Exhibit 4.21

     

    
      		 	
              101
                Hudson Street

              Suite
                3700

              Jersey
                City, NJ 07302

            	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	May 3, 2006	 


    

    
 

    VIA
      FEDERAL EXPRESS 

    AND
      FAX (403) 262-4472

    


    
      	
              Triangle
                Petroleum Corporation

            
	
              Suite
                1110, 521-3rd Avenue, SW

            
	
              Calgary,
                Alberta, Canada T2P 3T3

            
	
              Attention:
                Mark Gustafson

            


    

    


    


    
      	 	
              Re:

            	
              Amendment
                to Securities Purchase Agreement and Related
                Agreements.

            


    

    


    Dear
      Mr.
      Gustofson:

    


    This
      letter will memorialize the agreements by and between Triangle Petroleum
      Corporation (the “Company”)
      and
      Cornell Capital Partners, LP (the “Buyer”),
      in
      connection with an amendment to the Securities Purchase Agreement dated December
      7, 2005 (“SPA”)
      between the Company and the Buyer and the and Investor Registration Rights
      Agreement dated December 7, 2005 (“RRA”)
      between the Company and the Buyer. All capitalized terms herein, unless
      otherwise indicated, shall have the meaning ascribed to them in the SPA.


    


    In
      connection with the SPA, the Company, the Buyer, and David Gonzalez, Esq. (the
      “Escrow
      Agent”)
      entered into an Escrow Agreement (the “Escrow Agreement”) dated December 7, 2005
      for the purpose of establishing an escrow of funds and to effect certain
      provisions of the SPA. As of the date hereof, the Escrow Agent does not hold
      any
      escrowed funds of the Company or the Buyer, and has disbursed all funds that
      were previously placed into escrow pursuant to the First Closing and Second
      Closing in strict compliance with the joint instructions of the Company and
      the
      Buyer. On the date hereof, the Company and Buyer hereby remove David Gonzalez,
      Esq. as the escrow agent pursuant to the Escrow Agreement and terminate the
      Escrow Agreement. 

    


    The
      parties hereby amend the SPA and the RRA to reflect the termination of the
      Escrow Agreement as follows: 

    


    
      
         

      

      
         

        
          

        

      

      
         

      

    

    

      Triangle
        Petroleum Corporation

      May
        3,
        2006

      Page
        2
of
        4

    

     

    1.
      Section 1(a) of the SPA shall be deleted in its entirety and replaced with
      the
      following:

    


    Section
      1(a). Purchase of Convertible Debentures.
      Subject
      to the satisfaction (or waiver) of the terms and conditions of this Agreement,
      each Buyer agrees, severally and not jointly, to purchase at each Closing and
      the Company agrees to sell and issue to each Buyer, severally and not jointly,
      at each Closing, Convertible Debentures in amounts corresponding with the
      Subscription Amount set forth opposite each Buyer’s name on Schedule I
      hereto.

    


    2.
      Section 1(c) of the SPA shall be deleted in its entirety and replaced with
      the
      following:

    


    Section
      1(c). Form of Payment.
      Subject
      to the satisfaction of the terms and conditions of this Agreement, on the Third
      Closing Date, (i) the Buyers shall deliver to the Company such aggregate
      proceeds for the Convertible Debentures to be issued and sold to such Buyer(s),
      minus the fees to be paid directly from the proceeds of the Third Closing as
      set
      forth herein, and (ii) the Company shall deliver to each Buyer, Convertible
      Debentures which such Buyer(s) is purchasing in amounts indicated opposite
      such
      Buyer’s name on Schedule I, duly executed on behalf of the Company.

    


    3.
      Section 6(b) of the SPA shall be deleted in its entirety and replaced with
      the
      following

    


    Section
      6(b). The
      Buyer(s) shall have delivered to the Company the Purchase Price for Convertible
      Debentures in respective amounts as set forth next to each Buyer as outlined
      on
      Schedule I attached hereto, minus any fees to be paid directly from the proceeds
      the Closings as set forth herein, by wire transfer of immediately available
      U.S.
      funds pursuant to the wire instructions provided by the Company.

    


    4.
      All
      other references to the Escrow Agreement or the Escrow Agent in the SPA shall
      be
      removed including the inclusion of the Escrow Agreement in the definition of
      the
      Transaction Documents. 

    


    5.
      Section 10(e) of the RRA shall be deleted in its entirety and replaced with
      the
      following

    


    (e). This
      Agreement, the Irrevocable Transfer Agent Instructions dated December 8, 2005,
      the Securities Purchase Agreement and related documents including the
      Convertible Debentures issued thereto and the Security Agreement dated the
      date
      hereof (the “Security
      Agreement”)
      constitute the entire agreement among the parties hereto with respect to the
      subject matter hereof and thereof. There are no restrictions, promises,
      warranties or undertakings, other than those set forth or referred to herein
      and
      therein. This Agreement, the Irrevocable Transfer Agent Instructions, the
      Securities Purchase Agreement and related documents including the Convertible
      Debentures and the Security Agreement supersede all prior agreements and
      understandings among the parties hereto with respect to the subject matter
      hereof and thereof.

    


    
      
         

      

      
         

        
          

        

      

      
         

      

    

    

      Triangle
        Petroleum Corporation

      May
        3,
        2006

      Page
        3
of
        4

    

     

    In
      connection with the SPA, The Buyer and the Company entered into a Security
      Agreement (the “Security
      Agreement”)
      dated
      December 7, 2005, the Buyer and Elmworth Energy Corporation entered into a
      Security Agreement (the “Elmworth
      Security Agreement”)
      dated
      December 7, 2005, and the Buyer and Triangle USA Petroleum Corporation entered
      into a Security Agreement (the “Triangle
      USA Security Agreement”)
      dated
      December 7, 2005. The Buyer and the Company (with respect to the Security
      Agreement), Elmworth Energy Corporation (with respect to the Elmworth Security
      Agreement), and Triangle USA Petroleum Corporation (with respect to the Triangle
      USA Security Agreement), hereby amend the Security Agreement, the Elmworth
      Security Agreement, and the Triangle USA Petroleum Corporation, to remove all
      references to the Escrow Agreement or the Escrow Agent. 

    


    This
      letter shall also serve as a Joint Written Direction to the Escrow Agent in
      accordance with the Escrow Agreement providing notification that the parties
      hereto have removed David Gonzalez, Esq. as escrow agent and terminated the
      Escrow Agreement. 

    


    This
      letter agreement shall solely have the effect specifically described above
      and
      shall have no effect on any other terms or conditions of the SPA or related
      documents. 

    


    


    REMAINDER
      OF PAGE INTENTIONALLY LEFT BLANK

     

     

     

     

     

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    


    Triangle
      Petroleum Corporation

    May
      3,
      2006

    Page
      4
of
      4


     

      	 	 	 
	 	Cornell
              Capital Partners, LP
	 
 	 
 	 
 
	 	By:  	Yorkville
              Advisors, LLC
	 	Its: 	General Partner
	 	
            


    

    
      	 	 	 
	 	By:  	/s/ MARK
              ANGELO
	 	
              
Name: Mark
              Angelo
	 	Title:
               Portfolio
              Manager

 

    


    Agreed
      and acknowledged by: 

    


    Triangle
      Petroleum Corporation

    
      	 	 	 	 	 
	By: 	/s/ MARK
              GUSTAFSON	 	 	 
	 	
              
Name:
              Mark Gustafson	 	 	
            
	 	Title: Chief
              Executive Officer 	 	 	 
	 	Date: May
              3, 2006 	 	 	 


    

    
 

    
      	
              With
                Respect to the Elmworth Security Agreement:

            
	
              Elmworth
                Energy Corp.

            


    

    
      
        	 	 	 	 	 
	By: 	/s/ MARK
                GUSTAFSON	 	 	 
	 	
                
Name:
                Mark Gustafson	 	 	
              
	 	Title: Director	 	 	 
	 	Date: May
                3, 2006 	 	 	 


      

       

    

     

    
      	
              With
                Respect to the Triangle USA Security
                Agreement:

            
	
              Triangle
                USA Petroleum Corporation

            


    

    
      
        	 	 	 	 	 
	By: 	/s/ MARK
                GUSTAFSON	 	 	 
	 	
                
Name:
                Mark Gustafson	 	 	
              
	 	Title: Director	 	 	 
	 	Date: May
                3, 2006 	 	 	 
	 	 	 	 	 
	 	
                cc: David
                  Gonzalez, Esq.

                BY
                  HAND