Gran Tierra Completes Testing of Costayaco-8 in Colombia

Gran Tierra Energy has announced that testing of Costayaco-8, a new development well drilled in the Costayaco Field in Southern Colombia, is complete. During the test, the Upper T Sandstone of the Villeta formation produced 2,211 barrels of oil per day (BOPD) and the Caballos formation produced 2,640 BOPD.

"Our testing confirms the results from the previously announced logging operations on Costayaco-8, and further demonstrates the potential of this well to contribute to the field's overall production," said Dana Coffield, President and Chief Executive Officer of Gran Tierra Energy. "We remain on track to attain a gross production plateau of 19,000 BOPD on the Costayaco field in the fourth quarter of 2009."

Testing was carried out by perforating 44 feet of the Upper T Sandstone interval, from 8,144 feet measured depth (md) to 8,198 feet md, and perforating 104 feet of the Caballos formation, from 8,286 feet md to 8,432 feet md.

During testing, the Caballos interval produced oil at an average rate of 2,640 BOPD with no water for 11 hours using a jet pump. The Caballos and Upper T Sandstone intervals, when tested together using a jet pump, produced oil at an average rate of 2,988 BOPD with no water for 20 hours. After the Caballos and Upper T Sandstone commingled production test was completed, the Caballos interval was isolated. The Upper T Sandstone interval produced oil at an average rate of 2,211 BOPD with no water for 7 hours when tested with a jet pump.

Operations Update

Test results for Costayaco-7 will be finalized shortly. Site preparation for Costayaco-9 is complete, and the drilling rig is currently moving to the location which is 1,958 feet southwest of Costayaco-8. Costayaco-9 is expected to spud on July 14th. The drilling of Costayaco-10 is expected to follow immediately after Costayaco-9.