EXHIBIT 3.18
                                     BY-LAWS
                                       OF
                              DE GUELLE OIL COMPANY
                           (AS AMENDED MARCH 29, 2002)


                               ARTICLE I. OFFICES

         The principal office of the corporation in the State of Colorado shall
be located in the City of Durango, County of La Plata. The corporation may have
such other offices, either within or without the State of Colorado, as the Board
of Directors may designate or as the business of the corporation may require
from time to time.

                            ARTICLE II. SHAREHOLDERS

         SECTION 1. Annual Meeting. The annual meeting of the shareholders shall
be held on the 1st day in the month of September in each year, beginning with
the year 1979, at the hour of 4 o'clock p.m., for the purpose of electing
Directors and for the transaction of such other business as may come before the
meeting. If the day fixed for the annual meeting shall be a legal holiday in the
State of Colorado, such meeting shall be held on the next succeeding business
day. If the election of Directors shall not be held on the day designated herein
for any annual meeting of the shareholders, or at any adjournment thereof, the
Board of Directors shall cause the election to be held at a special meeting of
the shareholders as soon thereafter as conveniently may be.

         SECTION 2. Special Meetings. Special meetings of the shareholders for
any purpose or purposes, unless otherwise prescribed by statute, may be called
by the President or by the Board of Directors, and shall be called by the
President at the request of the holders of not less than fifty percent of all
the outstanding shares of the corporation entitled to vote at the meeting.

         SECTION 3. Place of Meeting. The Board of Directors may designate any
place, either within or without the State of Colorado unless otherwise
prescribed by statute, as the place of meeting for any annual meeting or for any
special meeting called by the Board of Directors. A waiver of notice signed by
all shareholders entitled to vote at a meeting may designate any place, either
within or without the State of Colorado, unless otherwise prescribed by statute,
as the place for the holding of such meeting. If no designation is made, or if a
special meeting be otherwise called, the place of meeting shall be the principal
office of the corporation in the State of Colorado.

         SECTION 4. Notice of Meeting. Written notice stating the place, day and
hour of the meeting and, in case of special meeting, the purpose or purposes for
which the meeting is called, shall unless otherwise prescribed by statute, be
delivered not less than ten days nor more than thirty days before the date of
the meeting, either personally or by mail, by or at the direction of the
President, or the Secretary, or the persons calling the meeting. If mailed, such
notice shall be deemed to be delivered when deposited in the United States mail,
addressed to the shareholder at his address as it appears on the stock transfer
books of the corporation, with postage thereon prepaid.

         SECTION 5. Closing of Transfer Books or Fixing of Record Date. For the
purpose of determining shareholders entitled to notice of or to vote at any
meeting of shareholders or any adjournment thereof, or shareholders entitled to
receive payment of any dividend, or in order to make a determination of
shareholders for any other proper purpose, the Board of Directors of the
corporation may provide that the stock transfer books shall be closed for a
stated period but not to exceed, in any case, 30 days. If the stock transfer
books shall be closed for the purpose of determining shareholders entitled to


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notice of or to vote at a meeting of shareholders, such books shall be closed
for at least 30 days immediately preceding such meeting. In lieu of closing the
stock transfer books, the Board of Directors may fix in advance a date as the
record date for any such determination of shareholders, such date in any case to
be not more than 30 days and, in case of a meeting of shareholders, not less
than 30 days prior to the date on which the particular action, requiring such
determination of shareholders, is to be taken. If the stock transfer books are
not closed and no record date is fixed for the determination of shareholders
entitled to notice of or to vote at a meeting of shareholders, or shareholders
entitled to receive payment of a dividend, the date on which notice of the
meeting is mailed or the date on which the resolution of the Board of Directors
declaring such dividend is adopted, as the case may be, shall be the record date
for such determination of shareholders. When a determination of shareholders
entitled to vote at any meeting of shareholders has been made as provided in
this section, such determination shall apply to any adjournment thereof.

         SECTION 6. Voting Lists. The officer or agent having charge of the
stock transfer books for shares of the corporation shall make a complete list of
the shareholders entitled to vote at each meeting of shareholders or any
adjournment thereof, arranged in alphabetical order, with the address of and the
number of shares held by each. Such list shall be produced and kept open at the
time and place of the meeting and subject to the inspection of any shareholder
during the whole time of the meeting for the purposes thereof.

         SECTION 7. Quorum. A majority of the outstanding shares of the
corporation entitled to vote, represented in person or by proxy, shall
constitute a quorum at a meeting of shareholders. If less than a majority of the
outstanding shares are represented at a meeting, a majority of the shares so
represented may adjourn the meeting from time to time without further notice. At
such adjourned meeting at which a quorum shall be present or represented, any
business may be transacted which might have been transacted at the meeting as
originally noticed. The shareholders present at a duly organized meeting may
continue to transact business until adjournment, not withstanding the withdrawal
of enough shareholders to leave less than a quorum.

         SECTION 8. Proxies. At all meetings of shareholders, a shareholder may
vote in person or by proxy executed in writing by shareholder or by his duly
authorized attorney in fact. Such proxy shall be filed with the secretary of the
corporation before or at the time of the meeting. No proxy shall be valid after
one month from the date of its execution, unless otherwise provided in the
proxy.

         SECTION 9. Voting of Shares. Subject to the provisions of Section 12 of
this Article II, each outstanding share entitled to vote shall be entitled to
one vote upon each matter submitted to a vote at a meeting of shareholders. In
accordance with the Articles of Incorporation previously filed for this
corporation, cumulative voting of shares shall not be authorized.

         SECTION 10. Voting of Shares by Certain Holders. Shares standing in the
name of another corporation may be voted by such officer, agent or proxy as the
By-Laws of such corporation may prescribe, or, in the absence of such provision,
as the Board of Directors of such corporation may determine.

         Shares held by an administrator, executor, guardian or conservator may
be voted by him either in person or by proxy, without a transfer of such shares
into his name. Shares standing in the name of a trustee may be voted by him,
either in person or by proxy, but no trustee shall be entitled to vote shares
held by him without a transfer of such shares into his name.


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         Shares standing in the name of a receiver may be voted by such
receiver, and shares held by or under the control of a receiver may be voted by
such receiver without the transfer thereof into his name if authority so to do
be contained in an appropriate order of the court by which such receiver was
appointed.

         A shareholder whose shares are pledged shall be entitled to vote such
shares until the shares have been transferred into the name of the pledgee, and
thereafter the pledgee shall be entitled to vote the shares so transferred.

         Shares of its own stock belonging to the corporation shall not be
voted, directly or indirectly, at any meeting, and shall not be counted in
determining the total number of outstanding shares at any given time.

         SECTION 11. Informal Action by Shareholders. Unless otherwise provided
by law, any action required to be taken at a meeting of the shareholders, or any
other action which may be taken at a meeting of the shareholders, may be taken
without a meeting if a consent in writing, setting forth the action so taken,
shall be signed by all of the stockholders entitled to vote with respect to the
subject matter thereof.

                         ARTICLE III. BOARD OF DIRECTORS

         SECTION 1. General Powers. The business and affairs of the corporation
shall be managed by its Board of Directors.

         SECTION 2. Number, Tenure and Qualifications. The number of directors
of the corporation shall be three. Each director shall hold office until the
next annual meeting of shareholders and until his successor shall have been
elected and qualified.

         SECTION 3. Regular Meetings. A regular meeting of the Board of
Directors shall be held without other notice than this By-Law immediately after,
and at the same place as, the annual meeting of shareholders. The Board of
Directors may provide, by resolution, the time and place for the holding of
additional regular meetings without other notice than such resolution.

         SECTION 4. Special Meetings. Special meetings of the Board of Directors
may be called by or at the request of the President or any two directors. The
person or persons authorized to call special meetings of the Board of Directors
may fix the place for holding any special meeting of the Board of Directors
called by them.

         SECTION 5. Notice. Notice of any special meeting shall be given at
least ten days previously thereto by written notice delivered personally or
mailed to each director at his business address, or by telegram. If mailed, such
notice shall be deemed to be delivered when deposited in the United States mail
so addressed, with postage thereon prepaid. If notice be given by telegram, such
notice shall be deemed to be delivered when the telegram is delivered to the
telegraph company. Any director may waive notice of any meeting. The attendance
of a director at a meeting shall constitute a waiver of such meeting, except
where a director attends a meeting for the express purpose of objecting to the
transaction of any business because the meeting is not lawfully called or
convened.

         SECTION 6. Quorum. A majority of the number of directors fixed by
Section 2 of this Article III shall constitute a quorum for the transaction of
business at any meeting of the Board of Directors, but if less than such
majority is present at a meeting, a majority of the directors present may
adjourn the meeting from time to time without further notice.


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         SECTION 7. Manner of Acting. The act of the majority of the directors
present at a meeting at which a quorum is present shall be the act of the Board
of Directors.

         SECTION 8. Action Without a Meeting. Any action that may be taken by
the Board of Directors at a meeting may be taken without a meeting if a consent
in writing, setting forth the action so to be taken, shall be signed before such
action by all of the Directors.

         SECTION 9. Vacancies. Any vacancy occurring in the Board of Directors
may be filled by the affirmative vote of a majority of the remaining directors
though less than a quorum of the Board of Directors, unless otherwise provided
by law. A director elected to fill a vacancy shall be elected for the unexpired
term of his predecessor in office. Any directorship to be filled by reason of an
increase in the number of directors may be filled by election by the Board of
Directors for a term of office continuing only until the next election of
Directors by the shareholders.

         SECTION 10. Compensation. By resolution of the Board of Directors, each
Director may be paid his expenses, if any, of attendance at each meeting of the
Board of Directors, and may be paid a stated salary as Director or a fixed sum
for attendance at each meeting of the Board of Directors or both. No such
payment shall preclude any Director from serving the corporation in any other
capacity and receiving compensation therefor.

         SECTION 11. Presumption of Assent. A director of the corporation who is
present at a meeting of the Board of Directors at which action on any corporate
matter is taken shall be presumed to have assented to the action taken unless
his dissent shall be entered in the minutes of the meeting or unless he shall
file his written dissent to such action with the person acting as the secretary
of the meeting before the adjournment thereof or shall forward such dissent by
registered mail to the secretary of the corporation immediately after the
adjournment of the meeting. Such right to dissent shall not apply to a Director
who voted in favor of such action.

                              ARTICLE IV. OFFICERS

         SECTION 1. Number. The officers of the corporation shall be a
President, a Vice-President, a Secretary and a Treasurer, each of whom shall be
elected by the Board of Directors. Such other officers and assistant officers as
may be deemed necessary may be elected or appointed by the Board of Directors.

         SECTION 2. Election and Term of Office. The officers of the corporation
to be elected by the Board of Directors shall be elected annually by the Board
of Directors at the first meeting of the Board of Directors held after each
annual meeting of the shareholders. If the election of officers shall not be
held at such meeting, such election shall be held as soon thereafter as
conveniently may be. Each officer shall hold office until his successor shall
have been duly elected and shall have qualified or until his death or until he
shall resign or shall have been removed in the manner hereinafter provided.

         SECTION 3. Removal. Any officer or agent may be removed by the Board of
Directors whenever in its judgment, the best interests of the corporation will
be served thereby, but such removal shall be without prejudice to the contract
rights, if any, of the person so removed. Election or appointment of an officer
or agent shall not of itself create contract rights.

         SECTION 4. Vacancies. A vacancy in any office because of death,
resignation, removal, disqualification or otherwise, may be filled by the Board
of Directors for the unexpired portion of the term.


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         SECTION 5. President. The President shall be the principal executive
officer of the corporation and, subject to the control of the Board of
Directors, shall in general supervise and control all of the business and
affairs of the corporation. He shall, when present, preside at all meetings of
the shareholders and the Board of Directors. He may sign, with the Secretary or
any other proper officer of the corporation thereunto authorized by the Board of
Directors, certificates for shares of the corporation, any deeds, mortgages,
bonds, contracts, or other instruments which the Board of Directors has
authorized to be executed, except in cases where the signing and execution
thereof shall be expressly delegated by the Board of Directors or by these
By-Laws to some other officer or agent of the corporation, or shall be required
by law to be otherwise signed or executed; and in general shall perform all
duties incident to the office of President and such other duties as may be
prescribed by the Board of Directors from time to time.

         SECTION 6. Vice-President. In the absence of the President or in the
event of his death, inability or refusal to act, the Vice-President shall
perform the duties of the President, and when so acting, shall have all the
powers of and be subject to all the restrictions upon the President. The
Vice-President shall perform such other duties as from time to time may be
assigned to him by the President or by the Board of Directors.

         SECTION 7. Secretary. The Secretary shall: (a) keep the minutes of the
proceedings of the shareholders and of the Board of Directors in one or more
books provided for that purpose; (b) see that all notices are duly given in
accordance with the provisions of these By-Laws or as required by law; (c) be
custodian of the corporate records and of the seal of the corporation and see
that the seal of the corporation is affixed to all documents the execution of
which on behalf of the corporation under its seal is duly authorized; (d) keep a
register of the post office address of each shareholder which shall be furnished
to the Secretary by such shareholder; (e) sign with the President certificates
for shares of the corporation, the issuance of which shall have been authorized
by resolution of the Board of Directors; (f) have general charge of the stock
transfer books of the corporation; and (g) in general, perform all duties
incident to the office of Secretary and such other duties as from time to time
may be assigned to him by the President or by the Board of Directors.

         SECTION 8. Treasurer. The Treasurer shall: (a) have charge and custody
of and be responsible for all funds and securities of the corporation; (b)
receive and give receipts for moneys due and payable to the corporation from any
source whatsoever, and deposit all such moneys in the name of the corporation in
such banks, trust companies or other depositories as shall be selected in
accordance with the provisions of Article V of these By-laws; and (c) in
general, perform all of the duties incident to the office of Treasurer and such
other duties as from time to time may be assigned to him by the President or by
the Board of Directors. If required by the Board of Directors, the Treasurer
shall give a bond for the faithful discharge of his duties in such sum and with
such surety or sureties as the Board of Directors shall determine.

         SECTION 9. Salaries. The salaries of the officers shall be fixed from
time to time by the Board of Directors and no officer shall be prevented from
receiving such salary by reason of the fact that he is also a Director of the
corporation.

                ARTICLE V. CONTRACTS, LOANS, CHECKS AND DEPOSITS

         SECTION 1. Contracts. The Board of Directors may authorize any officer
or officers, agent or agents, to enter into any contract or execute and deliver
any instrument in the name of and on behalf of the corporation, and such
authority may be general or confined to specific instances.


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         SECTION 2. Checks, Drafts, Etc. All checks, drafts or other orders for
the payment of money, notes or other evidences of indebtedness issued in the
name of the corporation, shall be signed by such officer or officers, agent or
agents of the corporation and in such manner as shall from time to time be
determined by resolution of the Board of Directors.

         SECTION 3. Deposits. All funds of the corporation not otherwise
employed shall be deposited from time to time to the credit of the corporation
in such banks, trust companies or other depositories as the Board of Directors
may select.

             ARTICLE VI. CERTIFICATES FOR SHARES AND THEIR TRANSFER

         SECTION 1. Certificates for Shares. Certificates representing shares of
the corporation shall be in such form as shall be determined by the Board of
Directors. Such certificates shall be signed by the President and by the
Secretary or by such other officers authorized by law and by the Board of
Directors so to do, and sealed with the corporate seal. All certificates for
shares shall be consecutively numbered and otherwise identified. The name and
address of the person to whom the shares represented thereby are issued, with
the number of shares and date of issue, shall be entered on the stock transfer
books of the corporation. All certificates surrendered to the corporation for
transfer shall be cancelled and no new certificate shall be issued until the
former certificate for a like number of shares shall have been surrendered and
cancelled, except that in case of a lost, destroyed or mutilated certificate a
new one may be issued therefor upon such terms and indemnity to the corporation
as the Board of Directors prescribe.

         SECTION 2. Transfer of Shares. Transfer of shares of the corporation
shall be made only on the stock transfer books of the corporation by the holder
of record thereof or by his legal representative, who shall furnish proper
evidence of authority to transfer, or by his attorney thereunto authorized by
power of attorney duly executed and filed with the Secretary of the corporation,
and on surrender for cancellation of the certificate for such shares. The person
in whose name shares stand on the books of the corporation shall be deemed by
the corporation to be the owner thereof for all purposes.

         SECTION 3. Encumbrance of Stock. No shareholder shall encumber any of
his stock in the company without first obtaining written consent to do so from
all other shareholders. Any encumbered stock shall have attached thereto a
notice that in the event of foreclosure and transfer of said stock, the new
stockholder shall be required to offer the stock for sale to the corporation and
to the remaining stockholders under the same terms and conditions and at the
same price as set forth in Section 4 hereof.

         SECTION 4. Restrictions on Sale of Stock. In the event that any
shareholder desires to sell or transfer his shares for a valuable consideration,
such shareholder must first offer said stock for sale to the corporation and the
offer shall be in writing and delivered to the Board of Directors. Within 20
days after receipt of the written offer, the Board of Directors shall call a
meeting of the shareholders, at which meeting the stock shall be offered for
sale to the company for the purpose of retirement of the shares or to place the
same in treasury stock. The corporation may exercise its option to purchase as
of the day of the meeting. Any stock which is offered for sale to the company
and not purchased in accordance with the offer shall then be offered on a
proportionate ownership basis to the remaining stockholders who desire to
purchase said stock upon the same terms and conditions as set forth in the offer
made to the company. In the event that the stock is not purchased by the company
or by the shareholders, then the shareholder offering the stock for sale shall
be free to sell the same to any third person for the same or a greater price but
not for a lesser price than the price at which the stock was offered to the
corporation and the shareholders.


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                            ARTICLE VII. FISCAL YEAR

         The fiscal year of the corporation shall begin and end on such days as
the Board of Directors shall fix by resolution.

                             ARTICLE VIII. DIVIDENDS

         The Board of Directors may from time to time declare, and the
corporation may pay, dividends on its outstanding shares in the manner and upon
the terms and conditions provided by law and its Articles of Incorporation.

                           ARTICLE IX. CORPORATE SEAL

         The Board of Directors shall provide a corporate seal which shall be
circular in form and shall have inscribed thereon the name of the corporation
and the state of incorporation and the words, "Corporate Seal".

                          ARTICLE X. WAIVER OF NOTICE.

         Unless otherwise provided by law, whenever any notice is required to be
given to any shareholder or director of the corporation under the provisions of
these By-Laws or under the provisions of the Small Business Corporation Act, a
waiver thereof in writing, signed by the person or persons entitled to such
notice, whether before or after the time stated therein, shall be deemed
equivalent to the giving of such notice.

                             ARTICLE XI. AMENDMENTS

         These By-Laws may be altered, amended or repealed and new By-Laws may
be adopted by the Board of Directors at any regular or special meeting of the
Board of Directors.


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