Gran Tierra Energy Tests 1,984 Barrels of Oil per Day (18.5 Degree API) with Peru Discovery Well

 Gran Tierra Energy Tests 1,984 Barrels of Oil per Day (18.5 Degree API) with
                             Peru Discovery Well

PR Newswire

CALGARY, Feb. 21, 2013

Planning Horizontal Sidetrack to Implement Long Term Test and Bring New Oil to
Market

CALGARY, Feb. 21, 2013 /PRNewswire/ - Gran Tierra Energy Inc. ("Gran Tierra
Energy") (NYSE MKT: GTE, TSX: GTE), a company focused on oil exploration and
production in South America, today provided updates for its exploration
drilling in Peru.

"Gran Tierra Energy has successfully completed initial testing of the  Bretaña 
Norte  95-2-1XD  exploration  well  in   Peru  at  rates  that  far   exceeded 
expectations. We are currently planning to extend the Bretaña Norte  95-2-1XD 
exploration well with a horizontal  leg, with operations expected to  commence 
by the end of February, to initiate long term testing and to fast-track  first 
production from  the Bretaña  discovery," said  Dana Coffield,  President  and 
Chief Executive Officer of  Gran Tierra Energy.  "This discovery has  material 
contingent resource potential, and is  expected to provide significant  growth 
for the company and assist Perupetro in achieving its objectives to bring  new 
oil to the market on behalf of the Government of Peru," concluded Coffield.

Peru

Block 95 (100% working interest and operator)

Gran Tierra Energy completed initial testing of the Vivian Formation sandstone
reservoir in the Bretaña Norte 95-2-1XD exploration well. Log  interpretations 
and MDT  fluid  and  pressure  sampling  had  indicated  the  presence  of  an 
oil-bearing sandstone reservoir  in the  Vivian Formation  beginning at  9,408 
feet measured depth ("MD") or 8,851  feet true vertical depth ("TVD") with  an 
approximate gross  oil  column  thickness of  99  feet  and 53  feet  net  pay 
thickness. Laboratory analyses  of the  oil samples  indicate the  oil has  a 
gravity of 18.5 degrees API.

A drill stem test was conducted over a 29 foot interval from 9,409 feet MD  to 
9,438 feet  MD. Approximately  1,170  barrels of  oil  per day  ("BOPD")  was 
produced on  natural flow  without pumps  for 19.65  hours with  0% water  cut 
through a 46/64 inch choke. The choke size was then increased to a 64/64  inch 
and oil flow  increased to approximately  1,984 BOPD on  natural flow  without 
pumps over a period of 1.5 hours with 0% water cut. Cumulative production over
the testing period  amounted to  1,082 barrels  of oil.  The wellhead  flowing 
pressure and temperature were increasing through the test, indicating that the
formation was cleaning up and oil flow was increasing over the duration of the
test. The test was  successfully concluded when  available crude oil  storage 
capacity had been achieved.

The horizontal  sidetrack,  which  is  expected to  commence  at  the  end  of 
February, will be completed and used to  initiate a Long Term Test ("LTT")  of 
the Bretaña Norte 95-2-1XD exploration well. Timing for initiation of the LTT
has not been determined yet, but it is expected to commence within a period of
12  months,  subject  to  facilities  upgrade,  and  execution  of  crude  oil 
transportation and delivery agreements.

In its press  release dated June  11, 2012, Gran  Tierra Energy announced  the 
results of a contingent gross lease resource estimate for the oil discovery on
Block  95,  provided  by  its  independent  reserves  auditor,  GLJ  Petroleum 
Consultants effective June 1, 2012, before  the drilling of the Bretaña  Norte 
95-2-1XD  exploration  well.  The  resource  estimate  has  been  prepared  in 
compliance with National Instrument 51-101  - Standards of Disclosure for  Oil 
and Gas Activities  and the  Canadian Oil  and Gas  Evaluation Handbook.  The 
estimates included a low  estimate "1C" contingent  resources of 11.5  million 
stock tank barrels of oil ("MMSTB"), a best estimate "2C" contingent resources
of 31.6 MMSTB, and a high  estimate "3C" contingent resources of 88.1  MMSTB. 
There is  no certainty  that it  will be  commercially viable  to produce  any 
portion  of  these  resources.     Additional  information  respecting   such 
contingent resource estimates is included in the June 11, 2012, press  release 
and under the heading "Forward-Looking Statements and Advisories" below.

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

Readers are cautioned that the well-flow test results disclosed in this  press 
release are not necessarily indicative of long term performance or of ultimate
recovery.

Contingent resources  are those  quantities of  petroleum estimated,  as of  a 
given date,  to  be potentially  recoverable  from known  accumulations  using 
established technology  or technology  under development,  but which  are  not 
currently considered  to  be  commercially  recoverable due  to  one  or  more 
contingencies. Contingencies  may include  factors  such as  economic,  legal, 
environmental, political, and regulatory matters, or a lack of markets. It  is 
also appropriate to classify as contingent resources the estimated  discovered 
recoverable quantities  associated  with a  project  in the  early  evaluation 
stage. Contingent  resources are  further classified  in accordance  with  the 
level of  certainty associated  with the  estimates and  may be  subclassified 
based on project maturity and/or characterized by their economic status.

This  news   release   contains  certain   forward-looking   information   and 
forward-looking statements (collectively, "forward-lookingstatements")  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 "planning", "will",  "expected", "estimate" and  "potential" 
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   the  anticipated   exploration   and 
development activities, expected  drilling locations,  expected benefits  from 
testing, and expected timing of activities and results, including the expected
resource potential and  effect on the  growth of Gran  Tierra Energy from  the 
discovery, the expected drilling of a horizontal well and the expected  timing 
and use thereof, and  the expected timing of  commencement of LTT.  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.  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 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  accuracy  of resource  estimates;  the 
accuracy of testing and  production results and seismic  data; the effects  of 
certain drilling  techniques;  cost  and  price  estimates;  and  the  general 
continuance of current or,  where applicable, assumed operational,  regulatory 
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:  unexpected technical  difficulties  and 
operational difficulties may occur, which could impact or delay the completion
or continuation of drilling; geographic, political and weather conditions  can 
interrupt  drilling,  which  could  impact   or  delay  the  commencement   or 
continuation of drilling; 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 
change its current drilling, production and testing plans. 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 
November 7, 2012. 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.

Contact:

For investor and media inquiries please contact:
Jason Crumley
Director, Investor Relations
403-265-3221
info@grantierra.com
www.grantierra.com
 
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