Gran Tierra Energy Inc, a company focused on oil exploration and production in South America, declares the results of a mid-year reserve update for the Costayaco Field in the Chaza Block located in the Putumayo Basin of Colombia. Gran Tierra Energy holds a 50% working interest and is the operator of the Costayaco Field and the Chaza Block. Solana Resources Limited holds the remaining 50% working interest.

An independent reserve evaluation of the Costayaco field conducted by GLJ Petroleum Consultants effective July 1, 2008, using 3-D seismic and drilling results from four wells (Costayaco-1 through -4, not including test results of Costayaco-4 as these test results are not yet available) indicates that the Costayaco field has gross proved reserves of 20.5 million barrels of oil (MMbbl), gross proved plus probable reserves of 34.9 million barrels of oil and gross proved plus probable plus possible reserves of 61.4 million barrels of oil. The following table summarizes gross reserves for the field, in addition to Gran Tierra Energy’s gross and net reserves:

Gran Tierra Energy’s reserves, net of royalty, compared to year end 2007 for the Costayaco Field as of July 1, 2008 are as follows:

Proved reserves are 6.67 million barrels of oil compared to 3.27 million barrels of oil at year end 2007, an increase of 104%; Probable reserves are 4.32 million barrels of oil compared to 3.32 million barrels of oil at year end 2007, an increase of 30%; Possible reserves are 7.91 million barrels of oil compared to 2.60 million barrels of oil at year end 2007, an increase of 204%; Total proved, probable and possible, net after royalty, reserves in the Costayaco Field are 18.90 million barrels of oil compared to 9.19 million barrels of oil at year end 2007, an increase of 106%.

Dana Coffield, President and Chief Executive Officer of Gran Tierra Energy Inc., stated, “The Costayaco Field in Colombia continues to exceed our expectations. Drilling in the first half of 2008 has added to our understanding of the reserve potential of the field. Pending test results from Costayaco-4 and drilling results from Costayaco-5 are expected to add material new information to the reserve potential as we continue to delineate and develop the field with a continuous drilling program through the balance of this year.”

Tags: Gran Tierra Energy Inc.