CALGARY, Alberta, June 27 /-- Gran Tierra Energy Inc. (AMEX: GTE; TSX: GTE), a company focused on oil exploration and production in South America, today announced that it had successfully drilled the Popa-2 exploration well in the Rio Magdalena Block in central Colombia, and was preparing to initiate well testing operations.

Gran Tierra Energy initiated drilling of the Popa-2 exploration well in the Rio Magdalena Block in the Middle Magdalena Basin, on May 8, 2008, and reached total measured depth of 8,646 feet in basement on June 21, 2008. Electric logs have been run and preparations are being made to run a 7 inch liner into the wellbore and then initiate drill stem testing operations. Gran Tierra Energy expects testing operations to take approximately two weeks and to be completed by mid-July.

Gran Tierra Energy encountered oil and gas shows during drilling in sandstones in the Cretaceous Monserrate Formation, the primary reservoir target in the Popa prospect, and in the underlying basement. Electric log interpretations together with mudlog and the shows encountered during drilling indicate potential net hydrocarbon pay of approximately 80 feet has been penetrated by the wellbore in the Monserrate Formation.

Popa-2 was drilled 2,035 meters from a non-commercial oil discovery made by Gran Tierra Energy in 2006 at Popa-1, which tested approximately 160 barrels of oil per day. Gran Tierra Energy acquired a new 89 kilometer 2-D seismic program after the initial discovery, and used it to pick the location of Popa-2.

Gran Tierra Energy, with a 100% working interest, is the operator of the 144,670 acre Rio Magdalena Block. Under the terms of a recently completed farm-in agreement, Omega Energy Colombia will earn a 60% share of the company's interest by paying 100% of the costs associated with drilling, testing and completing the Popa-2 well. In the event of a commercial discovery, Ecopetrol S.A. has a right to back in for a 30% working interest, to be split proportionally between Gran Tierra Energy and Omega Energy Colombia.

Commenting on progress, Dana Coffield, President and Chief Executive Officer of Gran Tierra Energy Inc., stated, "Preliminary results from Popa-2 are very exciting, building on the knowledge acquired from the drilling of Popa-1 and the new 2-D seismic data that we have acquired since then. Testing of Popa-2 will determine the potential of this prospect and, if successful, will confirm a new exploration play on our lands in Colombia."