Strong Reserves Replacement and Meaningful Reserves Growth in 2023

Achieved 154% 1P, 242% 2P and 303% 3P Reserves Replacement

Fifth Consecutive Year of 1P Total Company Reserves Growth

Incurred F&D Costs, Excluding Change in FDC, of $11.96 (1P), $7.58 (2P) and $6.06 (3P) per boe

Net Present Value Before Tax Discounted at 10% of $1.9 Billion (1P), $3.1 Billion (2P), and $4.3 Billion (3P)

Net Asset Value per Share of $18.79 Before Tax and $10.46 After Tax (PDP), $44.48 Before Tax and $24.06 After Tax (1P), and $79.13 Before Tax and $42.71 After Tax (2P)

CALGARY, Alberta, Jan. 23, 2024 (GLOBE NEWSWIRE) -- Gran Tierra Energy Inc. (“Gran Tierra” or the “Company”) (NYSE American:GTE)(TSX:GTE)(LSE:GTE), a company focused on international oil exploration and production with assets currently in Colombia and Ecuador, today announced the Company’s 2023 year-end reserves as evaluated by the Company’s independent qualified reserves evaluator McDaniel & Associates Consultants Ltd. (“McDaniel”) in a report with an effective date of December 31, 2023 (the “GTE McDaniel Reserves Report”).

All dollar amounts are in United States (“U.S.”) dollars and all reserves and production volumes are on a working interest before royalties (“WI”) basis. Production is expressed in barrels (“bbl”) of oil per day (“bopd”), while reserves are expressed in bbl, bbl of oil equivalent (“boe”) or million boe (“MMBOE”), unless otherwise indicated. The following reserves categories are discussed in this press release: Proved Developed Producing (“PDP”), Proved (“1P”), 1P plus Probable (“2P”) and 2P plus Possible (“3P”).

Gary Guidry, President and Chief Executive Officer of Gran Tierra, commented: “During 2023, a combination of our strong reserves growth, ongoing reductions in debt and share buybacks allowed Gran Tierra to achieve net asset values per share** before tax of $44.48 (1P), up 288% from 2020, and $79.13 (2P), up 144% from 2020. With this significant growth in our net asset values per share** over the last three years, we believe Gran Tierra is well positioned to offer exceptional long-term stakeholder value.

Gran Tierra achieved strong 154% (1P), 242% (2P) and 303% (3P) reserves replacement through our successful results from our development drilling, waterflooding programs, field performance and the Suroriente Block Continuation Agreement*. This multi-faceted success resulted in record highs for the Company’s year-end 1P, 2P and 3P oil reserves.

We completed our 2023 development plan on-budget including waterflooding efforts and development drilling in the Acordionero, Costayaco and Moqueta oil fields. We also continued to evaluate our successful ongoing production from key 2022 exploration discoveries in Colombia and Ecuador to plan for 2024 follow-up exploration drilling. We believe our success on multiple fronts during 2023 demonstrates Gran Tierra's ability to be a full-cycle oil and gas exploration, development and production company focused on value creation for all our stakeholders.

The success the Company achieved in 2023 also reflects our ongoing conversion of reserves from the Probable to the Proved category. With 147 booked Proved plus Probable Undeveloped future drilling locations, Gran Tierra is well positioned to continue to grow the Company's production and reserves in 2024 and beyond.

We have started 2024 strong with two rigs currently drilling our planned series of development wells in Acordionero and Costayaco. Both rigs began their development campaigns in December 2023. Later in 2024, we look forward to our planned resumption of exploration drilling in Colombia and Ecuador to build upon our successful exploration results in 2022, and the first development drilling in the Suroriente Block since 2018. Through our ongoing focus on the development of our existing assets, appraisal of our 2022 discoveries and exploration drilling, we plan to continue to strengthen our balance sheet, profitably increase production, grow our reserve base and return capital to shareholders through share buybacks.”

*See the section below titled “Suroriente Continuation Agreement”.

**See the below tables for the definitions of net asset values per share.

Highlights

2023 Year-End Reserves and Values

1Based on estimated 2023 year-end net debt of $511 million comprised of Senior Notes of $537 million (gross) plus the Credit Facility of $36 million (gross) less cash and cash equivalents of $62 million, prepared in accordance with GAAP.

2Outstanding Shares. Reflects Gran Tierra’s 1-for-10 reverse stock split that became effective May 5, 2023.

As of December 31, 2023, Gran Tierra achieved:

Before Tax NAV of $1.4 billion (1P), $2.6 billion (2P), and $3.8 billion (3P)

After Tax NAV of $0.8 billion (1P), $1.4 billion (2P), and $2.0 billion (3P)

Strong reserves replacement ratios of:

154% 1P, with 1P reserves additions of 18 MMBOE.

242% 2P, with 2P reserves additions of 29 MMBOE.

303% 3P, with 3P reserves additions of 36 MMBOE.

Meaningful 1P, 2P and 3P reserves additions largely driven by success with development drilling and waterflooding results in the Chaza Block (which contains Costayaco and Moqueta fields) and the Suroriente Continuation Agreement*.

Finding and development costs (“F&D”), including change in future development costs (“FDC”), on a per boe basis of $20.58 (1P), $16.09 (2P) and $14.67 (3P).

F&D costs excluding change in FDC, on a per boe basis of $11.96 (1P), $7.58 (2P) and $6.06 (3P).

F&D recycle ratios**, including change in FDC, of 1.8 times (1P), 2.2 times (2P) and 2.5 times (3P).

Gran Tierra’s four major oil assets, Acordionero, Costayaco, Moqueta and Suroriente (all on waterflood) represent 83% of the Company’s 1P reserves and 73% of its 2P reserves.

The Company’s PDP reserves account for 48% of 1P reserves and 1P reserves account for 61% of 2P reserves, which demonstrate the strength of Gran Tierra’s reserves base via the potential future conversion of Probable reserves into 1P reserves and Proved Undeveloped reserves into PDP reserves.

FDC are forecast to be $561 million for 1P reserves and $923 million for 2P reserves. Gran Tierra’s 2024 base case mid-point guidance for cash flow*** of $300 million is equivalent to 54% of 1P FDC and 33% of 2P FDC, which highlights the Company’s potential ability to fund future development capital. Increases in FDC relative to 2022 year-end reflect that the GTE McDaniel Reserves Report now assigns Gran Tierra 95 Proved Undeveloped future drilling locations (up from 78 at 2022 year-end) and 147 Proved plus Probable Undeveloped future drilling locations (up from 115 at 2022 year-end).

*See the section below titled “Suroriente Continuation Agreement”.

**F&D recycle ratio is defined as fourth quarter 2023 operating netback per WI sales volume boe divided by the appropriate F&D costs on a per boe basis. Operating netback does not have a standardized meaning under generally accepted accounting principles in the United States of America (“GAAP”) and is a non-GAAP measure. Operating netback is defined as oil sales less operating and transportation expenses. See “Non-GAAP Measures” in this press release.

*** “Cash flow” refers to GAAP line item “net cash provided by operating activities”. Gran Tierra’s 2024 base case guidance is based on a forecast 2024 average Brent oil price of $80/bbl. This forecast price used in Gran Tierra’s forecast is higher than the 2024 McDaniel Brent price forecast.

GTE McDaniel Reserves Report

All reserves values, future net revenue and ancillary information contained in this press release have been prepared by McDaniel and 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”) and derived from the GTE McDaniel Reserves Report, unless otherwise expressly stated.

Future Net Revenue

Future net revenue reflects McDaniel’s forecast of revenue estimated using forecast prices and costs, arising from the anticipated development and production of reserves, after the deduction of royalties, operating costs, development costs and abandonment and reclamation costs but before consideration of indirect costs such as administrative, overhead and other miscellaneous expenses. The estimate of future net revenue below does not necessarily represent fair market value.

Consolidated Properties at December 31, 2023

Proved (1P) Total Future Net Revenue ($ million)

Forecast Prices and Costs

Consolidated Properties at December 31, 2023

Proved Plus Probable (2P) Total Future Net Revenue ($ million)

Forecast Prices and Costs

Consolidated Properties at December 31, 2023

Proved Plus Probable Plus Possible (3P) Total Future Net Revenue ($ million)

Forecast Prices and Costs

*The after-tax future net revenue of the Company’s oil and gas properties reflects the tax burden on the properties on a stand-alone basis. It does not consider the corporate tax situation, or tax planning. It does not provide an estimate of the value at the Company level which may be significantly different. The Company’s financial statements, when available for the year ended December 31, 2023, should be consulted for information at the Company level.

Total Company WI Reserves

The following table summarizes Gran Tierra’s NI 51-101 and COGEH compliant reserves in Colombia and Ecuador derived from the GTE McDaniel Reserves Report calculated using forecast oil and gas prices and costs. Gran Tierra has determined that Ecuador reserves, included in the Total Proved, Total Probable and Total Possible reserve categories for Light and Medium Crude Oil, are not material enough to present separately on a country basis. Therefore all amounts are presented on a consolidated basis by foreign geographic area.

*Mbbl (thousand bbl of oil).

**MMcf (million cubic feet).

***Mboe (thousand boe).

Net Present Value Summary

Gran Tierra’s reserves were evaluated using the average of 3 independent qualified reserves evaluators’ commodity price forecasts at January 1, 2024 (McDaniel, Sproule and GLJ). See “Forecast Prices” for more information. It should not be assumed that the net present value of cash flow estimated by McDaniel represents the fair market value of Gran Tierra’s reserves.

* Calculated using Gran Tierra’s average fourth quarter 2023 WI production of 31,309 bopd.

Future Development Costs

FDC reflects McDaniel's best estimate of what it will cost to bring the Proved Undeveloped and Probable Undeveloped reserves on production. Changes in forecast FDC occur annually as a result of development activities, acquisition and disposition activities, and changes in capital cost estimates based on improvements in well design and performance, as well as changes in service costs. FDC for 2P reserves increased to $923 million at year-end 2023 from $677 million at year-end 2022. The increase in FDC in 2023 was predominantly attributed to the increase in the numbers of future development well locations identified by McDaniel in the Suroriente Continuation Agreement.

*Operating Netback is a Non-GAAP measure and does not have a standardized meaning under GAAP. Operating netback as presented is defined as oil sales less operating and transportation expenses. See "Non-GAAP Measures" in this press release.

Finding and Development Costs, Excluding FDC*

Year Ended December 31, 2023

Proved Developed Producing

*In all cases, the F&D number is calculated by dividing the identified capital expenditures by the applicable reserves additions both before and after changes in FDC costs. Both F&D costs take into account reserves revisions during the year on a per boe basis. F&D recycle ratio is defined as fourth quarter 2023 operating netback per WI sales volume boe divided by the appropriate F&D costs on a per boe basis. The aggregate of the exploration and development costs incurred in the financial year and the changes during that year in estimated future development costs may not reflect the total F&D costs related to reserves additions for that year. Operating Netback is a Non-GAAP measure and does not have a standardized meaning under GAAP. Operating netback is defined as oil sales less operating and transportation expenses. See “Non-GAAP Measures” in this press release.

Forecast Prices

The pricing assumptions used in estimating NI 51-101 and COGEH compliant reserves data disclosed above with respect to net present values of future net revenue are set forth below. The price forecasts are based on an average of three independent qualified reserves evaluators’ commodity price forecasts at January 1, 2024 (McDaniel, Sproule and GLJ). All three of these companies are independent qualified reserves evaluators and auditors pursuant to NI 51-101.

Suroriente Continuation Agreement

On April 11, 2023, the Company announced that it had entered into an agreement with Ecopetrol S.A., the national oil company of Colombia (the “Suroriente Continuation Agreement”), by which the parties renegotiated the terms and the duration of the contract for the Suroriente Block in the Department of Putumayo, which was scheduled to end in mid-2024. The Suroriente Continuation Agreement provides an opportunity to add significant value, as well as economic life, to the Suroriente Block by continuing its duration for 20 years from the Suroriente Continuation Agreement's effective date. On August 31, 2023, the Company announced that it had satisfied all outstanding conditions precedent to the effectiveness of the Suroriente Continuation Agreement.

Corporate Presentation:

About Gran Tierra Energy Inc.

Gran Tierra Energy Inc. together with its subsidiaries is an independent energy company currently focused on international oil and natural gas exploration and production in Colombia and Ecuador. The Company is currently developing its existing portfolio of assets in Colombia and Ecuador and will continue to pursue additional growth opportunities that would further strengthen the Company’s portfolio. The Company’s common stock trades on the NYSE American, the Toronto Stock Exchange and the London Stock Exchange under the ticker symbol GTE. Additional information concerning Gran Tierra is available at www.grantierra.com. Information on the Company’s website (including the Corporate Presentation referenced above) does not constitute a part of this press release. Investor inquiries may be directed to info@grantierra.com or (403) 265-3221.

Gran Tierra's U.S. Securities and Exchange Commission ("SEC") filings are available on the SEC website at www.sec.gov. The Company's Canadian securities regulatory filings are available on SEDAR at www.sedar.com and UK regulatory filings are available on the National Storage Mechanism (the "NSM") website at https://data.fca.org.uk/#/nsm/nationalstoragemechanism. Gran Tierra's filings on the SEC, SEDAR and the NSM websites are not incorporated by reference into this press release.

Non-GAAP Measures

This press release includes non-GAAP measures which do not have a standardized meaning under GAAP. Investors are cautioned that these measures should not be construed as alternatives to oil sales, net income or loss or other measures of financial performance as determined in accordance with GAAP. Gran Tierra's method of calculating these measures may differ from other companies and, accordingly, they may not be comparable to similar measures used by other companies.

Operating netback as presented is defined as oil sales less operating and transportation expenses. Management believes that operating netback is a useful supplemental measure for investors to analyze financial performance and provide an indication of the results generated by Gran Tierra's principal business activities prior to the consideration of other income and expenses. A reconciliation of operating netback per boe to the most directly comparable measure calculated and presented in accordance with GAAP is as follows:

Three months ended December 31, 2023

Unaudited Financial Information

Certain financial and operating results included in this press release, including debt, capital expenditures, and production information, are based on unaudited estimated results. These estimated results are subject to change upon completion of the Company's audited financial statements for the year ended December 31, 2023, and changes could be material. Gran Tierra anticipates filing its audited financial statements and related management's discussion and analysis for the year ended December 31, 2023 on or before February 20, 2024.

DISCLOSURE OF OIL AND GAS INFORMATION

All reserves values, future net revenue and ancillary information contained in this press release have been prepared by McDaniel and are derived from the GTE McDaniel Reserves Report, unless otherwise expressly stated. Any reserves values or related information contained in this press release as of a date other than December 31, 2023 has an effective date of December 31 of the applicable year and is derived from a report prepared by Gran Tierra's independent qualified reserves evaluator as of such date, and additional information regarding such estimate or information can be found in Gran Tierra's applicable Statement of Reserves Data and Other Oil and Gas Information on Form 51-101F1 filed on SEDAR at www.sedar.com.

Estimates of net present value and future net revenue contained herein do not necessarily represent fair market value. Estimates of reserves and future net revenue for individual properties may not reflect the same level of confidence as estimates of reserves and future net revenue for all properties, due to the effect of aggregation. There is no assurance that the forecast price and cost assumptions applied by McDaniel in evaluating Gran Tierra's reserves will be attained and variances could be material. All reserves assigned in the GTE McDaniel Reserves Report are located in Colombia and Ecuador and presented on a consolidated basis by foreign geographic area.

All evaluations of future net revenue contained in the GTE McDaniel Reserves Report are after the deduction of royalties, operating costs, development costs, production costs and abandonment and reclamation costs but before consideration of indirect costs such as administrative, overhead and other miscellaneous expenses. It should not be assumed that the estimates of future net revenues presented in this press release represent the fair market value of the reserves. There are numerous uncertainties inherent in estimating quantities of crude oil reserves and the future cash flows attributed to such reserves. The reserve and associated cash flow information set forth in the GTE McDaniel Reserves Report are estimates only and there is no guarantee that the estimated reserves will be recovered. Actual reserves may be greater than or less than the estimates provided therein.

References to a formation where evidence of hydrocarbons has been encountered is not necessarily an indicator that hydrocarbons will be recoverable in commercial quantities or in any estimated volume. Gran Tierra's reported production is a mix of light crude oil and medium and heavy crude oil for which there is no precise breakdown since the Company's oil sales volumes typically represent blends of more than one type of crude oil. Drilling locations disclosed herein are derived from the GTE McDaniel Reserves Report and account for drilling locations that have associated Proved Undeveloped and Proved plus Probable Undeveloped reserves, as applicable. Well test results should be considered as preliminary and not necessarily indicative of long-term performance or of ultimate recovery. Well log interpretations indicating oil and gas accumulations are not necessarily indicative of future production or ultimate recovery. If it is indicated that a pressure transient analysis or well-test interpretation has not been carried out, any data disclosed in that respect should be considered preliminary until such analysis has been completed. References to thickness of "oil pay" or of a formation where evidence of hydrocarbons has been encountered is not necessarily an indicator that hydrocarbons will be recoverable in commercial quantities or in any estimated volume.

Definitions

Oil and Gas Metrics

This press release contains a number of oil and gas metrics, including NAV per share, F&D costs, F&D recycle ratio, operating netback, reserve life index and reserves replacement, which do not have standardized meanings or standard methods of calculation and therefore such measures may not be comparable to similar measures used by other companies and should not be used to make comparisons. Such metrics have been included herein to provide readers with additional measures to evaluate the Company's performance; however, such measures are not reliable indicators of the future performance of the Company and future performance may not compare to the performance in previous periods.

NAV per share is calculated as NPV10 (before or after tax, as applicable) of the applicable reserves category minus estimated net debt, divided by the number of shares of Gran Tierra's common stock issued and outstanding. Management uses NAV per share as a measure of the relative change of Gran Tierra's net asset value over its outstanding common stock over a period of time.

F&D costs are calculated as estimated exploration and development capital expenditures, excluding acquisitions and dispositions, divided by the applicable reserves additions both before and after changes in FDC costs. The calculation of F&D costs incorporates the change in FDC required to bring proved undeveloped and developed reserves into production. The aggregate of the exploration and development costs incurred in the financial year and the changes during that year in estimated FDC may not reflect the total F&D costs related to reserves additions for that year. Management uses F&D costs per boe as a measure of its ability to execute its capital program and of its asset quality.

F&D recycle ratio is calculated as described in this press release. Management uses F&D recycle ratio as an indicator of profitability of its oil and gas activities.

Operating netback is calculated as described in this press release. Management believes that operating netback is a useful supplemental measure for investors to analyze financial performance and provide an indication of the results generated by Gran Tierra's principal business activities prior to the consideration of other income and expenses.

Reserve life index is calculated as reserves in the referenced category divided by the referenced estimated production. Management uses this measure to determine how long the booked reserves will last at current production rates if no further reserves were added.

Reserves replacement is calculated as reserves in the referenced category divided by estimated referenced production. Management uses this measure to determine the relative change of its reserve base over a period of time.

Disclosure of Reserve Information and Cautionary Note to U.S. Investors

Unless expressly stated otherwise, all estimates of proved, probable and possible reserves and related future net revenue disclosed in this press release have been prepared in accordance with NI 51-101. Estimates of reserves and future net revenue made in accordance with NI 51-101 will differ from corresponding estimates prepared in accordance with applicable U.S. Securities and Exchange Commission ("SEC") rules and disclosure requirements of the U.S. Financial Accounting Standards Board ("FASB"), and those differences may be material. NI 51-101, for example, requires disclosure of reserves and related future net revenue estimates based on forecast prices and costs, whereas SEC and FASB standards require that reserves and related future net revenue be estimated using average prices for the previous 12 months. In addition, NI 51-101 permits the presentation of reserves estimates on a "company gross" basis, representing Gran Tierra's working interest share before deduction of royalties, whereas SEC and FASB standards require the presentation of net reserve estimates after the deduction of royalties and similar payments. There are also differences in the technical reserves estimation standards applicable under NI 51-101 and, pursuant thereto, the COGEH, and those applicable under SEC and FASB requirements.

Proved reserves are reserves which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible from a given date forward from known reservoirs under existing economic conditions, operating methods, and government regulations prior to the time at which contracts providing the right to operate expires, unless evidence indicates that renewal is reasonably certain. Probable reserves are reserves that are less certain to be recovered than proved reserves but which, together with proved reserves, are as likely as not to be recovered. Estimates of probable reserves which may potentially be recoverable through additional drilling or recovery techniques are by nature more uncertain than estimates of proved reserves and accordingly are subject to substantially greater risk of not actually being realized by us. Possible reserves are reserves that are less certain to be recovered than probable reserves. Estimates of possible reserves are also inherently imprecise. Estimates of probable and possible reserves are also continually subject to revisions based on production history, results of additional exploration and development, price changes, and other factors.

Investors are urged to consider closely the disclosures and risk factors in the Company's Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and in the other reports and filings with the SEC, available from the Company's offices or website. These reports can also be obtained from the SEC website at www.sec.gov.