Oklahoma City (US), Sept 11 (AP) T Boone Pickens, a brash and quotable oil tycoon who grew even wealthier through corporate takeover attempts, died Wednesday. He was 91.

Pickens' spokesman Jay Rosser confirmed the death to The Associated Press. Pickens suffered a series of strokes in 2017 and was hospitalized that July after what he called a "Texas-sized fall".

An only child who grew up in a small railroad town in Oklahoma, Pickens followed his father into the oil and gas business. After just three years, he formed his own company and built a reputation as a maverick, unafraid to compete against oil-industry giants.

In the 1980s, Pickens switched from drilling for oil to plumbing for riches on Wall Street. He led bids to take over big oil companies including Gulf, Phillips and Unocal, castigating their executives as looking out only for themselves while ignoring the shareholders.

Even when Pickens and other so-called corporate raiders failed to gain control of their targets, they scored huge payoffs by selling their shares back to the company and dropping their hostile takeover bids.

Later in his career, Pickens championed renewable energy including wind power. He argued that the United States needed to reduce its dependence on foreign oil.

He sought out politicians to support his "Pickens Plan," which envisioned an armada of wind turbines across the middle of the country that could generate enough power to free up natural gas for use in vehicles.

Pickens' advocacy for renewable energy led to some unusual alliances.

He had donated to many Republican candidates since the 1980s, and in the 2004 presidential campaign he helped bankroll television ads by a group called Swift Boat Veterans for Truth that attacked Democratic nominee John Kerry. A few years later, Pickens endorsed a Kerry proposal to limit climate change.

Pickens couldn't duplicate his oil riches in renewable energy. In 2009, he scrapped plans for a huge Texas wind farm after running into difficulty getting transmission lines approved, and eventually his renewables business failed.

Pickens flirted with marketing water from West Texas, acquiring water rights in the early 2000s in hopes of selling it to thirsty cities. But he couldn't find a buyer, and in 2011 he signed a deal with nearby regional water supplier to sell the water rights beneath 211,000 acres for USD 103 million.

In 2007, Forbes magazine estimated Pickens' net worth at USD 3 billion. He eventually slid below USD 1 billion and off the magazine's list of wealthiest Americans. In 2016, the magazine put his worth at USD 500 million.

Besides his peripatetic business and political interests, Pickens made huge donations to his alma mater, Oklahoma State University.

Pickens' foundation gave USD 50 million each to the University of Texas' MD Anderson Cancer Centre in Houston and UT Southwestern Medical Centre at Dallas.

He was among those who signed a "giving pledge" started by billionaire investor Warren Buffet and Microsoft co-founder Bill Gates, promising to donate a majority of his wealth to charity.

Pickens was born in 1928 in Holdenville, Oklahoma. His father was a landman, someone who secures mineral-rights leases for oil and gas drilling.

His mother ran a government office that handled gasoline-rationing coupons for a three-county area during World War II.

A child of the Depression, Pickens credited his father with teaching him to take risks and praised his grandmother for lessons in being frugal. If young Boone continued to leave the lights on after leaving a room, she declared, she would hand the electric bill to the boy so he could pay it.

Pickens went to work by age 12, getting a newspaper route. He expanded it by buying the routes on either side of his — marking his first venture into acquisitions.

Although only 5-foot-8, Pickens was a star guard on his high school basketball team in Amarillo, Texas, and earned a sports scholarship to Texas A&M University.

After graduating with a degree in geology, he joined Phillips Petroleum Co, where his father, T Boone Pickens Sr, was working. The younger Pickens was unhappy with his job from the start.

After just three years, he borrowed some money and found two investors to start his own business, called Petroleum Exploration. That was a predecessor to Mesa Petroleum, an oil and gas company in Amarillo, which Pickens took public in 1964.

By the 1980s, the stock of the major petroleum producers was so cheap that it became cheaper to get new oil reserves by taking over a company than by drilling. Pickens set his sights on acquiring other companies.

In 1984, Mesa Petroleum made a profit of more than USD 500 million from a hostile bid for Gulf Corp, then the fifth-largest oil company in the United States, when Gulf maneuvered to sell itself instead to Chevron.

Before that, Pickens earned USD 31.5 million by driving Cities Service into the arms of Occidental Petroleum.

Later that year, Pickens launched a bid for his old employer, Phillips Petroleum. It was an unpopular move in Bartlesville, Oklahoma, where Phillips was headquartered. Residents held 24-hour prayer vigils to support the company.

Pickens' star faded in the 1990s. He lost control of debt-ridden Mesa, and his bullishness on natural gas prices turned out to be a costly mistake.

After leaving Mesa, Pickens in 1996 started BP Capital Management, a billion-dollar hedge fund focused on energy commodities and equities that delivered mammoth gains.

There were difficult times in his personal life. In 2005, Pickens looked on as one of his sons, Michael, was arrested on securities-fraud charges — he pleaded guilty and was sentenced to five years' probation and ordered to repay USD 1.2 million. (AP)

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