EX-99.3 16 ec-20231231xex99d3.htm EX-99.3

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Reserves Statement of Certain Fields,

Colombia

as of December 31, 2023

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Prepared for

Ecopetrol S.A.

February 20, 2024

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Exhibit 99.3

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​ | ​ | ​
​ | ​ | GaffneyCline
​ | ​ | 4425 Westway Park Blvd
​ | ​ | Houston, TX 77041
| ​ | ​ Tel: +1 713 850 9955 www.gaffneycline.com
​ | ​ | February 20, 2024

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Fidel Delgado Loria

Gerente de Reservas

Ecopetrol S.A.

Carrera 13 No. 36 - 24

Bogotá, D.C.

Colombia

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fidel.delgado@ecopetrol.com.co

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Dear Fidel,

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SEC Proved Reserves Statement

for Forty-Eigth Fields in which Ecopetrol has an Interest, Colombia

as of December 31, 2023

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Introduction

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This Proved reserves statement has been prepared by Gaffney, Cline & Associates (GaffneyCline) and issued on February 20, 2024 at the request of Ecopetrol S.A. (Ecopetrol, or “the Client”), operator, participant operator, and interest participant in 48 fields in the Lower, Middle and Upper Magdalena Valley, Piedemonte, Putumayo and Llanos Orientales Basins, Colombia.

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This report is intended for use in conjunction with Ecopetrol’s December 31, 2023 filing obligations with the US Securities and Exchange Commission (SEC).

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This report relates specifically and solely to the subject matter as defined in the scope of work in the Proposal for Services and is conditional upon the assumptions described herein. The report must be considered in its entirety and must only be used for the purpose for which it was intended.

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Ecopetrol S.A. | www.gaffneycline.com

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Summary and Conclusions

On the basis of technical and other information made available to GaffneyCline concerning these property units, GaffneyCline hereby provides the reserves statement in the following Table 1.

Table 1: Statement of Proved Hydrocarbon Reserves Volumes

Forty-eigth Fields, Colombia

as of December 31, 2023

Reserves | Reserves Net to Ecopetrol’s Interest
​ | Oil/Cond. (MBbl) | NGL (MBbl) | Sales Gas (Bscf) | Fuel Gas (Bscf) | Fuel Oil (MBbl)
Developed | 259,214 | 26,061 | 895.84 | 133.50 | ​
Producing | ​ | ​ | ​ | ​ | 5,988
Non-Producing | 97,733 | 8,456 | 226.82 | 27.80 | 3,773
Undeveloped | 108,790 | 6,000 | 142.41 | 16.61 | 4,010
Total Proved | 465,737 | 40,517 | 1,265.07 | 177.91 | 13,771

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Notes:

1. | Oil and condensate reserves net to Ecopetrol’s interest represent volumes after the deduction of royalties, under the concessions that govern the assets, based on Ecopetrol’s working interest.

2. | Gas and NGL reserves net to Ecopetrol’s working interest include gas and NGL royalty volumes that are required to be paid in cash according to Resolutions 877 and 351 from Agencia Nacional de Hidrocarburos (ANH) and the corresponding clarification note from ANH #20146240188522.

3. | Net sales gas reserves exclude volumes consumed in operations (fuel gas), which are reported separately.

4. | Fuel gas and fuel oil represents working interest volumes consumed in operations.

5. | Ecopetrol is the operator of 43 fields and 5 fields are operated by Hocol, a 100% owned subsidiary

6. | The above Reserves include production:

| a. | Until the economic limit when contracts are solely operated by Ecopetrol.

| b. | Beyond the end of the current license period in concession contracts that include an expiry date which are assumed to revert to Ecopetrol as the sole license holder at the expiry of the contract and, based on information provided by Ecopetrol, normally include a 12% increase in the royalty rate at contract expiry.

7. | Totals may not exactly equal the sum of the individual entries because of rounding.

Hydrocarbon liquid volumes represent crude oil and condensate, natural gasoline, and NGL estimated to be recovered during field separation and plant processing and are reported in thousands (103) of stock tank barrels (MBbl). The volumes reported as gas represent expected gas sales and are reported in billions (109) of standard cubic feet at standard conditions (Bscf). Standard conditions are defined as 14.7 psia and 60°F. The sales gas volumes have been reduced for fuel usage consumed in operations (CiO) and shrinkage because of processing. Royalties due on oil production payable to the State have been deducted from reported net

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interest volumes. Royalties due on NGL products, including sales gas, are not deducted, because they are paid in cash.

Gas reserves sales volumes are based on firm and existing gas contracts, or on the reasonable expectation of a contract or on the reasonable expectation that any such existing gas sales contracts will be renewed on similar terms in the future.

The development plan for the proved reserves category in the Rubiales field includes investments beyond the next five years because the field has constraints in water handling capacity which require the scheduling of the entry of the new wells based on spare capacity of the plant. GaffneyCline considers that these facilities constraints are a reasonable justification to extend the investments beyond the five-year limit established by the SEC.

The development plan for the proved reserves category in the La Cira Infantas field includes investments for next six years because the current waterflooding project considers the drilling of new injectors wells and starting the water injection before the drilling of producers in same pattern. GaffneyCline considers that this strategy is a reasonable justification to extend the investments beyond the five-year limit established by the SEC

Ecopetrol has advised GaffneyCline that the Proved volumes included in this report represent 35.35% of Ecopetrol’s total Proved reserves on an oil basis and 61.51% on gas basis. The volume Proved Undeveloped included in this report represent 30.58% of Ecopetrol’s total Proved Undeveloped reserves on an oil basis and 46.97% on gas basis. GaffneyCline is not in a position to verify these statements as it was not requested to review Ecopetrol’s other oil and gas assets.

Descriptions of the fields are included in the technical reports, which have been issued separately.

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Reserves Assessment

GaffneyCline’s estimate of reserves was based on data provided by Ecopetrol to GaffneyCline from September 2023 to December 2023. During this audit GaffneyCline used one or more of the following methods to assess the reserves: volumetric, performance or analogy, depending on the information available and the stage of development of the reservoir. Reserves volumes for existing wells were based on performance analysis (decline of production and behavior of appropriate fluid ratios). Reserves volumes for undrilled wells were based on established performance of analogous wells. Where appropriate, checks were made using estimates of hydrocarbons in place derived from a volumetric analysis. Production forecasts were first prepared to reasonable technical limits and then truncated by the economic limit.

GaffneyCline performed procedures necessary to enable it to render an opinion on the appropriateness of the methodologies employed, adequacy and quality of the data relied on, depth and thoroughness of the reserves estimation process, classification and categorization of reserves appropriate to the relevant definitions used, and reasonableness of the estimates.

The economic tests for the December 31, 2023 reserves volumes were based on prior twelve-month first-day-of-the-month average reference price for the Brent crude of US$82.80/Bbl, corrected for location and quality. Sales gas and plant product prices were advised by Ecopetrol according to existing contracts and/or regulations. No price escalation has been included, other than as provided for in existing contracts.

Future capital costs for operated and non-operated fields were provided by Ecopetrol.

Recent historical operating expense data were used as the basis for operating cost projections. Neither capital not operating costs were escalated for inflation. GaffneyCline has found that sufficient capital investments and operating expenses have been projected to produce the estimated volumes.

It is GaffneyCline’s opinion that the estimates of total remaining recoverable hydrocarbon liquid and gas volumes as of December 31, 2023 are, in the aggregate, reasonable and the reserves classification and categorization is appropriate and consistent with the definitions for reserves in Part 210 Rule 4-10(a) of Regulation S-X of the US Securities and Exchange Commission, which are provided in Appendix I. The technical qualifications of the person responsible for the reserves statement is presented in Appendix II and a glossary of terms is presented in Appendix III.

GaffneyCline is not aware of any potential changes in regulations applicable to these fields that could affect the ability of Ecopetrol to produce the estimated reserves.

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Basis of Opinion

This document reflects GaffneyCline’s informed professional judgment based on accepted standards of professional investigation and, as applicable, the data and information provided by the Client, the limited scope of engagement, and the time permitted to conduct the evaluation.

In line with those accepted standards, this document does not in any way constitute or make a guarantee or prediction of results, and no warranty is implied or expressed that actual outcome will conform to the outcomes presented herein. GaffneyCline has not independently verified any information provided by, or at the direction of, the Client, and has accepted the accuracy and completeness of this data. GaffneyCline has no reason to believe that any material facts have been withheld but does not warrant that its inquiries have revealed all of the matters that a more extensive examination might otherwise disclose.

The opinions expressed herein are subject to and fully qualified by the generally accepted uncertainties associated with the interpretation of geoscience and engineering data and do not reflect the totality of circumstances, scenarios and information that could potentially affect decisions made by the report’s recipients and/or actual results. The opinions and statements contained in this report are made in good faith and in the belief that such opinions and statements are representative of prevailing physical and economic circumstances.

There are numerous uncertainties inherent in estimating reserves, and in projecting future production, development expenditures, operating expenses and cash flows. Oil and gas reserves assessments must be recognized as a subjective process of estimating subsurface accumulations of oil and gas that cannot be measured in an exact way. Estimates of oil and gas reserves prepared by other parties may differ, perhaps materially, from those contained within this report.

The accuracy of any reserves estimate is a function of the quality of the available data and of engineering and geological interpretation. Results of drilling, testing and production that post-date the preparation of the estimates may justify revisions, some or all of which may be material. Accordingly, reserve estimates are often different from the quantities of oil and gas that are ultimately recovered, and the timing and cost of those volumes that are recovered may vary from that assumed.

GaffneyCline has not undertaken a site visit and inspection because it was not included in the scope of work. As such, GaffneyCline is not in a position to comment on the operations or facilities in place, their appropriateness and condition, or whether they are in compliance with the regulations pertaining to such operations. Further, GaffneyCline is not in a position to comment on any aspect of health, safety, or environment of such operation.

This report has been prepared based on GaffneyCline’s understanding of the effects of petroleum legislation and other regulations that currently apply to these properties. However, GaffneyCline is not in a position to attest to property title or rights, conditions of these rights (including environmental and abandonment obligations), or any necessary licenses and consents (including planning permission, financial interest relationships, or encumbrances thereon for any part of the appraised properties).

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Definition of Reserves

Reserves are estimated remaining quantities of oil and gas and related substances anticipated to be economically producible, as of a given date, by application of development projects to known accumulations. In addition, there must exist, or there must be a reasonable expectation that there will exist, the legal right to produce, or a revenue interest in, the production, installed means of delivering oil and gas or related substances to market, and all permits and financing required to implement the project.

Reserves are further categorized in accordance with the level of certainty associated with the estimates and may be sub-classified based on project maturity and/or characterized by development and production status. All categories of reserves volumes quoted herein have been derived within the context of an economic limit test (ELT) assessment (pre-tax and exclusive of accumulated depreciation amounts) prior to any net present value (NPV) analysis.

This report has been prepared based on GaffneyCline’s understanding of the effects of petroleum legislation and other regulations that currently apply to these properties.

GaffneyCline is not aware of any carbon pricing impost or GHG emissions related to regulations that are applicable to the evaluation of the assets that are the subject of this report. GaffneyCline has also not included the impact of any potential carbon pricing scheme or regulatory compliance costs for GHG emissions that may be implemented in the future.

Qualifications

In performing this study, GaffneyCline is not aware that any conflict of interest has existed. As an independent consultancy, GaffneyCline is providing impartial technical, commercial, and strategic advice within the energy sector. GaffneyCline’s remuneration was not in any way contingent on the contents of this report.

In the preparation of this document, GaffneyCline has maintained, and continues to maintain, a strict independent consultant-client relationship with Ecopetrol. Furthermore, the management and employees of GaffneyCline have no interest in any of the assets evaluated or related with the analysis performed as part of this report. The qualifications of the technical person primarily responsible for overseeing this estimate are provided in Appendix II.

Staff members who prepared this report hold appropriate professional and educational qualifications and have the necessary levels of experience and expertise to perform the work.

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Notice

This report was prepared for public disclosure in its entirety by Ecopetrol in filings made with the SEC in accordance with the disclosure requirements set forth in the SEC regulations. Ecopetrol will obtain GaffneyCline’s prior written approval for any other use of any results, statements or opinions expressed to Ecopetrol in this report that are attributed to GaffneyCline.

Yours sincerely,

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Gaffney, Cline & Associates

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​ | ​ | /s/ Eduardo Sanchez | ​ | ​
​ | ​ | Project Manager | ​ | ​
​ | ​ | Eduardo Sanchez, Principal Advisor | ​ | ​

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​ | ​ | /s/ Rawdon J.H. Seager | ​ | ​
​ | ​ | Reviewer | ​ | ​
​ | ​ | Rawdon J.H. Seager, Technical Director | ​ | ​

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Appendices

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Appendix I | SEC Reserves Definitions
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Appendix II | Technical Qualifications of Person Responsible for the Reserves Statement
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Appendix III | Glossary

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Appendix I

SEC Reserves Definitions

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Ecopetrol S.A. February 20, 2024 | ​

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U.S. SECURITIES AND EXCHANGE COMMISSION (SEC)

MODERNIZATION OF OIL AND GAS REPORTING1

Oil and Gas Reserves Definitions and Reporting

(a)Definitions

(1) Acquisition of properties. Costs incurred to purchase, lease or otherwise acquire a property, including costs of lease bonuses and options to purchase or lease properties, the portion of costs applicable to minerals when land including mineral rights is purchased in fee, brokers' fees, recording fees, legal costs, and other costs incurred in acquiring properties.

(2) Analogous reservoir. Analogous reservoirs, as used in resources assessments, have similar rock and fluid properties, reservoir conditions (depth, temperature, and pressure) and drive mechanisms, but are typically at a more advanced stage of development than the reservoir of interest and thus may provide concepts to assist in the interpretation of more limited data and estimation of recovery. When used to support proved reserves, an “analogous reservoir” refers to a reservoir that shares the following characteristics with the reservoir of interest:

| (i) | Same geological formation (but not necessarily in pressure communication with the reservoir of interest);

| (ii) | Same environment of deposition;

| (iii) | Similar geological structure; and

| (iv) | Same drive mechanism.

Instruction to paragraph (a)(2): Reservoir properties must, in the aggregate, be no more favorable in the analog than in the reservoir of interest.

(3) Bitumen. Bitumen, sometimes referred to as natural bitumen, is petroleum in a solid or semi- solid state in natural deposits with a viscosity greater than 10,000 centipoise measured at original temperature in the deposit and atmospheric pressure, on a gas free basis. In its natural state it usually contains sulfur, metals, and other non-hydrocarbons.

(4) Condensate. Condensate is a mixture of hydrocarbons that exists in the gaseous phase at original reservoir temperature and pressure, but that, when produced, is in the liquid phase at surface pressure and temperature.

(5) Deterministic estimate. The method of estimating reserves or resources is called deterministic when a single value for each parameter (from the geoscience, engineering, or economic data) in the reserves calculation is used in the reserves estimation procedure.

(6) Developed oil and gas reserves. Developed oil and gas reserves are reserves of any category that can be expected to be recovered:

1 Extracted from 17 CFR Parts 210, 211, 229, and 249 [Release Nos. 33-8995; 34-59192; FR-78; File No. S7-15-08] RIN 3235-AK00].

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| (i) | Through existing wells with existing equipment and operating methods or in which the cost of the required equipment is relatively minor compared to the cost of a new well; and

| (ii) | Through installed extraction equipment and infrastructure operational at the time of the reserves estimate if the extraction is by means not involving a well.

(7) Development costs. Costs incurred to obtain access to proved reserves and to provide facilities for extracting, treating, gathering and storing the oil and gas. More specifically, development costs, including depreciation and applicable operating costs of support equipment and facilities and other costs of development activities, are costs incurred to:

| (i) | Gain access to and prepare well locations for drilling, including surveying well locations for the purpose of determining specific development drilling sites, clearing ground, draining, road building, and relocating public roads, gas lines, and power lines, to the extent necessary in developing the proved reserves.

| (ii) | Drill and equip development wells, development-type stratigraphic test wells, and service wells, including the costs of platforms and of well equipment such as casing, tubing, pumping equipment, and the wellhead assembly.

| (iii) | Acquire, construct, and install production facilities such as lease flow lines, separators, treaters, heaters, manifolds, measuring devices, and production storage tanks, natural gas cycling and processing plants, and central utility and waste disposal systems.

| (iv) | Provide improved recovery systems.

(8) Development project. A development project is the means by which petroleum resources are brought to the status of economically producible. As examples, the development of a single reservoir or field, an incremental development in a producing field, or the integrated development of a group of several fields and associated facilities with a common ownership may constitute a development project.

(9) Development well. A well drilled within the proved area of an oil or gas reservoir to the depth of a stratigraphic horizon known to be productive.

(10) Economically producible. The term economically producible, as it relates to a resource, means a resource which generates revenue that exceeds, or is reasonably expected to exceed, the costs of the operation. The value of the products that generate revenue shall be determined at the terminal point of oil and gas producing activities as defined in paragraph (a)(16) of this section.

(11) Estimated ultimate recovery (EUR). Estimated ultimate recovery is the sum of reserves remaining as of a given date and cumulative production as of that date.

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(12) Exploration costs. Costs incurred in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of containing oil and gas reserves, including costs of drilling exploratory wells and exploratory-type stratigraphic test wells. Exploration costs may be incurred both before acquiring the related property (sometimes referred

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to in pail as prospecting costs) and after acquiring the property. Principal types of exploration costs, which include depreciation and applicable operating costs of support equipment and facilities and other costs of exploration activities, are:

| (i) | Costs of topographical, geographical and geophysical studies, rights of access to properties to conduct those studies, and salaries and other expenses of geologists, geophysical crews, and others conducting those studies. Collectively, these are sometimes referred to as geological and geophysical or "G&G" costs.

| (ii) | Costs of carrying and retaining undeveloped properties, such as delay rentals, ad valorem taxes on properties, legal costs for title defense, and the maintenance of land and lease records.

| (iii) | Dry hole contributions and bottom hole contributions.

| (iv) | Costs of drilling and equipping exploratory wells.

| (v) | Costs of drilling exploratory-type stratigraphic test wells.

(13) Exploratory well. An exploratory well is a well drilled to find a new field or to find a new reservoir in a field previously found to be productive of oil or gas in another reservoir. Generally, an exploratory well is any well that is not a development well, an extension well, a service well, or a stratigraphic test well as those items are defined in this section.

(14) Extension well. An extension well is a well drilled to extend the limits of a known reservoir.

(15) Field. An area consisting of a single reservoir or multiple reservoirs all grouped on or related to the same individual geological structural feature and/or stratigraphic condition. There may be two or more reservoirs in a field which are separated vertically by intervening impervious strata, or laterally by local geologic barriers, or by both. Reservoirs that are associated by being in overlapping or adjacent fields may be treated as a single or common operational field. The geological terms "structural feature" and "stratigraphic condition" are intended to identify localized geological features as opposed to the broader terms of basins, trends, provinces, plays, areas- of-interest, etc.

(16) Oil and gas producing activities.

| (i) | Oil and gas producing activities include:

| (A) | The search for crude oil, including condensate and natural gas liquids, or natural gas (“oil and gas”) in their natural states and original locations;

| (B) | The acquisition of property rights or properties for the purpose of further exploration or for the purpose of removing the oil or gas from such properties;

| (C) | The construction, drilling, and production activities necessary to retrieve oil and gas from their natural reservoirs, including the acquisition, construction, installation, and maintenance of field gathering and storage systems, such as:

| (1) | Lifting the oil and gas to the surface; and

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| (2) | Gathering, treating, and field processing (as in the case of processing gas to extract liquid hydrocarbons); and

| (D) | Extraction of saleable hydrocarbons, in the solid, liquid, or gaseous state, from oil sands, shale, coalbeds, or other nonrenewable natural resources which are intended to be upgraded into synthetic oil or gas, and activities undertaken with a view to such extraction.

Instruction 1 to paragraph (a)(16)(i): The oil and gas production function shall be regarded as ending at a “terminal point”, which is the outlet valve on the lease or field storage tank. If unusual physical or operational circumstances exist, it may be appropriate to regard the terminal point for the production function as:

| a. | The first point at which oil, gas, or gas liquids, natural or synthetic, are delivered to a main pipeline, a common carrier, a refinery, or a marine terminal; and

| b. | In the case of natural resources that are intended to be upgraded into synthetic oil or gas, if those natural resources are delivered to a purchaser prior to upgrading, the first point at which the natural resources are delivered to a main pipeline, a common carrier, a refinery, a marine terminal, or a facility which upgrades such natural resources into synthetic oil or gas.

Instruction 2 to paragraph (a)(16)(i): For purposes of this paragraph (a)(16), the term saleable hydrocarbons means hydrocarbons that are saleable in the state in which the hydrocarbons are delivered.

| (ii) | Oil and gas producing activities do not include:

| (A) | Transporting, refining, or marketing oil and gas;

| (B) | Processing of produced oil, gas or natural resources that can be upgraded into synthetic oil or gas by a registrant that does not have the legal right to produce or a revenue interest in such production;

| (C) | Activities relating to the production of natural resources other than oil, gas, or natural resources from which synthetic oil and gas can be extracted; or

| (D) | Production of geothermal steam.

(17) Possible reserves. Possible reserves are those additional reserves that are less certain to be recovered than probable reserves.

| (i) | When deterministic methods are used, the total quantities ultimately recovered from a project have a low probability of exceeding proved plus probable plus possible reserves. When probabilistic methods are used, there should be at least a 10% probability that the total quantities ultimately recovered will equal or exceed the proved plus probable plus possible reserves estimates.

| (ii) | Possible reserves may be assigned to areas of a reservoir adjacent to probable reserves where data control and interpretations of available data are progressively less certain. Frequently, this will be in areas where geoscience and engineering

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data are unable to define clearly the area and vertical limits of commercial production from the reservoir by a defined project.

| (iii) | Possible reserves also include incremental quantities associated with a greater percentage recovery of the hydrocarbons in place than the recovery quantities assumed for probable reserves.

| (iv) | The proved plus probable and proved plus probable plus possible reserves estimates must be based on reasonable alternative technical and commercial interpretations within the reservoir or subject project that are clearly documented, including comparisons to results in successful similar projects.

| (v) | Possible reserves may be assigned where geoscience and engineering data identify directly adjacent portions of a reservoir within the same accumulation that may be separated from proved areas by faults with displacement less than formation thickness or other geological discontinuities and that have not been penetrated by a wellbore, and the registrant believes that such adjacent portions are in communication with the known (proved) reservoir. Possible reserves may be assigned to areas that are structurally higher or lower than the proved area if these areas are in communication with the proved reservoir.

| (vi) | Pursuant to paragraph (a)(22)(iii) of this section, where direct observation has defined a highest known oil (HKO) elevation and the potential exists for an associated gas cap, proved oil reserves should be assigned in the structurally higher portions of the reservoir above the HKO only if the higher contact can be established with reasonable certainty through reliable technology. Portions of the reservoir that do not meet this reasonable certainty criterion may be assigned as probable and possible oil or gas based on reservoir fluid properties and pressure gradient interpretations.

(18) Probable reserves. Probable reserves are those additional 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.

| (i) | When deterministic methods are used, it is as likely as not that actual remaining quantities recovered will exceed the sum of estimated proved plus probable reserves. When probabilistic methods are used, there should be at least a 50% probability that the actual quantities recovered will equal or exceed the proved plus probable reserves estimates.

| (ii) | Probable reserves may be assigned to areas of a reservoir adjacent to proved reserves where data control or interpretations of available data are less certain, even if the interpreted reservoir continuity of structure or productivity does not meet the reasonable certainty criterion. Probable reserves may be assigned to areas that are structurally higher than the proved area if these areas are in communication with the proved reservoir.

| (iii) | Probable reserves estimates also include potential incremental quantities associated with a greater percentage recovery of the hydrocarbons in place than assumed for proved reserves.

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| (iv) | See also guidelines in paragraphs (a)(17)(iv) and (a)(17)(vi) of this section.

(19) Probabilistic estimate. The method of estimation of reserves or resources is called probabilistic when the full range of values that could reasonably occur for each unknown parameter (from the geoscience and engineering data) is used to generate a full range of possible outcomes and their associated probabilities of occurrence.

(20) | Production costs.

| (i) | Costs incurred to operate and maintain wells and related equipment and facilities, including depreciation and applicable operating costs of support equipment and facilities and other costs of operating and maintaining those wells and related equipment and facilities, they become part of the cost of oil and gas produced. Examples of production costs (sometimes called lifting costs) are:

| (A) | Costs of labor to operate the wells and related equipment and facilities.

| (B) | Repairs and maintenance.

| (C) | Materials, supplies, arid fuel consumed and supplies utilized in operating the wells and related equipment and facilities.

| (D) | Property taxes and insurance applicable to proved properties and wells and related equipment and facilities.

| (E) | Severance taxes.

| (ii) | Some support equipment or facilities may serve two or more oil and gas producing activities and may also serve transportation, refining, and marketing activities. To the extent that the support equipment and facilities are used in oil and gas producing activities, their depreciation and applicable operating costs become exploration, development or production costs, as appropriate. Depreciation, depletion, and amortization of capitalized acquisition, exploration, and development costs are not production costs but also become part of the cost of oil and gas produced along with production (lifting) costs identified above.

(21) Proved area. The part of a property to which proved reserves have been specifically attributed.

(22) Proved oil and gas reserves. Proved oil and gas reserves are those quantities of oil and gas, 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, and under existing economic conditions, operating methods, and government regulations—prior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain, regardless of whether deterministic or probabilistic methods are used for the estimation. The project to extract the hydrocarbons must have commenced or the operator must be reasonably certain that it will commence the project within a reasonable time.

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| (i) | The area of the reservoir considered as proved includes:

| (A) | The area identified by drilling and limited by fluid contacts, if any, and

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| (B) | Adjacent undrilled portions of the reservoir that can, with reasonable certainty, be judged to be continuous with it and to contain economically producible oil or gas on the basis of available geoscience and engineering data.

| (ii) | In the absence of data on fluid contacts, proved quantities in a reservoir are limited by the lowest known hydrocarbons (LKH) as seen in a well penetration unless geoscience, engineering, or performance data and reliable technology establishes a lower contact with reasonable certainty.

| (iii) | Where direct observation from well penetrations has defined a highest known oil (HKO) elevation and the potential exists for an associated gas cap, proved oil reserves may be assigned in the structurally higher portions of the reservoir only if geoscience, engineering, or performance data and reliable technology establish the higher contact with reasonable certainty.

| (iv) | Reserves which can be produced economically through application of improved recovery techniques (including, but not limited to, fluid injection) are included in the proved classification when:

| (A) | Successful testing by a pilot project in an area of the reservoir with properties no more favorable than in the reservoir as a whole, the operation of an installed program in the reservoir or an analogous reservoir, or other evidence using reliable technology establishes the reasonable certainty of the engineering analysis on which the project or program was based; and

| (B) | The project has been approved for development by all necessary parties and entities, including governmental entities.

| (v) | Existing economic conditions include prices and costs at which economic producibility from a reservoir is to be determined. The price shall be the average price during the 12-month period prior to the ending date of the period covered by the report, determined as an unweighted arithmetic average of the first-day-of-the- month price for each month within such period, unless prices are defined by contractual arrangements, excluding escalations based upon future conditions.

(23) Proved properties. Properties with proved reserves.

(24) Reasonable certainty. If deterministic methods are used, reasonable certainty means a high degree of confidence that the quantities will be recovered. If probabilistic methods are used, there should be at least a 90% probability that the quantities actually recovered will equal or exceed the estimate. A high degree of confidence exists if the quantity is much more likely to be achieved than not, and, as changes due to increased availability of geoscience (geological, geophysical, and geochemical), engineering, and economic data are made to estimated ultimate recovery (EUR) with time, reasonably certain EUR is much more likely to increase or remain constant than to decrease.

(25) Reliable technology. Reliable technology is a grouping of one or more technologies (including computational methods) that has been field tested and has been demonstrated to provide reasonably certain results with consistency and repeatability in the formation being evaluated or in an analogous formation.

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(26) Reserves. Reserves are estimated remaining quantities of oil and gas and related substances anticipated to be economically producible, as of a given date, by application of development projects to known accumulations. In addition, there must exist, or there must be a reasonable expectation that there will exist, the legal right to produce or a revenue interest in the production, installed means of delivering oil and gas or related substances to market, and all permits and financing required to implement the project.

Note to paragraph (a)(26): Reserves should not be assigned to adjacent reservoirs isolated by major, potentially sealing, faults until those reservoirs are penetrated and evaluated as economically producible. Reserves should not be assigned to areas that are clearly separated from a known accumulation by a non-productive reservoir (i.e., absence of reservoir, structurally low reservoir, or negative test results). Such areas may contain prospective resources (i.e., potentially recoverable resources from undiscovered accumulations).

(27) Reservoir. A porous and permeable underground formation containing a natural accumulation of producible oil and/or gas that is confined by impermeable rock or water barriers and is individual and separate from other reservoirs.

(28) Resources. Resources are quantities of oil and gas estimated to exist in naturally occurring accumulations. A portion of the resources may be estimated to be recoverable, and another portion may be considered to be unrecoverable. Resources include both discovered and undiscovered accumulations.

(29) Service well. A well drilled or completed for the purpose of supporting production in an existing field. Specific purposes of service wells include gas injection, water injection, steam injection, air injection, salt-water disposal, water supply for injection, observation, or injection for in-situ combustion.

(30) Stratigraphic test well. A stratigraphic test well is a drilling effort, geologically directed, to obtain information pertaining to a specific geologic condition. Such wells customarily are drilled without the intent of being completed for hydrocarbon production. The classification also includes tests identified as core tests and all types of expendable holes related to hydrocarbon exploration. Stratigraphic tests are classified as “exploratory type” if not drilled in a known area or “development type” if drilled in a known area.

(31) Undeveloped oil and gas reserves. Undeveloped oil and gas reserves are reserves of any category that are expected to be recovered from new wells on undrilled acreage, or from existing wells where a relatively major expenditure is required for recompletion.

| (i) | Reserves on undrilled acreage shall be limited to those directly offsetting development spacing areas that are reasonably certain of production when drilled, unless evidence using reliable technology exists that establishes reasonable certainty of economic producibility at greater distances.

| (ii) | Undrilled locations can be classified as having undeveloped reserves only if a development plan has been adopted indicating that they are scheduled to be drilled within five years, unless the specific circumstances, justify a longer time.

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| (iii) | Under no circumstances shall estimates for undeveloped reserves be attributable to any acreage for which an application of fluid injection or other improved recovery technique is contemplated, unless such techniques have been proved effective by actual projects in the same reservoir or an analogous reservoir, as defined in paragraph (a)(2) of this section, or by other evidence using reliable technology establishing reasonable certainty.

(32) Unproved properties. Properties with no proved reserves.

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Appendix II

Technical Qualifications of Person Responsible for the

Reserves Statement

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Statement of Qualifications

The reserves estimate of certain of Ecopetrol’s interests prepared by Gaffney, Cline & Associates (GaffneyCline), the results of which are presented in this report, was carried out by engineers and geoscientists under the managment of Mr. Eduardo Sanchez Josseaume and the technical direction of Mr. Rawdon Seager.

Eduardo Sanchez Josseaume

Mr. Eduardo Sanchez has more than 37 years of experience in the oil industry in Latin America and was the person primarily responsible for the audit. He is qualified as a Reserves Auditor through having more than 30 years’ experience in petroleum geology with estimation and evaluation of Reserves Information. He holds a Master of Science degree in Geological Sciences from Universidad Nacional de Buenos Aires, Argentina, and a Postgrad in Business Administration from International Business School, Neuquén Argentina.

Mr. Sanchez is a member in good standing of the American Association of Petroleum Geologists (AAPG).).

Rawdon Seager

Mr. Rawdon Seager, Technical Director, has over 50 years of diversified international experience in the upstream sector of the oil and gas exploration and production industry. He is qualified as a Reserves Auditor through having more than 40 years’ experience in petroleum engineering, with at least 30 years being in responsible charge of the estimation and evaluation of Reserves Information. He holds a Bachelor of Science degree in Physics from Bristol University, England, and a Master of Science degree in Petroleum Engineering from Imperial College, London. Mr. Seager is a member in good standing of the Society of Petroleum Engineers (SPE) and is past Chairman of the SPE Oil and Gas Reserves Committee. He is a past Board member of the Society of Petroleum Evaluation Engineers and is currently the Chairman of the Reserves Definitions Committee. He is also a member in good standing of the American Association of Petroleum Geologists and is a Chartered Petroleum Engineer in the UK. He is registered as a European Engineer with FEANI.

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Appendix III

Glossary

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% | Percentage | ​ | bwpd | Barrels water per day
1H05 | First half (6 months) of 2005 (example) | ​ | CBM | Coal Bed Methane
2Q06 | Second quarter (3 months) of 2006 (example) | ​ | CiO | Consumed in Operations
2D | Two dimensional | ​ | CO2 | Carbon Dioxide
3D | Three dimensional | ​ | CAPEX | Capital Expenditure
4D | Four dimensional | ​ | CCGT | Combined Cycle Gas Turbine
1P | Proved Reserves | ​ | cm | centimetres
2P | Proved plus Probable Reserves | ​ | CMM | Coal Mine Methane
3P | Proved plus Probable plus Possible Reserves | ​ | CNG | Compressed Natural Gas
ABEX | Abandonment Expenditure | ​ | Cp | Centipoise (a measure of viscosity)
ACQ | Annual Contract Quantity | ​ | CSG | Coal Seam Gas
oAPI | Degrees API (American Petroleum Institute) | ​ | CT | Corporation Tax
AAPG | American Association of Petroleum Geologists | ​ | D1BM | Design 1 Build Many
AVO | Amplitude versus Offset | ​ | DCQ | Daily Contract Quantity
A$ | Australian Dollars | ​ | Deg C | Degrees Celsius
B | Billion (109) | ​ | Deg F | Degrees Fahrenheit
Bbl | Barrels | ​ | DHI | Direct Hydrocarbon Indicator
/Bbl | per barrel | ​ | DLIS | Digital Log Interchange Standard
BBbl | Billion Barrels | ​ | DST | Drill Stem Test
BHA | Bottom Hole Assembly | ​ | DWT | Dead-weight ton
BHC | Bottom Hole Compensated | ​ | E&A | Exploration & Appraisal
Bscf or Bcf | Billion standard cubic feet | ​ | E&P | Exploration and Production
Bscfd or Bcfd | Billion standard cubic feet per day | ​ | EBIT | Earnings before Interest and Tax
Bm3 | Billion cubic metres | ​ | EBITDA | Earnings before interest, tax, depreciation and amortisation
bcpd | Barrels of condensate per day | ​ | ECS | Elemental Capture Spectroscopy
BHP | Bottom Hole Pressure | ​ | EI | Entitlement Interest
blpd | Barrels of liquid per day | ​ | EIA | Environmental Impact Assessment
bpd | Barrels per day | ​ | ELT | Economic Limit Test
boe | Barrels of oil equivalent @ xxx mcf/Bbl | ​ | EMV | Expected Monetary Value
boepd | Barrels of oil equivalent per day @ xxx mcf/Bbl | ​ | EOR | Enhanced Oil Recovery
BOP | Blow Out Preventer | ​ | EUR | Estimated Ultimate Recovery
bopd | Barrels oil per day | ​ | FDP | Field Development Plan
bwpd | Barrels of water per day | ​ | FEED | Front End Engineering and Design
BS&W | Bottom sediment and water | ​ | FPSO | Floating Production Storage and Offloading
BTU | British Thermal Units | ​ | FSO | Floating Storage and Offloading
​ | ​ | ​ | FWL | Free Water Level
​ | ​ | ​ | ft | Foot/feet

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Fx | Foreign Exchange Rate | ​ | LPG | Liquefied Petroleum Gas
g | gram | ​ | LTI | Lost Time Injury
g/cc | grams per cubic centimetre | ​ | LWD | Logging while drilling
gal | gallon | ​ | m | Metres
gal/d | gallons per day | ​ | M | Thousand
G&A | General and Administrative costs | ​ | m3 | Cubic metres
GBP | Pounds Sterling | ​ | Mcf or Mscf | Thousand standard cubic feet
GCoS | Geological Chance of Success | ​ | MCM | Management Committee Meeting
GDT | Gas Down to | ​ | MMcf or MMscf | Million standard cubic feet
GIIP | Gas Initially In Place | ​ | m3/d | Cubic metres per day
GJ | Gigajoules (one billion Joules) | ​ | mD | Measure of Permeability in millidarcies
GOC | Gas Oil Contact | ​ | MD | Measured Depth
GOR | Gas Oil Ratio | ​ | MDT | Modular Dynamic Tester
GRV | Gross Rock Volumes | ​ | Mean | Arithmetic average of a set of numbers
GTL | Gas to Liquids | ​ | Median | Middle value in a set of values
GWC | Gas water contact | ​ | MFT | Multi Formation Tester
HDT | Hydrocarbons Down to | ​ | mg/l | milligrams per litre
HSE | Health, Safety and Environment | ​ | MJ | Megajoules (One Million Joules)
HSFO | High Sulphur Fuel Oil | ​ | Mm3 | Thousand Cubic metres
HUT | Hydrocarbons up to | ​ | Mm3/d | Thousand Cubic metres per day
H2S | Hydrogen Sulphide | ​ | MM | Million
IOR | Improved Oil Recovery | ​ | MMm3 | Million Cubic metres
IPP | Independent Power Producer | ​ | MMm3/d | Million Cubic metres per day
IRR | Internal Rate of Return | ​ | MMBbl | Millions of barrels
J | Joule (Metric measurement of energy) I kilojoule = 0.9478 BTU) | ​ | MMBTU | Millions of British Thermal Units
k | Permeability | ​ | Mode | Value that exists most frequently in a set of values = most likely
KB | Kelly Bushing | ​ | Mscfd | Thousand standard cubic feet per day
KJ | Kilojoules (one Thousand Joules) | ​ | MMscfd | Million standard cubic feet per day
kl | Kilolitres | ​ | MW | Megawatt
km | Kilometres | ​ | MWD | Measuring While Drilling
km2 | Square kilometres | ​ | MWh | Megawatt hour
kPa | Thousands of Pascals (measurement of pressure) | ​ | mya | Million years ago
KW | Kilowatt | ​ | NGL | Natural Gas Liquids
KWh | Kilowatt hour | ​ | N2 | Nitrogen
LAS | Log ASCII Standard | ​ | NTG | Net/Gross Ratio
LKG | Lowest Known Gas | ​ | NPV | Net Present Value
LKH | Lowest Known Hydrocarbons | ​ | OBM | Oil Based Mud
LKO | Lowest Known Oil | ​ | OCM | Operating Committee Meeting
LNG | Liquefied Natural Gas | ​ | ODT | Oil-Down-To
LoF | Life of Field | ​ | ​ | ​

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OGIP | Original Gas in Place | ​ | Swi | irreducible water saturation
OIIP | Oil Initially In Place | ​ | sw | Water Saturation
OOIP | Original Oil in Place | ​ | T | Tonnes
OPEX | Operating Expenditure | ​ | TD | Total Depth
OWC | Oil Water Contact | ​ | Te | Tonnes equivalent
p.a. | Per annum | ​ | THP | Tubing Head Pressure
Pa | Pascals (metric measurement of pressure) | ​ | TJ | Terajoules (1012 Joules)
P&A | Plugged and Abandoned | ​ | Tscf or Tcf | Trillion standard cubic feet
PDP | Proved Developed Producing | ​ | TCM | Technical Committee Meeting
Phie | effective porosity | ​ | TOC | Total Organic Carbon
PI | Productivity Index | ​ | TOP | Take or Pay
PIIP | Petroleum Initially In Place | ​ | Tpd | Tonnes per day
PJ | Petajoules (1015 Joules) | ​ | TVD | True Vertical Depth
PSDM | Post Stack Depth Migration | ​ | TVDss | True Vertical Depth Subsea
psi | Pounds per square inch | ​ | UFR | Umbilical Flow Lines and Risers
psia | Pounds per square inch absolute | ​ | USGS | United States Geological Survey
psig | Pounds per square inch gauge | ​ | US$ | United States dollar
PUD | Proved Undeveloped | ​ | VLCC | Very Large Crude Carrier
PVT | Pressure, Volume and Temperature | ​ | Vsh | shale volume
P10 | 10% Probability | ​ | VSP | Vertical Seismic Profiling
P50 | 50% Probability | ​ | WC | Water Cut
P90 | 90% Probability | ​ | WI | Working Interest
RF | Recovery factor | ​ | WPC | World Petroleum Council
RFT | Repeat Formation Tester | ​ | WTI | West Texas Intermediate
RT | Rotary Table | ​ | wt% | Weight percent
R/P | Reserve to Production | ​ | ​ | ​
Rw | Resistivity of water | ​ | ​ | ​
SCAL | Special core analysis | ​ | ​ | ​
cf or scf | Standard Cubic Feet | ​ | ​ | ​
cfd or scfd | Standard Cubic Feet per day | ​ | ​ | ​
scf/ton | Standard cubic foot per ton | ​ | ​ | ​
SL | Straight line (for depreciation) | ​ | ​ | ​
so | Oil Saturation | ​ | ​ | ​
SPM | Single Point Mooring | ​ | ​ | ​
SPE | Society of Petroleum Engineers | ​ | ​ | ​
SPEE | Society of Petroleum Evaluation Engineers | ​ | ​ | ​
SPS | Subsea Production System | ​ | ​ | ​
SS | Subsea | ​ | ​ | ​
stb | Stock tank barrel | ​ | ​ | ​
STOIIP | Stock tank oil initially in place | ​ | ​ | ​

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