Second Supplemental Indenture



 Exhibit 4.21 
 Execution Copy 
  
  
 SECOND SUPPLEMENTAL INDENTURE 
 among 
 CARRIZO OIL & GAS, INC., 
 CARRIZO (MARCELLUS) LLC, 
 CARRIZO MARCELLUS HOLDING INC., 
 CHAMA PIPELINE HOLDING LLC, 
 PECOS
PIPELINE LLC, 
 and 
 WELLS FARGO BANK, NATIONAL ASSOCIATION, 
 as Trustee 
  
  
 May 14, 2009 
  
  
  







 TABLE OF CONTENTS 
  


					
	ARTICLE ONE AGREEMENT TO BE BOUND	  	2
			
	 SECTION 101
	  	Agreement to be Bound.	  	2
		
	ARTICLE TWO MISCELLANEOUS PROVISIONS	  	3
			
	 SECTION 201
	  	Integral Part.	  	3
	 SECTION 202
	  	General Definitions.	  	3
	 SECTION 203
	  	Adoption, Ratification and Confirmation.	  	3
	 SECTION 204
	  	Counterparts.	  	3
	 SECTION 205
	  	Governing Law.	  	3

  

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 CARRIZO OIL & GAS, INC. 
 SECOND SUPPLEMENTAL INDENTURE 
 THIS SECOND SUPPLEMENTAL INDENTURE, dated as of
May 14, 2009 (the “Second Supplemental Indenture”), among Carrizo (Marcellus) LLC, a Delaware limited liability company (“Marcellus LLC”), Carrizo Marcellus Holding Inc., a Delaware corporation (“Marcellus Holding”),
Chama Pipeline Holding LLC, a Delaware limited liability company (“Chama”), Pecos Pipeline LLC, a Delaware limited liability company (together with Marcellus LLC, Marcellus Holding and Chama, the “Potential New Guarantors”),
Carrizo Oil and Gas, Inc., a Texas corporation (the “Company”), and Wells Fargo Bank, National Association (the “Trustee”). 
 W I T N E S S E T H : 
 WHEREAS, the Company, certain
of its Subsidiaries and the Trustee heretofore executed and delivered an Indenture, dated as of May 28, 2008 (as amended, supplemented, waived or otherwise modified, the “Indenture”), providing for the issuance from time to time of
one or more series of the Company’s Securities; 
 WHEREAS, Section 9.01(4) of the Indenture permits the execution of supplemental
indentures without the consent of any Holders to provide any security for, or to add any guarantees of or additional obligors on, any series of Securities or the related Guarantees, if any; 
 NOW, THEREFORE: 
 In consideration of the
premises provided for herein, the Potential New Guarantors, the Company and the Trustee mutually covenant and agree for the equal and proportionate benefit of all Holders of the Notes as follows: 
 ARTICLE ONE 
 AGREEMENT TO BE BOUND

 SECTION 101 Agreement to be Bound. 
 Each Potential New Guarantor hereby becomes a party to the Indenture as a Potential Subsidiary Guarantor and as such will have all of the rights and be subject to all of the obligations and agreements of a Potential Subsidiary Guarantor
under the Indenture. Each Potential New Guarantor agrees to be bound by all of the provisions of the Indenture applicable to a Potential Subsidiary Guarantor and to perform all of the obligations and agreements of a Potential Subsidiary Guarantor
under the Indenture. 
  

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 ARTICLE TWO 
 MISCELLANEOUS PROVISIONS 
 SECTION 201 Integral Part. 
 This Second Supplemental Indenture constitutes an integral part of the Indenture. 
 SECTION 202 General Definitions. 
 For all purposes of this Second Supplemental Indenture: 

(a) capitalized terms used herein without definition shall have the meanings specified in the Indenture; and 
 (b) the terms “herein,” “hereof,” “hereunder” and other words of similar import refer to this Second Supplemental
Indenture. 
 SECTION 203 Adoption, Ratification and Confirmation. 
 The Indenture, as supplemented and amended by this Second Supplemental Indenture, is in all respects hereby adopted, ratified and confirmed. 
 SECTION 204 Counterparts. 
 This Second Supplemental Indenture may be executed in any number of
counterparts, each of which when so executed shall be deemed an original; and all such counterparts shall together constitute but one and the same instrument. 
 SECTION 205 Governing Law. 
 THIS SECOND SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE
LAWS OF THE STATE OF NEW YORK. 
  

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 IN WITNESS WHEREOF, the parties hereto have caused this Second Supplemental Indenture to be duly executed
as of the day and year first written above. 
  

			
	CARRIZO (MARCELLUS) LLC
		
	By:	 	 /s/ Paul F. Boling

	Name:	 	Paul F. Boling
	Title:	 	Vice President
	
	CARRIZO MARCELLUS HOLDING INC.
		
	By:	 	 /s/ Paul F. Boling

	Name:	 	Paul F. Boling
	Title:	 	Vice President
	
	CHAMA PIPELINE HOLDING LLC
		
	By:	 	 /s/ Paul F. Boling

	Name:	 	Paul F. Boling
	Title:	 	Vice President
	
	PECOS PIPELINE LLC
		
	By:	 	 /s/ Paul F. Boling

	Name:	 	Paul F. Boling
	Title:	 	Vice President
	
	CARRIZO OIL & GAS, INC.
		
	By:	 	 /s/ Paul F. Boling

	Name:	 	Paul F. Boling
	Title:	 	Vice President, Chief Financial Officer,
		 	Secretary and Treasurer
	
	WELLS FARGO BANK, NATIONAL ASSOCIATION, as Trustee
		
	By:	 	 /s/ Patrick T. Giordano

	Name:	 	Patrick T. Giordano
	Title:	 	Vice President


  

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