Global oil prices will need to decline over the coming year for U.S. shale oil production to slow down, Goldman Sachs analysts said Monday in cutting forecasts for West Texas Intermediate (WTI) and Brent prices through 2015.

In a note to clients, Damien Courvalin and his team said until now, a tight global oil market had required strong OPEC production and growth in the U.S. onshore.

However, analysts “now have higher confidence that a structural transition has been reached and that U.S. production growth needs to slow.”

Core OPEC producers also have lost their pricing power, moving toward the “marginal cost of U.S. shale oil production.”

WTI was cut to $75.00/bbl for 1Q2015 and for the second half of 2015 from $90.00. Brent for the same periods was cut to $85.00/bbl from $100.00.

For the second quarter of 2015, the expectation is that the prices will e weakest then when the global oversupply is largest. Brent prices in 2Q2015 are expected to fall to $80.00, with WTI at $70.00.

To strengthen, Goldman analysts said prices will need to be low enough by early 2015 to force U.S. exploration and production (E&P) companies to slow capital expenditures (capex), which they believe occurs at $75.00/bbl WTI prices.

“Given our expectation that Saudi will not cut production meaningfully until they see evidence of a strong capex cut from the U.S. E&Ps, and given that such capex cut would not materialize in slower production growth for another six months, we estimate that global inventories will rise in the first half of 2015…”

By the second half of next, they expect domestic shale production to slow and core OPEC also to cut output.

“This would allow for global crude inventories to stabilize with the market back in balance in 2016 on the back of stronger demand and slower U.S. production growth,” said analysts. “As a result, we forecast that oil prices will stabilize at $90.00/bbl Brent prices (and $80/bbl WTI) in 2016.”