CALGARY, Canada, April 18 - Gran Tierra Energy Inc. (OTC Bulletin Board: GTRE), a company focused on oil exploration and production in South America, today announced that it has begun mobilizing the Pride-6 service rig to the Juanambu-1 exploration well location in the Guayuyaco Block, Putumayo Basin, in southern Colombia.

Gran Tierra earlier reported that its Juanambu-1 well encountered reservoir quality sandstones with hydrocarbon shows in four zones. These zones will be evaluated with the test program, which is expected to last approximately three weeks once the service rig is on location.

Gran Tierra Energy holds a 50% working interest and is Operator of this block. Partner, Solana Resources Limited, holds a 50% working interest and Ecopetrol has a 30% interest back-in right on commercial discoveries. If Ecopetrol exercises its back-in right, then Gran Tierra Energy will hold a 35% working interest and retain Operatorship, and Solana Resources Limited will hold a 35% working interest in the new commercial field.

The Pride-17 drilling rig, which drilled the Juanambu-1 well, has been mobilized to the adjoining Chaza Block and has initiated the drilling of the Costayaco-1 exploration well. Gran Tierra is the operator of the Chaza block with a 50% working interest.

About Gran Tierra Energy Inc.

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. To date, Gran Tierra has pursued a strategy that focuses on establishing a portfolio of producing properties, development and exploration opportunities, through selective acquisitions, to provide a base for future growth. Additional information concerning Gran Tierra is available at http://www.grantierra.com. Investor inquiries may be directed to [email protected] or 1-800-916-GTRE (4873).

Forward Looking Statements

The statement in this press release regarding the duration of the testing of the Juanambu-1 exploration well is a 'forward-looking statement' within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934. Although this forward-looking statement reflects the good faith judgment of management, forward-looking statements are inherently subject to known and unknown risks and uncertainties that may cause actual results to be materially different from those discussed in these forward-looking statements including, but not limited to, in the case of this forward-looking statement, mechanical problems, equipment limitations and weather delays. Readers are urged not to place undue reliance on this forward-looking statement, which speaks only as of the date of this release. Gran Tierra assumes no obligation to update this forward-looking statement in order to reflect any event or circumstance that may arise after the date of this release, other than as may be required by applicable law or regulation. Readers are urged to carefully review and consider the various disclosures made by Gran Tierra in its reports filed with the Securities and Exchange Commission, including those risks set forth in the Gran Tierra's Registration Statement filed on April 13, 2007, which attempt to advise interested parties of the risks and factors that may affect Gran Tierra's business. If one or more of these risks or uncertainties materialize, or if the underlying assumptions prove incorrect, Gran Tierra's actual results may vary materially from those expected or projected.