Shares in European oil companies leaped on Thursday after OPEC surprised the market with an agreement to cut oil output, though analysts are skeptical the plan will be implemented or have any mid-term effect on oil prices.

BP (BP) - Get Report shares traded Thursday morning at 451.45 pence ($5.87), up 4.4%, Shell () was up 5.7% to 2,003 pence and France's Total (TOT) - Get Report rose 4.9% to €42.99 ($48.23). The gains outpaced those of U.S. oil majors ExxonMobil (XOM) - Get Report , which closed Wednesday up 3.6% at $86.90 and Chevron (CVX) - Get Report , up 3.2% to $102.15.

OPEC said in a statement late Wednesday that it will seek to cut its output to between 32.5 million barrels per day and 33 million barrels per day, though it noted that the agreement, and country output targets, wouldn't be finalized to until a meeting on Nov. 30. OPEC output came to a record 33.2 million barrels a day in August, Goldman analysts noted.

"The conference decided to establish a high level committee comprising representatives of member countries...to study and recommend the implementation of the production level of the member countries," OPEC said, giving no details beyond the target production range.

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Oil prices fell marginally in European trading Thursday after gaining more than 5% on Wednesday. West Texas Intermediate futures for delivery in November traded Thursday at $46.99, down $0.06, while Brent Crude futures traded at $48.55, down $0.14.

Thursday's muted response matched analysts' underwhelmed reaction to a plan that is yet to be ratified and might lop as little as 200,000 barrels per day off the record August output.

"This is still kicking the can down the road to the formal OPEC meeting in November," Citigroup analysts noted.

Goldman Sachs was similarly cautious, noting OPEC members' poor record of sticking to agreed production caps and suggesting that a significant increase in the oil price would lead to a sharp increase in ouput from non-OPEC producers.

"Strictly implemented in 1H17 and all else constant, the production quotas announced today should be worth $7/bbl to $10/bbl to the oil price," said Goldman analysts. "If this proposed cut is strictly enforced and supports prices, we would expect it to prove self defeating medium term with a large drilling response around the world."

Goldman left its oil price forecasts unchanged at $43 per barrel until the end of the year and $53 per barrel in 2017.