Exhibit 4.1






Exhibit 4.1


SECOND AMENDMENT TO INVESTMENT AGREEMENT




SECOND AMENDMENT TO INVESTMENT AGREEMENT dated as of September 1, 2009 (this “Amendment”) between
Allis-Chalmers Energy Inc., a Delaware corporation (the “Company”), and Lime Rock Partners V, L.P., a Cayman
Islands exempted limited partnership (the “Investor”).



BACKGROUND




WHEREAS, the Company and the Investor (each a “Party,” and together, the “Parties”) previously
entered into an Investment Agreement, dated May 20, 2009, as amended by the First Amendment thereto, dated June 25,
2009 (the “Investment Agreement”); and



WHEREAS, the Parties wish to further amend the Investment Agreement in order to effect certain modifications
deemed desirable by each of the Parties;



NOW, THEREFORE, in consideration of the mutual covenants and agreements contained in the Investment Agreement and
this Second Amendment, the receipt and sufficiency of which are hereby acknowledged, the Parties hereby agree to amend
the Investment Agreement as follows:



1. Capitalized terms used but not defined in this Amendment shall have the respective meanings given to
such terms in the Investment Agreement. Each reference to “hereof,” “hereunder,” “hereby” and “this
Agreement” in the Investment Agreement shall, from and after the date of this Amendment, refer to the
Investment Agreement as amended by this Amendment.



2. Section 8.1 of the Investment Agreement is hereby amended by amending and restating subsection
8.1(d) as follows: “(d) In the event that the Closings occur simultaneously, if the Investor shall
be entitled to designate four Initial Investor Nominees pursuant to Section 8.2(a) based on the Common Stock
of the Company (counting any shares of Preferred Stock on an as converted basis) to be owned by the Investor
13(d) Group after the Closings, then prior to such Closings, the Investor shall provide to the Company the
names of two Initial Investor Designees, each of whom shall be reviewed promptly by the Nominating Committee,
and on the date of such Closings, the Company shall cause to be elected or appointed to the Board such Initial
Investor Designees, subject to the satisfaction of all legal and governance requirements regarding service as
a director of the Company and, if not already received, the reasonable approval of the Nominating Committee.
The Company shall take all actions necessary to ensure that on the date of such Closings the Board shall have
at least two vacancies. By January 15, 2010, the Investor shall provide to the Company the names of two
additional Initial Investor Designees, each of whom shall be reviewed promptly by the Nominating Committee,
and as soon as reasonably practicable thereafter, the Company shall cause to be elected or appointed to the
Board such additional Initial Investor Designees, subject to the satisfaction of all legal and governance
requirements regarding service as a director of the Company and, if not already received, the reasonable
approval of the Nominating Committee. The Company shall take all actions necessary to ensure that on January 15, 2010 the Board
shall have at least two additional vacancies.”


This Amendment may be signed in any number of counterparts, each of which shall be an original, with the same
effect as if the signatures were on the same instrument.



[Signature page follows]


 


1










 





IN WITNESS WHEREOF, the Parties hereto have caused this Amendment to be duly executed by their respective
authorized officers as of the date first written above.



ALLIS-CHALMERS ENERGY INC.



By: /s/ Theodore F. Pound III               

Name: Theodore F. Pound III

Title: General Counsel and Secretary



 



LIME ROCK PARTNERS V, L.P.



By: Lime Rock Partners GP V, L.P., its 
general partner



By: LRP GP V, Inc., its general partner



By: /s/ Saad Bargach                             

Name: Saad Bargach

Title: Managing Director




 


2