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                                                                    EXHIBIT 3.18

                            ARTICLES OF INCORPORATION

                                       OF

                               CALPRODUCSUB, INC.


                                        I

         The name of this corporation is CALPRODUCSUB, INC.

                                       II

         (A)     The specific business in which this corporation is primarily
to engage is the oil well servicing and supply business.

         (B)     The general purposes and powers of this corporation are as
follows:

                 1.       To take, purchase, contract for, design, construct,
manufacture, lease or otherwise to acquire, to own, hold, use, operate and
maintain, and to sell, lease, exchange, hypothecate or otherwise dispose of or
deal in equipment, machinery, tools, parts, plants, factories, warehouses and
any other products, commodities or facilities.

                 2.       To make, enter into, perform, carry out and enforce
contracts, understandings and agreements of every kind, character and
description for any lawful purpose, without limit as to amount, with any one or
more individuals, partnerships, firms, associations, trusts or corporations, or
with governments or governmental authorities or agencies, whether foreign,
federal, state, municipal, local or otherwise, or with any public or municipal
corporations.

                 3.       To take, purchase, contract for or acquire by gift,
lease, grant, exchange, permit or otherwise, to own, hold, use, occupy, manage,
control, work, improve,





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develop, exploit, operate, subdivide, deal in or otherwise turn to account, and
to sell, lease, exchange, grant, convey, transfer, assign, mortgage, deed in
trust or otherwise hypothecate or dispose of real estate and real property and
any estate, right, title or interest therein and any buildings, tenements,
structures and improvements of whatsoever nature thereon, wheresoever situated.

                 4.       To take, purchase, contract for, lease or otherwise
acquire, to own, hold, use, possess, control and improve, to sell, lease,
exchange, grant, transfer, assign, deal in or otherwise turn to account and to
mortgage, deed in trust, pledge or otherwise hypothecate or dispose of goods,
wares, merchandise, products, articles and other personal property of every
kind, class, character and description, tangible or intangible, wheresoever
situated.

                 5.       To obtain, secure and accept from any governments or
governmental authorities or agencies, whether foreign, federal, state,
municipal, local or otherwise, or from any public or municipal corporations,
any rights, privileges, franchises, immunities, concessions, permits, licenses
and grants, and to carry out, exercise, enforce and enjoy, and to assign,
relinquish, transfer or otherwise dispose of the same.

                 6.       To form, promote, subsidize, organize, enter into,
control, or participate in corporations, joint stock companies, trusts,
associations, general or limited partnerships, joint ventures, firms and other
organizations.

                 7.       To take, purchase, contract for, or otherwise
acquire, and to own, hold, possess, enjoy or otherwise turn to account debts,
claims, demands, judgments and choses and things in action of every kind,
class, character and description, and while the





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owner or holder thereof to exercise all of the rights, powers, privileges and
remedies of or incident to ownership or possession, including the right to
enforce payment and to compromise or to forgive the same, and to sell, assign,
transfer, deliver, exchange or otherwise dispose of the same, either as
security or absolutely, to the same extent as a natural person might or could
do.

                 8.       To develop, apply for, obtain, register, purchase,
lease or otherwise acquire, and to own, hold, use, exercise, develop, maintain,
operate and introduce, and to sell, assign, grant licenses, territorial rights
or other rights in respect of or otherwise turn to account or dispose of any
copyrights, trade marks, trade names, brands, labels or other distinctive marks
similar thereto, patent rights, letters patent of the United States or of any
other country or government, and any inventions, improvements, processes,
formulas and the like, whether used in connection with or secured under letters
patent or otherwise.

                 9.       To purchase, subscribe for or otherwise acquire; to
hold, invest in, sell, assign, transfer, exchange, pledge or otherwise dispose
of shares of stock, bonds, voting trust certificates or other securities or
evidence of indebtedness or ownership of any corporation organized under the
laws of the State of California or of any other state, country, nation or
government; to pay therefor, in whole or in part, with cash or other property
or with shares, bonds or other securities or obligations of this corporation,
and, while the owner or holder thereof, to possess and exercise in respect
thereof all the rights, powers and privileges of ownership, including the right
to vote thereon and to consent in respect thereof, for any and all purposes.





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                 10.      To lend money, services or property to, and to
promote, aid and assist, financially or otherwise, corporations, partnerships,
joint ventures, joint stock companies, syndicates, trustees, associations and
individuals to the extent legally permissible under the laws of the State of
California, and to a like extent to endorse or underwrite the shares, bonds,
debentures, notes, securities or other obligations or undertakings of any
corporation, partnership, joint venture, joint stock company, association,
syndicate, trustee or individual, and to guarantee the payment of any dividends
on shares or the principal or interest on bonds, notes, debentures or other
obligations or the performance of any corporation, partnership, joint venture,
joint stock company, association, syndicate, trustee or individual.

                 11.      To acquire by purchase, or otherwise, the good will,
business, property, rights, franchises and assets of any kind of any person,
firm, association or corporation, with or without undertaking either wholly or
in part his or its liabilities, and to hold, maintain, conduct and operate and
to sell or otherwise dispose of the whole or any part of the good will,
business, property, rights, franchises and assets so acquired.

                 12.      To join and become a party to and to participate in
any plan or agreement for the reorganization, the readjustment of the capital
structure or the composition of creditors of any corporation whose shares,
voting trust certificates, bonds or other securities or evidences of
indebtedness or ownership or obligations this corporation may own, hold, or
possess, and the exercise and enjoy any and all rights, powers and privileges
under any such plan or agreement to the same extent that an individual might or
could do.

                 13.      To borrow money, without limitation as to amount, and
to issue bonds, debentures, notes, checks, bills of exchange, drafts, receipts,
warrants, certificates,





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negotiable or transferable instruments or obligations of any kind, whether
secured or unsecured, for moneys so borrowed or in payment for any property
acquired or for any of the other objects or purposes or in connection with the
business of this corporation, and to secure such bonds, debentures, notes or
other obligations by mortgage, deed of trust, pledge, assignment or other lien
upon any or all of the properties, rights, privileges, franchises, or assets of
the corporation, wheresoever situated.

                 14.      To act as broker, factor, agent or representative in
any matter, business or transaction for any individual, partnership, joint
venture, association, trust, syndicate or corporation.

                 15.      To carry on any business whatsoever, either as
principal or as agent or both as a partnership, which this corporation may deem
proper or convenient in connection with any of the foregoing purposes or
otherwise, or which may be calculated directly or indirectly to promote the
interests of this corporation or to enhance the value of its property or
business; to conduct its business in this state, and other states, in the
District of Columbia, in the Territories and colonies of the United States, and
in foreign countries.

                 16.      To have and to exercise all the powers conferred by
the laws of California upon corporations formed under the laws pursuant to and
under which this corporation is formed, as such laws are now in effect or may
at any time hereafter be amended.

                 The foregoing statement of purposes shall be construed as a
statement of both purposes and powers, and the purposes and powers stated in
each clause shall, except where otherwise expressed, be in nowise limited or
restricted by reference to or inference from the





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terms or provisions of any other clause, but shall be regarded as independent
purposes and powers.


                                      III

         The County in the State of California where the principal office for
the transaction of business of this corporation is to be located is Los Angeles
County.


                                       IV

         The number of directors of this corporation shall be three.  The names
and addresses of the persons who are appointed to act as the first directors of
this corporation are:

         Vernice J. Spinks            1858 West 71st Street
                                      Los Angeles, Calif.  90047

         Laura J. Luttrell            10514 National Boulevard
                                      Los Angeles, Calif.  90034

         Britt E. Holmberg            10554 Wilshire Boulevard
                                      Los Angeles, Calif.  90024


                                       V

         This corporation is authorized to issue only one class of shares of
stock, designated "Common Stock".  The total number of such authorized shares
shall be 200,000.  Each of such shares shall have a par value of $1.00, and the
aggregate par value of all such shares shall be $200,000.00.  No distinction
shall exist between the shares of this corporation or the rights of the
respective holders thereof.





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         IN WITNESS WHEREOF, for the purposes of forming this corporation under
the laws of the State of California, we, the undersigned, constituting the
incorporators of this corporation and the persons named herein as the first
directors of this corporation, have executed these Articles of Incorporation
this 15th day of May, 1973.

                                            /s/ VERNICE J. SPINKS
                                            ------------------------------------
                                            Vernice J. Spinks


                                            /s/ LAURA L. LUTTRELL
                                            ------------------------------------
                                            Laura L. Luttrell


                                            /s/ BRITT E. HOLMBERG
                                            ------------------------------------
                                            Britt E. Holmberg


STATE OF CALIFORNIA               )
                                  )ss.
COUNTY OF LOS ANGELES             )

         On May 15, 1993, before me, the undersigned, a Notary Public in and
for said County and State, personally appeared Vernice J. Spinks, Laura L.
Luttrell and Britt E. Holmberg, known to me to be the persons whose names are
subscribed to the foregoing Articles of Incorporation, and acknowledged to me
that they executed the same.

         WITNESS my hand and official seal.


                                            /s/
                                            ------------------------------------
                                                 Notary Public in and for
                                                 said County and State
                                                 [NOTARY SEAL AFFIXED HERE]




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                               CALPRODUCSUB, INC.


                            CERTIFICATE OF AMENDMENT
                                       OF
                           ARTICLES OF INCORPORATION

Robert D. Hillman and Charles R. Brockman certify:

         1.      That they are the president and the secretary-treasurer,
respectively, of CALPRODUCSUB, INC., a California corporation.

         2.      That at a meeting of the board of directors of said
corporation, duly held at Compton, California, on May 25, 1973, the following
resolution was adopted:

         "RESOLVED, that Article I of the Articles of Incorporation of this
corporation be amended to read as follows:

                                       I

         The name of this corporation is California Production Service, Inc."

         3.      That the shareholders have adopted said amendment by written
consent.  That the wording of the amended article, as set forth in the
shareholders' written consent, is the same as that set forth in the directors'
resolution in Paragraph 2 above.

         4.      That the number of shares represented by written consent is
200,000.  That the total number of shares entitled to vote on or consent to the
amendment is 200,000.

                                            /s/ ROBERT D. HILLMAN
                                            ------------------------------------
                                            Robert D. Hillman, President
                                            /s/ CHARLES R. BROCKMAN
                                            ------------------------------------
                                            Charles R. Brockman,
                                            Secretary-Treasurer

         Each of the undersigned declares under penalty of perjury that the
matters set forth in the foregoing certificate are true and correct.  Executed
at Compton, California, on May 25, 1973.
                                            /s/ ROBERT D. HILLMAN
                                            ------------------------------------
                                            Robert D. Hillman
                                            /s/ CHARLES R. BROCKMAN
                                            ------------------------------------
                                            Charles R. Brockman
   9





                            CERTIFICATE OF OWNERSHIP
                                    MERGING
                        Robert B. Doe Oil Field Service
                                      INTO
                      California Production Service, Inc.


         Alan B. Matt, Vice President, and June C. Scott, Secretary of
California Production Service, Inc., a California corporation, certify that:

         1.      California Production Service, Inc. owns 100 percent of the
outstanding stock of Robert B. Doe Oil Field Service, a California corporation.

         2.      The following resolutions were adopted by the Board of
Directors of California Production Service, Inc.:

                 WHEREAS, this corporation owns 100 percent of the outstanding
         stock of Robert B. Doe Oil Field Service, a California corporation;
         and

                 WHEREAS, it is deemed in the best interests of this
         corporation and its shareholders that this corporation merge Robert B.
         Doe Oil Field Service into itself pursuant to Section 1110 of the
         California Corporations Code and assume all of its obligation,

                 NOW, THEREFORE, BE IT RESOLVED, that this corporation merge
         Robert B. Doe Oil Field Service into itself as of the effective date
         of the Certificate of Ownership to be filed pursuant to Section 1110
         of the California Corporations Code; and

                 RESOLVED FURTHER, that this corporation hereby assumes all the
         liabilities of Robert B. Doe Oil Field Service; and

                 RESOLVED FURTHER, that the Vice President and Secretary of
         this corporation are directed to execute and file a Certificate of
         Ownership pursuant to Section 1110 of the California Corporations Code
         and to take such further actions as may be necessary or proper to
         accomplish such merger.


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         3.      Said resolutions were adopted by unanimous written consent of
the Directors of California Production Service, Inc., on December 4, 1984.

                                        /s/ ALAN B. MATT
                                        -------------------------------
                                        Alan B. Matt
                                        Vice President, Finance


                                        /s/ JUNE M. SCOTT
                                        -------------------------------
                                        June M. Scott
                                        Secretary


                                  Verification

Alan B. Matt and June M. Scott say:

         They are the Vice President and Secretary respectively of California
Production Service, Inc., a California corporation.

         They have read the foregoing Certificate of Ownership and know the
contents thereof.

         The same is true of their own knowledge.

         Executed on December 4, 1984, at Rancho Dominguez, Los Angeles County,
California.

         We declare under penalty of perjury that the foregoing is true and
correct.

                                        /s/ ALAN B. MATT
                                        -------------------------------
                                        Alan B. Matt

                                        /s/ JUNE M. SCOTT
                                        -------------------------------
                                        June M. Scott





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                            CERTIFICATE OF AMENDMENT
                                       OF
                            ARTICLES OF INCORPORATION
                                       OF
                       CALIFORNIA PRODUCTION SERVICE, INC.


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



The undersigned, J. T. Jongebloed and G. G. Arms do hereby certify:

1.       That they are the President and the Corporate Secretary, respectively,
         of California Production Service, Inc., a California corporation.

2.       That an amendment to the Articles of Incorporation of this corporation
         has been approved by the Board of Directors.

3.       That the amendment so approved by the Board of Directors is as follows:

         Article I of the Articles of Incorporation of this corporation is
         amended to read as follows:

                  "The name of this corporation is Pool California Energy
                  Services, Inc."

4.       That the shareholders have adopted said amendment by written consent.
         That the wording of said amendment as approved by written consent of
         the shareholders is the same as that set forth above. That said written
         consent was signed by the holders of outstanding shares having not less
         than the minimum number of required votes of shareholders necessary to
         approve said amendment in accordance with Section 902 of the California
         Corporations Code.

5.       That the designation and total number of outstanding shares entitled to
         vote on or give written consent to said amendment and the minimum
         percentage required of each class or series entitled to vote on or give
         written consent to said amendment for approval thereof are as follows:




                               Number of Shares
                               Outstanding Entitled         Minimum Percentage
                               to Vote or Give              Vote Required to
           Designation         Written Consent              Approve
         ---------------     ------------------------     ----------------------
                                                    
          Common Stock               200,000                   More than 50%


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6.       That the number of shares of each class which gave written consent in
         favor of said amendment equaled or exceeded the minimum percentage vote
         required of each class entitled to vote, as set forth above.


         Each of the undersigned declares under penalties of perjury that the
statements contained in the foregoing certificate are true of his own knowledge.

         EXECUTED at Houston, Texas, on the 20th day of June, 1995.


                                             /s/ J.T. JONGEBLOED
                                             -----------------------------------
                                             J.T. Jongebloed, President

                                             /s/ G.G. ARMS
                                             -----------------------------------
                                             G.G. Arms, Corporate Secretary
   13
 





                            CERTIFICATE OF OWNERSHIP
                                    MERGING
                              GOLDEN PACIFIC CORP.
                                      INTO
                     POOL CALIFORNIA ENERGY SERVICES, INC.


The undersigned, J. T. Jongebloed and G. G. Arms do hereby certify:

         1.      That they are the President and the Corporate Secretary,
                 respectively, of Golden Pacific Corp.

         2.      That this corporation is duly organized and existing under the
                 laws of the State of California.

         3.      That this corporation owns 100 percent of the outstanding
                 shares of Pool California Energy Services, Inc., a corporation
                 duly organized and existing under the laws of the State of
                 California.

         4.      That the following resolution was duly adopted and approved by
                 the Board of Directors of this corporation:

                                  RESOLVED, That Golden Pacific Corp. ("GPC")
                          merge, and it hereby does merge itself into Pool
                          California Energy Services, Inc. ("PCESI"), its
                          subsidiary, which assumes all of the obligations of
                          GPC pursuant to Section 1110 of the California
                          Corporations Code; and

                                  FURTHER RESOLVED, That the terms and
                          conditions of the merger are as follows:

                                  (a)      Each outstanding share of Common
                          Stock of GPC shall be converted into 4.949353268
                          shares of Common Stock of PCESI;

                                  (b)      Upon the merger becoming effective,
                          the separate existence of GPC shall cease and all the
                          property, rights, privileges, franchises, patents,
                          trademarks, licenses, registrations and other assets
                          of every kind and description of GPC shall be
                          transferred to, vested in and devolve upon PCESI
                          without further act or deed, and all property,
                          rights, and every other interest of GPC shall be as
                          effectively the property of PCESI as they were of
                          GPC;

                                  (c)      All such deeds, instruments and
                          other actions as may be necessary or desirable to be
                          executed or taken in the name of GPC may be executed
                          or taken on its behalf by PCESI, and the proper
                          officers and directors of PCESI are fully authorized
                          in the name of GPC or otherwise to take any and all
                          such action; and
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                                  (d)      All rights of creditors of GPC shall
                          be preserved unimpaired, and all debts, liabilities
                          and duties of GPC shall thenceforth attach to PCESI
                          and may be enforced against it to the same extent as
                          if said debts, liabilities and duties had been
                          incurred or contracted by it.

         5.      That the entire resolution of merger was approved by the Board
                 of Directors of Pool California Energy Services, Inc.

         6.      That the entire outstanding capital stock of GPC consist of
                 the following:



                          Class                            Shares Outstanding
                  --------------------                   ----------------------
                       Common Stock                             40,409.32
                     Preferred Stock                               -0-



Each of the undersigned declares under penalties of perjury that the statements
contained in the foregoing certificate are true of his own knowledge.

Executed at Houston, Texas, on July 11, 1995.



                                       /s/ J.T. JONGEBLOED
                                       ----------------------------------------
                                       J.T. Jongebloed
                                       President, Golden Pacific Corp.

                                       /s/ G.G. ARMS
                                       ----------------------------------------
                                       G.G. Arms
                                       Corporate Secretary, Golden Pacific Corp.