earlier this year.

The main reason the bank cited in making its call is simple supply and demand. There is more oil being produced now than the world needs, the bank says.

A boom in shale oil and gas in North America this year and last has drastically increased the amount of oil in circulation. This month, it's expected that the U.S. will pump out more crude oil than Saudi Arabia does — the first time that's been the case since the early 1970s.

Goldman says the North American oil price will average $73.75 for 2015 as a whole. Last year, the bank predicted the average price of North American oil would be $94.83 this year.