WASHINGTON (Bloomberg) -- The Organization of Petroleum Exporting Countries, source of 40 percent of the world’s oil, has slipped further away from self-imposed production limits amid rising crude prices, Exxon Mobil Corp. Chief Executive Officer Rex Tillerson said.

The organization had “been extraordinarily good” at adhering to reductions agreed to a year ago, Tillerson said in a speech to the Economic Club of Washington. Discipline among the 11 member nations subject to quotas has weakened as prices climbed. Crude futures traded in New York have risen more than 50 percent this year amid signs that demand is recovering from a recession-driven decline.
“At one point they had about 82 percent compliance, which is very good for OPEC,” said Tillerson, who oversees the world’s largest portfolio of oil refineries. “It’s running about 65 percent now. When the price of oil got back above $70, some people can’t help themselves.”
Tillerson’s comments diverge from a Bloomberg News survey of analysts and oil producers that estimated OPEC has trimmed output for two straight months. The group, which includes Saudi Arabia, Angola and Venezuela, pumped 28.395 million barrels of crude a day in September, a 1.8 percent decrease from August, the survey showed.
OPEC members agreed in September 2008 to lower collective output by 4.2 million barrels a day to 24.845 million, excluding Iraq, which is exempt from the group’s quota system. The planned cut would be enough to fill 64 supertankers every month.
--------Rising demand
Oil ministers meeting last month in Vienna left the target unchanged on an expectation that the global economy would recover and keep demand and prices up.
The Vienna meeting marks the third time this year that OPEC decided against changing production levels. The group’s next gathering is Dec. 22 in Luanda, Angola.
Irving, Texas-based Exxon produced 2.35 million barrels of crude a day during the April-to-June period, more than every member of OPEC except Saudi Arabia, Iran and Iraq. The company buys oil from other producers to help supply its refineries, which process about 5.3 million barrels a day.
Worldwide oil demand rose 280,000 barrels a day during the third quarter to 84.4 million, the first increase after five straight quarterly declines, the International Energy Agency said in a Sept. 10 report.
In addition to about 28.5 million barrels of crude output, OPEC pumps 5 million barrels of condensate a day, which combined account for 40 percent of the world’s oil supply.
Output cuts have left OPEC with 6.105 million barrels a day of spare capacity, the Bloomberg survey showed. Saudi Arabia can increase production by 2.785 million barrels, the most of any member.