EXHIBIT 10.1(A)

                              MARCIA BARBOSA SERRA
             Tradutora Publica Juramentada e Interprete Comercial
              Sworn Public Translator and Commercial Interpreter
                 Rua Aperana, 38 apt 301 - Leblon - 22450-190
                       ISS: 1261003-00 - CIC: 606442227-00
                                 Tel.: 274-3844

I, the undersigned, Sworn Public Translator and Commercial Interpreter in and
for this City and State of Rio de Janeiro, Federative Republic of Brazil,
registered at the Commercial Board of Rio de Janeiro under Number 97, do hereby
CERTIFY and ATTEST that a document in the Portuguese Language was submitted to
me for translation into English, which I performed according to my Office, as
follows:

                             Translation No. 2661/98

(On paper with letter of PETROBRAS.)./.

           RIDER No. 01 FOR THE ASSIGNMENT OF RIGHTS
           AND OBLIGATIONS ARISING FROM CONTRACT
           101.2.155.97-9, ENTERED INTO BETWEEN
           MARITIMA PETROLEO E ENGENHARIA LTDA.,
           SUCCESSOR OF MARITIMA NAVEGACAO E
           ENGENHARIA LTDA., and PETRODRILL SEVEN
           LTD., WITH THE CONSENT OF PETROLEO
           BRASILEIRO S.A.-PETROBRAS./.

PETROLEO BRASILEIRO S.A. - PETROBRAS, a mixed economy company, with head office
at Av. Republica do Chile 65, in the City of Rio de Janeiro, State of Rio de
Janeiro, Federative Republic of Brazil, enrolled in the General Taxpayers
Registry of the Ministry of Finance under No. 33.000.167/0001 01, henceforth
called PETROBRAS, represented herein by the Executive Superintendent of
Exploration and Production, Luiz Eduardo G. Carneiro, and the Company MARITIMA
PETROLEO E ENGENHARIA LTDA., successor of MARITIMA NAVEGACAO E ENGENHARIA LTDA.,
with head office at Av. Almirante Barroso, 52, Group 3400, City of Rio de
Janeiro, Federative Republic of Brazil, enrolled in the General Taxpayers
Registry of the Ministry of Finance under No. 46.828.596/0001/13, henceforth
called the ASSIGNOR, represented herein by its President, German Efromovich, and
the company PETRODRILL SEVEN LTD., with head office in Omar Hodge Building,
Wickhams Cay, Road Town, Tortola, Ilhas Virgens Britanicas, henceforth called
the ASSIGNEE, represented herein by its Director, German Efromovich, have agreed
to add a rider to contract 101.2.155.97-9 (AMETHYST 7), according to the
following clauses and conditions:/.


FIRST CLAUSE OBJECT./.

1.       The present Rider has as its object:/.

1.1.1    The total assignment, as of the date of the signature of this Rider,
         henceforth called the ASSIGNMENT DATE, by the ASSIGNOR to the ASSIGNEE
         of the rights and obligations arising from Contract No. 101.2.155.97-9
         and its Attachments./.

1.1.2.   To change the contract value foreseen in item 5.2 of the Fifth Clause-
         PRICES AND VALUE./.

1.1.3.   To change the redaction of the Seventh Clause-FORM OF PAYMENT./.

1.1.4.   To change the Fourth Clause-PETROBRAS OBLIGATIONS, including item
         4.12./.

SECOND CLAUSE-RESPONSIBILITY./.

2.1.     The ASSIGNEE, as of the ASSIGNMENT DATE, becomes the CONTRACTOR, being
         liable, before PETROBRAS for the fulfillment of all contract
         obligations undertaken by the ASSIGNOR, and will also have all rights
         arising from the Contract./.

2.2.     The ASSIGNEE is liable before PETROBRAS for the fulfillment of all
         contract obligations undertaken by the ASSIGNOR in the Contract, as
         well as for eventual losses and damages arising from its acts or
         omissions./.

2.3.     The ASSIGNOR will be jointly liable with the ASSIGNEE for the complete
         fulfillment of all obligations arising from the Contract./.

2.4.     The ASSIGNOR, as of the ASSIGNMENT DATE, will have no right arising
         from the Contract, giving PETROBRAS, full and complete acquittance for
         any and all contract value./.

THIRD CLAUSE-PRICES AND VALUE./.


3.1. The redaction of item 5.2 and its

           subitems becomes:/.

           "5.2.  The total estimated value of the present Contract becomes US$
                  317,145,762.45 (three hundred and seventeen million, one
                  hundred and forty-five thousand, seven hundred and sixty-two
                  dollars and forty-five cents), equivalent to R$

                  348,035,759.91 (three hundred

                  forty-eight million, thirty-five thousand, seven hundred and
                  fifty-nine reais and ninety-one cents), converted at the
                  exchange rate of R$ 1,0974/US$1,00, referring to the
                  following charges:/.

3.2. Item 5.5 is included with the following

         redaction:/.

          "5.5. Besides the value mentioned in
          5.2, the appropriation of
          US$100,000.00 is foreseen for the
          payment of eventual
          reimbursements"./.

FOURTH CLAUSE-PETROBRAS' OBLIGATIONS./.

4.1. Item 4.12 is included, with the following

         redaction:/.

          "4.12.  To adopt the measures necessary for the request to register
                   this Contract at the Central Bank of Brazil, immediately
                   after the receipt of the legal documents, the supply of which
                   is the CONTRACTOR's responsibility.".

FIFTH CLAUSE-FORM OF PAYMENT./.

5.1. The redaction of the Seventh Clause is changed to:/.

          "7.1 The payments of the rates foreseen in Attachment II and
          Attachment III shall be made by PETROBRAS to the CONTRACTOR in
          American Dollars, by bank remittance to a bank account abroad it
          indicates, after the present Contract is registered at the Central
          Bank of Brazil, 30 (thirty) days as of the date of the end of the
          measuring period considered, provided the CONTRACTOR has fulfilled the
          time limits set forth in subitem 6.3.1., for the submittal of the
          collection documents at the docket of the Financial Department
          indicated by PETROBRAS, with exception of the provision appearing in
          subitem 7.2.4./.


          7.1.1. For the reimbursable expenses foreseen in this Contract, the
          instructions contained in item 7.4 and their developments should be
          complied with, and the payments will be made in the currency of origin
          of said expenses, within 30 (thirty) days after the submittal of the
          collection documents at the docket of the Financial Department
          indicated by PETROBRAS./.

          7.1.2. Collection documents comprise any type of billing, such as:
          Invoice, Invoice with separate Bill of Sale, Service Invoice, besides
          others foreseen in fiscal laws./.

         7.1.3. For payment purposes, the CONTRACTOR shall supply the Contract
Manager, after its signature, the following information:/.

               a)   Bank name and number;/.

               b)   Bank branch name and code;/.

               c)   Bank branch address;/.

               d)   CONTRACTOR's current account number./

             7.1.3.1. Whenever a billing is submitted with information
             different from those indicated in subitem 7.1.3, these changes will
             only be considered if accompanied by a formal communication by the
             CONTRACTOR and shall prevail only for the specific purpose of such
             payment.

         7.2. The collection documents shall be issued without erasures,
complying with the pertinent laws in force, for submittal at the Financial
Department indicated in item 7.1 of this Clause, in its original copy,
accompanied by 1 (one) copy of the respective Measurement Bulletin (MB), and/or
Reimbursement Document (RD), as the case may be, duly approved by this
contract's Manager, containing, obligatorily, but not exclusively, the following
information:/.

                a)   Number of the collection document;/.

                b)   Place and date of its issuing;/.

                c)   Brief description of the object of this Contract;/.

                d)   Indication of the number and date of this Contract;/.

                e)   Indication of the month/year or period which the collection
                     document refers to;/.


                f)   Number and date of the Measurement Bulletin (MB) and/or
                     Reimbursement Document (RD)./.

                g)   Place of the rendering and/or execution of the chartering.
                     In the event the chartering has been rendered in different
                     locations, its value should be broken down by locations of
                     performance and the period in which it was rendered at each
                     of the locations shall be indicated;/.

                h)   Gross amount of the collection document, by numbers and in
                     writing;/.

                i)   Place for payment purpose, as provided for in subitem
                     7.1.3 of this Clause;/.

                j)   Signature by the CONTRACTOR'S representative, accredited
                     before PETROBRAS, above his/her name and position
                     typewritten or above the CONTRACTOR'S company stamp
                     identifying him/her;/.

                l)   In case of Rider or Letter of Agreement to the Contract
                     which implies in payments, mention its number and date of
                     signature, besides the data above./.

            7.2.1. The omission of any of the above mentioned data will cause,
           within 5 (five) working days, the return of the collection documents
           by PETROBRAS' Financial Department./.

            7.2.2. If the above situation occurs and in case the collection
          document shows errors, it will be returned to the CONTRACTOR, and the
          time limits for the payment foreseen in item 7.1 and subitem 7.1.1
          shall be added to the period that becomes necessary for the
          explanation and re-submittal of the collection document./.

             7.2.2.1. The above mentioned condition also applies in case the
             collection document is submitted in another department, and not as
             indicated in item 7.1./.

            7.2.3. Independent of the data above, the invoices in foreign
          currency shall be also submitted in the Portuguese language , or if
          issued abroad, they shall be notarizes at the Brazilian Consulate,
          under which jurisdiction the CONTRACTOR is located, and translated by
          a sworn public translator./.

7.2.4. The CONTRACTOR shall, obligatorily, submit monthly, together with the
invoice, the payroll of the CONTRACTOR's Brazilian crew who are involved in the
chartering object of this Contract, as well as with a photocopy of the GRPS
(Social Security Payment Slip), duly settled and authenticated, with the data
identifying the entity to whom the service was rendered being obligatorily
filled out, informing in field 8 of the GRPS (other information) PETROBRAS'
name and CGC, number, date, and amount of the invoice or bill of sale referring
to the chartering rendered in the month, subitems 8.9, 10.1.15, and 10.1.16
being also complied with./.


7.3.     The collection documents referring to reimbursements shall also be
         issued, itemizing, individually, the reimbursable expenses, their total
         amount, such itemization also to appear in the respective Reimbursement
         Document (RD)./.

7.3.1.   The original vouchers of the reimbursable expenses due to the
         CONTRACTOR, by force of the contract instrument, shall be previously
         submitted to the Contract Manager, for checking, besides being duly
         paid for by the respective supplier or service rendered, when such is
         the case./.

7.3.1.1. In the event the original vouchers cannot remain in PETROBRAS'
possession, copies thereof may be submitted, which shall be checked by the
Contract Manager, and the following text is to be placed on each original
document: "COPY SUBMITTED FOR REIMBURSEMENT ON (specify date)", followed by
the signature and identification by name, position and registry number, and the
original are to be returned to the CONTRACTOR.
 In the copies that are in PETROBRAS' possession, the following text will be
place on each document: "CHECKED WITH THE ORIGINAL ON (specify the data)" and
the Contract Manager will sign, identifying the signature by name, position
and registry number./.

 7.3.1.2.    The receipt, duly made formal by PETROBRAS, of any reimbursable
             expense voucher, does not represent the recognition of debt, nor
             the proof that the expense has been made./.

 7.3.2.      The collection of reimbursable expenses can only be made by means
             of issuing and submittal, by the CONTRACTOR, of the Bill of Sale
             for the equipment and accessories, with the respective
             Reimbursement Document (RD) duly attached thereto, and previously
             approved by the Contract Manager./.

 7.3.2.1.    The submittal of the collection document mentioned in subitem
             7.3.2, shall comply with the provisions appearing in items 7.1. and
             7.2 of this Clause./.

 7.3.2.2.    The vouchers shall be legal documents to explain doubts referring
             to the collections, which shall be settled, as a last resort, by
             PETROBRAS' Disbursement Office, who will be in possession of the
             vouchers approved by PETROBRAS to prepare the payment process./.

 7.4.        Eventual payments made for more or for less by PETROBRAS shall be
             compensated as soon as they are detected, by issuing the Debit/
             Credit Notes, as the case may be./.

7.5. The amounts corresponding to reimbursable expenses, without budget
allotment foreseen in this contract instrument, do not burden this contract's
estimated total, but should, however, be foreseen in the Budget Programs of the
Executive Superintendence of Exploration and Production (E&P)./.


          7.6.     The collection documents submitted by the CONTRACTOR, as well
                   as the final collection document, shall be paid with the
                   deduction of amounts that, at any title, under the conditions
                   set forth in the contract, or others specially agreed upon,
                   that are due to PETROBRAS./.

          7.7.     The CONTRACTOR agrees that, at PETROBRAS exclusive option,
                   the present Contract can be paid by means of third party
                   financing, provided the time limits, currency amounts, and
                   place of payment, and the CONTRACTOR's rights foreseen in
                   this Contract, are complied with"./.

SIXTH CLAUSE-RESPONSIBILITY./.

6.1 The present rider brinds the parties as of the date of its signature and
enters in force as of the ASSIGNMENT DATE./.

SEVENTH CLAUSE-RATIFICATION./.

 7.1.     PETROBRAS, the ASSIGNOR and the ASSIGNEE ratify the terms and
          conditions of the Contract that are not incompatible with the
          provisions of this instrument./.

     And being thus agreed, the parties sign the present Rider in 4 (four)
copies of the same tenor and fashion, together with the witnesses below./.

Rio de Janeiro, July 10, 1998./.

(Signed:) (Illegible)-Luiz Eduardo G. Carneiro./.
Executive Superintendent of Exploration and Production South-Southeast./.
PETROLEO BRASILEIRO S.A./.
(Signed:) (Illegible) - German Efromovich./.
President - MARITIMA PETROLEO E ENGENHARIA LTDA (ASSIGNOR)./.
(Signed:) (Illegible) - German Efromovich./.
Director - PETRODRILL SEVEN LTD. (ASSIGNEE)./.
WITNESSES:/.
(Signed:) Victor Archer (Rubber stamp:) Victor Archer - Administrator-Registry
012730-0./.
(Signed:) (Illegible)./.

      (The rubber stamp and the initials of Victor Archer appeared on the first
 page of the document.)/.

      (An initial appeared on all pages of the documents.)/.
 .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
(.-THESE BEING) the precise terms and content of the aforementioned document, I
hereby set my Hand and Seal on this Translation, performed on November 20, 1998
in this City of Rio de Janeiro, Federative Republic of Brazil.
                            ------------------------

                          /s/ MARCIA BARBOSA SERRA
                              Marcia Barbosa Serra
                             Sworn Public Translator