Exhibit 4.5

TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



SUPPLEMENTARY AGREEMENT No. 02 TO CONTRACT
ESTF-029-2008



CONTRACT INFORMATION



|Purpose of the Supplementary Agreement | : | To add an Entry Point and an Exit Point and amend the contracted capacity.
|-------------------------------------- | - | --------------------------------------------------------------------------
|Estimated Value of the Supplementary   |   |                                                                           
|                                       |   |                                                                           
|Agreement                              | : | $4,673,691,634.                                                           
|                                       |   |                                                                           
|Term of the Contract                   | : | December 31, 2020.                                                        
|                                       |   |                                                                           
|TRANSPORTER’S INFORMATION              |   |                                                                           
|                                       |   |                                                                           
|Company Name                           | : | TRANSPORTADORA DE GAS INTERNACIONAL S.A. E.S.P. – TGI S.A. E.S.P.         
|                                       |   |                                                                           
|Tax Identification No.                 | : | 900.134.459-7                                                             
|                                       |   |                                                                           
|Legal Representative                   | : | RICARDO ROA BARRAGÁN                                                      
|                                       |   |                                                                           
|Identification                         | : | 19.451.246 from Bogotá                                                    
|                                       |   |                                                                           
|Address                                | : | Carrera 34 No. 41-51                                                      
|                                       |   |                                                                           
|City                                   | : | Bucaramanga                                                               
|                                       |   |                                                                           
|Telephone                              | : | 632-0002                                                                  
|                                       |   |                                                                           
|Fax                                    | : | 632-5525                                                                  



SHIPPER’S INFORMATION:



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



|Company Name              | : | ECOPETROL S.A.                      
|------------------------- | - | ------------------------------------
|                          |   |                                     
|Tax Identification No.    | : | 899.999.068-1                       
|                          |   |                                     
|Authorized Representative | : | CLAUDIA L. CASTELLANOS R.           
|                          |   |                                     
|Identification            | : | 63.314.635 from Bucaramanga         
|                          |   |                                     
|Address:                  | : | Calle 37 No. 8-43, 3rd floor, Bogotá
|                          |   |                                     
|City:                     | : | Bogotá, Capital District            
|                          |   |                                     
|Telephone:                | : | 2344438                             



SUPPLEMENTARY AGREEMENT No. 02 TO NATURAL
GAS TRANSPORTATION CONTRACT ESTF-029-2008



The undersigned parties, namely: RICARDO
ROA BARRAGÁN, who is of legal age, identified as appears below his signature, acting as President in name and legal
representation of TRANSPORTADORA DE GAS INTERNACIONAL S.A. E.S.P. – TGI S.A. E.S.P., (formerly Transportadora de Gas
del Interior S.A. ESP), Sociedad Anónima y Empresa Prestadora de Servicios Públicos, created via Notarial Instrument
No. 67 dated February 16, 2007, executed at the Office of Notary 11 of the Notarial District of Bucaramanga-Santander, registered
in the Chamber of Commerce of the same city on February 19, 2007 under No. 69863, with trade registration number 05-000138524-04
and Tax Identification No. 900.134.459-7 and primary domicile in the city of Bucaramanga, hereinafter referred to as theTRANSPORTER;
and CLAUDIA L. CASTELLANOS, who is of legal age, identified as appears below her signature, in her capacity as Vice President
of Supply and Marketing, exercising the authorization contained in the Delegation Manual, acting in name and on behalf of ECOPETROL
S.A., a federal decentralized agency created by Statute 165 of 1948, with Tax Identification No. 899.999.068-1, organized as
a Joint Venture Entity in accordance with the provisions of Article 2 of Statute 1118 of 2006, under the Ministry of Energy and
Mines, with its primary domicile in Bogotá, Capital District, whose Bylaws are contained in their entirety in Notarial Instrument
No. 5314 of December 14, 2007 and the successive amendments thereto, all executed in the Office of Notary Two of the Notarial District
of Bogotá, Capital District, and registered in the Chamber of Commerce of Bogotá, Capital District, hereinafter referred to as
theSHIPPER; have agreed to execute this supplementary agreement, in accordance with the following:



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



WHEREAS:



1. On October 1, 2008, Ecopetrol S.A. and
TGI S.A. E.S.P. executed Natural Gas Firm Transportation Contract No. ESTF-029-2008, hereinafter the Contract, in force from December
1, 2012 through December 31, 2020.



2. On December 5, 2008, Ecopetrol and TGI
S.A. E.S.P. signed Supplementary Agreement No. 1 to the Contract, amending the firm capacity contracted and the estimated value
of the Contract, expanding the capacity initially contracted by the Parties.



3. In a letter dated January 13, 2012,
the SHIPPER requested to be informed of the maximum natural gas firm transportation capacity and the respective assignment it would
have in the Cusiana Porvenir – Exit Point 1 (CIB) route from the Contract, from December 1, 2012 through December 2014.



4. For the gas from Cusiana/Cupiagua to
be able to physically arrive at the Barrancabermeja Refinery and, therefore, for the capacity to be contracted from Cusiana Porvenir
to be Firm, some changes must be made to the TRANSPORTER’S Transportation System. For this purpose, the Parties signed Supplementary
Agreement No. 5 to Contract ESTF-004-2006, in which they included the terms under which these changes would be made once the Certificate
to which Clause Five of the Supplementary Agreement in question makes reference was signed.



5. The TRANSPORTER has stated that it is
expanding the Cusiana-El Porvenir-La Belleza-Vasconia transportation system (hereinafter "Phase II").



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



6. The SHIPPER requested that, while the
changes are being made to facilitate physically receiving gas from Cusiana/Cupiagua at the Barrancabermeja Refinery and until
these are operational, the firm capacity assigned on the Cusiana Porvenir – Exit Point 1 (CIB) route be contracted for the
Cusiana – Barranca E route, starting December 1, 2012.



7. The TRANSPORTER’S Commercial Committee
No. 04 of 2012 recommended the execution of this Supplementary Agreement.



8. In the Fiscal Debtor Bulletin prepared
and published by the General Government Accounting Office of the Republic, the SHIPPER verified that the TRANSPORTER is not listed
in this bulletin as one of the persons against whom a final tax liability decision has been issued and who has not paid the obligation
contained therein.



9. The TRANSPORTER evidences, via a certification
issued by its internal auditor within the month prior to the date of signing of this supplementary agreement, that it has satisfied
its obligations vis-à-vis health systems, occupational hazards, pensions and contributions to the Family Compensation Funds,
Colombian Institute of Family Welfare and National Apprenticeship Service, with respect to all its employees.



10. Prior to the signing of this supplementary
agreement, the SHIPPER’S Gas Department implemented Asset Laundering Prevention Control Mechanisms and developed the Instruments
for Proper Application thereof, in compliance with its General Policy for the Prevention and Control of Asset Laundering from May
2007.



11. Neither the SHIPPER nor the TRANSPORTER
is affected by the disqualifications or incompatibilities provided for in the Law for entering into this supplementary agreement.



12. Both the TRANSPORTER’S and the
SHIPPER’S representatives have the necessary authorization to sign this supplementary agreement.



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



In keeping with the foregoing, the Parties
have agreed to amend the Contract in the following manner:



CLAUSE ONE: Amend numerals 4.1 “Entry
Hub,” 4.2 “Exit Hub,” 4.3 “Entry Point” and 4.4. “Exit Point” of Section I-ESTF of the
Contract, starting on December 1, 2012, provided that Phase II of the capacity expansion from Cusiana has become operational, as
follows:



|4.1 Entry Hub                |  | 4.2 Exit Hub                                         
|---------------------------- |  | -----------------------------------------------------
|Ballena and Cusiana Porvenir |  | 1. CIB.
        2. Gas turbine
        3. Barranca E.



|4.3 Entry Point                                                                                                                                                                                                                                                                                         |  | 4.4 Exit Point                                                                                                                                                                                                                                                                                                                                                                                                                     
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Ballena: Outlet flange of the meter located at the Ballena
        Station at Centragas.
        
        Cusiana Porvenir: Physical interconnection point between
        the facilities of the partners to the Santiago de las Atalayas contract in Cusiana and the Cusiana el Porvenir Gas Pipeline. |  | 1.  CIB: The outlet
        flange of the meters located on the 16” line at COGB.
        2.  Gas turbine: Hot
        tap installed on the 20” Gas line between Centragas and COGB located on Petrosantander property, which carries Gas to the
        gas turbine of the Barrancabermeja Refinery Facility (GRB) owned by the Shipper.
        3.  Barranca E: Outlet
        flange of the Centragas meters in Barrancabermeja.



CLAUSE TWO: Amend numeral 6.1 “Firm
Capacity Contracted (kcf/d)” of Section I-ESTF of the Contract, provided that Phase II of the capacity expansion from Cusiana
has become operational, as follows:



6.1. Firm Capacity Contracted (kcf/d)



|Route                                  |  | December 2012 |        |  | January to  December 2013 |  |        | January to August  2014 |  |  | September 2014  to December 2020 | 
|-------------------------------------- |  | ------------- | ------ |  | ------------------------- |  | ------ | ----------------------- |  |  | -------------------------------- | 
|Ballena – Exit Point 1 (CIB)           |  |               | 79,394 |  |                           |  | 79,394 |                         |  |  | 80,867                           | 
|Ballena – Exit Point 2 (GAS TURBINE)   |  |               | 15,000 |  |                           |  | 15,000 |                         |  |  | 15,000                           | 
|Cusiana Porvenir – Exit Point 1 (CIB)* |  |               | 24,762 |  |                           |  | 25,613 |                         |  |  | 25,613                           | 



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                              
| | ----------------------------------------- | -----------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English
| | BUCARAMANGA, COLOMBIA, S.A.               |                              
| | WWW.TGI.COM.CO                            |                              



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



* Until such time as the modifications
that will make it possible to receive gas from Cusiana/Cupiagua at Exit Point 1 (CIB) of the Contract are operational, the firm
capacity contracted on the Cusiana Porvenir – Exit Point 1 (CIB) route will be assigned to the Cusiana Porvenir – Exit
Point 3 (Barranca E) route. This capacity will be firm, using the Structure of Charges contained in the table for the Cusiana Porvenir
– Exit Point 3 (Barranca E) route, established in number 7 of Section I-ESTF.



In addition, when it is technically and
operationally feasible, the TRANSPORTER will allow for the possibility of diverting the firm capacity contracted from Cusiana-Porvenir,
from Exit Point 3 (Barranca E) to Exit Point 1 (CIB).



CLAUSE THREE: Amend numerals 7.2 “Fixed
Charge (USD/KCFD/Year),” 7.3 Variable Charge (USD/KCF),” 7.4 Fixed Charge for Administration, Operation and Maintenance
($/KCFD/Year)” and 7.6 “Estimated Value of the Contract” from Section I-ESTF of the Contract, provided that Phase
II of the capacity expansion from Cusiana has become operational, as follows:



|Route                                        |  | 7.2 Fixed Charge  (USD/KCFD-Year) |         |  | 7.3 Variable Charge  (USD/KCF) |  |   | 7.4 Fixed Charge for  Administration,  Operation and  Maintenance ($/KCFD-
Year) | 
|-------------------------------------------- |  | --------------------------------- | ------- |  | ------------------------------ |  | - | -------------------------------------------------------------------------------- | 
|Ballena – Exit Point 1 (CIB)                 |  |                                   | 239,771 |  |                                |  | 0 |                                                                                  | 
|Ballena – Exit Point 2 (GAS TURBINE)         |  |                                   | 239,771 |  |                                |  | 0 |                                                                                  | 
|Cusiana Porvenir – Exit Point 1 (CIB)        |  |                                   | 300,255 |  |                                |  | 0 |                                                                                  | 
|Cusiana Porvenir – Exit Point 3 (Barranca E) |  |                                   | 300,255 |  |                                |  | 0 |                                                                                  | 

*Charges from December 2011 applicable to
2012



7.6 Estimated Value of the Contract



|USD         |  | $              
|----------- |  | ---------------
|230,236,653 |  | 437,853,718,767



CLAUSE FOUR: Amend point 2.3 of
numeral 2 “Charges” of Chapter IV of the Contract, provided that Phase II of the capacity expansion from Cusiana has
become operational, as follows:



2.3 In the event that the TRANSPORTER authorizes
average daily transportation for one Gas Day greater than the Firm Capacity Contracted as established in



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



[handwritten:] [initials]



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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TGI

BOGOTÁ ENERGY GROUP

Tax ID No. 900.134.459-7



Paragraph number 1 of this Chapter, the
transportation of this higher daily volume will incur an additional fee in dollars and an additional fee in pesos corresponding
to the maximum tariff of the “0% fixed, 100% variable” structure defined in Resolution CREG 125 of 2003, or in any
resolution that amends, adds to or replaces it, as shown in the following table:



|Route                                         |  | USD/KCF |       |  | $/ KCF | 
|--------------------------------------------- |  | ------- | ----- |  | ------ | 
|Ballena – Exit Point 1 (CIB)                  |  |         | 0.850 |  |        | 
|Ballena – Exit Point 2 (GAS TURBINE)          |  |         | 0.850 |  |        | 
|Cusiana Porvenir – Exit Point 1 (CIB)         |  |         | 1.220 |  |        | 
|Cusiana Porvenir – Exit Point 3 (Barranca E)* |  |         | 1.220 |  |        | 

*Charges from December 2011 applicable to
2012



CLAUSE FIVE: All other stipulations of
the Contract remain in force and unchanged.



Signed for the record on the eleventh (11th)
of April of the year two thousand twelve (2012).



|TRANSPORTADORA DE GAS INTERNACIONAL   |  | ECOPETROL S.A.                       
|------------------------------------- |  | -------------------------------------
|S.A. E.S.P.                           |  |                                      
|                                      |  |                                      
|[signature]                           |  | [signature]                          
|                                      |  |                                      
|RICARDO ROA BARRAGAN                  |  | CLAUDIA L. CASTELLANOS R.            
|National Identity Card No. 19.451.246 |  | National Identity Card No. 63.314.635
|from Bogotá                           |  | from Bucaramanga                     
|[initials]                            |  | [three sets of initials]             



|Prepared by: | María C. Gómez       |                        
|------------ | -------------------- | -----------------------
|Reviewed by: | Sonia R. Sanabria M. | [four sets of initials]
|             | Laura M. Parra R.    |                        
|             | Nubia Prada S.       |                        
|Approved by: | Ricardo Roa B.       |                        



SUPPLEMENTARY AGREEMENT NO. 02 to ESTF-029-2008



| | CARRERA 34 NO. 41 – 51                    |                               
| | ----------------------------------------- | ------------------------------
| | PBX 57 (7) 632 00 02 FAX 57 (7) 632 55 25 | [ISO Certification in English]
| | BUCARAMANGA, COLOMBIA, S.A.               |                               
| | WWW.TGI.COM.CO                            |                               



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