Associated Press
Matthew Simmons

ROCKLAND, Maine — Matthew Simmons, a Utah native and energy investment banker who espoused the peak oil theory, became an advocate for alternative energy and served as energy adviser to President George W. Bush, has died at his North Haven island home, officials said Monday. He was 67.

The founder of Houston-based Simmons & Co. International wrote the 2005 book "Twilight in the Desert: The Coming Saudi Oil Shock and the World Economy," raising concerns about Saudi Arabia's oil reserves and laying out his theory that the world was approaching peak oil production.

Two years later, Simmons founded The Ocean Energy Institute, a think tank and venture capital fund in Rockland to promote offshore wind energy research and development.

The institute is a part of the consortium led by the University of Maine, which aims to design and test floating deep-water wind turbine platforms.

Simmons, who was raised in Kaysville and Layton, graduated from Davis High School and the University of Utah before going on to earn his MBA from Harvard Business School, according to his brother, Harris Simmons, chairman and chief executive officer of Salt Lake-based Zions Bancorp.

Harris Simmons said his brother was a "very entrepreneurial fellow" who loved building businesses and helping other people do the same.

"For somebody from a state which has very little in the way of energy industry presence, he really became a very notable figure in the industry," Harris Simmons said Monday. "He built a firm that did over 750 investment banking projects over the last 35 years totaling about $140 billion in total size, and he never shied away from controversy. ... The energy industry has lost one of its greatest fans and one of its sharpest critics at the same time."

Matthew Simmons loved visiting Utah, Harris Simmons said, and he enjoyed the friends and heritage he had here. All four brothers in their family were influenced by their businessman father, Roy W. Simmons.

"Business was kind of a theme around our home," Harris Simmons said. "Building businesses, and how to help others build businesses, was something my dad was focused on throughout his career, and it rubbed off on us."

Matthew Simmons' body was found Sunday night in his hot tub, investigators said. An autopsy by the state medical examiner's office concluded Monday that he died from accidental drowning with heart disease as a contributing factor.

In 1974, Matthew Simmons founded Simmons & Co. International, which grew into one of the largest investment banking companies serving the energy industry. He continued to serve as chairman emeritus until last month, when he retired to give his full energy to the Ocean Energy Institute.

"We are deeply saddened by the unexpected loss of a true visionary and friend. As a pivotal figure in the lives of many of our employees, and countless others across the energy industry, Matt will be sorely missed," Simmons & Co. CEO Mike Frazier said in a statement.

Matthew Simmons was critical of BP PLC's handling of the Gulf oil spill and predicted the company would file for bankruptcy. In one interview, he said the cleanup costs could top $1 trillion.

As an international energy expert, Matthew Simmons correctly predicted in 2007 that oil would surpass $100 a barrel. The following year, it peaked at $147 a barrel.

Contributing: Greg Kratz, Deseret News