Moqueta-3 Testing Confirms Additional Oil Pay at Moqueta Discovery in Colombia

Oct 28, 2010, 07:00 ET from Gran Tierra Energy Inc.

Well flows approximately 850 BOPD from three zones

CALGARY, Oct. 28 /PRNewswire/ - Gran Tierra Energy Inc. (NYSE AMEX: GTE; TSX: GTE) ("Gran Tierra Energy"), a company focused on oil and gas exploration and production in South America, today announced that it had completed initial testing of the Moqueta-3 delineation well in the Moqueta new field discovery on the Chaza Block in the Putumayo Basin, Colombia. Oil and gas shows were recorded through the Villeta Lower U Sandstone, the Villeta T Sandstone and the Caballos zones, with electric logs indicating total net oil pay in the Moqueta-3 well increasing to 118 feet, from 44 feet encountered in the Moqueta-2 delineation well.  Gran Tierra Energy has a 100% working interest and is the Operator of the Chaza Block.

"The Moqueta-3 delineation well testing has confirmed the increase in oil column thickness and additional oil productivity of the Moqueta field," said Dana Coffield, President and Chief Executive Officer of Gran Tierra Energy. "We are continuing civil construction on the Moqueta-4 well site, located 1.5 kilometers southwest of Moqueta-1. The Moqueta-4 delineation well will allow Gran Tierra Energy to further assess the aerial extent of the Moqueta oil accumulation. In parallel, we are continuing design and permitting for construction of a pipeline to connect Moqueta to existing infrastructure, with the intent to establish first production in the first quarter of 2011."

Moqueta-3 Delineation Well, Chaza Block

Gran Tierra Energy has completed initial testing on the Moqueta-3 delineation well by collecting reservoir data and fluid samples from four zones - the Lower Caballos, the Middle Caballos, the Upper Caballos and the Villeta T Sandstone. No testing was conducted in the Villeta Lower U Sandstone zones to preserve the casing integrity for future oil production.

In the Villeta T Sandstone zone, two intervals totaling 48 feet were perforated and tested from 4,549 feet measured depth ("MD") to 4,561 feet MD and from 4,568 feet MD to 4,604 feet MD. Oil flowed without assistance from pumps at 514 barrels of oil per day ("BOPD") with a gravity and watercut of 28.4° API and 0.2%, respectively. No oil-water contact is evident in the Villeta T Sandstone zone penetrated by the well bore.

In the Upper Caballos zone, two intervals totaling 26 feet were perforated and tested from 4,690 feet MD to 4,708 feet MD and from 4,715 feet MD to 4,723 feet MD. Oil flowed with swabbing stimulation at 120 BOPD, with a gravity and watercut of 28.3° API and 0.2%, respectively. No oil-water contact is evident in the Upper Caballos formation penetrated by the well bore.

In the Middle Caballos formation, two intervals totaling 27 feet were perforated and tested from 4,734 feet MD to 4,750 feet MD and from 4,761 feet MD to 4,772 feet MD. Oil flowed with swabbing stimulation at 219 BOPD, with a gravity and watercut of 28.6° API and 0.2%, respectively. No oil-water contact is evident in the Middle Caballos formation penetrated by the well bore.

The Lower Caballos formation was previously determined to have lower oil saturation than Moqueta-1 and Moqueta-2. After low productivity fluid testing, Gran Tierra Energy has preliminary indications the lowermost part of the Lower Caballos is water bearing in the Moqueta-3 delineation well.

Gran Tierra Energy is currently undertaking civil construction at the Moqueta-4 well site, which is located approximately 1.5 kilometers southwest of Gran Tierra Energy's Moqueta-1 well. The Moqueta-4 well is scheduled to spud in early December.

Design and permitting of a six inch diameter, eight kilometer long pipeline from Moqueta to Costayaco facilities is continuing, with construction beginning in the fourth quarter of 2010 and first oil production associated with long term testing scheduled to begin in the first quarter of 2011.

About Gran Tierra Energy Inc.

Gran Tierra Energy Inc. is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated in the United States, trading on the NYSE Amex Exchange (GTE) and the Toronto Stock Exchange (GTE), and operating in South America. Gran Tierra Energy holds interests in producing and prospective properties in Argentina, Colombia, Peru and Brazil. Gran Tierra Energy has a strategy that focuses on establishing a portfolio of producing properties, plus production enhancement and exploration opportunities to provide a base for future growth.

Gran Tierra Energy's Securities and Exchange Commission filings are available on a web site maintained by the Securities and Exchange Commission at http://www.sec.gov and on SEDAR at http://www.sedar.com

Forward Looking Statements:

This news release contains certain forward-looking information and forward-looking statements (collectively, "forward-looking statements") under the meaning of applicable securities laws, including Canadian Securities Administrators' National Instrument 51-102 - Continuous Disclosure Obligations and the United States Private Securities Litigation Reform Act of 1995. The use of the words "expect", "anticipate", "potential", "will", "suggests" and "scheduled" identify these forward-looking statements. In particular, but without limiting the foregoing, this news release contains forward-looking statements regarding planned and expected testing and results regarding Moqueta-4, along with expected drilling and spudding of Moqueta-4, and the timing of construction and completion of a pipeline to connect Moqueta to existing infrastructure at Costayaco facilities.

The forward-looking statements contained in this news release reflect several material factors and expectations and assumptions of Gran Tierra Energy including, without limitation, assumptions relating to log evaluations, that Gran Tierra Energy will continue to conduct its operations in a manner consistent with past operations, the effects of drilling down-dip and the general continuance of current or, where applicable, assumed operational and industry conditions. Gran Tierra Energy believes the material factors, expectations and assumptions reflected in the forward-looking statements are reasonable at this time but no assurance can be given that these factors, expectations and assumptions will prove to be correct.

The forward-looking statements contained in this news release are subject to risks, uncertainties and other factors that could cause actual results or outcomes to differ materially from those contemplated by the forward-looking statements, including, among others: Gran Tierra Energy's operations are located in South America, and unexpected problems can arise due to guerilla activity, technical difficulties and operational difficulties which impact or delay its testing and drilling operations; geographic, political and weather conditions can impede testing and drilling operations; and the risk that current global economic and credit market conditions may impact oil prices and oil consumption more than Gran Tierra Energy currently predicts, which could cause Gran Tierra Energy to modify its exploration activities. Further information on potential factors that could affect Gran Tierra Energy are included in risks detailed from time to time in Gran Tierra Energy's Securities and Exchange Commission filings, including, without limitation, under the caption "Risk Factors" in Gran Tierra Energy's Quarterly Report on Form 10-Q filed August 6, 2010. These filings are available on a Web site maintained by the Securities and Exchange Commission at http://www.sec.gov and on SEDAR at www.sedar.com. The forward-looking statements contained herein are expressly qualified in their entirety by this cautionary statement. The forward-looking statements included in this press release are made as of the date of this press release and Gran Tierra Energy disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as expressly required by applicable securities legislation.

SOURCE Gran Tierra Energy Inc.