Twelfth Supplemental Indenture



 Exhibit 4.15 
 TWELFTH SUPPLEMENTAL INDENTURE 
 This TWELFTH SUPPLEMENTAL INDENTURE, dated
as of December 23, 2011, among Barnett Operating LLC, a Delaware limited liability company (the “Guaranteeing Subsidiary”), a subsidiary of Quicksilver Resources Inc. (or its permitted successor), a Delaware corporation (the
“Company”), the Company, the other Subsidiary Guarantors (as defined in the Indenture referred to herein) and The Bank of New York Mellon Trust Company, N.A., as Trustee. 

W I T N E S S E T H 
 WHEREAS, the Company and the Trustee entered into an Indenture (the “Original Indenture”), dated as of December 22, 2005, as supplemented by an Eighth Supplemental Indenture, dated
as of August 14, 2009 among the Company, the Subsidiary Guarantors and the Trustee (the “Eighth Supplemental Indenture”; and together with the Original Indenture, the “Indenture”), pursuant to which the Company
has issued $300,000,000 of aggregate principal amount of 9 1/8% Senior Notes due 2019 (the “Notes”); 
 WHEREAS,
Section 5.01(b) of the Eighth Supplemental Indenture provides that the Company, the Subsidiary Guarantors and the Trustee may amend or supplement the Indenture in order to add Subsidiary Guarantees with respect to the Notes, without the consent
of the Holders; and 
 WHEREAS, all acts and things prescribed by the Indenture, by law and by the certificate of incorporation
and the bylaws (or comparable constituent documents) of the Company, the Subsidiary Guarantors, the Guaranteeing Subsidiary and the Trustee necessary to make this Supplemental Indenture a valid instrument legally binding on the Company, the
Subsidiary Guarantors, the Guaranteeing Subsidiary and the Trustee, in accordance with its terms, have been duly done and performed; 
 NOW THEREFORE, to comply with the provisions of the Indenture, and in consideration of the foregoing, the Guaranteeing Subsidiary, the Company, the Subsidiary Guarantors and the Trustee mutually covenant
and agree for the equal and ratable benefit of the Holders as follows: 
 ARTICLE 1 

Section 1.01 This Supplemental Indenture is supplemental to the Indenture and does and shall be deemed to form a part of, and shall
be construed in connection with and as part of, the Indenture for any and all purposes. 
 Section 1.02 This Supplemental
Indenture shall become effective immediately upon its execution and delivery by the Guaranteeing Subsidiary, the Company, the Subsidiary Guarantors and the Trustee. 







 ARTICLE 2 
 Section 2.01 The Guaranteeing Subsidiary hereby agrees to be bound by the terms, conditions and other provisions of the Indenture with all attendant rights, duties and obligations stated therein, on
a joint and several basis with the Subsidiary Guarantors parties hereto and thereto, with the same force and effect as if originally named as a Subsidiary Guarantor therein and as if such party executed the Indenture on the date thereof. 

ARTICLE 3 

Section 3.01 Except as specifically modified herein, the Indenture and the Notes are in all respects ratified and confirmed (mutatis
mutandis) and shall remain in full force and effect in accordance with their terms. 
 Section 3.02 All capitalized terms
used but not defined herein shall have the same respective meanings ascribed to them in the Indenture. 
 Section 3.03
Except as otherwise expressly provided herein, no duties, responsibilities or liabilities are assumed, or shall be construed to be assumed, by the Trustee by reason of this Supplemental Indenture. This Supplemental Indenture is executed and accepted
by the Trustee subject to all of the terms and conditions set forth in the Indenture with the same force and effect as if those terms and conditions were repeated at length herein and made applicable to the Trustee with respect hereto. 

Section 3.04 THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

 Section 3.05 The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an
original, but all of them together represent the same agreement. 
 Section 3.06 The headings herein are inserted for
convenience of reference only and are not intended to be part of, or to affect the meaning or interpretation of, this Supplemental Indenture. 
 Section 3.07 The recitals hereto are statements only of the Company, the Subsidiary Guarantors and the Guaranteeing Subsidiary and shall not be considered statements of or attributable to the
Trustee. 
 Section 3.08 The Guaranteeing Subsidiary hereby designates the obligations with respect to the Notes and the
Subsidiary Guarantees as Senior Indebtedness which is senior in right of payment in full to any Subordinated Obligation of the Company or any Subsidiary Guarantor. The Guaranteeing Subsidiary further designates the obligations with respect to the
Notes and the Subsidiary Guarantees as “Designated Senior Indebtedness” (as defined by the (i) 2024 Convertible Subordinated Debentures Indenture and (ii) the 2016 Senior Subordinated


  
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Notes Indenture) for all purposes under (x) the 2024 Convertible Subordinated Debentures Indenture and (y) the 2016 Senior Subordinated Notes Indenture, with respect to the Notes and
the Subsidiary Guarantees, respectively. 
 [Signature Pages Follow] 

  
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 IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly
executed and attested, all as of the date first above written. 
  

			
	BARNETT OPERATING LLC
		
	By:	 	QUICKSILVER RESOURCES INC.,
		 	its member


  

			
		
	By:	 	/s/ Glenn Darden
		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


  

			
	QUICKSILVER RESOURCES INC.
		
	By:	 	/s/ Glenn Darden
		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


  

			
	COWTOWN PIPELINE FUNDING, INC.
		
	By:	 	/s/ Glenn Darden
		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


  

			
	COWTOWN PIPELINE MANAGEMENT, INC.
		
	By:	 	/s/ Glenn Darden
		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


 [Signature Page to Twelfth Supplemental Indenture] 

  
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 COWTOWN PIPELINE L.P.

		
	By:	 	 COWTOWN PIPELINE MANAGEMENT, INC
 its general partner

		
	By:	 	/s/ Glenn Darden
		 	  

		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


  

			
	COWTOWN GAS PROCESSING L.P.
		
	By:	 	 COWTOWN PIPELINE MANAGEMENT, INC
 its general partner

		
	By:	 	/s/ Glenn Darden
		 	  

		 	Name: Glenn Darden
		 	Title: President and Chief Executive Officer


  

			
	THE BANK OF NEW YORK MELLON TRUST     COMPANY, N.A., as Trustee
		
	By:	 	/s/ Alejandro Hoyos
		 	  

		 	Name: Alejandro Hoyos
		 	Title: Associate


 [Signature Page to Twelfth Supplemental Indenture] 

  
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