Document:

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                                                                    Exhibit 10.6

                                                                [Execution Copy]

                                PLEDGE AGREEMENT

      This PLEDGE AGREEMENT, dated as of May 3, 2004 (the "Agreement"), is made
and entered into by WILLIAMS FIELD SERVICES GROUP, INC., a Delaware corporation
("Pledgor"), in favor of Citicorp USA, Inc., as collateral agent ("Collateral
Agent") for its benefit and the ratable benefit of the other Financial
Institutions.

                             PRELIMINARY STATEMENTS

      A.    The Williams Companies, Inc., a Delaware corporation (the
"Company"), Northwest Pipeline Corporation, a Delaware corporation ("NWP"),
Transcontinental Gas Pipe Line Corporation, a Delaware corporation ("TGPL", and
together with TWC and NWP, the "Borrowers"), have entered into a Credit
Agreement dated as of May 3, 2004 (as amended or otherwise modified from time to
time, the "Credit Agreement"; the defined terms from the Credit Agreement are
used in this Agreement as defined therein unless otherwise defined herein),
together with Citicorp USA, Inc., as administrative agent and collateral agent
("Collateral Agent"), Bank of America, N.A., as syndication agent ("Syndication
Agent"), Citibank, N.A. and Bank of America N.A., as issuing banks ("Issuing
Banks"), the banks named therein (the "Banks"), JPMorgan Chase Bank, The Bank of
Nova Scotia and The Royal Bank of Scotland plc, as co-documentation agents
(collectively, the "Co-Documentation Agents"), and Citigroup Global Markets Inc.
and Banc of America Securities LLC, as joint lead arrangers and co-book runners
(collectively, the "Co-Arrangers") providing for the extension of credit and the
issuance of Letters of Credit. The Collateral Agent, Syndication Agent, Issuing
Banks, Banks, Co-Documentation Agents and Co-Arrangers and each of the
successors and permitted assigns of the foregoing are collectively referred to
herein as the "Financial Institutions".

      B.    It is a condition to certain transactions under the Credit Documents
that the Pledgor shall have executed and delivered this Agreement.

      C.    The Company is the principal financing entity for all capital
requirements of its Subsidiaries, and from time to time the Company has made
capital contributions and advances to certain of its Subsidiaries. The Pledgor
is a wholly owned Subsidiary of the Company and will derive substantial direct
or indirect benefit from the transactions contemplated by the Credit Documents.

      D.    The terms defined in Articles 8 and 9 of the Uniform Commercial Code
in effect in the State of New York (as amended from time to time, the "UCC") are
used herein as defined therein unless otherwise defined herein or in the Credit
Agreement.

                                    AGREEMENT

      Therefore, in order to induce the Financial Institutions to enter into
and/or continue certain financing transactions described in the Credit
Documents, Pledgor hereby agrees with

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Collateral Agent for the benefit of the Collateral Agent and the other Financial
Institutions as follows:

      1. Pledge. To secure the Secured Obligations (as defined in Section 2
below), Pledgor hereby TRANSFERS, GRANTS, BARGAINS, SELLS, CONVEYS,
HYPOTHECATES, SETS OVER, DELIVERS AND PLEDGES to the Collateral Agent, for the
benefit of the Collateral Agent and the other Financial Institutions, and GRANTS
to the Collateral Agent, for the benefit of the Collateral Agent and the other
Financial Institutions, a security interest in all of Pledgor's right, title and
interest of every kind and character now owned or hereafter acquired, created or
arising in and to the following (the "Pledged Collateral"):

            (a)   the Pledged Shares (as defined below);

            (b)   all certificates and similar evidence of ownership
representing the Pledged Collateral;

            (c)   all cash dividends, stock dividends, cash, instruments and
other property or proceeds from time to time received, receivable or otherwise
distributed in respect of or in exchange for any or all of the Pledged
Collateral; and

            (d)   all additions to and substitutions for any of the foregoing
and all products and proceeds of any of the Pledged Collateral, together with
all renewals and replacements of any of the Pledged Collateral.

      "Pledged Shares" means all shares of capital stock, general and limited
partnership interests, limited liability company interests and trust interests
described in Schedule I as being held by Pledgor, as amended from time to time,
together with: (i) any rights derivative thereof; (ii) all rights, contingent or
otherwise, of Pledgor to acquire interests in the entities or organizations
represented by the interests described in Schedule I (whether such shares are
described as being held by Pledgor or not), as amended from time to time, and
all rights to receive cash dividends, stock or like dividends, and distributions
upon redemption or liquidation on account of the foregoing or with respect to
any such entities; (iii) distributions as a result of split-ups,
recapitalizations or rearrangements on account of the foregoing; (iv) stock
rights, rights to subscribe, voting rights, rights to receive securities,
options, warrants, calls, and commitments with respect to any such entities or
organizations; and (v) all new securities and other property which Pledgor now
owns or may hereafter become entitled to receive on account of the foregoing or
with respect to any such entities or organizations, all ownership rights
associated with any of the foregoing arising under the law of any jurisdiction
and all rights derivative thereof;

      "Obligors" means those entities listed on Schedule I whose shares are
owned by Pledgor and which shares constitute Pledged Shares

      TO HAVE AND TO HOLD the Pledged Collateral, together with all rights,
title, interests, powers, privileges and preferences pertaining or incidental
thereto, unto the Collateral Agent, forever; subject, however, to the terms,
covenants and conditions set forth in this Agreement and subject in all cases to
the limitation that the obligations of Pledgor under the Security Documents are
limited to an aggregate transfer equal to the largest amount that would

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not render Pledgor's grant and obligations under the Security Documents subject
to avoidance under Section 548 of the United States Bankruptcy Code or any
comparable provisions of any applicable state law.

      2. Security for Obligations. The security interests and other rights
granted pursuant to Section 1 secure, and the Pledged Collateral is security
for, the prompt performance and payment in full in cash when due, whether at
stated maturity, by acceleration or otherwise of the Secured Obligations. As
used in this Agreement the term "Secured Obligations" shall mean the
Obligations. Notwithstanding that the balance of the Secured Obligations may at
certain times be zero and that no letters of credit may at certain times be
outstanding under the Credit Documents, the Liens granted hereunder to the
Collateral Agent shall remain in full force and effect at all times and with the
same priority until the payment in full in cash of the Secured Obligations and
the termination of the Commitments.

      3. Delivery of Pledged Collateral. The Pledgor shall make all deliveries
required by Section 5.1(l)(ix) of the Credit Agreement in accordance with the
terms thereof, accompanied by, if required thereby, a duly executed but blank
stock power in the form of Schedule III, or otherwise reasonably acceptable to
the Collateral Agent. The Collateral Agent shall have the right, at any time
after the occurrence and during the continuance of an Event of Default, in its
discretion and without notice to Pledgor, to transfer to or to register in its
name or any of its nominees, any or all of the Pledged Collateral, subject only
to the revocable rights of Pledgor specified in Section 6(a) hereof. In
addition, the Collateral Agent shall have the right at any time after the
occurrence and during the continuance of an Event of Default to exchange
certificates or instruments representing or evidencing Pledged Collateral for
certificates or instruments of smaller or larger denominations.

      4. Representations, Warranties and Covenants. In addition to such
representations, warranties and covenants as are made by the Borrowers and by
and on behalf of the Pledgor under the Credit Documents, which representations,
warranties and covenants are hereby deemed made and incorporated into this
Agreement each as though set forth in its entirety herein, Pledgor represents,
warrants and covenants to the Collateral Agent and the other Financial
Institutions, as of the date hereof and as of the date of each extension of
credit under any of the Credit Documents, as follows:

            (a)   The shares described on Schedule I include all of the
authorized, issued and outstanding shares of capital stock of each of the
companies listed thereon and the rights to acquire shares in such companies.

            (b)   Pledgor is the sole legal and equitable owner and holder of
the Pledged Shares shown to be owned by Pledgor on Schedule I, which are free
and clear of all Liens, or rights or interests of any other Person, of every
kind and nature except for the Lien created by this Agreement.

            (c)   The shares of stock described in Section 4(a) are duly
authorized, validly issued, fully paid, non-assessable, and free from any
restriction on transfer, and none of such shares has been issued or transferred
in violation of the securities registration, securities disclosure or similar
laws of any jurisdiction to which such issuance or transfer may be subject.

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            (d)   There are no options, warrants, financing statements, calls or
commitments of any character relating to the Pledged Shares, nor are there any
rights of first refusal, voting trusts, voting agreements or similar agreements
relating to the Pledged Shares.

            (e)   The pledge, assignment and delivery of the Pledged Collateral
pursuant to this Agreement will create a valid first priority lien on and a
first priority perfected security interest in the Pledged Collateral and the
proceeds thereof.

            (f)   The appropriate office to file a financing statement in favor
of the Collateral Agent is described on Schedule II hereto.

            (g)   When additional Pledged Collateral of Pledgor is delivered to
the Collateral Agent in accordance with Section 3, the representations,
warranties and covenants made by Pledgor in Sections 4(b) - (f) shall be deemed
to have been made with respect to such additional Pledged Collateral as of the
date of such delivery to the Collateral Agent.

      5. Further Assurances.

            (a)   Subject to Pledgor's rights under Section 6, at the Collateral
Agent's request from time to time, Pledgor shall instruct (and hereby instructs)
any third party holding such Pledged Collateral to obey only the instructions
and entitlement orders of the Collateral Agent with respect to such Pledged
Collateral and any proceeds thereof.

            (b)   If the validity or priority of this Agreement or of any
rights, titles, security interests or other interests created or evidenced by
this Agreement shall be attacked, endangered or questioned or if any legal
proceedings are instituted with respect thereto, Pledgor agrees that it will
take all necessary and proper steps for the defense of such legal proceedings.
The Collateral Agent is authorized and empowered to take such additional steps
as in its judgment and discretion may be necessary or proper for the defense of
any such legal proceedings or the protection of the validity or priority of this
Agreement and the rights, titles, security interests and other interests created
or evidenced by this Agreement, and the Secured Obligations include all
reasonable out-of-pocket costs and expenses so incurred of every kind and
character.

            (c)   Regarding any proceedings directly regarding the Pledged
Collateral, or any portion thereof, the Collateral Agent may participate
therein, and Pledgor agrees that it shall from time to time deliver to the
Collateral Agent all instruments reasonably requested by it to permit such
participation. Pledgor shall adequately or vigorously, in the reasonable
judgment of Collateral Agent, defend Pledgor's or Collateral Agent's rights to
the Pledged Collateral.

            (d)   Pledgor has and will defend the title to the Pledged
Collateral held by it and the Liens created by this Agreement against all claims
and demands of any Person at any time claiming the Pledged Collateral or any
interest therein and will maintain and preserve such Liens until the termination
of this Agreement.

      6. Voting Rights; Dividends; Etc.

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            (a)   The Pledgor shall have the rights described in (i), (ii) and
(iii) below until (x) an Event of Default has occurred and is continuing and (y)
the notice requirement in Section 6(c) has been complied with:

                  (i)   Pledgor shall be entitled to exercise any and all voting
            and/or other consensual rights pertaining to the Pledged Collateral
            or any part thereof for any purpose consistent with the terms of
            this Agreement or the Credit Documents; provided, however, that
            Pledgor shall not exercise or refrain from exercising any such right
            with the intent of causing a material adverse effect.

                  (ii)  Pledgor shall be entitled to receive and retain any and
            all dividends paid in respect of the Pledged Collateral, other than
            any and all:

                        (A)   dividends paid or payable other than in cash in
                  respect of, and instruments and other property received,
                  receivable or otherwise distributed in respect of, or in
                  exchange for, any Pledged Collateral, provided, however,
                  Pledgor may pay or retain non-cash dividends in the form of
                  equipment, goods, and real property interests to the Company
                  or any of its Subsidiaries to the extent such disposition is
                  permitted by Section 5.2(k) of the Credit Agreement,

                        (B)   dividends and other distributions paid or payable
                  in cash in respect of any Pledged Collateral in connection
                  with a partial or total liquidation or dissolution or in
                  connection with a return of capital, capital surplus or
                  paid-in-surplus, and

                        (C)   cash paid, payable or otherwise distributed in
                  redemption of, or in exchange for, any Pledged Collateral,

                  and all of the foregoing described dividends, if any, received
                  by Pledgor, (i) shall be received in trust for the benefit of
                  the Collateral Agent and segregated from the other property or
                  funds of Pledgor and (ii) shall be forthwith delivered to the
                  Collateral Agent as Pledged Collateral in the same form as so
                  received (with any necessary endorsement).

                  (iii) The Collateral Agent shall execute and deliver (or cause
            to be executed and delivered) to Pledgor all such proxies and other
            instruments as Pledgor may reasonably request for the purpose of
            enabling Pledgor to exercise the voting and other rights which it is
            entitled to exercise pursuant to clause (i) above.

            (b)   Regardless of Pledgor's right described in Section 6(a) above
to receive and retain certain rights and property, such rights and property
nonetheless secure the repayment of the Secured Obligations and are a part of
the Pledged Collateral.

            (c)   Upon the occurrence and during the continuance of an Event of
Default and notice by the Collateral Agent to the Company that an Event of
Default exists and that the Collateral Agent has elected to exercise its rights
pursuant to Section 6(a), all rights of Pledgor to exercise the voting and other
consensual rights which it would otherwise be entitled to exercise

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pursuant to Section 6(a)(i), and to receive all dividends which it may be
entitled to receive under Section 6(a)(ii), and the obligations of the
Collateral Agent under Section 6(a)(iii) shall cease, and all such rights shall
thereupon become vested in the Collateral Agent who shall thereupon have the
sole right to exercise such voting and other rights.

            (d)   In order to permit the Collateral Agent to exercise the voting
and other rights which it may be entitled to exercise pursuant to Section 6(c),
Pledgor agrees that it shall, from time to time execute and deliver to the
Collateral Agent appropriate documents and instruments as the Collateral Agent
may reasonably request. To this end, Pledgor hereby irrevocably constitutes and
appoints the Collateral Agent the proxy and attorney-in-fact of Pledgor, with
full power of substitution, to vote, and to act with respect to, any and all
Pledged Collateral standing in the name of Pledgor or with respect to which
Pledgor is entitled to vote and act, subject to the understanding that such
proxy may not be exercised unless an Event of Default has occurred and is
continuing. The proxy herein granted is coupled with an interest, is
irrevocable, and shall continue until payment in full in cash of the Secured
Obligations and the termination of the Commitments.

      7. Collateral Agent's Rights and Appointed as Attorney-in-Fact. The
provisions of Article VII of the Credit Agreement shall inure to the benefit of
Collateral Agent in respect of this Agreement and shall be binding upon the
parties hereto. Pledgor hereby appoints the Collateral Agent as Pledgor's true
and lawful attorney-in-fact, with full authority in the place and stead of
Pledgor and in the name of Pledgor or otherwise, from time to time after the
occurrence and during the continuance of an Event of Default in the Collateral
Agent's discretion, subject to Section 6, to take any action and to execute any
document or instrument which the Collateral Agent may reasonably deem necessary
or desirable to accomplish the purposes of this Agreement, including, without
limitation, to receive, endorse and collect all instruments made payable to
Pledgor representing any dividend, interest payment or other distribution in
respect of the Pledged Collateral or any part thereof and to give full discharge
for the same. The Collateral Agent's liability, if any, otherwise arising under
applicable law shall be limited to amounts actually received as a result of the
exercise of the powers granted to it herein. No Collateral Agent or Financial
Institution, and no officer, director, employee or collateral trustee of the
Collateral Agent or any Financial Institution, shall be responsible to Pledgor
for any act or failure to act hereunder, except that any such Person shall be
responsible for its own gross negligence or willful misconduct.

      8. Collateral Agent May Perform. If any Pledgor fails to perform any
agreement contained herein, Collateral Agent may itself perform, or cause the
performance of, such agreement, and the reasonable expenses of Collateral Agent
incurred in connection therewith shall be payable by Pledgor. The Collateral
Agent is further authorized in its discretion after the occurrence and during
the continuance of an Event of Default to take any other action, either on its
own behalf or on behalf of Pledgor (and as regards actions taken on behalf of
Pledgor, this authorization is irrevocable and is an agency coupled with an
interest), as the Collateral Agent may elect, which the Collateral Agent may
deem necessary or appropriate to protect and preserve the rights, titles and
interests of the Collateral Agent hereunder. The powers conferred on the
Collateral Agent pursuant to this Agreement are conferred solely to protect the
Collateral Agent and Financial Institutions' interest in the Pledged Collateral
and shall not impose any duty or obligation on the Collateral Agent or any
Financial Institution to perform any of the powers

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herein conferred. No exercise of any of the rights provided for in this
Agreement constitutes a retention of collateral in satisfaction of indebtedness.

      9. No Responsibility for Certain Actions; Indemnity. Neither the
Collateral Agent nor any other Financial Institution shall have responsibility
for (a) ascertaining or taking action with respect to calls, conversions,
exchanges, maturities, tenders or other matters relative to any Pledged
Collateral, whether or not the Collateral Agent or any other Financial
Institution has or is deemed to have knowledge of such matters, (b) taking any
necessary steps to preserve any rights against any Person with respect to any
Pledged Collateral or (c) supervising, monitoring or controlling any aspect of
the character or condition of any of the Pledged Collateral or any operations
conducted in connection with it for the benefit of Pledgor or any other Person.

      10. Remedies upon Default. If any Event of Default shall have occurred and
be continuing:

            (a)   The Collateral Agent may exercise in respect of the Pledged
Collateral, in addition to other rights and remedies provided for herein or
otherwise available to it, all the rights and remedies of a secured party after
default under the UCC, and, subject to applicable regulatory and legal
requirements, the Collateral Agent may also, without notice except as specified
below, sell the Pledged Collateral or any part thereof in one or more parcels at
public or private sale, at any exchange, broker's board or at any of the
Collateral Agent's offices or elsewhere, for cash, on credit or for future
delivery, and upon such other terms as the Collateral Agent may deem
commercially reasonable. Upon consummation of any such sale, the Collateral
Agent shall have the right to assign, transfer and deliver to the purchaser or
purchasers thereof the Pledged Collateral so sold. Each such purchaser at any
such sale shall hold the property sold absolutely free from any claim or right
on the part of Pledgor, and Pledgor, for itself and for its successors,
receivers, trustees and assigns, and for any and all persons ever claiming any
interest in the Pledged Collateral, to the extent permitted by law, hereby
WAIVES all rights of extension, redemption, stay, valuation and appraisal, and
any similar right arising under the law of any country, which Pledgor now has or
may at any time in the future have under any rule of law or statute now existing
or hereafter enacted. Pledgor agrees that, to the extent notice of sale shall be
required by law, at least 10 days' notice to Pledgor of the time and place of
any public sale or the time after which any private sale is to be made shall
constitute reasonable notification. The Collateral Agent shall not be obligated
to make any sale of Pledged Collateral regardless of notice of sale having been
given. The Collateral Agent may adjourn any public or private sale from time to
time by announcement at the time and place fixed therefor, and such sale may,
without further notice, be made at the time and place to which it was so
adjourned. Pledgor hereby WAIVES any claims against the Collateral Agent arising
by reason of the fact that the price at which any Pledged Collateral may have
been sold at such a private sale was less than the price which might have been
obtained at a public sale, even if the Collateral Agent accepts the first offer
received and does not offer such Pledged Collateral to more than one offeree. At
any public sale made pursuant to this Section 10, any Financial Institution may
bid for or purchase, free from any right of redemption, stay or appraisal, and
any similar right arising under the law of any country, on the part of Pledgor
(all said rights being also hereby WAIVED and released by Pledgor), the Pledged
Collateral or any part thereof offered for sale and may make payment on account
thereof by using any claim then due and payable to it from any Obligor and/or
Pledgor as a credit against the purchase price, and it may, upon compliance with
the terms of

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sale, hold, retain and dispose of such property without further accountability
to Pledgor therefor. As an alternative to exercising the power of sale herein
conferred upon it, the Collateral Agent may proceed by a suit or suits at law or
in equity to foreclose upon the Pledged Collateral and to sell the Pledged
Collateral or any portion thereof pursuant to a judgment or decree of a court or
courts having competent jurisdiction or pursuant to a proceeding by a
court-appointed receiver. Any sale pursuant to the provisions of this Section 10
shall be deemed to conform to the commercially reasonable standards as provided
in the UCC. Pledgor covenants and agrees that it will execute and deliver such
documents and take such other action as the Collateral Agent deems necessary or
advisable in order that any such sale may be made in compliance with applicable
law.

            (b)   The Collateral Agent shall have all the rights of a secured
party after default under the UCC and in conjunction with and in addition to
such rights and remedies:

                  (i)   it shall not be necessary that the Pledged Collateral or
            any part thereof be present at the location of any sale pursuant to
            the provisions of this Section 10;

                  (ii)  the sale by the Collateral Agent of less than the whole
            of the Pledged Collateral shall not exhaust the rights of the
            Collateral Agent hereunder, and the Collateral Agent is specifically
            empowered to make successive sale or sales hereunder until the whole
            of the Pledged Collateral shall be sold; and, if the proceeds of
            such sale of less than the whole of the Pledged Collateral shall be
            less than the aggregate of the Secured Obligations, this Agreement
            and the security interest created hereby shall remain in full force
            and effect as to the unsold portion of the Pledged Collateral just
            as though no sale had been made;

                  (iii) in the event any sale hereunder is not completed or is
            defective in the opinion of the Collateral Agent, such sale shall
            not exhaust the rights of the Collateral Agent hereunder and the
            Collateral Agent shall have the right to cause a subsequent sale or
            sales to be made hereunder; and

                  (iv)  demand of performance, advertisement and presence of
            property at sale are hereby WAIVED and the Collateral Agent is
            hereby authorized to sell hereunder any financial asset it may hold
            as security for the Secured Obligations. All demands and
            presentments of any kind or nature are expressly, WAIVED by Pledgor.
            Pledgor hereby WAIVES the right to require the Collateral Agent to
            pursue any other remedy for the benefit of Pledgor and agrees that
            Collateral Agent may proceed against any Person for the amount of
            the Secured Obligations owed to the Collateral Agent without taking
            any action against any other Person and without selling or otherwise
            proceeding against or applying any of the Pledged Collateral in the
            Collateral Agent's possession.

            (c)   Pledgor recognizes that, by reason of certain prohibitions
contained in the Securities Act of 1933 and applicable state securities laws,
the Collateral Agent may be compelled, with respect to any sale of all or any
part of the Pledged Collateral, to limit purchasers to those who will agree,
among other things, to acquire such securities for their own

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account, for investment, and not with a view to the distribution or resale
thereof. Pledgor acknowledges and agrees that any such sale may result in prices
and other terms less favorable to the seller than if such sale were a public
sale without such restrictions and agrees that such circumstances shall not be a
factor in determining whether such sale has been made in a commercially
reasonable manner. The Collateral Agent shall be under no obligation to delay
the sale of any of the Pledged Collateral for the period of time necessary to
permit Pledgor to register such securities for public sale under the Securities
Act of 1933, or under applicable state securities laws, even if Pledgor would
agree to do so.

            (d)   If the Collateral Agent determines to exercise its right to
sell any or all of the Pledged Collateral, upon written request, Pledgor shall,
and shall cause each of its Subsidiaries to, from time to time, furnish to the
Collateral Agent all such information as the Collateral Agent may reasonably
request in order to determine the number of shares and other instruments
included in the Pledged Collateral which may be sold by the Collateral Agent as
exempt transactions under the Securities Act of 1933 and rules of the Securities
and Exchange Commission thereunder, as the same are from time to time in effect.

            (e)   Any cash held by the Collateral Agent as Pledged Collateral
and all cash proceeds received by the Collateral Agent in respect of any sale
of, collection from, or other realization upon all or any part of the Pledged
Collateral shall be at Collateral Agent's discretion either held as Pledged
Collateral or applied by the Collateral Agent to the Secured Obligations in the
manner determined by Collateral Agent in its sole discretion.

            (f)   All remedies herein expressly provided for are cumulative of
any and all other remedies existing at law or in equity and are cumulative of
any and all other remedies provided for in any other instrument securing the
payment of the Secured Obligations, or any part thereof, or otherwise benefiting
the Financial Institutions, and the resort to any remedy provided for hereunder
or under any such other instrument or provided for by law shall not prevent the
concurrent or subsequent employment of any other appropriate remedy or remedies.

            (g)   The Collateral Agent may resort to any security given by this
Agreement or to any other security now existing or hereafter given to secure the
payment of the Secured Obligations, in whole or in part, and in such portions
and in such order as may seem best to the Collateral Agent in its sole
discretion, and any such action shall not in anywise be considered as a waiver
of any of the rights, benefits or security interests evidenced by this
Agreement.

      11. Amendments, Etc. Any amendment or waiver to this Agreement or any
provision hereof shall only be effective to the extent such amendment or waiver
(a) complies with all of those requirements set forth in Section 8.1 of the
Credit Agreement and (b) is executed by the Persons that would be required to
execute a like amendment of the Credit Agreement. Furthermore, all amendments
and waivers to this Agreement will be subject to the limitations and
restrictions applicable to amendments and waivers of the Credit Agreement. The
waiver of any default may be made without waiving any other prior or subsequent
default. The failure by the Collateral Agent to exercise any right, power or
remedy upon any default shall not be construed as a waiver of such default or as
a waiver of the right to exercise any such right, power or remedy at a later
date. No single or partial exercise by the Collateral Agent of any right, power
or remedy hereunder shall exhaust the same or shall preclude any other or
further exercise

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thereof, and every such right, power or remedy hereunder may be exercised at any
time and from time to time. No notice to nor demand on Pledgor in any case shall
of itself entitle Pledgor to any other or further notice or demand in similar or
other circumstances. Acceptance by the Collateral Agent of any payment in an
amount less than the amount then due on the Secured Obligations shall be deemed
an acceptance on account only and shall not in any way affect the existence of a
default. No waiver, release, consent by Collateral Agent pursuant to this
Agreement shall affect or impair the rights of a Financial Institution against
any third party, except to the extent specifically agreed to by such Financial
Institution in such writing.

      12. Address for Notices. Except as otherwise specified herein, all
notices, requests, demands, consents, instructions or other communications
hereunder shall be given in accordance with the terms of Section 8.2 of the
Credit Agreement; however, any notice to Pledgor shall be effective if delivered
to the Company.

      13. Continuing Security Interest. This Agreement shall create a continuing
security interest in the Pledged Collateral and shall (a) remain in full force
and effect until termination of the Commitments and payment in full in cash of
the Secured Obligations; (b) continue to be effective or be reinstated, as the
case may be, if at any time payment and performance of the Secured Obligations
is rescinded or reduced in amount, or must otherwise be restored by the
Collateral Agent or any other Financial Institution upon the insolvency,
bankruptcy, or reorganization of the Company or otherwise, all as though such
payment had not been made; (c) be binding upon Pledgor, its successors and
permitted assigns, and any trustee, receiver, or conservator of Pledgor, and any
successors in interest of Pledgor in and to all or any part of the Pledged
Collateral; and (d) inure, together with the rights and remedies of the
Collateral Agent hereunder, to the benefit of the Collateral Agent, the other
Financial Institutions and their respective successors, transferees and
permitted assigns. Without limiting the generality of the foregoing clause (d),
the Collateral Agent and/or any Financial Institution may assign or otherwise
transfer its rights and obligations under the Credit Documents to any other
Person or entity, and such other Person or entity shall thereupon become vested
with all the benefits in respect thereof granted to such Collateral Agent and/or
Financial Institution herein or otherwise, provided that such assignment shall
be subject to the limitations on assignments set forth in the Credit Agreement.
Upon the completion of both (i) the termination of the Commitments and (ii) the
payment in full in cash of the Secured Obligations, the Pledgor shall be
entitled to the return, upon its request and at its expense, of such of the
Pledged Collateral as shall not have been sold or otherwise applied pursuant to
the terms hereof.

      14. Security Interest and Obligations Absolute. Each Pledgor agrees,
severally, that it will perform its obligations hereunder strictly in accordance
with the terms of this Agreement regardless of any law, regulation or order now
or hereafter in effect in any jurisdiction affecting the Secured Obligations of
the other Credit Parties or the rights of any of the Financial Institutions with
respect thereto. The liability of each of the Pledgor under this Agreement shall
be absolute and unconditional irrespective of:

            (a)   any lack of validity or enforceability of any of the Credit
Documents or any other agreement or instrument relating thereto;

                                       10
<PAGE>

            (b)   any change in the time, manner or place of payment of, or in
any other term of, all or any of the Secured Obligations, or any other
amendment, renewal or waiver of or any consent to any departure from any of the
Credit Documents, including, without limitation, any extension of the term and
any increase in the Secured Obligations or any other liabilities resulting from
the extension of additional credit or otherwise;

            (c)   any taking, exchange, release or non-perfection of any other
collateral, or any release or amendment or waiver of or consent to departure
from any guaranty, for all or any of the Secured Obligations or any other
liability;

            (d)   any manner of application of collateral, or proceeds thereof
or of collections on account of any guaranty, to all or any of the Secured
Obligations or any other liabilities, or any manner of sale or other disposition
of any collateral for all or any of the Secured Obligations or any other
liabilities or of any other assets of the Company or any other Person;

            (e)   any liquidation, dissolution or termination of existence of,
or other change in, the Company or any other Person;

            (f)   any bankruptcy, insolvency, receivership or other proceeding
involving the Company or any other Person or any defense that may arise in
connection with or as a result of any such bankruptcy, insolvency, receivership
or other proceeding or otherwise;

            (g)   any indulgence, moratorium or release granted by any Financial
Institution, including but not limited to (i) any renewal, extension or
modification which a Financial Institution may grant with respect to the Secured
Obligations, (ii) any surrender, compromise, release, renewal, extension,
exchange or substitution which a Financial Institution may grant in respect of
any item securing the Secured Obligations, or any part thereof or any interest
therein, or (iii) any release or indulgence granted to any endorser, guarantor
or surety of the Secured Obligations; or

            (h)   any other circumstance which might otherwise constitute a
defense available to, or a discharge of, the Company, Pledgor, a third party
pledgor or any other Person (other than the satisfaction of the Secured
Obligations).

      15. Severability. Any provision hereof that is prohibited or unenforceable
in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent
of such prohibition or unenforceability without invalidating the remaining
provisions hereof and without affecting the validity or enforceability of any
provision in any other jurisdiction.

      16. Waiver of Jury Trial. THE PLEDGOR, THE COLLATERAL AGENT, AND THE
FINANCIAL INSTITUTIONS HEREBY IRREVOCABLY WAIVE ANY AND ALL RIGHT TO TRIAL BY
JURY IN ANY LEGAL PROCEEDING ARISING OUT OF OR RELATING TO THIS AGREEMENT OR ANY
OF THE TRANSACTIONS CONTEMPLATED HEREBY.

      17. Governing Law; Jurisdiction; Damages.

                                       11
<PAGE>

            (a)   This Agreement shall be governed by and construed in
accordance with the laws of the State of New York.

            (b)   ANY LITIGATION BASED HEREON, OR ANY COURSE OF CONDUCT, COURSE
OF DEALING, STATEMENTS (WHETHER ORAL OR WRITTEN) OR ACTIONS OF THE COLLATERAL
AGENT, THE FINANCIAL INSTITUTIONS OR THE PLEDGOR IN CONNECTION HEREWITH MAY BE
BROUGHT AND MAINTAINED IN THE COURTS OF THE STATE OF NEW YORK OR IN THE UNITED
STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW YORK; PROVIDED, HOWEVER,
THAT ANY SUIT SEEKING ENFORCEMENT AGAINST ANY PLEDGED COLLATERAL OR OTHER
PROPERTY MAY BE BROUGHT, AT THE PLEDGED COLLATERAL AGENT'S OPTION, IN THE COURTS
OF ANY JURISDICTION WHERE SUCH COLLATERAL OR OTHER PROPERTY MAY BE FOUND.
PLEDGOR IRREVOCABLY CONSENTS TO THE SERVICE OF PROCESS BY REGISTERED MAIL,
POSTAGE PREPAID, OR BY PERSONAL SERVICE WITHIN OR WITHOUT THE STATE OF NEW YORK
AT THE ADDRESS FOR NOTICES TO THE COMPANY SPECIFIED IN SECTION 8.2 OF THE CREDIT
AGREEMENT. PLEDGOR HEREBY EXPRESSLY AND IRREVOCABLY WAIVES, TO THE FULLEST
EXTENT PERMITTED BY LAW, ANY OBJECTION WHICH IT MAY HAVE OR HEREAFTER MAY HAVE
TO THE LAYING OF VENUE OF ANY SUCH LITIGATION BROUGHT IN ANY SUCH COURT REFERRED
TO ABOVE AND ANY CLAIM THAT ANY SUCH LITIGATION HAS BEEN BROUGHT IN AN
INCONVENIENT FORUM. TO THE EXTENT THAT PLEDGOR HAS OR HEREAFTER MAY ACQUIRE ANY
IMMUNITY FROM JURISDICTION OF ANY COURT OR FROM ANY LEGAL PROCESS (WHETHER
THROUGH SERVICE OR NOTICE, ATTACHMENT PRIOR TO JUDGMENT, ATTACHMENT IN AID OF
EXECUTION OR OTHERWISE) WITH RESPECT TO ITSELF OR ITS PROPERTY, PLEDGOR HEREBY
IRREVOCABLY WAIVES TO THE FULLEST EXTENT PERMITTED BY LAW SUCH IMMUNITY IN
RESPECT OF ITS OBLIGATIONS UNDER THIS AGREEMENT.

            (c)   PLEDGOR AND THE FINANCIAL INSTITUTIONS HEREBY IRREVOCABLY AND
UNCONDITIONALLY WAIVES, TO THE FULLEST EXTENT IT MAY EFFECTIVELY DO SO UNDER
APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO CLAIM OR RECOVER IN ANY ACTION OR
PROCEEDING REFERRED TO IN THIS SECTION 18 ANY EXEMPLARY, PUNITIVE, SPECIAL OR
CONSEQUENTIAL DAMAGES; PROVIDED THAT NOTHING HEREIN SHALL CONSTITUTE A WAIVER BY
THE AGENT, PLEDGOR, ANY ISSUING BANK OR ANY BANK OF THE RIGHT TO RECEIVE FULL
PAYMENT OF ALL OBLIGATIONS. PLEDGOR HEREBY APPOINTS TWC TO SERVE AS ITS AGENT
FOR SERVICE OF PROCESS ON BEHALF OF PLEDGOR IN CONNECTION WITH THE CREDIT
DOCUMENTS AND THE OBLIGATIONS.

            (d)   THIS AGREEMENT TOGETHER WITH THE OTHER CREDIT DOCUMENTS
EMBODIES THE ENTIRE AGREEMENT AND UNDERSTANDING AMONG THE PARTIES WITH RESPECT
TO ITS SUBJECT MATTER AND SUPERSEDES ALL PRIOR OR CONTEMPORANEOUS AGREEMENTS AND

                                       12
<PAGE>

UNDERSTANDINGS OF SUCH PERSONS, VERBAL OR WRITTEN, RELATING TO SUCH SUBJECT
MATTER.

      18. Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original for all purposes;
but such counterparts shall be deemed to constitute but one and the same
instrument. Delivery of an executed counterpart of a signature page to this
Agreement by telecopier shall be as effective as delivery of an original
executed counterpart of this Agreement.

      19. Waiver. Pledgor hereby waives promptness, diligence, notice of
acceptance and any other notice (except notices expressly required to be given
to Pledgor under this Agreement) with respect to any of the Secured Obligations
and this Agreement and any requirement that any of the Financial Institutions
protect, secure, perfect or insure any security interest or other Lien or any
property subject thereto or exhaust any right to take any action against the
Company or any other Person or any collateral.

      20. Subrogation. Pledgor irrevocably WAIVES any and all rights to which it
may be entitled (by operation of law or otherwise) by performing its obligations
under this Agreement to be subrogated to the rights of any Financial Institution
against the Company until the Obligations have been paid in full and the
Commitments have been terminated. If any amount shall be paid to Pledgor on
account of such subrogation rights, Pledgor agrees to hold such amount of such
payment, as the case may be, in trust for the benefit of the Financial
Institutions, and Pledgor agrees to forthwith pay such amount or such payment,
as the case may be, to the Collateral Agent to be credited against and applied
upon the Secured Obligations, in such order as may be determined by the
Collateral Agent in its sole discretion.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       13
<PAGE>

IN WITNESS WHEREOF, the Pledgor caused this Agreement to be duly executed and
delivered by their respective officers or representatives thereunto duly
authorized as of the date first above written.

                                            PLEDGOR:

                                            WILLIAMS FIELD SERVICES GROUP, INC.

                                            By:    /s/ Travis N. Campbell
                                                -------------------------
                                            Name:  Travis N. Campbell
                                            Title: Assistant Treasurer

Agreed to:

CITICORP USA, INC.,
SOLELY IN ITS CAPACITY AS COLLATERAL AGENT

By:     /s/ Todd J. Mogil
    ---------------------
Name:   Todd J. Mogil
Title:  Vice President<PAGE>

                                                                    Exhibit 10.7

                                                                [Execution Copy]

                           WESTERN MIDSTREAM GUARANTY

      This Guaranty dated as of May 3, 2004, (the "Guaranty") is by each of the
entities named on the signature pages hereto (each a "Guarantor" and
collectively, the "Guarantors"), in favor of Citicorp USA, Inc., solely in its
capacity as collateral agent ("Collateral Agent") for the Financial Institutions
(as defined below).

                                  INTRODUCTION

      A.    The Williams Companies, Inc., a Delaware corporation (the
"Company"), Northwest Pipeline Corporation, a Delaware corporation ("NWP"), and
Transcontinental Gas Pipe Line Corporation, a Delaware corporation ("TGPL", and
together with TWC and NWP, the "Borrowers"), have entered into a Credit
Agreement dated as of May 3, 2004 (as amended or otherwise modified from time to
time, the "Credit Agreement", the defined terms from the Credit Agreement are
used in this Guaranty as defined therein unless otherwise defined herein),
together with Citicorp USA, Inc., as administrative agent and collateral agent
("Collateral Agent"), Bank of America, N.A., as syndication agent ("Syndication
Agent"), Citibank, N.A. and Bank of America, N.A., as issuing banks ("Issuing
Banks"), the banks named therein (the "Banks"), JPMorgan Chase Bank, The Bank of
Nova Scotia and The Royal Bank of Scotland PLC as co-documentation agents
(collectively, the "Co-Documentation Agents"), and Citigroup Global Markets Inc.
and Banc of America Securities LLC, as joint lead arrangers and co-book runners
(collectively, the "Co-Arrangers"), providing for the extension of credit and
the issuance of Letters of Credit. The Collateral Agent, Syndication Agent,
Issuing Banks, Banks, Co-Documentation Agents and Co-Arrangers and the
successors and permitted assigns of the foregoing are collectively referred to
herein as the "Financial Institutions."

      B.    It is a condition to certain transactions under the Credit
Documents, that the Guarantors shall have executed and delivered this Guaranty.

      C.    The Company is the principal financing entity for all capital
requirements of its Subsidiaries, and from time to time the Company has made
capital contributions and advances to each Guarantor. Each Guarantor is a wholly
owned Subsidiary of the Company and will derive substantial direct or indirect
benefit from the transactions contemplated by the Credit Documents.

      THEREFORE, in order to induce the Financial Institutions to enter into
and/or continue certain financing transactions described in the Credit
Documents, each of the Guarantors hereby agrees for the benefit of the Financial
Institutions as follows:

Section 1.  Guaranty. Each of the Guarantors, severally, hereby unconditionally
and irrevocably guarantees the punctual payment when due, whether at stated
maturity, by acceleration or otherwise, of the Guaranteed Obligations (defined
below). For purposes of this Guaranty, the term "Guaranteed Obligations" shall
mean collectively (a) all obligations under this Guaranty and (b) all
Obligations (as such term is defined in the Credit Agreement, including, without
limitation, the outstanding principal amount of indebtedness, reimbursement
obligations

<PAGE>

for draws on letters of credit, and cash collateralization obligations for
letters of credit under the Credit Documents, all accrued but unpaid interest
thereon under the Credit Documents, all premiums, if any, in connection
therewith under the Credit Documents, all fees in connection therewith under the
Credit Documents, and all other reimbursement, indemnification, and other
payment obligations in connection therewith under the Credit Documents; provided
that Guaranteed Obligations shall not include any increases which occur after
the date hereof in the principal amount of the obligations under the Credit
Documents (other than (i) increases in the principal amount of such obligations
that are provided for as of the date of the execution of this Agreement but not
yet funded and (ii) increases contemplated by Section 2.19 of the Credit
Agreement) and/or the commitments to advance funds or letters of credit
thereunder. Without limiting the generality of the foregoing, each Guarantor's
liability shall extend to all amounts which constitute part of the Guaranteed
Obligations even if such Guaranteed Obligations are declared unenforceable or
not allowable in a bankruptcy, reorganization, or similar proceeding involving
any Borrowers, or any guarantor of any portion of the foregoing Guaranteed
Obligations (collectively such guarantors together with the Guarantors and the
Borrowers are referred to herein as the "Obligors"). This Guaranty is a
guarantee of payment, not of collection, and each Guarantor is primarily liable
for the payment of the Guaranteed Obligations. In the event that Collateral
Agent wishes to enforce the guarantee contained in this Section 1 hereof against
any Guarantor, it shall make written demand for payment from such Guarantor,
provided that no such demand shall be required if such Guarantor is in
bankruptcy, liquidation, or other insolvency proceedings, and provided that
failure by Collateral Agent to make such demand shall not affect any Guarantor's
obligations under this Guaranty.

Section 2.  Limit of Liability. The liabilities and obligations of each
Guarantor under the Credit Documents shall be limited to an aggregate amount
equal to the largest amount that would not render such Guarantor's obligations
hereunder subject to avoidance under Section 548 of the United States Bankruptcy
Code or any comparable provisions of any applicable state law.

Section 3.  Guaranty Absolute. Each of the Guarantors guarantees that the
Guaranteed Obligations will be paid strictly in accordance with the Credit
Documents, regardless of any law, regulation, or order now or hereafter in
effect in any jurisdiction affecting any of the obligations described in clause
(b) of Section 1 above or the rights of the Collateral Agent or any other
Financial Institution with respect thereto. The obligations of each Guarantor
under this Guaranty are independent of the Guaranteed Obligations in each and
every particular, and a separate action or actions may be brought and prosecuted
against any other Obligor, or any other Person regardless of whether any other
Obligor or any other Person is joined in any such action or actions. The
liability of each Guarantor under this Guaranty shall be absolute and
unconditional irrespective of:

      (a)   The lack of validity or unenforceability of the Guaranteed
Obligations or any Credit Document (other than this Guaranty against such
Guarantor) for any reason whatsoever, including that the act of creating the
Guaranteed Obligations is ultra vires, that the officers or representatives
executing the documents creating the Guaranteed Obligations exceeded their
authority, that the Guaranteed Obligations violate usury or other laws, or that
any Obligor has defenses to the payment of the Guaranteed Obligations, including
breach of warranty, statute of frauds, bankruptcy, statute of limitations,
lender liability, or accord and satisfaction;

      (b)   Any change in the time, manner, or place of payment of, or in any
term of, any of the Guaranteed Obligations, any increase (subject to Section 1),
reduction, extension, or

<PAGE>

rearrangement of the Guaranteed Obligations, any amendment, supplement, or other
modification of the Credit Documents, or any waiver or consent granted under the
Credit Documents, including waivers of the payment and performance of the
Guaranteed Obligations;

      (c)   Any release, exchange, subordination, waste, or other impairment
(including negligent, willful, unreasonable, or unjustifiable impairment) of any
collateral securing payment of the Guaranteed Obligations; the failure of
Collateral Agent, any other Financial Institution or any other person to
exercise diligence or reasonable care in the preservation, protection,
enforcement, sale, or other handling of the collateral; the fact that any
security interest, lien, or assignment related to any collateral for the
Guaranteed Obligations shall not be properly perfected, or shall prove to be
unenforceable or subordinate to any other security interest, lien, or
assignment;

      (d)   Any full or partial release of any Obligor (other than the full or
partial release of such Guarantor);

      (e)   The failure to apply or the manner of applying collateral or
payments of the proceeds of collateral against the Guaranteed Obligations;

      (f)   Any change in the organization or structure of any Obligor; any
change in the shareholders, directors, or officers of any Obligor; or the
insolvency, bankruptcy, liquidation, or dissolution of any Obligor or any
defense that may arise in connection with or as a result of any such insolvency,
bankruptcy, liquidator or dissolution;

      (g)   The failure to give notice of any extension of credit made by
Collateral Agent or any other Financial Institution to any Obligor, notice of
acceptance of this Guaranty, notice of any amendment, supplement, or other
modification of any Credit Document, notice of the execution of any document or
agreement creating new Guaranteed Obligations, notice of any default or event of
default, however denominated, under the Credit Documents, notice of intent to
demand, notice of demand, notice of presentment for payment, notice of
nonpayment, notice of intent to protest, notice of protest, notice of grace,
notice of dishonor, notice of intent to accelerate, notice of acceleration,
notice of bringing of suit, notice of Collateral Agent or any other Financial
Institution's transfer of the Guaranteed Obligations, notice of the financial
condition of or other circumstances regarding any Obligor, or any other notice
of any kind relating to the Guaranteed Obligations;

      (h)   Any payment or grant of collateral by any Obligor to Collateral
Agent or any other Financial Institution being held to constitute a preference
under bankruptcy laws, or for any reason Collateral Agent or any other Financial
Institution is required to refund such payment or release such collateral;

      (i)   Any other action taken or omitted which affects the Guaranteed
Obligations, whether or not such action or omission prejudices any Guarantor or
increases the likelihood that any Guarantor will be required to pay the
Guaranteed Obligations pursuant to the terms hereof;

      (j)   The fact that all or any of the Guaranteed Obligations cease to
exist by operation of law, including, without limitation, by way of discharge,
limitation or tolling thereof under applicable bankruptcy laws; and

<PAGE>

      (k)   Any other circumstances which might otherwise constitute a defense
available to, or a discharge of any Obligor (other than the discharge of such
Guarantor or the satisfaction of the Guaranteed Obligations).

Section 4.  Collateral Agent's Rights and Certain Waivers.

      4.01. Notice and Other Remedies. Each of the Guarantors hereby waives
promptness, diligence, notice of acceptance, notice of acceleration, notice of
intent to accelerate, and any other notice with respect to any of the Guaranteed
Obligations and this Guaranty and any requirement that Collateral Agent or any
other Financial Institution protect, secure, perfect or insure any security
interest or other Lien or any property subject thereto or exhaust any right to
take any action against any Obligor or any other Person or any collateral.

      4.02. Waiver of Subrogation and Contribution. (a) Until such time as the
Guaranteed Obligations are irrevocably paid in full, each of the Guarantors
hereby irrevocably waives any claim or other rights which it may acquire against
any Obligor that arise from such Guarantor's Guaranteed Obligations under this
Guaranty or any other Credit Document, including, without limitation, any right
of subrogation (including, without limitation, any statutory rights of
subrogation under Section 509 of the Bankruptcy Code, 11 U.S.C. Section 509),
reimbursement, exoneration, contribution, indemnification, or any right to
participate in any claim or remedy of Collateral Agent or any other Financial
Institution against any Obligor, or any collateral which Collateral Agent or any
other Financial Institution now has or acquires. If any amount shall be paid to
any Guarantor in violation of the preceding sentence and the Guaranteed
Obligations shall not have been paid in full, such amount shall be held in trust
for the benefit of Collateral Agent and the Financial Institutions, and shall
promptly be paid to Collateral Agent for the benefit of Collateral Agent and the
Financial Institutions to be applied to the Guaranteed Obligations, whether
matured or unmatured, as Collateral Agent may elect. Each of the Guarantors
acknowledges that it will receive direct and indirect benefits from the
financing arrangements contemplated by the Credit Documents and that the waiver
set forth in this Section 4.02(a) is knowingly made in contemplation of such
benefits.

      (b)   Each of the Guarantors agrees that, to the extent that any Borrower
makes payments to Collateral Agent or any other Financial Institution, or
Collateral Agent or any other Financial Institution receives any proceeds of
collateral, and such payments or proceeds or any part thereof are subsequently
invalidated, declared to be fraudulent or preferential, set aside, or otherwise
required to be repaid, then to the extent of such repayment the Guaranteed
Obligations shall be reinstated and continued in full force and effect as of the
date such initial payment or collection of proceeds occurred. EACH OF THE
GUARANTORS SHALL INDEMNIFY THE COLLATERAL AGENT AND ANY OTHER FINANCIAL
INSTITUTION AND EACH AFFILIATE THEREOF AND THEIR RESPECTIVE DIRECTORS, OFFICERS,
EMPLOYEES AND AGENTS FROM, AND DISCHARGE, RELEASE, AND HOLD EACH OF THEM
HARMLESS AGAINST, ANY AND ALL LOSSES, LIABILITIES, PENALTIES, ACTIONS,
JUDGMENTS, SUITS, COSTS, DISBURSEMENTS, CLAIMS OR DAMAGES TO WHICH ANY OF THEM
MAY BECOME SUBJECT, INSOFAR AS SUCH LOSSES, LIABILITIES, PENALTIES, ACTIONS,
JUDGMENTS, SUITS, COSTS, DISBURSEMENTS, CLAIMS OR DAMAGES ARISE OUT OF OR RESULT
FROM (I) ANY ACTUAL OR PROPOSED USE BY ANY BORROWER, OR ANY AFFILIATE OF ANY
BORROWER OF THE PROCEEDS OF ANY ADVANCE, (II) ANY BREACH BY ANY GUARANTOR OF ANY
PROVISION OF THIS GUARANTY OR ANY OTHER CREDIT DOCUMENT, (III) ANY
INVESTIGATION, LITIGATION OR OTHER PROCEEDING (INCLUDING ANY THREATENED
INVESTIGATION OR PROCEEDING) RELATING TO THE FOREGOING, OR (IV) ANY
ENVIRONMENTAL CLAIM OR REQUIREMENT OF ENVIRONMENTAL LAWS CONCERNING OR RELATING
TO THE PRESENTLY OR

<PAGE>

PREVIOUSLY-OWNED OR OPERATED PROPERTIES, OR THE OPERATIONS OR BUSINESS, OF ANY
OBLIGOR, AND EACH OF THE GUARANTORS SHALL REIMBURSE THE COLLATERAL AGENT AND
EACH FINANCIAL INSTITUTION, AND EACH AFFILIATE THEREOF AND THEIR RESPECTIVE
DIRECTORS, OFFICERS, EMPLOYEES AND AGENTS, UPON DEMAND FOR ANY REASONABLE
OUT-OF-POCKET EXPENSES (INCLUDING LEGAL FEES) INCURRED IN CONNECTION WITH ANY
SUCH INVESTIGATION, LITIGATION OR OTHER PROCEEDING; SUCH INDEMNIFIATION AND
REIMBURSEMENT OBLIGATIONS EXPRESSLY INCLUDE ANY SUCH LOSSES, LIABILITIES,
PENALTIES, ACTIONS, JUDGMENTS, SUITS, COSTS, DISBURSEMENTS, CLAIMS, DAMAGES, OR
EXPENSE INCURRED BY REASON OF THE NEGLIGENCE (OTHER THAN GROSS NEGLIGENCE) OF
THE PERSON BEING INDEMNIFIED, BUT EXCLUDE ANY SUCH LOSSES, LIABILITIES,
PENALTIES, ACTIONS, JUDGMENTS, SUITS, COSTS, DISBURSEMENTS, CLAIMS, DAMAGES OR
EXPENSES INCURRED BY REASON OF THE GROSS NEGLIGENCE OR WILLFUL MISCONDUCT OF THE
PERSON TO BE INDEMNIFIED.

      Collateral Agent shall have the absolute right to make demands, file suits
and claims, engage in other proceedings and exercise any other rights or
remedies available to Collateral Agent to collect amounts owed to it pursuant to
the terms of the indemnities set forth in this Guaranty, and Collateral Agent
shall not need the consent of any other Financial Institution or Person
whatsoever to do so.

      4.03. Modifications and Amendment to the Credit Documents. As provided in
Section 1 above, certain increases in the principal indebtedness outstanding
under the Credit Documents shall not constitute Guaranteed Obligations. Except
as to the foregoing, the parties to the Credit Documents shall have the right to
amend or modify such Credit Documents without affecting the rights provided for
in this Guaranty.

Section 5.  Representations, Warranties and Covenants. In addition to such
representations, warranties and covenants as are made by the Borrowers and by
and on behalf of the Guarantors under the Credit Documents, which
representations, warranties and covenants are hereby deemed made and
incorporated into this Agreement each as though set forth in its entirety
herein, each Guarantor covenants, to the Collateral Agent and the other
Financial Institutions, that such Guarantor will comply with all provisions of
the Credit Documents that are applicable to such Guarantor including the
provisions of Article V of the Credit Agreement and Article III of the Midstream
Security Agreement.

Section 6.  Miscellaneous.

      6.01. Amendments, Waivers. Any amendment or waiver to this Guaranty or any
provision hereof shall only be effective to the extent such amendment or waiver
(a) complies with all of those requirements set forth in Section 8.1 of the
Credit Agreement and (b) is executed by the Persons that would be required to
execute a like amendment of the Credit Agreement. Furthermore, all amendments
and waivers to this Guaranty will be subject to the limitations and restrictions
applicable to amendments and waivers of the Credit Agreement.

      6.02. Notices. All notices and other communications to a Guarantor shall
be delivered to the address of the Company set forth in Section 8.2 of the
Credit Agreement, or to such other address as shall be designated by such
Guarantor by written notice to the Collateral Agent. All notices and other
communications provided for under this Guaranty shall be in writing (including
telecopy communication), shall be mailed, telecopied, or delivered, and shall,
when mailed or telecopied, be effective when received in the mail or sent by
telecopier.

<PAGE>

      6.03. No Waiver; Remedies. No failure on the part of Collateral Agent or
any other Financial Institution to exercise, and no delay in exercising, any
right hereunder shall operate as a waiver thereof, nor shall any single or
partial exercise of any right hereunder preclude any other or further exercise
thereof or the exercise of any other right. The remedies herein provided are
cumulative and not exclusive of any remedies provided by law.

      6.04. Right of Set-Off. Upon the occurrence and during the continuance of
any Event of Default, and (ii) either (a) the Revolving Credit Advances owed by
any Borrower having become due and payable in accordance with the terms of the
Credit Agreement or (b) the making of the request or the granting of the consent
specified by Section 6.1 of the Credit Agreement to authorize the Agent to
declare the Revolving Credit Advances owed by any Borrower due and payable
pursuant to the provisions of Section 6.1 of the Credit Agreement, each of
Collateral Agent and the other Financial Institutions is hereby authorized at
any time, to the fullest extent permitted by law, to set off and apply any
deposits (general or special, time or demand, provisional or final) and other
indebtedness owing by Collateral Agent or such Financial Institution to the
accounts of the Guarantors against any and all of the obligations of the
Guarantors under this Guaranty, irrespective of whether or not Collateral Agent
or such Financial Institution shall have made any demand under this Guaranty and
although such obligations may be contingent and unmatured. Collateral Agent and
each Financial Institution agree promptly to notify the Guarantors after any
such set-off and application made by Collateral Agent or such Financial
Institution provided that the failure to give such notice shall not affect the
validity of such set-off and application. The rights of Collateral Agent and the
Financial Institutions under this Section 6.04 are in addition to any other
rights and remedies (including, without limitation, other rights of set-off)
which Collateral Agent and the Financial Institutions may have.

      6.05. Continuing Guaranty; Assignments under Credit Documents. This
Guaranty is a continuing guaranty and shall (a) remain in full force and effect
until the indefeasible payment in full of the Guaranteed Obligations and all
other amounts payable under this Guaranty, (b) be binding upon each Guarantor
and its respective successors and assigns, (c) inure to the benefit of, and be
enforceable by, Collateral Agent and each of the Financial Institutions and
their respective successors, transferees and assigns, and (d) not be terminated
by any Guarantor or any other Person. Without limiting the generality of the
foregoing clause (c), Collateral Agent and any other Financial Institution may
assign or otherwise transfer all or any portion of its rights and obligations
under this Guaranty and the assignee shall thereupon become vested with all the
benefits in respect thereof granted to Collateral Agent or such Financial
Institution herein or otherwise, provided that such assignment shall be subject
to the limitations on assignments set forth in the Credit Agreement. Upon the
indefeasible payment in full and termination of the Guaranteed Obligations, each
guaranty granted hereby shall terminate and all rights hereunder shall revert to
the Guarantor to the extent such rights have not been applied pursuant to the
terms hereof. Upon any such termination, Collateral Agent will, at such
Guarantor's expense, execute and deliver to any Guarantor such documents as such
Guarantor shall reasonably request and take any other actions reasonably
requested to evidence or effect such termination. This Guaranty is not
assignable by any Guarantor without the written consent of the Collateral Agent.

      6.06  Governing Law; Submission to Jurisdiction; Damages; Suits and
Claims.

<PAGE>

      (a)   This Guaranty shall be governed by, and construed and enforced in
accordance with, the laws of the State of New York, except to the extent
provided in Section 6.06(b) hereof and to the extent that the federal laws of
the United States of America may otherwise apply.

      (b)   Notwithstanding anything in Section 6.06(a) hereof to the contrary,
nothing in this Guaranty shall be deemed to constitute a waiver of any rights
which Collateral Agent or any of the other Financial Institutions may have under
the National Bank Act or other federal law, including without limitation the
right to charge interest at the rate permitted by the laws of the state where
Collateral Agent or any other applicable Financial Institution is located.

      (c)   ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER, OR IN
CONNECTION WITH, ANY CREDIT DOCUMENT, OR ANY COURSE OF CONDUCT, COURSE OF
DEALING, STATEMENTS (WHETHER ORAL OR WRITTEN) OR ACTIONS OF THE COLLATERAL
AGENT, THE FINANCIAL INSTITUTIONS OR ANY GUARANTOR IN CONNECTION HEREWITH OR
THEREWITH MAY BE BROUGHT AND MAINTAINED IN THE COURTS OF THE STATE OF NEW YORK
OR IN THE UNITED STATES DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW YORK;
PROVIDED, HOWEVER, THAT ANY SUIT SEEKING ENFORCEMENT AGAINST ANY COLLATERAL OR
OTHER PROPERTY MAY BE BROUGHT, AT COLLATERAL AGENT'S OPTION, IN THE COURTS OF
ANY JURISDICTION WHERE SUCH COLLATERAL OR OTHER PROPERTY MAY BE FOUND. EACH
GUARANTOR IRREVOCABLY CONSENTS TO THE SERVICE OF PROCESS BY REGISTERED MAIL,
POSTAGE PREPAID, OR BY PERSONAL SERVICE WITHIN OR WITHOUT THE STATE OF NEW YORK
AT THE ADDRESS FOR NOTICES PROVIDED FOR HEREIN. EACH GUARANTOR HEREBY EXPRESSLY
AND IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ANY OBJECTION
WHICH IT MAY HAVE OR HEREAFTER MAY HAVE TO THE LAYING OF VENUE OF ANY SUCH
LITIGATION BROUGHT IN ANY SUCH COURT REFERRED TO ABOVE AND ANY CLAIM THAT ANY
SUCH LITIGATION HAS BEEN BROUGHT IN AN INCONVENIENT FORUM. TO THE EXTENT THAT
ANY GUARANTOR HAS OR HEREAFTER MAY ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY
COURT OR FROM ANY LEGAL PROCESS (WHETHER THROUGH SERVICE OR NOTICE, ATTACHMENT
PRIOR TO JUDGMENT, ATTACHMENT IN AID OF EXECUTION OR OTHERWISE) WITH RESPECT TO
ITSELF OR ITS PROPERTY, EACH GUARANTOR HEREBY IRREVOCABLY WAIVES TO THE FULLEST
EXTENT PERMITTED BY LAW SUCH IMMUNITY IN RESPECT OF ITS OBLIGATIONS UNDER THIS
GUARANTY AND THE CREDIT DOCUMENTS. EACH OF THE GUARANTORS, THE COLLATERAL AGENT,
AND THE FINANCIAL INSTITUTIONS HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES, TO
THE FULLEST EXTENT IT MAY EFFECTIVELY DO SO UNDER APPLICABLE LAW, ANY RIGHT IT
MAY HAVE TO CLAIM OR RECOVER IN ANY ACTION OR PROCEEDING REFERRED TO IN THIS
SECTION 6.06 ANY EXEMPLARY, PUNITIVE SPECIAL OR CONSEQUENTIAL DAMAGES; PROVIDED
THAT NOTHING HEREIN SHALL CONSTITUTE A WAIVER BY THE COLLATERAL AGENT, OR ANY
OTHER FINANCIAL INSTITUTION OF THE RIGHT TO RECEIVE FULL PAYMENT OF THE
GUARANTEED OBLIGATIONS.

      (d)   EACH GUARANTOR, COLLATERAL AGENT AND THE FINANCIAL INSTITUTIONS
HEREBY IRREVOCABLY WAIVE ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL
PROCEEDING ARISING OUT OF OR RELATING TO THIS GUARANTY OR ANY OF THE
TRANSACTIONS CONTEMPLATED HEREBY.

      (e)   The provisions set forth in this Guaranty shall only be enforceable
by Collateral Agent, the Financial Institutions and their respective successors
and permitted assigns, and no other Person shall have the right to bring any
claim or cause of action based on this Guaranty.

      6.07. Survival. All agreements, statements, representations and warranties
made by the Guarantors herein or in any certificate or other instrument
delivered by the Guarantors or on the behalf of the Guarantors under this
Guaranty shall be considered to have been relied upon by Collateral Agent and
the Financial Institutions and shall survive the execution and delivery of

<PAGE>

this Guaranty and the other Credit Documents regardless of any investigation
made by Collateral Agent or any other Financial Institution or on their behalf.

      6.08. Headings Descriptive. The headings of the various articles, sections
and paragraphs of this Guaranty are for convenience of reference only, do not
constitute a part hereof and shall not affect the meaning or construction of any
provision hereof.

      6.9.  Severability. In the event any one or more of the provisions
contained in this Guaranty or in any Security Document should be held invalid,
illegal or unenforceable in any respect, the validity, legality and
enforceability of the remaining provisions contained herein and therein shall
not in any way be affected or impaired thereby. The parties shall endeavor in
good-faith negotiations to replace the invalid, illegal or unenforceable
provisions with valid provisions the economic effect of which comes as close as
possible to that of the invalid, illegal or unenforceable provisions.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

<PAGE>

      Each Guarantor has caused this Guaranty to be duly executed as of the date
first above written.

                                          GUARANTORS:

                                          WILLIAMS FIELD SERVICES COMPANY

                                          By:    /s/ Travis N. Campbell
                                              -------------------------
                                          Name:  Travis N. Campbell
                                          Title: Assistant Treasurer

                                          WILLIAMS GAS PROCESSING COMPANY

                                          By:    /s/ Travis N. Campbell
                                              -------------------------
                                          Name:  Travis N. Campbell
                                          Title: Assistant Treasurer

                                          WILLIAMS GAS PROCESSING - WAMSUTTER
                                          COMPANY

                                          By:    /s/ Travis N. Campbell
                                              -------------------------
                                          Name:  Travis N. Campbell
                                          Title: Assistant Treasurer

                     [SIGNATURE PAGE TO MIDSTREAM GUARANTY]

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