The Costayaco-16 development well spud on June 6, 2012; this well is intended to be a producing well to assist with maintaining plateau production in the Costayaco Field.Azar Block, Putumayo Basin (Gran Tierra Energy 40% WI and Operator, Lewis Energy Colombia Inc. 40% WI, Gold Oil 20% WI subject to Agencia Nacional de Hidrocarburos approval) The La Vega Este-1 oil exploration well spud on May 14, 2012 and is targeting the same Cretaceous sandstone intervals present in the Costayaco and Moqueta discoveries. Gran Tierra Energy expects the La Vega Este well to reach total depth at the end of June, with results expected in July. Garibay Block, Llanos Basin (Gran Tierra Energy 50% WI, CEPSA 50% WI and operator) The Bordon-1 oil exploration well spud on June 6, 2012 and is expected to reach total depth in late July, with results expected in August. Argentina Puesto Guevara Block, Neuquen Basin (Gran Tierra Energy 100% WI and operator) The Los Incas x-1 oil exploration well in the Puesto Guevara Block has been drilled and is being plugged and abandoned after encountering only minor oil shows. Production Update May production and sales have been impacted by additional disruptions on the Ecopetrol-operated Oleoducto Transandino (" OTA") pipeline in Colombia. Gran Tierra Energy continued production at a reduced rate while the OTA pipeline was down, selling a portion of its crude through trucking and storing excess crude. Production, net after royalties and before changes in inventory and losses for the months of April and May averaged approximately 18,000 barrels of oil equivalent per day. Production is expected to return to normal levels mid-June. About Gran Tierra Energy Inc. Gran Tierra Energy is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated in the United States, trading on the NYSE MKT (GTE) and the Toronto Stock Exchange (GTE), and operating in South America. Gran Tierra Energy holds interests in producing and prospective properties in Colombia, Argentina, 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 and Advisories 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 "expected", "intends", "will", "targeting", "planning", "could", "estimate", "potential", "scheduled", and derivations thereof and similar terms identify forward-looking statements. In particular, but without limiting the foregoing, this news release contains forward-looking statements regarding Gran Tierra Energy's intended and expected drilling operations in Colombia, Argentina and Peru including, without limitation, anticipated well uses, drilling targets and timelines, estimated additional reserves and resource potential and estimated contingent resources and expectations respecting the resumption of service of the OTA pipeline. Statements relating to "resources" are forward-looking statements as they involve the implied assessment, based on estimates and assumptions, that the resources described exist in the quantities predicted or estimated and can be profitably produced in the future.