* Rystad study includes yet to find oil
* Global reserves stand at 2.09 trillion barrels
* Venezuela reserves well below official data
The US holds the world's biggest recoverable reserves of oil putting it ahead of OPEC giants Saudi Arabia and Venezuela as well as Russia, according to an independent study by Norwegian research group Rystad Energy.
In estimates which include potential reserves in recent discoveries and in yet to be discovered fields, US reserves total 264 billion barrels, ahead of 256 billion barrels in Russia and 212 billion barrels in Saudi Arabia.
For the US, more than half of the remaining oil reserves are made up of unconventional shale oil with Texas alone holding over 60 billion barrels of shale oil, Rystad said Monday citing the new data.
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Under a more conservative measure based on proven and probable reserves in existing fields, however, the US holds 40 billion barrels of oil, well below Saudi Arabia's 120 billion barrels but almost double Venezuela's 22 billion barrels, the Rystad figures show.
Rystad differentiates its estimates from those such as BP's closely-watched Statistic Review, which are based on reporting from national authorities often using an "opaque" set of reporting standards.
Some OPEC countries like Venezuela, for example, report official reserves apparently including yet undiscovered oil, Rystad noted, while others like China and Brazil report conservative estimates based only on existing fields. Rystad's own figures include just crude and condensate, whereas BP's figures also include natural gas liquids.
"An established standard approach for estimating reserves is applied to all fields in all countries, so reserves can be compared apple to apple across the world, both for OPEC and non-OPEC countries," Rystad said in a statement.
VENEZUELAN RESERVES HIT
Under the report, Venezuela sees the biggest impact from Rystad's reserves criteria compared the country's official reported proven oil reserves. Widely reported to hold the world's biggest oil reserves ahead of Saudi Arabia, Venezuela only holds 95 billion barrels of reserve under Rystad's widest measure, well below the official estimates of 301 billion barrels.
Excluding estimates of yet to be discovered oil in Venezuela, the OPEC member's oil reserves are on par with Brazil at 41 billion barrels, making it OPEC's sixth largest reserves holder, the data shows.
As a result, total OPEC oil reserves, excluding undiscovered fields, make up just over half of the global total. By contrast, BP estimates that more than than 70% of the world's reserves sits in OPEC member countries.
Based on the widest measure, total global oil reserves currently stand at 2.09 trillion barrels, Rystad said, compared to BP's latest estimate of 1.69 trillion barrels at the end of 2015.
Based on current global crude and condensate production of 81.2 million b/d, or 30 billion barrels a year, the world's oil reserves would last 71 years, Rystad said.
Unconventional oil recovery accounts for 30% of the global recoverable oil reserves while offshore accounts for 33% of the total.
The study confirms previous estimates by BP that the integrated oil majors control a small fraction of the world's reserves. The world's seven biggest oil companies hold less than 10% of the total reserves, Rystad said.
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