Gran Tierra Energy Announces 2010 Year-End Reserves

New field discoveries along with reservoir performance at Costayaco results in another record year for reserves

CALGARY, Feb. 8 /PRNewswire/ – Gran Tierra Energy Inc. (NYSE Amex: GTE; TSX:
GTE) (“Gran Tierra Energy“), a company focused on oil exploration and production in South
America, today announced the results of an independent reserve
evaluation of the company’s reserves by GLJ Petroleum Consultants Ltd.
effective December 31, 2010.

Year-end 2010 Highlights (net after royalties (“NAR“), calculated in accordance with Securities and Exchange Commission (“SEC“) rules):

• Total Proved (“1P“) oil reserves increased 7% to approximately 23.6 million barrels of
  oil;
• Total Proved plus probable (“2P“) oil reserves increased 11% to approximately 31.0 million barrels of
  oil;
• Total Proved plus probable plus possible (“3P“) oil and liquids reserves increased 20% to approximately 47.3 million
  barrels of oil and liquids;
• Reservoir performance expectations were exceeded at the Costayaco field
  in Colombia  and Costayaco 1P reserves changed to 17.7 million barrels
  of oil at year-end 2010, from 18.7 million barrels of oil at year-end
  2009 despite total production of 4.4 million barrels of oil NAR at the
  Costayaco field in 2010;
• The Moqueta new field discovery in Colombia added total 3P working
  interest reserves of 12.3 million barrels of oil or NAR 3P reserves of 9.7 million barrels of oil based on the evaluation of three wells completed before year-end 2010. The 2010
  year-end reserves do not include the results of the Moqueta-4
  delineation well, which is currently testing;
• Gran Tierra Energy produced approximately 7.1 million barrels of company
  interest oil before royalties and 338.6 million cubic feet of company
  interest gas before royalties in 2010;
• Annual production for 2010 averaged approximately 19,300 company
  interest barrels of oil per day (“BOPD“) before royalties, or 14,300 BOPD NAR, an increase of approximately
  13% versus 12,684 BOPD NAR in 2009. Production in the fourth quarter of
  2010 averaged approximately 15,800 BOPD NAR.

All reserves values contained in the 2010 Highlights, provided above,
have been calculated using United States SEC rules. For reserves values
calculated in compliance with Canadian National Instrument 51-101 – Standards of Disclosure for Oil and Gas Activities (“NI 51-101“) and the Canadian Oil and Gas Evaluation Handbook (“COGEH“), see “Reserves Reported in Accordance with Canadian Reporting
Requirements” below in this press release.

“Gran Tierra Energy attained record levels of reserves and production in
2010 through successful exploration for new reserves and successful
management of existing reserves,” said Dana Coffield, President and
CEO. “In 2011, we are focused on continuing growing reserves through
exploration drilling in Colombia, Peru and Brazil, continued
delineation drilling of new reserves discovered at the Moqueta oil
field in Colombia, and growing production through development drilling
and reservoir management in existing producing fields in Colombia,
Argentina and Brazil. It remains our intent to execute our capital
program in 2011 through available cash and cash flow from operations,
allowing the company to remain debt free.”

Reserves Reported in Accordance with United States Reporting
Requirements

The following reserves are reported consistent with United States
Securities and Exchange Commission rules.

The following table summarizes Gran Tierra Energy’s year-end 2010
working interest reserves and net after royalty reserves (with average
start-of month 2010 oil prices). Also shown in the following table are
Gran Tierra Energy’s net after royalty reserves for year-end 2009 (with
average start-of month 2009 oil prices).

Total Company

*NAR (net after royalty).

**MBO (thousand barrels of oil).

• Reserves were added through development drilling and technical revisions
  in the Costayaco and Juanambu fields, along with the Moqueta discovery
  on the Chaza block and the Jilguero discovery on the Garibay block,
  both in Colombia.
• Partially offsetting reserve additions was 2010 full year production of
  7.1 million barrels of company interest oil before royalties and 338.6
  million cubic feet of company interest gas before royalties.
• 1P light and medium oil reserves increased 7% largely due to development
  drilling in the Costayaco Field and the Moqueta and Jilguero
  discoveries, partially offset by full year 2010 production.
• 2P light and medium oil reserves increased 11% mainly due to development
  drilling at Costayaco combined with the Moqueta and Jilguero
  discoveries.
• 3P light and medium oil and liquids reserves increased by 20% or 7.9
  million barrels, largely due to Moqueta discovery.

***MMSCF (million standard cubic feet).

• Gran Tierra Energy has year-end 2010 NAR 3P gas reserves of
  approximately 43.4 billion cubic feet, an increase of 14% from 38.1 billion cubic feet NAR
  at year-end 2009 largely associated with the Valle Morado block in
  northern Argentina.

Colombia

Gran Tierra Energy’s Colombia year-end 2010 working interest and net
after royalty reserves are shown in the following table (with average
start-of month 2010 oil prices). Also shown in the following table is
Gran Tierra Energy’s Colombian net after royalty reserves for year-end
2009 (with average start-of month 2009 oil prices).

• The increase in proved oil reserves is mainly associated with
  development drilling in the Costayaco Field in Colombia.
• The increase in 3P reserves is mainly associated with the Moqueta
  discovery on the Chaza block and the Jilguero discovery on the Garibay
  block in Colombia.

• Colombian gas reserves are associated with the Magangue field in the
  Lower Magdalena basin.

The Costayaco Field 2010 year-end net after royalty reserves are shown
in the following table (with average start-of month 2010 oil prices).
Also shown in the following table is a comparison of the Costayaco
Field 2010 year-end gross lease reserves (with average start-of month
2010 oil prices) to the gross lease reserves estimated in December 31,
2009 (with average start-of month 2009 oil prices).

• Gran Tierra Energy successfully completed workovers on Costayaco-1, -3
  and -11 thereby enhancing the productivity of the field. 
• In September 2010, a water injection facility was completed with water
  injection commencing in October 2010 into the T Sand reservoir through
  the Costayaco-5 and -6 wells. 
• The Costayaco-11 well was put on production in early July, 2010. 
• Approximately 4.4 million barrels of oil NAR was produced from the
  Costayaco field in 2010. Through a successful field development program
  in 2010, Gran Tierra Energy managed to successfully mitigate reserve
  declines at the Costayaco field.

Argentina

Gran Tierra Energy’s Argentina working interest and net after royalty
reserves are shown in the following table (with average start-of month
2010 oil prices). Also shown in the following table is Gran Tierra
Energy’s Argentina net after royalty reserves for year-end 2009 (with
average start-of month 2009 oil prices).

Gran Tierra Energy recorded no 1P or 2P gas reserves at year-end 2010 at
Valle Morado as the indicated reserves were uneconomic based on
budgeted expenditures.

Reserves Reported in Accordance with Canadian Reporting Requirements

The following reserves are compliant with NI 51-101 and COGEH (with
forecasted oil price and costs):

Total Company

*MBbl (thousand barrels of oil).

Colombia

Gran Tierra Energy’s year-end 2010 Colombia working interest and net
after royalty reserves are shown in the following table (NI 51-101
compliant with forecast oil price and cost). Also shown in the
following table are Gran Tierra Energy’s Colombian net after royalty
reserves for year-end 2009 (NI 51-101 compliant with forecast oil price
and cost).

The Costayaco Field 2010 year-end net after royalty reserves are shown
in the following table (with forecast oil price and cost). Also shown
in the following table is a comparison of the Costayaco Field 2010
year-end gross lease reserves (with forecast oil price and cost) to the
gross lease reserves estimated at December 31, 2009 (with forecast oil
price and cost).

Argentina

Gran Tierra Energy’s Argentina year-end 2010 working interest and net
after royalty reserves are shown in the following table (NI 51-101
compliant with forecast oil price and cost). Also shown in the
following table is Gran Tierra Energy’s Argentina net after royalty
reserves for year-end 2009 (NI 51-101 compliant with forecast oil price
and cost).

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, subject to regulatory approval, in
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.

Additional information concerning Gran Tierra Energy is available at www.grantierra.com, on SEDAR (www.sedar.com) and with the Securities and Exchange Commission (www.sec.gov).

Cautionary Statements:

Possible reserves are those additional reserves that are less certain to
be recovered than probable reserves. There is a 10% probability that
the quantities actually recovered will equal or exceed the sum of
proved plus probable plus possible reserves. The estimate of reserves
for individual properties may not reflect the same confidence level as
estimates of reserves for all properties, due to the effects of
aggregation.

A barrel of oil equivalent (BOE) is calculated using the conversion
factor of 6,000 cubic feet (“6Mcf”) of natural gas being equivalent to
one barrel of oil. BOEs may be misleading, particularly if used in
isolation. A BOE conversion ratio of 6 Mcf : 1 barrel of oil is based
on an energy equivalency conversion method primarily applicable at the
burner tip and does not represent a value equivalency at the wellhead.

Forward-Looking Statements

The statements in this press release regarding Gran Tierra Energy’s
expectations, plans, projections and actions including Gran Tierra
Energy’s expectations regarding its 2011 exploration drilling campaign,
reservoir management and production, and expected funding of Gran
Tierra Energy’s 2011 capital program are “forward-looking statements”
within the meaning of the U.S. federal and Canadian securities laws,
including Canadian Securities Administrators’ National Instrument
51-102 – Continuous Disclosure Obligations and the U.S. Private Securities Litigation Reform Act of 1995.
Statements containing the words “estimates”, “expects”, “will”,
“scheduled”, “may”, “intends” and variations of these words are
forward-looking statements. 

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
the accuracy of its reserves estimates, the continuity of certain
industry conditions, the ability of Gran Tierra Energy to execute its
current business and operational plans in the manner currently planned.
Although Gran Tierra Energy believes that the assumptions underlying,
and expectations reflected in, these forward-looking statements are
reasonable, it can give no assurance that these assumptions and
expectations will prove to be correct. 

The forward-looking statements contined in this press 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. Factors that could cause results to
differ materially from those described in the forward-looking
statements include: 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 the production, transportation or sale of oil and gas; changing
prices for crude oil may cause some scheduled projects or actions to
become uneconomical, or may change Gran Tierra Energy’s focus to other
projects or actions which could be of more benefit to Gran Tierra
Energy, which could cause projects or actions currently contemplated to
be postponed or cancelled; unexpected problems due to technical
difficulties, operational difficulties, and weather conditions; and
those other risks found in the periodic reports filed by Gran Tierra
Energy with the United States Securities and Exchange Commission,
including in the section entitled “Risk Factors” in its Quarterly
Report on Form 10-Q filed with the Securities and Exchange Commission
on November 5, 2010, and available at the Securities and Exchange
Commission’s internet site www.sec.gov and on SEDAR at www.sedar.com.  

All forward-looking statements in this press release are expressly
qualified by information contained in Gran Tierra Energy’s filings with
regulatory authorities and, subject to its obligations under applicable
securities laws, Gran Tierra Energy does not undertake to publicly
update forward-looking statements, whether as a result of new
information, future events or otherwise.

SOURCE Gran Tierra Energy Inc.