(Corrects headline and first paragraph to say that quantities refer to resources, not reserves)
BOGOTA, Aug 19 (Reuters) - Toronto-listed oil producer Pacific Rubiales said on Tuesday its oil resources estimate from exploration blocks had risen 45 percent to 6.2 billion barrels of oil equivalent by the end of March versus its 2012 estimate.
The independent estimate carried out by Petrotech Engineering was a best-case figure from 36 exploration sites spanning Colombia, where most of its production originates, as well as Peru, Brazil, Guyana, Guatemala and Papua New Guinea.
The company's best-case contingent resources rose 62 percent to 272 million of barrels of oil equivalent (MMboe) from 168 MMboe in 2012, it said in a regulatory filing.
Forty percent of the total prospective resource opportunities are in Peru, 25 percent in Colombia, 21 percent in Guyana and 12 percent in Brazil, with one percent each in Papua New Guinea and Guatemala.
Resources refer to early estimates of available oil based on preliminary studies but are not added to a producer's reserves which are calculated by more elaborate research and only include quantities that are expected to be profitable to recover. (Reporting by Nelson Bocanegra; Writing by Peter Murphy; Editing by Chizu Nomiyama)