CUSIP NO. 723655106

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
                               (Amendment No. 1)*

                    Under the Securities Exchange Act of 1934

                            PIONEER DRILLING COMPANY
                            ------------------------
                                (Name of Issuer)

                          Common Stock, par value $.10
                          ----------------------------
                         (Title of Class of Securities)

                                    723655106
                                    ---------
                                 (CUSIP Number)

                              Shannon Self, Esquire
                           Commercial Law Group, P.C.
                               2725 Oklahoma Tower
                                 210 Park Avenue
                          Oklahoma City, Oklahoma 73102
                                 (405) 232-3001
                            ------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                 August 11, 2004
                                 ---------------

             (Date of Event Which Requires Filing of this Statement)


If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  which is the subject of this  Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box. [X]

NOTE: Six (6) copies of this statement,  including all exhibits, should be filed
with the  Commission.  See Rule 13d-1(a) for other parties to whom copies are to
be sent.

* The remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for  any  subsequent   amendment   containing   information  which  would  alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).



CUSIP NO. 723655106


   (1)     Name of Reporting Person                           Chesapeake Energy
                                                                    Corporation
           I.R.S. Identification No. of Above Person                 73-1395733

   (2)     Check the Appropriate Box if a Member of a Group           (a)  [  ]
           (See Instructions)                                         (b)  [x]

   (3)     SEC Use Only

   (4)     Source of Funds (See Instructions)                                WC

   (5)     Check if Disclosure of Legal Proceedings is Required            [  ]
           Pursuant to Items 2(d) or 2(e)

   (6)     Citizenship or Place of Organization                        Oklahoma

           ----------------------------------------------------

Number of Shares     (7)   Sole Voting Power                          6,441,466
-------------------------------------------------------------------------------

Beneficially Owned   (8)   Shared Voting Power                                -
-------------------------------------------------------------------------------

By Each Reporting    (9)   Sole Dispositive Power                     6,441,466
-------------------------------------------------------------------------------

Person With:        (10)   Shared Dispositive Power                           -
-------------------------------------------------------------------------------


  (11)     Aggregate Amount Beneficially Owned by Each                6,441,466
           Reporting Person

  (12)     Check if the Aggregate Amount in Row (11) Excludes              [  ]
           Certain Shares (See Instructions)

  (13)     Percent of Class Represented by Amount in Row (11)            17.04%

  (14)     Type of Reporting Person (See Instructions)                       CO


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CUSIP NO. 723655106


Item 1.  Security and Issuer.

         The common  stock,  par value  $.10 (the  "Common  Stock"),  of Pioneer
         Drilling Company, a Texas corporation ("Pioneer").  Pioneer's principal
         executive  offices  are  located  at 9310  Broadway,  Building  1,  San
         Antonio, Texas 78217.

Item 2.  Identity and Background.

         Chesapeake Energy  Corporation,  an Oklahoma  corporation  ("Chesapeake
         Energy"),  is located  at 6100 North  Western  Avenue,  Oklahoma  City,
         Oklahoma 73118, and is primarily engaged in the ownership,  development
         and operation of oil and gas assets in the United States. The executive
         officers and directors of Chesapeake Energy are set forth below.

                  Aubrey K. McClendon
                  Chairman of the Board and Chief Executive Officer
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Tom L. Ward
                  Director, Chief Operating Officer and President
                  6200 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Marcus C. Rowland
                  Chief Financial Officer and Executive Vice President
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Martha A. Burger
                  Treasurer and Senior Vice President
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Michael A. Johnson
                  Senior Vice President
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Frank A. Keating
                  Director
                  c/o Chesapeake Energy Corporation
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Breene M. Kerr
                  Director
                  c/o Chesapeake Energy Corporation
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Shannon Self
                  Director
                  c/o Chesapeake Energy Corporation
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

                  Frederick B. Whittemore
                  Director
                  c/o Chesapeake Energy Corporation
                  6100 North Western
                  Oklahoma City, Oklahoma 73118

                  Charles T. Maxwell
                  Director
                  c/o Chesapeake Energy Corporation
                  6100 North Western Avenue
                  Oklahoma City, Oklahoma 73118

         Chesapeake  Energy and each of the listed  individuals have not, during
         the last five years, been convicted in a criminal proceeding (excluding
         traffic violations or similar misdemeanors) and have not been or become
         subject  to  a  judgment,   decree  or  final  order  enjoining  future
         violations  of, or  prohibiting  or  mandating  activities  subject to,
         federal or state  securities laws or finding any violation with respect
         to such laws. Each individual is a United States citizen.

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CUSIP NO. 723655106


Item 3.  Source and Amount of Funds or Other Consideration.

         On March 31,  2003,  Chesapeake  Energy  acquired  5,333,333  shares of
         Common Stock at a cost of $3.75 per share  pursuant to the Common Stock
         Purchase  Agreement dated March 31, 2003, between Chesapeake Energy and
         Pioneer (the "Stock Purchase  Agreement").  The total consideration for
         this purchase was $20.0 million.

         On August 11, 2004,  Chesapeake  Energy  exercised  certain  preemptive
         rights set forth in Section  1.3 of the Stock  Purchase  Agreement  and
         purchased  631,133  shares of Common  Stock  from  Pioneer at a cost of
         $6.90  per  share.  The  total  consideration  for  this  purchase  was
         $4,354,818.00.

         On August 16,  2004,  Chesapeake  Energy  purchased  477,000  shares of
         Common Stock at a cost of $7.25 per share. The total  consideration for
         this purchase was $3,458,250.00

         The  purchase  price for the  foregoing  shares of  Common  Stock  (the
         "Acquired Shares") was funded by Chesapeake Energy from working capital
         and  general  corporate  funds,  one of the  sources  of  which  is the
         revolving  bank  facility  maintained  by  Chesapeake  Energy  and  its
         subsidiary entities in the ordinary course of business.

Item 4.  Purpose of Transaction.

         The  Acquired   Shares  were  acquired  by  Chesapeake   Energy  as  an
         investment.   Chesapeake  Energy  may  in  the  future:   (1)  purchase
         additional  Common Stock, debt securities or other equity securities of
         Pioneer;  (2) sell all or part of the  Acquired  Shares in  private  or
         registered  transactions;  (3)  communicate  with the  management,  the
         directors or shareholders of Pioneer regarding Pioneer's business plans
         and operations; or (4) enter into additional transactions in connection
         with Pioneer or Pioneer's assets.

         In connection with the Stock Purchase Agreement,  Chesapeake Energy was
         granted the preemptive right to acquire equity  securities to be issued
         by Pioneer in the future and the right to require the  registration  of
         the Acquired  Shares under the  Securities  Act of 1933.  Except as set
         forth  above,  Chesapeake  Energy  has no present  plans or  intentions
         relating to the transactions described in subparagraphs (a) through (j)
         of Item 4 of Schedule 13D.

Item 5.  Interest in Securities of the Issuer.

         (a)  Chesapeake  Energy  owns  6,441,466  shares of Common  Stock as of
         August 19, 2004,  representing  17.04% of the outstanding Common Stock.
         The foregoing  percentage is based on 38,401,645 shares of Common Stock
         disclosed as issued and  outstanding  after the completion of Pioneer's
         public offering of Common Stock and the other transactions described in
         Pioneer's 424(b)(4) prospectus, filed with the SEC on August 6, 2004.

         (b)  Chesapeake  Energy  has the sole  power to vote or  dispose of the
         Acquired Shares.

         (c) On August 11, 2004,  Chesapeake Energy exercised certain preemptive
         rights set forth in Section  1.3 of the Stock  Purchase  Agreement  and
         purchased  631,133  shares of Common  Stock  from  Pioneer at $6.90 per
         share. The total consideration for this purchase was $4,354,818.00.  On
         August 16, 2004,  Chesapeake  Energy purchased 477,000 shares of Common
         Stock  at a cost of  $7.25  per  share.  The  shares  of  Common  Stock
         described  in  the  prior   sentence  were  acquired  in  a  negotiated
         transaction  effectuated  through a broker to broker  transfer  through
         DTC. The total consideration for this purchase was $3,458,250.00.

         (d) Inapplicable

         (e) Inapplicable

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CUSIP NO. 723655106


Item 6.  Contracts, Agreements, Underwritings or Relationships With Respect to
         Securities of the Issuer.

         Under  the  Stock  Purchase   Agreement,   Chesapeake  Energy  has  the
         preemptive  right to participate in future equity  issuances by Pioneer
         and has the right to attend and  observe all board  meetings  and board
         committee  meetings of Pioneer and  Pioneer's  subsidiaries.  Under the
         Stock Purchase  Agreement  Chesapeake Energy granted Pioneer a right of
         first refusal with respect to any Acquired Shares to be sold other than
         into the public trading market.  Under a registration  rights agreement
         (the  "Registration  Rights  Agreement")  among  Pioneer,  WEDGE Energy
         Services,  L.L.C.,  a Delaware  limited  liability  company  ("WEDGE"),
         William H. White, an individual  affiliated with WEDGE,  and Chesapeake
         Energy  dated  March  31,  2003,  Chesapeake  Energy  can  request  the
         registration  of a portion of the  Acquired  Stock as  provided  in the
         Registration Rights Agreement.

Item 7.  Materials to be filed as Exhibits.

1.        Common Stock Purchase  Agreement dated March 31, 2003, between Pioneer
          Drilling  Company and Chesapeake  Energy  Corporation is  incorporated
          herein by reference to Exhibit 99.1. to Schedule 13D filed on April 3,
          2003.

2.        Registration  Rights  Agreement  dated March 31, 2003,  among  Pioneer
          Drilling Company, WEDGE Energy Services,  L.L.C., William H. White, an
          individual,  and Chesapeake Energy Corporation is incorporated  herein
          by reference to Exhibit 99.2 to Schedule 13D filed on April 3, 2003.

                                    SIGNATURE

After  reasonable  inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

DATED:   August 19, 2004



                                             Chesapeake Energy Corporation
                                             an Oklahoma corporation



                                             By    /s/ Aubrey K. McClendon
                                                   ----------------------------
                                                       Aubrey K. McClendon
                                                    Chairman of the Board and
                                                     Chief Executive Officer


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