The decision to quit the bloc of 15 oil-producing countries that account for a significant percentage of the world's oil production was confirmed by Qatar Petroleum, the state oil company, on Monday.
Speaking at a news conference in the capital Doha, al-Kaabi said: "The withdrawal decision reflects Qatar's desire to focus its efforts on plans to develop and increase its natural gas production from 77 million tonnes per year to 110 million tonnes in the coming years."
Qatar is the first Gulf country to leave the bloc of oil-producing countries.
Al Jazeera's Charlotte Bellis said that Qatar made the decision just days ahead of a December 6 OPEC meeting.
"They say it has nothing to do with the blockade on Qatar and that they have been thinking about it for several months now," Bellis said, referring to a diplomatic blockade on Qatar by Saudi Arabia, the United Arab Emirates ( UAE ), Egypt and Bahrain.
"They also said that if you want to withdraw from OPEC it had to be done before the end of the year," she added. "They said they wanted to do this now and be transparent ahead of a December 6 OPEC meeting."
Since 2013, the amount of oil Qatar produced has steadily declined from about 728,000 barrels per day in 2013 to about 607,000 barrels per day in 2017, or just under two percent of OPEC's total output.
Sheikh Hamad bin Jassim Al Thani, Qatar's former prime minister, called the withdrawal a "wise decision".
"This organisation has become useless and adds nothing to us," Sheikh Hamad wrote on Twitter. "They are used only for purposes that are detrimental to our national interest."
Alex Schindelar, executive editor of Energy Intelligence, told Al Jazeera that Qatar would not leave OPEC if there was no blockade on the country.
"The GCC countries meet ahead of OPEC meetings to discuss their policies. It is a small group, where Qatar had a voice," he said.
"Post-embargo, obviously Qatar was shut out of that. Now, they have little opportunity to have a say. They are hardly consulted now."
Meanwhile, total production during the same period increased from 30.7 million barrels per day to 32.4 million barrels per day.
Qatar joined OPEC in 1961, one year after the organisation's establishment.
Earlier this week, OPEC and Russia, who together produce about 40 percent of the world's oil, said they had agreed on new oil production cuts to ensure the oil price does not drop too much in the coming months.
In October, the oil price reached a four-year high of $86, but since then the price has dropped again to about $60 per barrel.
Qatar is the world's biggest supplier of liquefied natural gas (LNG), producing almost 30 percent of the world total.
According to Al Jazeera's Bellis, Al-Kaabi said the declaration was purely a business decision.
"Al-Kaabi said 'We are a small player in OPEC, and I'm a businessman, it doesn't make sense for me to focus on things that are not our strength, and gas is our strength so that is why we've made this decision'," Bellis said.
Al-Kaabi added that the decision to increase the supply of natural gas is to "develop a future strategy based on growth and expansion, both in its activities at home and abroad".
"Achieving our ambitious growth strategy will undoubtedly require focused efforts, commitment and dedication to maintain and strengthen Qatar's position as the leading natural gas producer," he added.
Qatar shares the world's largest known natural gas field, the North Field, with Iran.
In September, Qatar announced it would increase its production of natural gas by adding a fourth production line to raise capacity from the North Field to 110 million tonnes a year.
Most of Qatar's almost 80 million tonnes of annual LNG supplies are shipped in tankers to different countries, including the UAE, which is one of the countries imposing the blockade on Qatar.
Following the announcement of the blockade, Qatar said it would not shut down the gas pipeline to its fellow Gulf country.