##### Table of Contents



As filed with the Securities and Exchange Commission on
    October 11, 2007
 Registration
    No. 333-
    UNITED STATES SECURITIES AND
    EXCHANGE COMMISSION
 Washington, D.C.
    20549
      Form S-3
 REGISTRATION
    STATEMENT
 UNDER
 THE SECURITIES ACT OF
    1933
      Allis-Chalmers Energy
    Inc.
 (Exact name of registrant as
    specified in its charter)
  Delaware

1389

39-0126090(State or other jurisdiction
    of

(Primary standard
    industrial

(I.R.S. employerincorporation or
    organization)

classification code
    number)

identification number)   5075 Westheimer, Suite 890
 Houston, Texas 77056
 (713) 369-0550
 (Address, including zip code,
    and telephone number, including area code, of registrants
    principal executive offices)
  Victor M. Perez
 Chief Financial Officer
 5075 Westheimer, Suite 890
 Houston, Texas 77056
 (713) 369-0550
 (Name, address, including zip
    code, and telephone number, including area code, of agent for
    service)
      With a copy to:
 Robert V. Jewell
 Henry Havre
 Andrews Kurth LLP
 600 Travis, Suite 4200
 Houston, Texas 77002
 (713) 220-4200
     Approximate date of commencement of proposed sale to the
    public:
 o
 þ
 o
 o
 o
 o
  CALCULATION
    OF REGISTRATION FEE
  Title of Each Class of


Amount to be


Proposed Maximum


Proposed Maximum


Amount ofSecurities to be Registered


Registered(1)


Offering Price Per Share(2)


Aggregate Offering Price(2)


Registration FeeCommon Stock


3,200,000


$18.12


$57,984,000


$1,781   (1)
    All of the shares of common stock offered hereby are for the
    accounts of the selling stockholder.(2)
    Estimated solely for the purpose of calculating the registration
    fee pursuant to Rule 457(c) under the Securities Act of
    1933. The calculation of the registration fee is based on the
    average of the high and low price for the Common Stock on
    October 10, 2007 as reported by the New York Stock Exchange.   The Registrant hereby amends this Registration Statement on
    such date or dates as may be necessary to delay its effective
    date until the Registrant shall file a further amendment which
    specifically states that this Registration Statement shall
    thereafter become effective in accordance with Section 8(a)
    of the Securities Act of 1933 or until the Registration
    Statement shall become effective on such date as the SEC, acting
    pursuant to said Section 8(a), may determine.




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The
information in this prospectus supplement is not complete and
may be changed. The selling stockholder may not sell these
securities until the registration statement filed with the
Securities and Exchange Commission is effective. This prospectus
is not an offer to sell these securities and it is not
soliciting an offer to buy these securities in any jurisdiction
where the offer or sale is not permitted.  SUBJECT TO COMPLETION, DATED
    OCTOBER 11, 2007
  PROSPECTUS
  3,200,000 Shares
  
 ALLIS-CHALMERS ENERGY
    INC.
  Common Stock
              Investing in our common stock involves risks, including those
    contained or incorporated by reference herein as described under
    Risk Factors on page 2 of this prospectus.
  Neither the Securities and Exchange Commission nor any state
    securities commission has approved or disapproved of these
    securities or has determined if this prospectus is truthful or
    complete. Any representation to the contrary is a criminal
    offense.




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##### 



TABLE OF
    CONTENTS
  
 PageAbout This Prospectus

iWhere You Can Find More Information

iiIncorporation By Reference

iiCautionary Statement Regarding Forward-Looking
    Statements

iiiIndustry and Market Data

iiiProspectus Summary

1Risk Factors

2Use of Proceeds

3Selling Stockholder

3Plan of Distribution

4Legal Matters

5Experts

5Opinion of Andrews Kurth LLPConsent of UHY LLPConsent of Wright, Moore, Dehart, Dupuis & Hutchinson, LLCConsent of Curtis Blakely & Co., PCConsent of Accounting & Consulting Group, LLPConsent of UHY LLPConsent of SibilleConsent of Broussard, Poche, Lewis & Breaux, L.L.P.Consent of UHY Mann Frankfort Stein & Lipp CPAs, LLP  
   ABOUT
    THIS PROSPECTUS
    You should rely only on the information contained or
    incorporated by reference in this prospectus. We have not, and
    the selling stockholder has not, authorized any other person to
    provide you with different information. If anyone provides you
    with different or inconsistent information, you should not rely
    on it. The selling stockholder is not making offers to sell or
    seeking offers to buy any of the securities covered by this
    prospectus in any state where the offer is not permitted. You
    should assume that the information appearing in this prospectus
    and any other document incorporated by reference is accurate
    only as of the date on the front cover of those documents. Our
    business, financial condition, results of operations and
    prospects may have changed since those dates.
  Under no circumstances should the delivery to you of this
    prospectus or any offer or sale made pursuant to this prospectus
    create any implication that the information contained in this
    prospectus is correct as of any time after the date of this
    prospectus.
   i




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WHERE
    YOU CAN FIND MORE INFORMATION
    1-800-SEC-0330 http://www.sec.gov Form 10-K, Form 10-Q Form 8-K, http://www.alchenergy.com
  INCORPORATION
    BY REFERENCE
  Form 8-K
  
    our annual report on
    Form 10-K
    for the year ended December 31, 2006, as filed with the SEC
    on March 15, 2007, which we refer to collectively as our
    2006
    Form 10-K;
    our quarterly report on
    Form 10-Q
    for the quarter ended March 31, 2007, as filed with the SEC
    on May 10, 2007, which we refer to collectively as our
    First Quarter 2007
    Form 10-Q;
    our quarterly report on
    Form 10-Q
    for the quarter ended June 30, 2007, as filed with the SEC
    on August 9, 2007, which we refer to as our Second Quarter
    2007
    Form 10-Q;
    our current reports on
    Form 8-K
    and 8-K/A,
    as filed with the SEC on January 4, 2007, January 24,
    2007, January 25, 2007, January 29, 2007 (two
    reports), February 13, 2007, March 7, 2007,
    April 3, 2007, April 16, 2007, April 19, 2007,
    May 2, 2007, May 17, 2007, July 13, 2007,
    July 24, 2007 and August 9, 2007;
    our current reports on
    Form 8-K
    and 8-K/A
    containing additional information required by
    Rule 3-05
    and Article 11 of
    Regulation S-X,
    as filed with the SEC on April 5, 2005, May 6, 2005,
    June 10, 2005, July 15, 2005, September 2, 2005,
    July 17, 2006, August 14, 2006, September 29,
    2006, October 19, 2006, October 26, 2006,
    December 13, 2006 and December 18, 2006; and
    the description of our common stock in our Registration
    Statement on
    Form 8-A
    (File
    No. 001-02199)
    under Section 12(b) of the Exchange Act.   ii




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(713) 369-0550
   CAUTIONARY
    STATEMENT
    REGARDING FORWARD-LOOKING STATEMENTS
    INDUSTRY
    AND MARKET DATA
   iii




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PROSPECTUS
    SUMMARY
  This summary highlights selected information contained
    elsewhere in this prospectus or in documents incorporated by
    reference in this prospectus. This summary does not contain all
    of the information that you should consider before investing in
    our common stock. You should read carefully the entire
    prospectus, including Risk Factors and the other
    information contained or incorporated by reference in this
    prospectus before making an investment decision.
  Our
    Business
        (800) 997-9534. http://www.alchenergy.com
 1




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RISK
    FACTORS
  An investment in our common stock is subject to numerous
    risks, including those listed below and the other risks listed
    under the caption Risk Factors incorporated by
    reference to our 2006
    Form 10-K
    and our Second Quarter 2007
    Form 10-Q.
    You should carefully consider these risks, along with the
    information provided elsewhere in this prospectus and the
    documents we incorporate by reference in this prospectus before
    investing in the common stock. You could lose all or part of
    your investment in the common stock.
  Additional
    Risks Associated With an Investment in Our Common
    Stock
  We may
    have a contingent liability arising out of a possible violation
    of Section 5 of the Securities Act in connection with
    electronic communications sent to potential investors in our
    common stock.
  e-mails and/or
  Substantial
    sales of our common stock could adversely affect our stock
    price.
       2




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USE
    OF PROCEEDS
    SELLING
    STOCKHOLDER
      successors-in-interest
  Shares Beneficially Owned





Shares Beneficially OwnedBefore the Offering


Shares That May be


After the Offering(2)Name

Number


Percent


Offered Hereby


Number


PercentOil & Gas Rental Services, Inc.(1)


3,200,000



9.1
%


3,200,000







     (1)
    
    The address of OGR is 948 Degravelle Road, Amelia, Louisiana
    70340.(2)
    
    Assumes the selling stockholder disposes of all the shares of
    common stock covered by this prospectus. 3




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PLAN
    OF DISTRIBUTION
    
    transactions in the over-the-counter market, the New York Stock
    Exchange, or on one or more exchanges on which the securities
    may be listed or quoted at the time of sale;
    negotiated transactions;
    transactions otherwise than on the NYSE or exchanges;
    underwritten offerings;
    distributions to equity security holders, partners or other
    stockholders of the selling stockholder;
    through the writing of options, whether such options are listed
    on an options exchange or otherwise; or
    through a combination of these methods of sale.    
    fixed prices which may be changed;
    market prices prevailing at the time of sale;
    prices related to prevailing market prices;
    negotiated prices; or
    any other method permitted by law.  successors-in-interest
      Direct
    Sales, Agents, Dealers and Underwriters
    
    directly to purchasers; or 4




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
    to or through agents, dealers or underwriters designated from
    time to time.  and/or
  Regulation M
    Supplements
    State
    Securities Law
    Expenses,
    Indemnification
      LEGAL
    MATTERS
    EXPERTS
   5




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6




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PART II
  INFORMATION
    NOT REQUIRED IN PROSPECTUS
  Item 14.
    Other
    Expenses of Issuance and Distribution    SEC registration fee

$
1,781Printing expenses


2,000Accounting fees and expenses


35,000Legal fees and expenses


20,000Miscellaneous


1,219Total

$
60,000   Item 15.
    Indemnification
    of Directors and Officers     II-1




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and/or
    Item 16.
    Exhibits    Item 17.
    Undertakings                 II-2




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II-3




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SIGNATURES
      By:
    /s/  Victor
    M. Perez 
    POWER OF
    ATTORNEY
      Signature

Title

Date/s/  Munawar
    H. HidayatallahMunawar
    H. Hidayatallah

Chairman of the Board of Directors;
    Chief Executive Officer
    (Principal Executive Officer)

October 11, 2007/s/  Burt
    A. AdamsBurt
    A. Adams

President & Chief Operating Officer;
    Vice Chairman of the Board of Directors

October 11, 2007/s/  Victor
    M. PerezVictor
    M. Perez

Chief Financial Officer
    (Principal Financial and Accounting
    Officer)

October 11, 2007Ali
    H. M. Afdhal

Director

October 11, 2007/s/  Alejandro
    P. BulgheroniAlejandro
    P. Bulgheroni

Director

October 11, 2007/s/  Carlos
    A. BulgheroniCarlos
    A. Bulgheroni

Director

October 11, 2007/s/  Victor
    F. GermackVictor
    F. Germack

Director

October 11, 2007




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Signature

Title

Date/s/  James
    M. HennessyJames
    M. Hennessy

Director

October 11, 2007/s/  Jonathan
    E. McConnaughy, Jr.Jonathan
    E. McConnaughy, Jr.

Director

October 11, 2007/s/  Robert
    E. NederlanderRobert
    E. Nederlander

Director

October 11, 2007Zane
    Tankel

Director

October 11, 2007/s/  Leonard
    ToboroffLeonard
    Toboroff

Director

October 11, 2007




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EXHIBITS
  Number

Exhibit Title**1
.1

Underwriting Agreement2
.1

First Amended Disclosure Statement pursuant to Section 1125
    of the Bankruptcy Code, dated September 14, 1988, which
    includes the First Amended and Restated Joint Plan of
    Reorganization dated September 14, 1988 (incorporated by
    reference to Registrants Current Report on
    Form 8-K
    dated December 1, 1988).2
.2

Reorganization Trust Agreement dated September 14,
    1988 by and between Registrant and John T. Grigsby, Jr., Trustee
    (incorporated by reference to Exhibit D of the First
    Amended and Restated Joint Plan of Reorganization dated
    September 14, 1988 included in Registrants Current
    Report on
    Form 8-K
    dated December 1, 1988).2
.3

Agreement and Plan of Merger dated as of May 9, 2001 by and
    among Registrant, Allis-Chalmers Acquisition Corp. and OilQuip
    Rentals, Inc. (incorporated by reference to Registrants
    Current Report on
    Form 8-K
    filed May 15, 2001).2
.4

Stock Purchase Agreement dated February 1, 2002 by and
    between Registrant and Jens H. Mortensen, Jr. (incorporated by
    reference to Registrants Current Report on
    Form 8-K
    filed February 21, 2002).2
.5

Stock Purchase Agreement dated February 1, 2002 by and
    among Registrant, Energy Spectrum Partners LP, and Strata
    Directional Technology, Inc. (incorporated by reference to
    Registrants Annual Report on
    Form 10-K
    for the year ended December 31, 2001).2
.6

Stock Purchase Agreement dated August 10, 2004 by and among
    Allis-Chalmers Corporation and the investors named thereto
    (incorporated by reference to Exhibit 10.37 to the
    Registration Statement on
    Form S-1
    (Registration No. 118916) filed on September 10,
    2004).2
.7

Amendment to Stock Purchase Agreement dated August 10, 2004
    (incorporated by reference to Exhibit 10.38 to the
    Registration Statement on
    Form S-1
    (Registration No. 118916) filed on September 10,
    2004).2
.8

Addendum to Stock Purchase Agreement dated September 24,
    2004 (incorporated by reference to Exhibit 10.55 to
    Registrants Current Report on
    Form 8-K
    filed on September 30, 2004).2
.9

Asset Purchase Agreement dated November 10, 2004 by and
    among AirComp LLC, a Delaware limited liability company, Diamond
    Air Drilling Services, Inc., a Texas corporation, and Marquis
    Bit Co., L.L.C., a New Mexico limited liability company, Greg
    Hawley and Tammy Hawley, residents of Texas and Clay Wilson and
    Linda Wilson, residents of New Mexico (incorporated by reference
    to the Current Report on
    Form 8-K
    filed on November 15, 2004).2
.10

Purchase Agreement and related Agreements by and among
    Allis-Chalmers Corporation, Chevron USA, Inc., Dale Redman and
    others dated December 10, 2004 (incorporated by reference
    to Exhibit 10.63 to the Registrants Current Report on
    Form 8-K
    filed on December 16, 2004).2
.11

Stock Purchase Agreement dated April 1, 2005, by and among
    Allis-Chalmers Energy Inc., Thomas Whittington, Sr., Werlyn R.
    Bourgeois and SAM and D, LLC. (incorporated by reference to
    Exhibit 10.51 to the Registrants Current Report on
    Form 8-K
    filed on April 5, 2005).2
.12

Stock Purchase Agreement effective May 1, 2005, by and
    among Allis-Chalmers Energy Inc., Wesley J. Mahone, Mike T.
    Wilhite, Andrew D. Mills and Tim Williams (incorporated by
    reference to Exhibit 10.51 to the Registrants Current
    Report on
    Form 8-K
    filed on May 6, 2005).2
.13

Purchase Agreement dated July 11, 2005 among Allis-Chalmers
    Energy Inc., Mountain Compressed Air, Inc. and M-I, L.L.C.
    (incorporated by reference to Exhibit 10.42 to the
    Registrants Current Report on
    Form 8-K
    filed on July 15, 2005).2
.14

Asset Purchase Agreement dated July 11, 2005 between
    AirComp LLC, W.T. Enterprises, Inc. and William M. Watts
    (incorporated by reference to Exhibit 10.43 to the
    Registrants Current Report on
    Form 8-K
    filed on July 15, 2005).2
.15

Asset Purchase Agreement by and between Patterson Services, Inc.
    and Allis-Chalmers Tubular Services, Inc. (incorporated by
    reference to Exhibit 10.44 to the Registrants Current
    Report on
    Form 8-K
    filed on September 8, 2005).2
.16

Stock Purchase Agreement dated as of December 20, 2005
    between the Registrant and Joe Van Matre (incorporated by
    reference to Exhibit 10.33 to the Registrants Annual
    Report on
    Form 10-K
    for the year ended December 31, 2005).




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Number

Exhibit Title2
.17

Stock Purchase Agreement, dated as of April 27, 2006, by
    and among Bridas International Holdings Ltd., Bridas Central
    Company Ltd., Associated Petroleum Investors Limited, and the
    Registrant. (incorporated by reference to the Registrants
    Quarterly Report on
    Form 10-Q
    for the quarter ended March 31, 2006).2
.18

Stock Purchase Agreement, dated as of October 17, 2006, by
    and between Allis-Chalmers Production Services, Inc. and
    Randolph J. Hebert (incorporated by reference to the
    Registrants Current Report on
    Form 8-K
    filed on October 19, 2006).2
.11

Asset Purchase Agreement, dated as of October 25, 2006, by
    and between Allis-Chalmers Energy Inc. and Oil & Gas
    Rental Services, Inc. (incorporated by reference to the
    Registrants Current Report on
    Form 8-K
    filed on October 26, 2006).4
.1

Specimen Stock Certificate of Common Stock of Registrant
    (incorporated by reference to the Registrants Quarterly
    Report on
    Form 10-Q
    for the quarter ended June 30, 2004).4
.2

Registration Rights Agreement dated as of March 31, 1999,
    by and between Allis-Chalmers Corporation and the Pension
    Benefit Guaranty Corporation (incorporated by reference to
    Exhibit 10.3 to the Registrants Quarterly Report on
    Form 10-Q
    for the quarter ended June 30, 1999).4
.3

Registration Rights Agreement dated April 2, 2004 by and
    between Registrant and the Stockholder signatories thereto
    (incorporated by reference to Exhibit 10.43 to Amendment
    No. 1 to the Registrants Annual Report on
    Form 10-K
    for the year ended December 31, 2003).4
.4

Registration Rights Agreement dated as of January 29, 2007
    by and among Allis-Chalmers Energy Inc., the Guarantors named
    therein and the Initial Purchasers named therein (incorporated
    by reference to Exhibit 10.2 to the Registrants
    Current Report on
    Form 8-K
    filed on January 29, 2007).4
.5

Registration Rights Agreement dated as of January 18, 2006
    by and among Allis-Chalmers Energy Inc., the Guarantors named
    therein and the Initial Purchasers named therein (incorporated
    by reference to Exhibit 10.2 to the Registrants
    Current Report on
    Form 8-K
    filed on January 24, 2006).4
.6

Registration Rights Agreement dated as of August 14, 2006
    by and among the Registrant, the guarantors listed on
    Schedule A thereto and RBC Capital Markets Corporation
    (incorporated by reference to Exhibit 10.1 to the
    Registrants
    Form 8-K
    filed on August 14, 2006).4
.7

Indenture dated as of January 18, 2006 by and among the
    Registrant, the Guarantors named therein and Wells Fargo Bank,
    N.A., as trustee (incorporated by reference to Exhibit 4.1
    to the Registrants Current Report on
    Form 8-K
    filed on January 24, 2006).4
.8

First Supplemental Indenture dated as of August 11, 2006 by
    and among Allis-Chalmers GP, LLC, Allis-Chalmers LP, LLC,
    Allis-Chalmers Management, LP, Rogers Oil Tool Services, Inc.,
    the Registrant, the other Guarantors (as defined in the
    Indenture referred to therein) and Wells Fargo Bank, N.A
    (incorporated by reference to Exhibit 4.2 to the
    Registrants
    Form 8-K
    filed on August 14, 2006).4
.9

Second Supplemental Indenture dated as of January 23, 2007
    by and among Petro-Rentals, Incorporated, the Registrant, the
    other Guarantor parties thereto and Wells Fargo Bank, N.A., as
    trustee (incorporated by reference to Exhibit 10.1 to the
    Registrants Current Report on
    Form 8-K
    filed on January 24, 2007).4
.10

Indenture, dated as of January 29, 2007, by and among the
    Registrant, the Guarantors named therein and Wells Fargo Bank,
    N.A. (incorporated by reference to Exhibit 4.1 to the
    Registrants Current Report on
    Form 8-K
    filed on January 29, 2007).4
.11

Form of 9.0% Senior Note due 2014 (incorporated by
    reference to Exhibit A to Exhibit 4.1 to the
    Registrants Current Report on
    Form 8-K
    filed on January 24, 2006).4
.12

Form of 8.5% Senior Note due 2017 (incorporated by
    reference to Exhibit A to Exhibit 4.1 to the
    Registrants Current Report on
    Form 8-K
    filed on January 29, 2007).4
.13

Investors Rights Agreement, dated August 14, 2006, by and
    among the Company, Bridas International Holdings, Ltd., Bridas
    Central Company, Ltd. and Associated Petroleum Investors Limited
    (incorporated by reference to the Registrants Current
    Report on
    Form 8-K
    filed on August 14, 2006).4
.14

Investor Rights Agreement, dated as of December 18, 2006,
    by and between the Registrant and Oil & Gas Rental
    Services, Inc. (incorporated by reference to the
    Registrants Current Report on
    Form 8-K
    filed on December 18, 2006).*5
.1

Opinion of Andrews Kurth LLP regarding legality of the
    securities being registered by Allis-Chalmers Energy Inc.




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Number

Exhibit Title9
.1

Shareholders Agreement dated February 1, 2002 by and among
    Jens Oilfield Service, Inc., a Texas corporation, Jens H.
    Mortensen, Jr., and Registrant (incorporated by reference to
    Registrants Annual Report on
    Form 10-K
    for the year ended December 31, 2001).*23
.1

Consent of UHY LLP.*23
.2

Consent of Wright, Moore, Dehart, Dupuis & Hutchinson,
    LLC.*23
.3

Consent of Curtis Blakely & Co., PC.*23
.4

Consent of Accounting & Consulting Group, LLP.*23
.5

Consent of UHY LLP.*23
.6

Consent of Sibille (formerly Finsterbusch Pickenhayn Sibille).*23
.7

Consent of Broussard, Poché, Lewis & Breaux,
    L.L.P.*23
.8

Consent of UHY Mann Frankfort Stein & Lipp CPAs, LLP.*23
.9

Consent of Andrews Kurth LLP (included in Exhibit 5.1).*24
.1

Powers of Attorney (included in Part II as a part of the
    signature pages of the Registration Statement).     *
    
    Filed herewith.**
    
    If an underwriting agreement is utilized, it will be filed by
    amendment or as an exhibit to Current Report on
    Form 8-K
    filed at a later date in connection with a specific offering.