Spain’s biggest oil company Repsol said it intends to add oil and gas to its reserves by 2010.

It did not, however, include declining Argentine fields in this calculation.

Repsol’s recent success with offshore oil and gas exploration will boost the rate at which new reserves are added to over 100% of those that it uses outside the country, by next year.

“Our reserve replacement ratio (RRR) grew to 90% in 2009 and will probably exceed 100% in 2010,” the group’s director of upstream activities, Nemesio Fernandez Cuesta, told Reuters.

Repsol hopes recent exploration success in Brazil, the Gulf of Mexico and Venezuela – including its stakes in some of the largest oil and gas strikes in 2008 and 2009 – will boost a reserve replacement ratio that was at just 65% of production in 2008.

Repsol decided to invest €9bn in its upstream division as part of its 2008 to 2012 strategic plan after the company was obliged to slash its reserves due to regulatory changes in Bolivia in 2006, writes Reuters.

The company estimates that its possible, probable and proven reserves will have risen to 2.053 billion barrels of oil equivalent by the end of 2009 from 1.986 billion at the end of 2008, with production excluding Argentina remaning the same at 122 million barrels.