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Gran Tierra hikes Putumayo field's oil reserves

Midyear 2012 reserves for Costayaco field in the Putumayo basin of Colombia are up sharply since the end of 2011, said Gran Tierra Energy Inc., Calgary.

Costayaco proved reserves are up 38% to 20.4 million bbl of oil. Proved and probable reserves are up 40% to 23.2 million bbl, and proved, probable, and possible reserves are up 21% to 26.7 million bbl. Calculated in accordance with US Securities & Exchange Commission rules, the increases are several percentage points less, Gran Tierra said. Costayaco is the company’s largest asset.

Gran Tierra revised its 2012 capital program to $396 million, a $60 million reduction, deferring spending from area not expected to affect production capacity or near-term high value reserve addition projects.

The company’s production in the quarter ended June 30 averaged 10,308 b/d of oil equivalent in Colombia, down 33% due to three pipeline disruptions, 3,693 boe/d in Argentina, up 31%, and 126 b/d in Brazil. Oil production increased from the Moqueta, Jilguero, and Melero oil discoveries.

Reservoir performance at Costayaco field, on Gran Tierra’s 100% owned Chaza block, continues to exceed expectation. Consulting engineers have increased the original oil in place estimate by using lower water saturation combined with more production history and pressure data. The company believes further reserve growth is possible given the reservoir’s strong response to water injection.

The 3D seismic over Moqueta indicates that the structure’s eastern flank extends more than 2.5 km northeast at the level of lowest known oil in existing wellbores, implying that reserve potential may exist on the east flank of the structure. Moqueta-8, to spud in September 2012, will evaluate this.

Moqueta-7, to spud in early August, will evaluate further downdip potential of the oil columns encountered in the Villeta U, Villeta T, and Caballos reservoirs 960 m west-southwest of the Moqueta-4 appraisal well. Gran Tierra intends to target the interpreted oil-water contact, not yet encountered by drilling, some 225 ft below the lowest known oil in existing wellbores. Moqueta-7 may be used as an oil producer or water injector depending on results.

Combining the results of Moqueta-7 and 8 with the seismic interpretation will aid in the full field development plan, expected to be completed in the fourth quarter of 2012.

Gran Tierra, Ecopetrol, and others are looking at multiple transportation and storage options to help mitigate the risk of pipeline disruptions in Colombia. The options include more continuous use of the San Miguel pipeline through Ecuador, more storage at Orito and higher utilization of the Colombian pipeline when operational, and more trucking.

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