Following a stunning decline, oil prices have clawed back near the $50 level this year. Production boomed in the U.S. but is now slumping. Globally, OPEC is in disarray and major producers can't agree on steps to boost prices.

Daniel Yergin is the vice chairman of research firm IHS Inc. He has written two books on energy, including the Pulitzer-winning opus "The Prize: The Epic Quest for Oil, Money and Power," which is essential reading for anyone interested in the subject.

Yergin recently talked to The Associated Press about oil prices, the shale revolution, the fate of coal, and the next big thing in energy. The answers have been edited for length.

Q. Where is the price of oil headed?

A. I think the worst of the collapse is over. Prices where they are today (around $48) are not going to provide a signal for the investment that will be needed to meet demand by 2020, so I think we will see higher prices. But unless there is some big surprise or disruption they wouldn't go back to $100 a barrel.

Q. Have we seen the worst of the defaults and bankruptcies in the oil patch?

A. The pace of bankruptcies will slow with the price recovery, but companies that are heavily laden with debt continue to be vulnerable in this environment.

Q. Should we expect Saudi Arabia, with a new oil minister, to change its thinking about how much oil they produce?

A. They are not going to cut back in order to balance the market and enable other people to increase production. That is their new policy since the November 2014 OPEC meeting, and that is a big change. The tension between Saudi Arabia and Iran is a very decisive force in the oil market today. The Saudis do not want to reduce their number of barrels in order to make room for more barrels from Iran.

Q. Is the idea of a production freeze dead?

A. The Russians have floated the idea again for June, but the Saudis have made clear they are not going to join any freeze unless everybody joins. That means Iran, and Iran is saying 'We're not going to join a freeze because we want to get our production back to where it was.'

Q. U.S. production is falling. When will it recover?

A. The shale producers were quite amazing in terms of their resilience and innovation. For quite a number of months after prices fell they were continuing to increase production. The realities, the economics have finally caught up with them. Our estimate is that next year U.S. production will be down 1 million barrels from its peak in April 2015. At around $50 is where you would see U.S. production stabilize.

Q. What will our energy mix look like in 2040 or 2050?

Q. Hydrocarbons are still going to be dominant by 2040. Renewables are going to be a growing part. In terms of new-build in U.S. electricity, we think all the new capacity will either be natural gas or renewables.

Q. Will efforts to limit carbon emissions and climate change affect that?

A. I think people don't understand how pervasive oil and gas is in our whole economy, not just in terms of transportation, not just in terms of fuel, but in everything from your cellphone to cosmetics. I think also the ironic thing is that if shale gas and shale oil hadn't come along, we would be much more concerned about energy security, prices would be much higher, and our nation's carbon footprint would be much larger because gas has been a key element in bringing down our CO2 emissions.

Q. Is coal's decline inevitable?

A. Between coal (plant) retirements and reducing plants and the fact that all new plants will either be gas or renewables, coal's share of electricity will continue to decline in the United States. I think it will grow in other parts of the world, particularly in Asia.

Q. What's the next big innovation in energy?

A. The biggest energy innovation of the 21st century is shale, and I say that because wind and solar have been around for about 40 years. The shale breakthrough has had enormous impact, not only in terms of energy supply but in terms of foreign policy. There would not have been an Iranian deal (to lift sanctions over Iran's nuclear program) without it because sanctions on Iranian oil probably would not have worked without the additional supply. And it has also made the U.S. much more competitive in the world economy. What's next? The one to keep your eye on is what happens with storage of electricity -- of renewables, of electricity. That could be the next game-changer. Another one would be some new way that is cost-competitive of capturing carbon. CCS, carbon capture and storage, is feasible but it's expensive.

Q. What is your next book about?

A. I want to write about some of the major geopolitical issues around the world and how energy fits into them. Part of the book will deal with how the shale revolution is changing the position of the United States in the world. You listen to the political debates in the United States ... people talk about the decline of the United States. This is an example of the rise of the United States. It is enhancing U.S. power and position in the world.