The secret wealth of the world's richest oil billionaires

The revelations were particularly loaded with hypocrisy because of Nazarbayev's push to encourage his country's wealthy to repatriate funds from abroad in order to make them taxable.

"We've raised many rich people: billionaires, millionaires," he said, when oil prices tanked in 2014 and the government began using sovereign wealth funds to fund operations. "They are showing off; (their) pictures in Forbes… They look good, with makeup, well-groomed, well-dressed. But it is Kazakhstan that enabled you to earn all this money… Bring the money here. We'll forgive you."

Angola

Things here may be about to change, because President Jose Eduardo dos Santos has said he plans to step down after decades in power, and won't be running in August's presidential elections, but still plans to control the ruling party. Here, wealth is all about Sonangol, which has been marred in controversy since the president last year named his daughter as the head of the state-run oil company.

Angola has massive oil wealth, yet the bulk of the country's 22 million people live in poverty, and critics say he's mismanaged the country's oil wealth and created an elite that largely consists of his massively rich family. But this scheme is being hit hard by the fall in oil prices that began in mid-2014, and the people are no longer complacent in their poverty.

The president's daughter, worth an estimated US$3.4 billion before she took over the state-run oil company, has been described by Forbes as Africa's richest woman.

Brunei

And here's one that's probably not even on your radar, but it will be—sooner rather than later.

Vast reserves of oil and natural gas have made Sultan Hassanal Bolkiah of Brunei one of the richest leaders in the world. The Sultan is believed to be worth US$40 billion at the low end, and while ‘his' holdings officially belong to Brunei, in reality they belong to the royal family.

Brunei is the third-largest oil producer in Southeast Asia, and pumps out, on average, 180,000 barrels per day. The royal family has controlled everything to do with oil and gas since the 1970s, and the line here between royal family assets and national assets is exceedingly blurry.

Vulnerable or Not?

The thing about these political oil leaders is that they're not really vulnerable—yet. It would take an event such as that which brought down Gaddafi (said to secretly be worth US$200 billion) in Libya to change this.