The International Energy Agency is planning to unveil plans in October that it hopes will lead to a mandatory global standard for accounting of oil and gas reserves.
Controversial rules on oil industry reserves amid the fall-out from the Royal Dutch/Shell Group's slashing of its oil reserves by 20 per cent this year has raised the need for harmonising standards.
The controversy stems from the interpretation of the reserve rules adopted by the US Securities and Exchange Commission, which the oil industry has criticised for being vague and out of date.
The SEC is in the early stages of a review and is veering towards increased disclosure on a voluntary basis, and has said it is not looking at a move towards an international standard. This would create a large block to the IEA initiative.
Despite the SEC's stance, the IEA maintains there is a need to create a harmonised system for investors. "There are no consistent rules on oil reserves," said Dr Fatih Birol, its chief economist.
Dr Birol said the IEA planned to release details of a global oil reserves accounting standard in October, and would embark on a campaign for its adoption in the oil industry.
He said this would include lobbying governments and corporate regulators as any global standard would have to be enforced rather than introducing a voluntary code, he said.
BP increased global oil reserves by 10 per cent for 2003 in the latest annual statistical review of the industry released last month. The UK-based oil group also said that at current rates there was was enough oil to last another 41 years.
This revision, however, was due to a change in methodology by using more sources for the information and by including the Canadian tar sands reserves, which produce less than 1m b/d of oil as it is very expensive compared with convention oil production and is more environmentally challenging.
Energy analysts also said with global oil consumption accelerating over the past 10 years at twice the rate of the previous 20 years the current longevity given to current reserves may look optimistic.
"We need to know whether we have enough reserves to support long term oil demand," Dr Birol said.
Neither BP or Shell would comment on oil reserves accounting. The issue of oil reserves has also become a debate with Middle Eastern oil producers.
In February, Matthew Simmons, president of Simmons and Company International, an energy investment bank, said the Ghawar oilfield in Saudi Arabia, the world's largest oilfield, was more mature than Saudi Aramco, the field's operator, admits.
The claims prompted a rare response from Saudi Aramco, which said at the time that Mr Simmons' analysis was based on "flawed" statistics. Saudi Arabia is estimated to have 262.7bn barrels of oil in reserves.
Dr Birol said the oil producing countries should also be open to an international recognised oil audit.
Alastair Syme, energy analyst at Merrill Lynch, said it would be more difficult to enforce international oil audits on countries than on companies.