Document:

<PAGE>
                                                                     EXHIBIT 4.1

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                             PARKER DRILLING COMPANY
                            and Subsidiary Guarantors

                          9 3/4% SENIOR NOTES DUE 2006

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

                          FIRST SUPPLEMENTAL INDENTURE

                             Dated as of May 3, 2000

             Supplementing the Indenture dated as of March 11, 1998

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

                   CHASE BANK OF TEXAS, NATIONAL ASSOCIATION,
                                   as Trustee

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<PAGE>
                          FIRST SUPPLEMENTAL INDENTURE

         This First Supplemental Indenture dated and effective as of May 3, 2000
(the "First Supplemental Indenture") is made and entered into by and among
Parker Drilling Company, a Delaware corporation (the "Company"), and Parker
Drilling Offshore International, Inc., a Cayman Islands corporation and Parker
Drilling Offshore Corporation, a Texas corporation which are wholly-owned
indirectly by the Company, the "New Guarantors", and Chase Bank of Texas,
National Association, a national banking association, as Trustee (the
"Trustee").

                  RECITALS OF THE COMPANY AND THE NEW GUARANTOR

         WHEREAS, the Company, the Subsidiary Guarantors and the Trustee have
executed and delivered an Indenture dated as of March 11, 1998 by and among the
Company, the Trustee and the Subsidiary Guarantors, (the "1998 Indenture")
providing for the issuance by the Company of $150,000,000 in aggregate principal
amount of the Company's 9 3/4% Senior Notes due 2006 (the "Notes") and pursuant
to which the Subsidiary Guarantors have agreed, jointly and severally, to
unconditionally guarantee the due and punctual payment of the principal of,
premium, if any, and interest on the Notes and all other amounts due and payable
under the 1998 Indenture and the Notes by the Company (the "Indenture
Obligations");

         WHEREAS, Section 9.01(a)(vi) of the 1998 Indenture provides that under
certain conditions the Company and the Trustee may, without the consent of any
Holder of a Note, amend or supplement the 1998 Indenture to add any Restricted
Subsidiary as an additional Subsidiary Guarantor as provided in Section 10.02 of
the 1998 Indenture or to evidence the succession of another Person to any
Subsidiary Guarantor pursuant to Section 10.04 of the 1998 Indenture and the
assumption by any such successor of the covenants and agreements of such
Subsidiary Guarantor contained in the 1998 Indenture and in the Subsidiary
Guarantee of such Subsidiary Guarantor and to release a Subsidiary Guarantor
from its obligations under this Indenture and its Subsidiary Guarantee pursuant
to Section 10.05 hereof;

         WHEREAS, the Company has determined that the New Guarantors are
required to be added as Subsidiary Guarantors pursuant to Section 10.02 of the
1998 Indenture as a result of the transfer of certain assets from one Subsidiary
Guarantor to the New Guarantors;

         WHEREAS, Section 10.02 of the 1998 Indenture provides that as a result
of said actions the following is required: (i) the execution and delivery by the
New Guarantors of this First Supplemental Indenture whereby the New Guarantors
agree to be bound by the terms of the 1998 Indenture as applicable to a
Subsidiary Guarantor; and (ii) the execution of a Subsidiary Guarantee of the
Notes by the New Guarantors; and

         WHEREAS, the execution and delivery of this First Supplemental
Indenture has been duly authorized by a Board Resolution of the respective
Boards of the Company and each of the New Guarantors; and

         WHEREAS, all conditions and requirements necessary to make this First
Supplemental Indenture valid and binding upon the Company and the New
Guarantors, and enforceable against the Company and the New Guarantors in
accordance with its terms, have been performed and fulfilled;

         NOW, THEREFORE, in consideration of the above premises, the parties
hereto mutually covenant and agree for the equal and ratable benefit of the
respective Holders of the Notes, as follows:

                                      -1-
<PAGE>
                                    ARTICLE I

                              ADDITIONAL GUARANTOR

         Section 1.1. Addition of Guarantors. The New Guarantors, by execution
and delivery of this First Supplemental Indenture, hereby agree to be bound by
the terms of the Indenture as a Subsidiary Guarantor.

         Section 1.2. Guarantee of Each Subsidiary Guarantor. Attached as
Exhibit A-1 and A-2 and incorporated here by reference, are the notations of
Subsidiary Guarantees of each New Guarantor in the form prescribed in the 1998
Indenture, by which the New Guarantor agrees to guarantee the obligations of the
Company, in accordance with the terms set out in such notation of Subsidiary
Guarantee.

                                   ARTICLE II

                    PARTICULAR REPRESENTATIONS AND COVENANTS

         Section 2.1. Authority. The Company is duly authorized by a resolution
of its Board of Directors to execute and deliver this First Supplemental
Indenture, and all corporate action on its part required for the execution and
delivery of this First Supplemental Indenture has been duly and effectively
taken.

         Section 2.2. Correctness of Recitals. The Company represents and
warrants that all recitals and statements in this First Supplemental Indenture
are true and correct.

                                   ARTICLE III

                             CONCERNING THE TRUSTEE

         Section 3.1 Acceptance of Trusts. The Trustee accepts the trusts
hereunder and agrees to perform same, but only upon the terms and conditions set
forth in the Indenture.

         Section 3.2 Responsibility for Recitals. The recitals and statements
contained in this First Supplemental Indenture shall be taken as recitals and
statements of the Company, and the Trustee assumes no responsibility for the
correctness of same. The Trustee makes no representations as to the validity or
sufficiency of this First Supplemental Indenture, except that the Trustee is
duly authorized to deliver it.

                                   ARTICLE IV

                            MISCELLANEOUS PROVISIONS

         Section 4.1 Relation to the 1998 Indenture. This First Supplemental
Indenture shall become effective immediately upon execution and delivery. All
terms and conditions in it shall form a part of the 1998 Indenture as fully and
with the same effect as if all such terms and conditions had been set forth in
the 1998 Indenture. The 1998 Indenture is hereby ratified and confirmed and
shall remain and continue in full force and effect in accordance with its terms,
as supplemented by this First Supplemental Indenture. The 1998 Indenture and the
First Supplemental Indenture shall be read, taken and construed together as one
instrument. Capitalized terms used but not defined in this First Supplemental
Indenture have the meaning ascribed to such terms in the 1998 Indenture.

                                      -2-
<PAGE>
         Section 4.2 Execution in Counterparts. This First Supplemental
Indenture may be executed in several counterparts, each of which shall be deemed
an original, but all of which together shall constitute one instrument.

         Section 4.3 Governing Law. The internal laws of the State of New York
shall govern and be used to construe this First Supplemental Indenture and the
new notations of Subsidiary Guarantees executed and delivered pursuant to it.

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

                                    PARKER DRILLING COMPANY

                                    By:
                                       -----------------------------------------
                                    Name:   James J. Davis
                                    Title:  Sr. Vice President-Finance and
                                            Chief Financial Officer

                                    PARKER DRILLING OFFSHORE INTERNATIONAL, INC.

                                    By:
                                       -----------------------------------------
                                    Name:   John R. Gass
                                    Title:  President

                                    PARKER DRILLING OFFSHORE CORPORATION

                                    By:
                                       -----------------------------------------
                                    Name:   Thomas L. Wingerter
                                    Title:  President

                                    CHASE BANK OF TEXAS, NATIONAL ASSOCIATION

                                    By:
                                       -----------------------------------------
                                    Name:
                                    Title:

                                      -3-<PAGE>
                                                                     EXHIBIT 4.2

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                             PARKER DRILLING COMPANY
                            and Subsidiary Guarantors

                          9 3/4% SENIOR NOTES DUE 2006

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

                          SECOND SUPPLEMENTAL INDENTURE

                            Dated as of June 5, 2001

             Supplementing the Indenture dated as of March 11, 1998

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

                   CHASE BANK OF TEXAS, NATIONAL ASSOCIATION,
                                   as Trustee

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<PAGE>
                          SECOND SUPPLEMENTAL INDENTURE

         This Second Supplemental Indenture dated and effective as of June 5,
2001 (the "Second Supplemental Indenture") is made and entered into by and among
Parker Drilling Company, a Delaware corporation (the "Company"), and Parker
Drilling Company of Colombia Limited, a Nevada corporation and International
Equipment Leasing Company, a Nevada corporation which are wholly-owned
indirectly by the Company, the "New Guarantors", and Chase Bank of Texas,
National Association, a national banking association, as Trustee (the
"Trustee").

                 RECITALS OF THE COMPANY AND THE NEW GUARANTORS

         WHEREAS, the Company, the Subsidiary Guarantors and the Trustee have
executed and delivered an Indenture dated as of March 11, 1998 by and among the
Company, the Trustee and the Subsidiary Guarantors, (the "1998 Indenture")
providing for the issuance by the Company of $150,000,000 in aggregate principal
amount of the Company's 9 3/4% Senior Notes due 2006 (the "Notes") and pursuant
to which the Subsidiary Guarantors have agreed, jointly and severally, to
unconditionally guarantee the due and punctual payment of the principal of,
premium, if any, and interest on the Notes and all other amounts due and payable
under the 1998 Indenture and the Notes by the Company (the "Indenture
Obligations");

         WHEREAS, Section 9.01(a)(vi) of the 1998 Indenture provides that under
certain conditions the Company and the Trustee may, without the consent of any
Holder of a Note, amend or supplement the 1998 Indenture to add any Restricted
Subsidiary as an additional Subsidiary Guarantor as provided in Section 10.02 of
the 1998 Indenture;

         WHEREAS, the Company has determined that the New Guarantors are
required to be added as Subsidiary Guarantors pursuant to Section 10.02 of the
1998 Indenture as a result of the transfer of certain assets from one Subsidiary
Guarantor to the New Guarantors;

         WHEREAS, Section 10.02 of the 1998 Indenture provides that as a result
of said actions the following is required: (i) the execution and delivery by the
New Guarantors of this Second Supplemental Indenture whereby the New Guarantors
agree to be bound by the terms of the 1998 Indenture as applicable to a
Subsidiary Guarantor; and (ii) the execution of a Subsidiary Guarantee of the
Notes by the New Guarantors; and

         WHEREAS, the execution and delivery of this Second Supplemental
Indenture has been duly authorized by a board resolution of the respective board
of directors of the Company and each of the New Guarantors; and

         WHEREAS, all conditions and requirements necessary to make this Second
Supplemental Indenture valid and binding upon the Company and the New
Guarantors, and enforceable against the Company and the New Guarantors in
accordance with its terms, have been performed and fulfilled;

         NOW, THEREFORE, in consideration of the above premises, the parties
hereto mutually covenant and agree for the equal and ratable benefit of the
respective Holders of the Notes, as follows:

                                      -1-
<PAGE>
                                    ARTICLE I

                              ADDITIONAL GUARANTOR

         Section 1.1. Addition of Guarantors. The New Guarantors, by execution
and delivery of this Second Supplemental Indenture, hereby agree to be bound by
the terms of the Indenture as a Subsidiary Guarantor.

         Section 1.2. Guarantee of Each Subsidiary Guarantor. Attached as
Exhibit A-1 and A-2 and incorporated here by reference, are the notations of
Subsidiary Guarantees of each New Guarantor in the form prescribed in the 1998
Indenture, by which the New Guarantor agrees to guarantee the obligations of the
Company, in accordance with the terms set out in such notation of Subsidiary
Guarantee.

                                   ARTICLE II

                    PARTICULAR REPRESENTATIONS AND COVENANTS

         Section 2.1. Authority. The Company is duly authorized by a resolution
of its board of directors to execute and deliver this Second Supplemental
Indenture, and all corporate action on its part required for the execution and
delivery of this Second Supplemental Indenture has been duly and effectively
taken.

         Section 2.2. Correctness of Recitals. The Company represents and
warrants that all recitals and statements in this Second Supplemental Indenture
are true and correct.

                                   ARTICLE III

                             CONCERNING THE TRUSTEE

         Section 3.1 Acceptance of Trusts. The Trustee accepts the trusts
hereunder and agrees to perform same, but only upon the terms and conditions set
forth in the Indenture.

         Section 3.2 Responsibility for Recitals. The recitals and statements
contained in this Second Supplemental Indenture shall be taken as recitals and
statements of the Company, and the Trustee assumes no responsibility for the
correctness of same. The Trustee makes no representations as to the validity or
sufficiency of this Second Supplemental Indenture, except that the Trustee is
duly authorized to deliver it.

                                   ARTICLE IV

                            MISCELLANEOUS PROVISIONS

         Section 4.1 Relation to the 1998 Indenture. This Second Supplemental
Indenture shall become effective immediately upon execution and delivery. All
terms and conditions in it shall form a part of the 1998 Indenture as fully and
with the same effect as if all such terms and conditions had been set forth in
the 1998 Indenture. The 1998 Indenture is hereby ratified and confirmed and
shall remain and continue in full force and effect in accordance with its terms,
as supplemented by this Second Supplemental Indenture. The 1998 Indenture and
all supplements thereto, including the Second Supplemental Indenture shall be
read, taken and construed together as one instrument. Capitalized terms used but
not

                                      -2-
<PAGE>
defined in this Second Supplemental Indenture have the meaning ascribed to such
terms in the 1998 Indenture.

         Section 4.2 Execution in Counterparts. This Second Supplemental
Indenture may be executed in several counterparts, each of which shall be deemed
an original, but all of which together shall constitute one instrument.

         Section 4.3 Governing Law. The internal laws of the State of New York
shall govern and be used to construe this Second Supplemental Indenture and the
new notations of Subsidiary Guarantees executed and delivered pursuant to it.

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

                                     PARKER DRILLING COMPANY

                                     By:
                                        ----------------------------------------
                                     Name:   James J. Davis
                                     Title:  Sr. Vice President-Finance and
                                             Chief Financial Officer

                                     PARKER DRILLING COMPANY OF COLOMBIA LIMITED

                                     By:
                                        ----------------------------------------
                                     Name:
                                     Title:

                                     INTERNATIONAL EQUIPMENT LEASING COMPANY

                                     By:
                                        ----------------------------------------
                                     Name:
                                     Title:

                                     CHASE BANK OF TEXAS, NATIONAL ASSOCIATION

                                     By:
                                        ----------------------------------------
                                     Name:
                                     Title:

                                      -3-
<PAGE>
                                   Exhibit A-1

         Each of the Subsidiary Guarantors under the Indenture (the "Indenture")
referred to in the Note upon which this notation is endorsed, has
unconditionally guaranteed the obligations of the Company under the Notes and
the Indenture, jointly and severally (each such guarantee being "Subsidiary
Guarantee"), to each Holder of a Note authenticated and delivered by the Trustee
irrespective of the validity or enforceability of the Indenture, the Notes or
the obligations of the Company under the Indenture or the Notes, that: (i) the
principal of, premium, if any, and interest on the Notes of every series issued
hereunder shall be paid in full when due, whether at the maturity or interest
payment or mandatory redemption date, by acceleration, call for redemption or
otherwise, and interest on the overdue principal and interest, if any, of the
Notes and all other obligations of the Company to the Holders or the Trustee
under the Indenture or the Notes shall be promptly paid in full or performed,
all in accordance with the terms of the Indenture and the Notes; and (ii) in
case of any extension of time of payment or renewal of and Notes or any of such
other obligations, they shall be paid in full when due or performed in
accordance with the terms of the extension or renewal, whether at maturity, by
acceleration or otherwise. Failing payment when due of any amount so guaranteed
for whatever reason, each Subsidiary Guarantor shall be obligated to pay the
same whether or not such failure to pay has become an Event of Default that
could cause acceleration pursuant to Section 6.02 of the Indenture. Each
Subsidiary Guarantor agrees that this is a guarantee of payment, not a guarantee
of collection. Capitalized terms used herein have the meanings assigned to them
in the Indenture unless otherwise indicated, and the obligations of the
Subsidiary Guarantors pursuant to the Subsidiary Guarantees are subject to the
terms of the Indenture, to which reference is hereby made for the precise terms
thereof. The obligations of each subsidiary Guarantor to the Holders of Notes
and to the Trustee pursuant to the Subsidiary Guarantee and the Indenture are
expressly set forth, and are senior unsecured obligations of each such
Subsidiary Guarantor to the extent and in the manner provided, in Article 10 of
the Indenture, and may be released or limited under certain circumstances.
Reference is hereby made to such Indenture for the precise terms of the
Subsidiary Guarantee therein made.

         The Subsidiary Guarantees shall not be valid or obligatory for any
purpose until the certificate of authentication on the Note on which the
Subsidiary Guarantees are noted shall have been executed by the Trustee under
the Indenture by the manual signature of one of its authorized officers.

         By each of the following, and any other Subsidiary Guarantor as may be
added or substituted from time to time, as Subsidiary Guarantors:

                                            Parker Drilling Company of Colombia
                                            Limited, Subsidiary Guarantor

                                            By:____________________________
                                            Its:

                                      -4-
<PAGE>
                                   Exhibit A-2

         Each of the Subsidiary Guarantors under the Indenture (the "Indenture")
referred to in the Note upon which this notation is endorsed, has
unconditionally guaranteed the obligations of the Company under the Notes and
the Indenture, jointly and severally (each such guarantee being "Subsidiary
Guarantee"), to each Holder of a Note authenticated and delivered by the Trustee
irrespective of the validity or enforceability of the Indenture, the Notes or
the obligations of the Company under the Indenture or the Notes, that: (i) the
principal of, premium, if any, and interest on the Notes of every series issued
hereunder shall be paid in full when due, whether at the maturity or interest
payment or mandatory redemption date, by acceleration, call for redemption or
otherwise, and interest on the overdue principal and interest, if any, of the
Notes and all other obligations of the Company to the Holders or the Trustee
under the Indenture or the Notes shall be promptly paid in full or performed,
all in accordance with the terms of the Indenture and the Notes; and (ii) in
case of any extension of time of payment or renewal of and Notes or any of such
other obligations, they shall be paid in full when due or performed in
accordance with the terms of the extension or renewal, whether at maturity, by
acceleration or otherwise. Failing payment when due of any amount so guaranteed
for whatever reason, each Subsidiary Guarantor shall be obligated to pay the
same whether or not such failure to pay has become an Event of Default that
could cause acceleration pursuant to Section 6.02 of the Indenture. Each
Subsidiary Guarantor agrees that this is a guarantee of payment, not a guarantee
of collection. Capitalized terms used herein have the meanings assigned to them
in the Indenture unless otherwise indicated, and the obligations of the
Subsidiary Guarantors pursuant to the Subsidiary Guarantees are subject to the
terms of the Indenture, to which reference is hereby made for the precise terms
thereof. The obligations of each subsidiary Guarantor to the Holders of Notes
and to the Trustee pursuant to the Subsidiary Guarantee and the Indenture are
expressly set forth, and are senior unsecured obligations of each such
Subsidiary Guarantor to the extent and in the manner provided, in Article 10 of
the Indenture, and may be released or limited under certain circumstances.
Reference is hereby made to such Indenture for the precise terms of the
Subsidiary Guarantee therein made.

         The Subsidiary Guarantees shall not be valid or obligatory for any
purpose until the certificate of authentication on the Note on which the
Subsidiary Guarantees are noted shall have been executed by the Trustee under
the Indenture by the manual signature of one of its authorized officers.

         By each of the following, and any other Subsidiary Guarantor as may be
added or substituted from time to time, as Subsidiary Guarantors:

                                        International Equipment Leasing Company,
                                        Subsidiary Guarantor

                                        By:____________________________
                                        Its:

                                      -5-

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