CANCUN, Mexico (Reuters) - OPEC is worried it may invest far more in new oil production capacity than is needed due to uncertainty over demand, according to a speech to be delivered by OPEC Secretary General Abdullah al-Badri on Wednesday.

In a copy of prepared remarks to be given at the International Energy Forum in Cancun, Mexico, Badri said the lingering effects of the financial crisis and consuming nations' efforts to reduce their dependence on petroleum posed a multibillion dollar problem for the Organization of the Petroleum Exporting Countries.

The oil exporters' group, which has committed to spending $165 billion through 2013 on new oil production capacity, thinks the actual requirement for new investment could range between $70 billion and $170 billion due to the uncertainty over demand.

"Even to 2013, which represents a time frame over which investments are effectively locked in, requirements could be as low as $70 billion or as high as $170 billion," the OPEC chief said.

"There is a very real possibility of wasting financial resources on unneeded capacity."

Badri said that the "uncertainty gap" between the minimum and maximum needed for upstream investments by OPEC could grow to $250 billion in real terms by 2020.

Badri went on to say that both producers and consumers understood that an oil price that is neither too high nor too low is favorable to all. He expressed hope that oil market volatility, which saw prices rise to a record near $150 a barrel in 2008 then collapse to $33 later that year, as over.

"It is my hope that the large price swings and the extreme volatility that we have witnessed in 2008 and 2009 are consigned to the past," said Badri.

OPEC spare crude production capacity currently exceeds six million barrels per day, he said.