Gran Tierra Begins Testing of Colombia Discovery

Gran Tierra Energy, Inc. has initiated a drill stem test (DST) program on its recently drilled Costayaco-1 exploration well in the Chaza Block, Putumayo Basin, in southern Colombia.

Oil shows were encountered in four different reservoir packages during the drilling of the well. Oil saturations were subsequently confirmed by electric logging. The zones being tested include (from the lower to upper zones) the Caballos sandstone, T sandstone, U sandstone, and Kg sandstone. The well has been cased and approximately 155 feet of reservoir section will be perforated in the six DSTs. The DST program is expected to last approximately six weeks.

These reservoirs are the same reservoirs that were recently tested in the Juanambu-1 exploration well in the adjacent Guayuyaco Block, for which an application for commerciality is currently under preparation, and are the same reservoirs that are producing oil in adjacent oil fields operated by Gran Tierra Energy.

Gran Tierra Energy holds a 50% working interest and is the Operator of the Chaza Block. Solana Resources Limited holds the remaining 50% working interest. The Chaza Block is subject to the new and fiscally attractive Agencia Nacional de Hidrocarburos royalty/tax contract which includes no additional state participation.

Dana Coffield, President and CEO stated: "The initiation of testing in Costayaco-1 is another milestone in the continuation of the ongoing success of our 2007 drilling campaign. This is our second exploration well in the Putumayo Basin to encounter hydrocarbons this year and, like Juanambu-1, is located near infrastructure operated by Gran Tierra Energy which should enable rapid initiation of production if we are able to successfully complete testing at commercial rates."

Gran Tierra Energy Inc. is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated and traded in the United States and operating in South America. Gran Tierra holds interests in producing and prospective properties in Argentina, Colombia and Peru.