Gran Tierra Confirms Oil Discoveries in South America

Gran Tierra announced results of two exploration wells.

Colombia
Garibay Block, Llanos Basin

Initial testing of the Melero-1 exploration well, located on the Garibay Block in the Llanos Basin, has been completed. The well spud on June 22, 2011, and reached total measured depth at 9,748 feet or 9,561 feet true vertical depth on July 16, 2011. Four drill stem tests were run and average production of 922 barrels of oil per day of 16.8 degrees API gravity with a 0.3% water cut was obtained from an interpreted 16 feet of net pay in the Upper Mirador reservoir. This well is currently suspended for long-term testing.

In addition, the Jilguero-2 appraisal well on the Garibay Block was spud on September 10, 2011. This well is located at the Jilguero oil discovery made by the joint venture between a subsidiary of Gran Tierra Energy and CEPSA Colombia S.A., a wholly-owned subsidiary of Compania Espanola de Petroleos, S.A. ("CEPSA").

The joint venture is also in the process of acquiring an additional 80 square kilometers of 3D seismic data to assist in the evaluation of other structures identified on 2D seismic on the block.

Gran Tierra Energy, through an indirect wholly owned subsidiary, holds a 50% working interest in the Garibay Block while, CEPSA holds the remaining 50% and is the operator of the property.

Argentina
Rinconada Norte Block, Neuquen Basin

The first of three exploration wells to be drilled in the Rinconada Norte Block located in the Neuquen Basin of Argentina has made a new discovery of oil, testing 1,023 barrels of oil equivalent per day.

The RN x-1004 well flowed a total combined test rate of approximately 944 barrels of oil per day and approximately 0.5 million cubic feet per day of natural gas for a total of approximately 1,023 barrels of oil equivalent per day from two intervals tested separately in the Precuyo formation. This well also flowed 43 barrels of water per day or a 4% water cut.

Test and electric log data from the depths of the zones tested (3,222 - 3,255 feet and 3,353 - 3,386 feet) suggests a gross oil column thickness of approximately 197 feet. The oil is 29.6 degrees API gravity.

Having completed the first of the three exploratory wells, the service rig is set to move to complete and test the next two wells, which have already been drilled and cased.

Americas Petrogas Argentina S.A., the wholly-owned subsidiary of America Petrogas Inc., is the operator of the Rinconada Norte Block with a 65% working interest upon completing certain work program obligations, while Gran Tierra Energy, through an indirect wholly owned subsidiary holds a 35% working interest.

"Gran Tierra is pleased these oil discoveries will contribute to our existing base of reserves and production in Colombia and Argentina, while we prepare for additional exploration drilling in these countries and in Brazil in 2011", said Dana Coffield, President and CEO of Gran Tierra Energy.