Gran Tierra Tests 6,600 bbl/d and Up in Colombia

Gran Tierra Energy Inc., a company focused on oil exploration and production in South America, has successfully completed five drill stem tests (DSTs) on its recently drilled Costayaco-2 step out well in the Costayaco Field, Chaza Block, Putumayo Basin, in southern Colombia. A combined maximum flow rate in excess of 6,600 barrels of oil per day (BOPD) was attained.

The cased hole DST program, designed to evaluate only the primary reservoirs in the field, commenced on February 2, 2008. Five DSTs were completed over the Lower, Middle and Upper Caballos Formation, and in the Villeta T Formation. Secondary reservoirs in the U Sandstone Unit of the Villeta Formation and the Kg Sandstone Unit of the Rumiyaco Formation, which had potential pay zones indicated from log interpretations and which were successfully tested in the Costayaco-1 discovery well, were not tested. These zones will be tested and considered for completion later in field life when primary reservoirs become depleted.

The Costayaco-2 well bore is currently being completed for production. Produced oil will be transported through a new six inch flow line to the Costayaco-1 truck loading facility, where it will be mixed with crude oil from Costayaco-1 for trucking to Uchupayaco and the existing pipeline network.

DST-1 (8,494 - 8,498 foot interval; 4 feet of perforations) tested the Lower Caballos reservoir. No flow was obtained. Additional perforations were added in DST-1A (8,490 - 8,498 foot interval; 8 feet of perforations) and 26 BOPD of 17.4 API gravity oil with 40% water cut was obtained by swabbing.

DST-2 (8,330 - 8,342 foot interval; 12 feet of perforations) tested the Upper Caballos reservoir. Swabbing produced 25 BOPD of 29.1 API oil with 8% water cut.

DST-3 (8,330 - 8,474 foot interval; 88 feet of perforations) tested the Upper and the primary Middle Caballos reservoirs combined. Initial swabbing was followed by production of a maximum of 2,376 BOPD of 30.7 API oil through a 122/64 inch choke by stabilized natural flow. Only a trace of water (0.3%) was noted.

DST-4 (8,200 - 8,236 foot interval; 31 feet of perforations) tested the primary Villeta T Formation reservoir. Initial swabbing was followed by production of a maximum of 4,208 BOPD of 30.3 API oil through a 192/64 inch choke by stabilized natural flow. Only a trace of water (0.3%) was noted.

The Costayaco-1 discovery well is continuing to produce approximately 3,500 BOPD gross with only a trace of water (0.3%) from the Caballos and Villeta T sandstone reservoirs.

Costayaco-3, the third well in the Costayaco Field, reached TD at 8,620 feet on February 20, and is currently logging.

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.

Separately, Gran Tierra Energy is the operator of a total of seven independent license areas in the Putumayo Basin, and is the largest private license holder in the basin.

Dana Coffield, President and CEO of Gran Tierra Energy stated "The outstanding production rates by natural flow established in Costayaco-2, without the assistance of supplementary pumping, confirms the superior reservoir continuity and production capacity found in the original discovery well can be replicated in the Costayaco Field. Planning and permitting for additional drilling in the Costayaco field is continuing, and results from the new drilling are being integrated with the recently acquired seventy square kilometer 3-D seismic program to optimize the development of this field through the balance of 2008 and continuing into 2009."


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