Exhibit
4.1

     

    Execution
Version

     

    FIRST
AMENDMENT TO REGISTRATION RIGHTS AGREEMENT

     

    This
First Amendment (this “Amendment”) to the
Registration Rights Agreement is made and entered into as of April 5, 2010, by
and between BreitBurn Energy Partners L.P., a Delaware limited partnership
(“BBEP”), and
Quicksilver Resources Inc., a Delaware corporation (“Quicksilver”).  Capitalized
terms used herein and not otherwise defined are used as defined in the
Registration Rights Agreement, dated as of November 1, 2007, between BBEP and
Quicksilver (as amended, the “Registration Rights
Agreement”).

     

    WHEREAS, the Registration
Rights Agreement was made and entered into in connection with the issuance on
November 1, 2007 of the Acquired Units pursuant to the Contribution Agreement,
dated as of September 11, 2007, by and between BreitBurn Operating L.P., a
Delaware limited partnership, and Quicksilver (as amended, the “Contribution
Agreement”);

     

    WHEREAS, BBEP agreed to
provide the registration and other rights set forth in the Registration Rights
Agreement for the benefit of Quicksilver pursuant to the Contribution
Agreement;

     

    WHEREAS, BBEP prepared and
filed the Registration Statement (File Number 333-153179) with the Securities
and Exchange Commission (the “SEC”), and the SEC
declared the Registration Statement effective on October 28, 2008, all in
accordance with Section 2.1 of the Registration Rights Agreement;

     

    WHEREAS, the Registration
Statement has remained continuously effective under the Securities Act since
October 28, 2008;

     

    WHEREAS, BBEP has been
involved in litigation with Quicksilver relating to matters other than the
Registration Rights Agreement since October 31, 2008 (the “Litigation”);

     

    WHEREAS, in connection with
the Litigation, BBEP, Quicksilver, Provident Energy Trust, Randall H.
Breitenbach and Halbert S. Washburn entered into the Settlement Agreement dated
April 5, 2010 (the “Settlement
Agreement”), pursuant to which BBEP and Quicksilver agreed to the
dismissal of the Litigation in exchange for mutual promises and covenants;
and

     

    WHEREAS, BBEP and Quicksilver
have agreed to amend the Registration Rights Agreement pursuant to the
Settlement Agreement.

     

    NOW THEREFORE, in
consideration of the mutual covenants and agreements set forth herein and for
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged by each party hereto, the parties hereby agree as
follows:


    
      
         


      

      
         


        
          

        

      

      
         


      

    

     

    I.           AMENDMENT.

     

    A.           Section
2.2 of the Registration Rights Agreement shall be amended by deleting (i) the
second proviso of the first sentence of Section 2.2(a) and (ii) the penultimate
sentence of Section 2.2(a).

     

    B.           Section
2.2 of the Registration Rights Agreement shall be amended by deleting the third
sentence of Section 2.2(a) and replacing it with a new third sentence that reads
as follows:

     

    “Each
such Holder shall then have three Business Days after receiving such notice to
request inclusion of Registrable Securities in the Underwritten
Offering.”

     

    C.           Section
2.2 of the Registration Rights Agreement shall be amended by inserting a new
subsection (c) thereof that reads as follows:

     

    “(c)           Notwithstanding
any provision to the contrary in this Section 2.2,
Quicksilver shall have the right to include its Common Units in any Underwritten
Offering subject to this Section 2.2 in a
number up to the greater of (i) 20% of the number of Common Units to be sold in
such Underwritten Offering or (ii) the number of Common Units that Quicksilver
could include in such Underwritten Offering without regard to this Section 2.2(c),
provided that Quicksilver complies with the notice provisions for requesting
inclusion of its Registrable Securities in any such Underwritten Offering as set
forth in this Section
2.2.”

     

    D.           Article
III of the Registration Rights Agreement shall be amended by inserting a new
Section 3.15 at the end thereof that reads as follows:

     

    “Section
3.15.  Termination.  Sections
2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.9, 2.10 and 2.11 of this Agreement shall
terminate on the date that is the three month anniversary of the date on which
Quicksilver ceases to be an affiliate of BBEP.”

     

    II.           MISCELLANEOUS.

     

    A.           Full Force and
Effect.  Except to the extent modified hereby, the Registration
Rights Agreement shall remain in full force and effect.

     

    B.           Counterparts.  This
Amendment may be executed in any number of counterparts and by different parties
hereto in separate counterparts, each of which counterparts, when so executed
and delivered, shall be deemed to be an original and all of which counterparts,
taken together, shall constitute but one and the same agreement.

     

    C.           Governing
Law.  The Laws of the State of New York shall govern this
Amendment.

     

    D.           Effectiveness.  This
Amendment shall be effective as of the Effective Time (as such term is defined
in the Settlement Agreement).

     

    [Signature
Page Follows]


    
      
         


      

      
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      Exhibit
4.1

       

      Execution
Version

    

     

    IN
WITNESS WHEREOF, the parties have executed this Agreement as of the date first
written above.

     

    
      
        
          
            
              
                
                  
                    
                      
                        
                          	
                                  BREITBURN
      ENERGY PARTNERS L.P.

                                
	 
      	 
      	 
      
	
                                  By:

                                	
                                  BreitBurn
      GP, LLC,

                                
	 
      	
                                  its
      general partner

                                
	 
      	 
      	 
      
	 
      	
                                  By:

                                	
                                  /s/Halbert S. Washburn

                                
	 
      	
                                  Name:  

                                	
                                  Halbert
      S. Washburn

                                
	 
      	
                                  Title:

                                	
                                  Chief
      Executive Officer

                                
	 
      	 
      	 
      
	
                                  QUICKSILVER
      RESOURCES INC.

                                
	 
      	 
      
	

                                  By:

                                	/s/Glenn Darden
	

                                  Name:  

                                	
                                  Glenn
      Darden

                                
	

                                  Title:

                                	President
      and Chief Executive
Officer


                        

                      

                    

                  

                

              

            

          

        

      

    

     

    
      
         


      

      
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