Exhibit 10.1

EXECUTION COPY

AMENDMENT NO. 1 AND AGREEMENT dated as of September 14, 2007 (this “Amendment”),
to the Unsecured Subordinated Credit Agreement dated as of September 7, 2007
(the “Credit Agreement”), among ATP OIL & GAS CORPORATION (the “Borrower”), the
Lenders (as defined therein) and CREDIT SUISSE, as administrative agent (in such
capacity, the “Administrative Agent”) for the Lenders.

A. Pursuant to the Credit Agreement, the Lenders have extended credit to the
Borrower.

B. The Borrower has requested that the existing Lenders or other persons that
will thereby become lenders (collectively, the “Additional Lenders”) make
Additional Loans (as defined below) to the Borrower on the Additional Loan
Closing Date (as defined below), in an aggregate principal amount of
$50,000,000, subject to the terms and conditions set forth herein.

C. The Borrower has further requested certain amendments to and other agreements
regarding the Credit Agreement as set forth herein.

D. The proceeds of the Additional Loans will be used by the Borrower to fund
near-term development and acquisition opportunities and other general corporate
purposes of the Borrower and its Subsidiaries.

E. The Additional Lenders are willing to make the Additional Loans, and the
Required Lenders are willing to agree to such amendments and other agreements,
in each case on the terms and subject to the conditions set forth herein.

F. Capitalized terms used but not defined herein shall have the meanings
assigned to them in the Credit Agreement.

Accordingly, in consideration of the mutual agreements herein contained and
other good and valuable consideration, the sufficiency and receipt of which are
hereby acknowledged, the parties hereto agree as follows:

SECTION 1. Defined Terms. As used in this Amendment, the following terms shall
have the meanings set forth below:

“Additional Loan Commitment” shall mean, with respect to each Additional Lender,
the commitment of such Additional Lender to make Additional Loans on the
Additional Loan Closing Date as set forth on Schedule I hereto. The aggregate
amount of Additional Loan Commitments shall be $50,000,000.

“Additional Loans” shall mean the term loans made by the Additional Lenders to
the Borrower pursuant to Section 2(a) hereof, the terms and provisions of which
shall be identical to the existing Loans.

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SECTION 2. Additional Loans. (a) Subject to the terms and conditions set forth
herein and relying upon the representations and warranties set forth herein and
in the Credit Agreement, each Additional Lender agrees, severally and not
jointly, to make an Additional Loan to the Borrower on the Additional Loan
Closing Date in a principal amount not to exceed its Additional Loan Commitment.
Amounts paid or prepaid in respect of Additional Loans may not be reborrowed.

(b) The Additional Loan Commitments shall automatically terminate upon the
earlier to occur of (a) the making of the Additional Loans on the Additional
Loan Closing Date and (b) 5:00 p.m., New York City time, on September 14, 2007.

(c) Unless the context shall otherwise require, the term “Loans” as used in the
Credit Agreement shall include the Additional Loans (provided that the
Additional Loans shall bear interest from and including the Additional Loan
Closing Date), and the term “Lenders” as used herein and in the Credit Agreement
shall include each person that has an Additional Loan Commitment or that has
made an Additional Loan (other than any such person that has ceased to be a
party to the Credit Agreement pursuant to an Assignment and Acceptance).

SECTION 3. Amendments. (a) Section 1.01 of the Credit Agreement is hereby
amended by deleting the following terms and related definitions: “Right of First
Refusal Notice”, “Subsequent Financing”, “Rights Option” and “Option Period”.

(b) Section 5.04(j) of the Credit Agreement is hereby amended by deleting the
words “any Loan Document” therein and substituting therefor the words “this
Agreement (including any amendment thereto or promissory note issued
thereunder)”.

(c) Section 6.01(b)(x) of the Credit Agreement is hereby deleted and the word
“[Reserved]” substituted therefor.

(d) Section 10.07 of the Credit Agreement is hereby amended by deleting the
words “AND THE OTHER LOAN DOCUMENTS (OTHER THAN LETTERS OF CREDIT AND AS
EXPRESSLY SET FORTH IN OTHER LOAN DOCUMENTS OR TO THE EXTENT THE LAWS OF ANOTHER
JURISDICTION MANDATORILY GOVERN ANY LOAN DOCUMENT)” therein.

SECTION 4. Other Agreement. Pursuant to Section 10.08(b) of the Credit
Agreement, the Required Lenders hereby agree that the Additional Loans shall
constitute “Indebtedness Incurred hereunder” for purposes of Section 6.01(b)(ii)
of the Credit Agreement.

SECTION 5. Representations and Warranties. To induce the other parties hereto to
enter into this Amendment, the Borrower represents and warrants to the
Administrative Agent and each of the Lenders that, as of the Amendment Effective
Date:

(a) This Amendment has been duly authorized, executed and delivered by the
Borrower and the Credit Agreement, as amended hereby, constitutes a legal, valid
and binding obligation of the Borrower, and this Amendment constitutes a legal,
valid and binding obligation of the Borrower.

 

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(b) The representations and warranties set forth in Article III of the Credit
Agreement are true and correct in all material respects on and as of the
Amendment Effective Date with the same effect as though made on and as of the
Amendment Effective Date, except to the extent such representations and
warranties expressly relate to an earlier date (in which case such
representations and warranties were true and correct in all material respects as
of such earlier date).

(c) No Default or Event of Default has occurred and is continuing.

SECTION 6. Effectiveness. (a) This Amendment shall become effective as of the
date first set forth above on the date (the “Amendment Effective Date”) that the
Administrative Agent (or its counsel) shall have received counterparts of this
Amendment that, when taken together, bear the signatures of the Borrower, the
Administrative Agent, the Required Lenders, and each Additional Lender.

(b) The obligations of the Lenders with Additional Loan Commitments to make
Additional Loans are subject to the satisfaction of each of the following
conditions (the date on which such conditions are satisfied, the “Additional
Loan Closing Date”):

(i) The Administrative Agent shall have received a notice of the borrowing of
the Additional Loans that satisfies the requirements of Section 2.03 of the
Credit Agreement.

(ii) The representations and warranties set forth in Article III of the Credit
Agreement shall be true and correct in all material respects on and as of the
date of such borrowing with the same effect as though made on and as of such
date, except to the extent such representations and warranties expressly relate
to an earlier date (in which case such representations and warranties were true
and correct in all material respects as of such earlier date).

(iii) The Borrower shall be in compliance with all the terms and provisions set
forth herein and in the Credit Agreement on its part to be observed or performed
at or prior to the time of such borrowing, and at the time of and immediately
after such borrowing, no Event of Default or Default shall have occurred and be
continuing.

(iv) The Administrative Agent shall have received, on behalf of itself and the
Lenders, a favorable written opinion of Jackson Walker L.L.P., counsel for the
Borrower, (A) dated the Additional Loan Closing Date, (B) addressed to the
Administrative Agent and the Lenders and (C) covering such other matters
relating to this Amendment and the transactions contemplated hereby as the
Administrative Agent shall reasonably request, and otherwise in form and
substance reasonably satisfactory to the Administrative Agent, and the Borrower
hereby requests such counsel to deliver such opinion.

 

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(v) All legal matters incident to this Amendment and to the borrowing of the
Additional Loans shall be satisfactory to the Lenders and to the Administrative
Agent.

(vi) The Administrative Agent shall have received (A) a certificate, dated the
Additional Loan Closing Date and signed by the Secretary or Assistant Secretary
of the Borrower, certifying that (1) except as set forth on any schedule
attached thereto, the certificate or articles of incorporation of the Borrower
previously delivered pursuant to the Credit Agreement on September 7, 2007 (the
“Prior Closing Date”) have not been amended since the date of such delivery,
(2) except as set forth on any schedule attached thereto, the by-laws of the
Borrower as in effect and delivered on the Prior Closing Date have not been
amended since the date of such delivery, (3) attached thereto is a true and
complete copy of resolutions duly adopted by the Board of Directors of the
Borrower authorizing the execution, delivery and performance of this Amendment
and the borrowing of the Additional Loans, and that such resolutions have not
been modified, rescinded or amended and are in full force and effect,
(4) attached thereto is a certificate as to the good standing of the Borrower as
of a recent date by the Secretary of State (or other similar official) of the
jurisdiction of its organization, and (5) as to the incumbency and specimen
signature of each officer executing this Amendment or any other document
delivered in connection herewith on behalf of the Borrower; (B) a certificate of
another officer as to the incumbency and specimen signature of the Secretary or
Assistant Secretary executing the certificate pursuant to clause (A) above; and
(C) such other documents as the Lenders or the Administrative Agent may
reasonably request.

(vii) The Administrative Agent shall have received a certificate dated the
Additional Loan Closing Date and signed by a Financial Officer of the Borrower,
confirming compliance with the conditions precedent set forth in paragraphs
(ii) and (iii) of this Section 6(b).

(viii) The Administrative Agent shall have received a certificate dated the
Closing Date and signed by the chief financial officer of the Borrower,
certifying that the Borrower, after giving effect to the transactions
contemplated hereunder, is solvent.

(ix) The Administrative Agent shall have received all fees and other amounts due
and payable on or prior to the Additional Loan Closing Date, including, to the
extent invoiced, reimbursement or payment of all reasonable out-of-pocket
expenses required to be reimbursed or paid by the Borrower hereunder or under
the Credit Agreement and the fees, charges and disbursements of Kramer Levin
Naftalis & Frankel LLP, counsel for the Lenders, in connection with this
Amendment.

 

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SECTION 7. Effect of Amendment. Except as expressly set forth herein, this
Amendment shall not by implication or otherwise limit, impair, constitute a
waiver of or otherwise affect the rights and remedies of the Lenders or the
Administrative Agent under the Credit Agreement or any other document related
thereto, and shall not alter, modify, amend or in any way affect any of the
terms, conditions, obligations, covenants or agreements contained in the Credit
Agreement or any other document related thereto, all of which are ratified and
affirmed in all respects and shall continue in full force and effect. Nothing
herein shall be deemed to entitle the Borrower to a consent to, or a waiver,
amendment, modification or other change of, any of the terms, conditions,
obligations, covenants or agreements contained in the Credit Agreement or any
other document related thereto in similar or different circumstances. This
Amendment shall apply and be effective only with respect to the provisions of
the Credit Agreement specifically referred to herein. After the date hereof, any
reference to the Credit Agreement shall mean the Credit Agreement, as modified
hereby. This Amendment shall be deemed to constitute part of the Credit
Agreement for all purposes of the Credit Agreement and any other document
related thereto.

SECTION 8. Counterparts. This Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed and delivered shall be deemed an original, but all such
counterparts together shall constitute but one and the same contract. Delivery
of an executed counterpart of a signature page of this Amendment by facsimile
transmission shall be as effective as delivery of a manually executed
counterpart hereof.

SECTION 9. Applicable Law. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

SECTION 10. Headings. The headings of this Amendment are for purposes of
reference only and shall not limit or otherwise affect the meaning hereof.

SECTION 11. Expenses. The Borrower agrees to reimburse (i) the Administrative
Agent for all reasonable out-of-pocket expenses incurred in connection with this
Amendment, including the reasonable fees, charges and disbursements of Cravath,
Swaine & Moore LLP, counsel for the Administrative Agent, and (ii) Kramer Levin
Naftalis & Frankel LLP, counsel for the Lenders as of the date of this Amendment
for all reasonable out-of-pocket expenses incurred in connection with this
Amendment.

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

 

ATP OIL & GAS CORPORATION

By

 

 

Name:

 

Title:

 

 

[Subordinated Amendment - ATP]

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CREDIT SUISSE, CAYMAN ISLANDS

BRANCH, individually as an Additional Lender

and as Administrative Agent

By

 

 

Name:

 

Title:

 

By

 

 

Name:

 

Title:

 

 

[Subordinated Amendment - ATP]

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SIGNATURE PAGE TO

AMENDMENT NO. 1 AND AGREEMENT

TO ATP OIL & GAS CORPORATION

UNSECURED SUBORDINATED

CREDIT AGREEMENT

 

Name of Lender:

  SOF INVESTMENTS, L.P.

By

 

 

Name:

 

Title:

 

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SCHEDULE I

LENDERS AND ADDITIONAL LOAN COMMITMENT

 

Additional Lender

  

Additional

Loan Commitment

Credit Suisse

   $ 50,000,000

Total

   $ 50,000,000