Gran Tierra Energy is operator and holds interests in 9 blocks in Colombia. Santana, Guayuyaco and Chaza blocks are currently producing. The Rio Magdalena, Talora, Mecaya, Azar and 2 TEA blocks are in their exploration phases.

Santana

• Participation – Gran Tierra (Operator) 35%, Ecopetrol 65%
• Area – 1,119 acres (gross); 392 acres (net)
• Production – 223 bbl/day (net after royalty, Q1, 2008)

The Santana Contract area includes 4 producing fields – Linda, Mary, Miraflor and Toroyaco – and 15 wells. Activities are governed by terms of an Association Contract with Ecopetrol. The properties are subject to a 20% royalty and Gran Tierra holds a 35% interest in all fields with the exception of the Inchyaco-1 well in the Mary field, where the Company holds a 25.83% working interest. The Block has been producing since 1991; a total of 21.3 million barrels (gross) have been produced to date (to March 31, 2008).

Oil is sold to Ecopetrol and is exported via the Trans-Andean pipeline. Oil quality is approximately 26 degrees API. Oil prices are defined by contract and are related to a WTI reference. By contract, 25% of sales are denominated in pesos and 75% in US dollars.

Guayuyaco

• Participation – Gran Tierra (Operator) 35%, Solana 35%, Ecopetrol 30%
• Area – 52,366 acres (gross); 18,328 acres (net)
• Production – 148 b/d (net after royalty, Q1 2008), for the Guayuyaco field.
• Production - 384 b/d (net after royalty, Q1 2008), for the Juanambu field.

The Guayuyaco Block covers the area surrounding the 4 producing fields of the Santana Contract area and is governed by an Association Contract with Ecopetrol, providing a sliding scale royalty beginning at 8% and 30% participation for Ecopetrol. The Guayuyaco field within the Block was discovered in 2005. The Guayuyaco Block includeds two production fields, the Guayuyaco & the Juanambu fields. The Guayuyaco field has two producing wells with Guayuyaco-1 on stream in February 2005 and Guayuyaco-2 on stream in September 2005.The Juanambu field has one producing well with Juanambu 1 on stream in November, 2007. A second Junanambu well is planned for Q4 2008. Oil quality and sales terms are comparable to Santana oil and volumes are similarly transported via the Trans-Andean pipeline for export.

A combined 2D and 3D seismic survey was acquired over the Block in 2005. Gran Tierra Energy has identified four exploration prospects and three leads within the Guayuyaco area. The Juanambu field was discovered in March 2007 and testing was completed in May 2007. Pre-commercial test production began in June 2007. Commerciality was declared in November, 2007. Production has avereged at approximately 384 b/d (net after royalty) during Q1, 2008. Ecopetrol has exercised their back-in right with a 30% participation.

Rio Magdalena

• Participation – Gran Tierra (Operator) 100%
• Area – 144,670 acres
• Non-Producing – exploration acreage

Gran Tierra Energy entered into the Rio Magdalena Association Contract in February 2002. A sliding scale royalty, beginning at 8%, is payable on production from the contract area. A third party has been assigned, subject to receipt of appropriate regulatory approvals, the right to explore the shallow (Tertiary and younger) formations underlying portions of the contact area.

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. GTE expects drilling to be completed in late June. This well is currently drilling near a non-commercial oil discovery made by Gran Tierra Energy in 2006, the Popa-1 well, which tested approximately 160 b/d. GTE is the operator of the Rio Magdalena Block and has a 100% working interest. Under the terms of a recently completed farm-in agreement, Omega Energy Colombia will earn a 60% working interest by paying 100% of the costs associated with Popa-2 well. In the event of a commercial discovery, Ecopetrol has the right to back-in for a 30% working interest, to be split proportionally between GTE and Omega.