EXHIBIT 3.7(a)

                       CERTIFICATE OF LIMITED PARTNERSHIP
                                       OF
                           EAP ENERGY SERVICES, L.P.

The undersigned General Partner, desiring to form a limited partnership (the
"Partnership"), pursuant to Section 2.01 of the Texas Revised Limited
Partnership Act (the "Act"), hereby duly executes this Certificate of Limited
Partnership, to be effective as of the date of filing with the Secretary of
State.

1.    The name of the Partnership is EAP Energy Services, L.P.

2.    The address of the registered office of the Partnership is 201 Main
      Street, Suite 1455, Fort Worth, Texas, 76102, and the name of the
      registered agent whose business office address will be the same as the
      registered office address is Bruce B. Selkirk, III.

3.    The address of the principal office of the Partnership in the United
      States where its partnership records are to be kept or made available
      under Section 1.07 of the Art is 201 Main Street, Suite 1455, Fort Worth,
      Texas, 76102.

4.    The name, the mailing address, and the street address of the business or
      residence of each general partner of the Partnership is as follows:

                                                MAILING ADDRESS
                       NAME                     AND STREET-ADDRESS

              EAP Energy, Inc.,                 201 Main Street, Suite 1455
              a Delaware corporation            Fort Worth, Texas  76102

SIGNED on this the 5th day of March, 1999.

                                      GENERAL PARTNER

                                      EAP ENERGY, INC
                                      a Delaware corporation

                                      By: /s/ Bruce B. Selkirk, III
                                          --------------------------------------
                                          Bruce B. Selkirk, III, Executive
                                          Vice President



                  CHANGE OF REGISTERED AGENT/REGISTERED OFFICE

1.    The name of the entity is EAP Energy Services, L.P.

      and the file number issued to the entity by the secretary of state is
      __________________________

2.    The entity is: (Check one.)

      -     a business corporation, which has authorized the changes indicated
            below through its board of directors or by an officer of the
            corporation so authorized by its board of directors, as provided by
            the Texas Business Corporation Act.

      -     a non-profit corporation, which has authorized the changes indicated
            below through its board of directors or by an officer of the
            corporation so authorized by its board of directors, or through its
            members in whom management of the corporation is vested pursuant to
            article 2.14C, as provided by the Texas Non-Profit Corporation Act.

      -     a limited liability company, which. has authorized the changes
            indicated below through its members or managers, as provided by the
            Texas Limited Liability Company Act.

      -     a limited partnership, which has authorized the changes indicated
            below through its partners, as provided by the Texas Revised Limited
            Partnership Act.

      -     an out-of-state financial institution, which has authorized the
            changes indicated below in the manner provided under the laws
            governing its formation.

3.    The registered office address as PRESENTLY shown in the records of the
      Texas secretary of state is 201 Main St., Suite 1455, Ft. Worth, TX 76102.

4.    - A. The address of the NEW registered office is: (Please provide street
      address, city, state and zip code. The address must be in Texas.) 777 Main
      Street, Suite 1400, Ft. Worth, TX 76102.

OR    - B. The registered office address will not change.

5.    The name of the registered agent as PRESENTLY shown in the records of the
      Texas secretary of state is Bruce Selkirk, III.

6.    - A. The name of the NEW registered agent is John Karnes.

OR    - B. The registered agent will not change.

7.    Following the changes shown above, the address of the registered office
      and the address of the office of the registered agent will continue to be
      identical, as required by law.

                                             By: /s/ John Karnes
                                                 -------------------------------
                                                 (A person authorized to sign
                                                  on behalf of the entity)



                                  INSTRUCTIONS

1.    It is recommended that you call (512) 463-5555 to verify the information
      in items 3 and 5 as it currently appears on the records of the secretary
      of state before submitting the statement for filing. You also may e-mail
      an inquiry to corpinfor@sos.state.tx.us. As information on out-of-state
      financial institutions is maintained on a separate database, a financial
      institution must call (512) 463-5701 to verify registered agent and
      registered office information. If the information on the form is
      inconsistent with the records of this office, the statement will be
      returned.

2.    You are required by law to provide a street address in item 4 unless the
      registered office is located in a city with a population of 5,000 or less.
      The purpose of this requirement is to provide the public with notice of a
      physical location at which process may be served on the registered agent.
      A statement submitted with a post office box address or a lock box address
      will not be filed.

3.    An authorized officer of the corporation or financial institution must
      sign the statement. In the case of a limited liability company, an
      authorized member or manager of a limited liability company must sign the
      statement. A general partner must sign the statement on behalf of a
      limited partnership. A person commits on an offense under the Texas
      Business Corporation Act, the Texas Non-Profit Corporation Act or the
      Texas Limited Liability Company Act if the person signs a document the
      person knows is false in any material respect with the intent that the
      document be delivered to the secretary of state for filing. The offense is
      a Class A misdemeanor.

4.    Please attach the appropriate fee:


                                                             
Business Corporation                                            $15.00
Financial Institution, other than Credit Unions                 $15.00
Financial Institution that is a Credit Union                    $ 5.00
Non-Profit Corporation                                          $ 5.00
Limited Liability Company                                       $10.00
Limited Partnership                                             $50.00


      Personal checks and MasterCard(R), Visa(R), and Discover(R) are accepted
      in payment of the filing fee. Checks or money orders must be payable
      through a U.S. bank or other financial institution and made payable to the
      secretary of state. Fees paid by credit card are subject to a statutorily
      authorized processing cost of 2.1% of the total fees.

5.    Two copies of the form along with the filing fee should be mailed to the
      address shown in the heading of this form. The delivery address is:
      Secretary of State, Statutory Filings Division, Corporations Section,
      James Earl Rudder Office Building, 1019 Brazos, Austin, Texas 78701. We
      will place one document on record and return a file stamped copy, if a
      duplicate copy is provided for such purpose. The telephone number is (512)
      463-5555, TDD: (800) 735-2989, FAX: (512) 463-5709.



                  CHANGE OF REGISTERED AGENT/REGISTERED OFFICE

1.    The name of the entity is EAP Energy Services, L.P.

      and the file number issued to the entity by the secretary of state is
      __________________________

2.    The entity is: (Check one.)

      -     a business corporation, which has authorized the changes indicated
            below through its board of directors or by an officer of the
            corporation so authorized by its board of directors, as provided by
            the Texas Business Corporation Act.

      -     a non-profit corporation, which has authorized the changes indicated
            below through its board of directors or by an officer of the
            corporation so authorized by its board of directors, or through its
            members in whom management of the corporation is vested pursuant to
            article 2.14C, as provided by the Texas Non-Profit Corporation Act.

      -     a limited liability company, which. has authorized the changes
            indicated below through its members or managers, as provided by the
            Texas Limited Liability Company Act.

      -     a limited partnership, which has authorized the changes indicated
            below through its partners, as provided by the Texas Revised Limited
            Partnership Act.

      -     an out-of-state financial institution, which has authorized the
            changes indicated below in the manner provided under the laws
            governing its formation.

3.    The registered office address as PRESENTLY shown in the records of the
      Texas secretary of state is 777 Main St., Suite 1400, Ft. Worth, TX 76102.

4.    - A. The address of the NEW registered office is: (Please provide street
      address, city, state and zip code. The address must be in Texas.)

OR    - B. The registered office address will not change.

5.    The name of the registered agent as PRESENTLY shown in the records of the
      Texas secretary of state is John Karnes.

6.    - A. The name of the NEW registered agent is Morris B. Smith.

OR    - B. The registered agent will not change.

7.    Following the changes shown above, the address of the registered office
      and the address of the office of the registered agent will continue to be
      identical, as required by law.

                                            By: /s/ Morris B. Smith
                                                --------------------------------
                                                (A person authorized to sign
                                                on behalf of the entity)



                                  INSTRUCTIONS

1.    It is recommended that you call (512) 463-5555 to verify the information
      in items 3 and 5 as it currently appears on the records of the secretary
      of state before submitting the statement for filing. You also may e-mail
      an inquiry to corpinfor@sos.state.tx.us. As information on out-of-state
      financial institutions is maintained on a separate database, a financial
      institution must call (512) 463-5701 to verify registered agent and
      registered office information. If the information on the form is
      inconsistent with the records of this office, the statement will be
      returned.

2.    You are required by law to provide a street address in item 4 unless the
      registered office is located in a city with a population of 5,000 or less.
      The purpose of this requirement is to provide the public with notice of a
      physical location at which process may be served on the registered agent.
      A statement submitted with a post office box address or a lock box address
      will not be filed.

3.    An authorized officer of the corporation or financial institution must
      sign the statement. In the case of a limited liability company, an
      authorized member or manager of a limited liability company must sign the
      statement. A general partner must sign the statement on behalf of a
      limited partnership. A person commits on an offense under the Texas
      Business Corporation Act, the Texas Non-Profit Corporation Act or the
      Texas Limited Liability Company Act if the person signs a document the
      person knows is false in any material respect with the intent that the
      document be delivered to the secretary of state for filing. The offense is
      a Class A misdemeanor.

4.    Please attach the appropriate fee:


                                                             
Business Corporation                                            $15.00
Financial Institution, other than Credit Unions                 $15.00
Financial Institution that is a Credit Union                    $ 5.00
Non-Profit Corporation                                          $ 5.00
Limited Liability Company                                       $10.00
Limited Partnership                                             $50.00


      Personal checks and MasterCard(R), Visa(R), and Discover(R) are accepted
      in payment of the filing fee. Checks or money orders must be payable
      through a U.S. bank or other financial institution and made payable to the
      secretary of state. Fees paid by credit card are subject to a statutorily
      authorized processing cost of 2.1% of the total fees.

5.    Two copies of the form along with the filing fee should be mailed to the
      address shown in the heading of this form. The delivery address is:
      Secretary of State, Statutory Filings Division, Corporations Section,
      James Earl Rudder Office Building, 1019 Brazos, Austin, Texas 78701. We
      will place one document on record and return a file stamped copy, if a
      duplicate copy is provided for such purpose. The telephone number is (512)
      463-5555, TDD: (800) 735-2989, FAX: (512) 463-5709.