Document:

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                                                                     EXHIBIT 4.1

                             REGISTRATION AGREEMENT

         THIS REGISTRATION AGREEMENT (the "AGREEMENT") is made and entered into
as of September 15, 2000, by and among Universal Compression Holdings, Inc., a
Delaware corporation (the "COMPANY"), The Reuben James Helton Trust Dated
January 24, 2000 (the "TRUST INVESTOR"), and Michael Pahl (the "INDIVIDUAL
INVESTOR") (the Trust Investor and the Individual Investor collectively referred
to as the "INVESTORS" and individually as the "INVESTOR").

         This Agreement is made in connection with the proposed merger (the
"MERGER") of Gas Compression Services, Inc., a Michigan corporation, with and
into Universal Compression, Inc., a Texas corporation and wholly owned
subsidiary of the Company. In connection with the Merger, the Company has agreed
to provide the Investor with the registration and sale rights set forth in this
Agreement.

         In consideration of the foregoing, the parties hereto agree as follows:

         SECTION 1. CERTAIN DEFINITIONS:

                  "COMMON STOCK" shall mean the common stock of the Company,
         $.01 par value per share.

                  "ELIGIBLE COMMON STOCK" shall mean the shares of Common Stock
         acquired in the Merger and held by the Investors and any of such shares
         thereafter held by any transferee or assignee of an Investor pursuant
         to Section 11(c) hereof on the date of determination.

                  "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934,
         as amended, and the rules and regulations thereunder.

                  "PERMITTED TRANSFEREE" shall mean a Person (i) to whom the
         Investor has transferred Eligible Common Stock pursuant to Section
         11(c) hereof and (ii) who has executed and delivered to the Company an
         Additional Party Counterpart in the form set forth in Exhibit A.

                  "PERSON" shall mean any individual, partnership, corporation,
         trust or unincorporated organization, or a government or agency or
         political subdivision thereof.

                  "PROSPECTUS" shall mean the prospectus included in a
         Registration Statement, including any preliminary prospectus, and any
         such prospectus as amended or supplemented by any prospectus supplement
         with respect to the terms of the offering of the Common Stock covered
         by the Registration Statement, and by all other amendments and
         supplements to such Prospectus, including post-effective amendments,
         and in each case including all materials incorporated by reference
         therein.

                  "REGISTRATION STATEMENT" shall mean any registration statement
         of the Company on an appropriate form under the Securities Act (other
         than any registration statement with respect to equity securities filed
         on a Form S-4 or S-8 or any other forms prescribed for the same or
         similar purposes) and all amendments and supplements to such

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         registration statement, including post-effective amendments, in each
         case including the Prospectus contained therein, all material
         incorporated by reference therein and all exhibits thereto.

                  "REQUISITE COMMON STOCK" shall mean shares of Eligible Common
         Stock as to which registration is requested hereunder aggregating at
         least $11 million in the case of a Underwritten Offering and $3 million
         in the case of a non-Underwritten Offering.

                  "SEC" shall mean the Securities and Exchange Commission.

                  "SECURITIES ACT" shall mean the Securities Act of 1933, as
         amended, and the rules and regulations thereunder.

                  "UNDERWRITTEN REGISTRATION" or "UNDERWRITTEN OFFERING" shall
         mean an offering of the Common Stock pursuant to a Registration
         Statement in which the Common Stock of the Company is sold to an
         underwriter in a firm commitment underwriting for reoffering to the
         public or sold through an investment banker or manager on a best
         efforts basis.

         SECTION 2. COMMON STOCK SUBJECT TO REGISTRATION RIGHTS.

         Shares of Eligible Common Stock will cease to be Eligible Common Stock
when (i) a Registration Statement covering such Eligible Common Stock has been
declared effective by the SEC and such Eligible Common Stock has been disposed
of pursuant to such effective Registration Statement, (ii) they may be
distributed without a holding period or volume amount limitations or are
distributed to the public pursuant to Rule 144 (or any similar provision then in
force) under the Securities Act, (iii) they have otherwise been transferred
(other than to a Permitted Transferee), or (iv) at all times after the first
anniversary hereof if the Investor ceases to be the beneficial holder of at
least 1% of the then issued and outstanding Common Stock.

         SECTION 3. DEMAND REGISTRATION RIGHTS.

         (a) The Investors hereby request that the Company file, and (x) subject
to Section 4 hereof, the Company agrees with the Investors to file within two
business days after the closing date of the Merger a Registration Statement with
respect to 450,000 shares of Eligible Common Stock held by the Trust Investor
and 50,000 shares of Eligible Common Stock held by the Individual Investor (the
"CLOSING DEMAND") and (y) the Company agrees with the Investors to file on
November 20, 2000 a Registration Statement (or, if available, at the Company's
option, a post-effective amendment to an existing Registration Statement) with
respect to the remaining Requisite Common Stock held by the Investors (the
"NOVEMBER DEMAND") (the Closing Demand and the November Demand collectively
referred to as the "DEMANDS" or individually a "DEMAND"), each such Registration
Statement to be filed on Form S-3 (or, if unavailable, Form S-2 or Form S-1) or
any other appropriate or successor form under the Securities Act; provided, that
the Company shall not be obligated to effect, or take any action to effect, any
such registration pursuant to this Section 3(a) in any particular jurisdiction
in which the Company would be required to execute a general consent to service
of process in effecting such registration, qualification or compliance, unless
the Company is already subject to service in

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such jurisdiction and except as may be required by the Securities Act or
applicable rules or regulations thereunder.

         (b) With respect to each Demand, the Company will, at the request of
the Trust Investor, file either a post-effective amendment to the effective
Registration Statement or a Form 8-K incorporated by reference into the
Registration Statement in order to permit a firm commitment underwriting. The
Company shall be required to effect an additional registration pursuant to
Section 3(a) if the Company fails to effect either of the two registrations upon
the Demands referred to in Section 3(a) (unless such registration has not been
effected solely by reason of the fault of an Investor).

         (c) If any offering or sale of Common Stock by the Investor pursuant to
a Registration Statement is not consummated due to any failure by the Company to
perform its obligations under this Agreement, the Demand with respect to which
such Registration Statement was filed shall not be included among the Demands
contemplated by Sections 3(a) and (b) above.

         (d) Subject to compliance with rights and obligations under the
Company's existing registration rights agreements, the Company will not include
in any Registration Statement any securities other than the Requisite Common
Stock without the prior written consent of the applicable Investors, which
consent shall not be unreasonably withheld.

         SECTION 4. COMPANY PURCHASE RIGHT.

         (a) If the Trust Investor proposes to sell shares of Common Stock
pursuant to the Registration Statement relating to the Closing Demand prior to
November 20, 2000, it shall notify (a "SALE NOTICE") the Company as to the
shares proposed to be sold. The Company shall have the right (but not the
obligation) to purchase (and shall be deemed to have effected registration as to
the shares so purchased) from the Investor a number determined by the Company of
the shares referenced in the Sale Notice, but the number of shares subject to
such purchase right shall not exceed the lesser of 450,000 shares of Common
Stock or such number of shares as would not cause the Merger to fail to qualify
as a reorganization under Section 368 of the Internal Revenue Code, as amended.
If the Company elects to exercise its right pursuant to this Section 4(a), it
shall notify (the "PURCHASE NOTICE") the Investor of such election and shall
thereafter proceed to consummate the purchase within three business days of such
Purchase Notice.

         (b) The purchase price to be paid to the Investor for such shares of
Eligible Common Stock shall be the weighted average sales price per share of
Common Stock as quoted on the New York Stock Exchange for the 20 business days
ended on the business day immediately prior to the date of the Purchase Notice.

         SECTION 5. HOLDBACK AGREEMENTS.

         (a) Each Investor agrees, if it is requested by the managing
underwriter or underwriters in an Underwritten Offering by the Company, not to
effect any public sale or distribution of securities of the Company of the same
class as the securities included in the

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Registration Statement, during the 15 day period prior to, and during the 90 day
period (or such longer period requested for all similar holders by the
underwriters) beginning on, the effective date of such Registration Statement,
including a sale pursuant to Rule 144 under the Securities Act, to the extent
timely notified in writing by the Company or the managing underwriters;
provided, however, that the restrictions contained in this sentence shall
terminate on the first anniversary of the date hereof unless such Investor is a
5% or greater stockholder of the Company at the time of such primary offering by
the Company.

         (b) The Company agrees, if requested by the Trust Investor, not to
effect a public or private sale or distribution of its Common Stock, or any
securities convertible into or exchangeable for such securities (other than any
such sale or distribution of such securities in connection with any merger or
consolidation by the Company or a subsidiary thereof or the acquisition by the
Company or a subsidiary thereof of the capital stock or assets of any other
Person or registration on Form S-4 or Form S-8 or any successor forms) during
the 15-day period prior to, and during the 90-day period beginning on, the
effective date of any underwritten Registration Statement filed pursuant to
Section 3(a) hereof unless the underwriters managing the requested public
offering otherwise agree; provided, however, that the provisions of this
paragraph (b) shall not prevent the sale, distribution, conversion or exchange
of any securities and grants of options during such periods pursuant to stock
option or benefit plans of the Company.

         SECTION 6. REGISTRATION PROCEDURES.

         In connection with the Company's registration obligations pursuant to
Section 3(a) hereof, the Company will make reasonable efforts to effect the
registration of the Eligible Common Stock in accordance with the intended method
or methods of distribution thereof, and pursuant thereto the Company shall:

                  (a) prepare and file with the SEC, as soon as practicable, a
         Registration Statement, which form shall include all financial
         statements and other information required by the SEC to be filed
         therewith, and use its reasonable best efforts to cause such
         Registration Statement to become effective;

                  (b) prepare and file with the SEC such amendments to the
         Registration Statement as may be necessary to keep the Registration
         Statement effective until the distribution of the Eligible Common Stock
         under the Registration Statement is complete (which period shall not
         extend beyond the earlier to occur of (i) the first anniversary of the
         date hereof or (ii) the date on which all of the Eligible Common Stock
         has been disposed of by the Investors); cause the Prospectus to be
         supplemented by any required prospectus supplement, and as so
         supplemented to be filed pursuant to Rule 424 under the Securities Act;
         and comply with the provisions of the Securities Act with respect to
         the disposition of all securities covered by such Registration
         Statement;

                  (c) notify the Investor and the managing underwriters
         promptly, and (if requested by any such Person) confirm such advice in
         writing, (i) when the Registration Statement has become effective and
         when any post-effective amendment or supplements thereto become
         effective, (ii) of the issuance by the SEC of any stop order suspending
         the

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         effectiveness of the Registration Statement or the initiation of any
         proceedings for the purpose, (iii) if between the effective date of the
         Registration Statement and the closing of the sale of the securities
         covered thereby, the representations and warranties of the Company
         contained in any underwriting agreement entered into pursuant to
         Section 6(m) below cease to be true and correct, (iv) of the receipt by
         the Company of any notification with respect to the suspension of the
         qualification of the Eligible Common Stock for sale in any jurisdiction
         or the initiation or threatening of any proceeding for such purpose and
         (v) of the happening of any event which makes any material statement
         made in the Registration Statement or the Prospectus or any document
         incorporated therein by reference untrue or which requires the making
         of any changes in the Registration Statement or the Prospectus or any
         document incorporated therein by reference to make the statements
         therein not misleading;

                  (d) use its reasonable best efforts to obtain the withdrawal
         of any order suspending the effectiveness of the Registration Statement
         at the earliest possible time;

                  (e) as promptly as practicable prior to the filing of any
         document which is to be incorporated by reference into the Registration
         Statement or the Prospectus (after initial filing of the Registration
         Statement), provide copies of such document to the Investor and to the
         managing underwriters, if any, make the Company's representatives
         available for discussion of such document and make such changes in such
         document prior to the filing thereof as the Investor or underwriters
         may reasonably request;

                  (f) upon request, furnish to each managing underwriter, if
         any, and the Investor, without charge, at least one signed copy of the
         Registration Statement and any post-effective amendment thereto,
         including financial statements and schedules, all documents
         incorporated therein by reference and all exhibits (including those
         incorporated by reference);

                  (g) deliver to the Investor and each underwriter, if any,
         without charge, as many copies of the Prospectus (including each
         preliminary prospectus) and any amendment or supplement thereto as the
         Investor may reasonably request; the Company consents to the use of the
         Prospectus or any amendment or supplement thereto by the Investor and
         the underwriters, if any, in connection with the offering and sale of
         the Eligible Common Stock covered by the Prospectus or any amendment or
         supplement thereto;

                  (h) prior to any public offering of Eligible Common Stock, use
         its reasonable best efforts to register or qualify or cooperate with
         the Investor, the underwriters, if any, and their respective counsel in
         connection with the registration or qualification of such Eligible
         Common Stock for offer and sale under the securities or blue sky laws
         of such jurisdictions as the Investor or any underwriter reasonably
         requests in writing and do any and all other acts or things necessary
         or advisable to enable the underwriters or the Investor, as the case
         may be, to consummate the disposition in such jurisdictions of the
         Eligible Common Stock covered by the Registration Statement; provided
         that the Company will not be required to (i) qualify generally to do
         business in any jurisdiction where it is not then so qualified; (ii)
         subject itself to taxation in any such jurisdiction; or

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         (iii) take any action which would subject it to general service of
         process in any such jurisdiction where it is not then so subject;

                  (i) cooperate with the Investor and the managing underwriters
         to facilitate the timely preparation and delivery of certificates
         representing the Eligible Common Stock to be sold and not bearing any
         restrictive legends; and enable such Eligible Common Stock to be in
         such denominations and registered in such names as the managing
         underwriters or the Investor, as the case may be, may request at least
         two business days prior to any sale of the Eligible Common Stock;

                  (j) as promptly as practicable following the occurrence of any
         event contemplated by Section 6(c)(v) above, use its reasonable best
         efforts to prepare a supplement or post-effective amendment to the
         Registration Statement or the related Prospectus or any document
         incorporated therein by reference or file any other required document
         so that, as thereafter delivered to the purchasers of the Eligible
         Common Stock, the Prospectus will not contain an untrue statement of a
         material fact or omit to state any material fact required to be stated
         therein or necessary to make the statements therein, in the light of
         the circumstances under which they were made, not misleading;

                  (k) use its reasonable best efforts to cause all the Eligible
         Common Stock covered by the Registration Statement to be listed on each
         securities exchange or automated quotation system, if any, on which
         similar securities issued by the Company are then listed if requested
         by the Investor or by the managing underwriters,

                  (l) provide a CUSIP number for all Eligible Common Stock, not
         later than the effective date of the applicable Registration Statement;

                  (m) if requested by the Investor, enter into an underwriting
         agreement with an underwriter or underwriters providing for the sale of
         such Eligible Common Stock in an Underwritten Offering which shall be
         customary in form, substance and scope and shall contain customary
         requirements for representations, warranties, covenants and opinions of
         counsel; and make reasonable efforts to obtain any customary opinions
         of counsel or customary accountants' "cold comfort" letters referred to
         in such underwriting agreement, and enter into such other customary
         agreements and take all such other reasonable actions in connection
         therewith to expedite or facilitate the disposition of Eligible Common
         Stock as contemplated by such agreements;

                  (n) make available for inspection by the Investor and
         representatives of the underwriters participating in any disposition
         pursuant to the Registration Statement, and any attorney or accountant
         retained by the Investor or an underwriter, all relevant financial and
         other records, pertinent corporate documents and properties of the
         Company, and cause the Company's officers, directors and employees to
         supply all information reasonably requested by the Investor or any such
         representative, attorney or accountant in connection with such
         Registration Statement; provided, however, that any records,
         information or documents that are designated by the Company in writing
         as confidential shall be kept confidential by such Persons unless
         disclosure of such records, information or documents is required by
         court or administrative order; provided, further,

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         if the Investor or such representative, counsel or accountant is
         ordered to disclose any of such records, documents or information, the
         Investor or such representative, counsel or accountant will provide the
         Company with prompt written notice of such requirement so that the
         Company at its expense may seek a protective order or other appropriate
         remedy and/or waive compliance with this Section 6(n), and, in the
         event that such protective order or other remedy is not obtained, or
         that the Company waives compliance with the provisions hereof, the
         Investor and such representative, counsel and accountant agrees to
         furnish only that portion of such records, documents or information
         which the Investor or such representative, counsel or accountant is
         legally required to disclose in the opinion of the special counsel or
         counsel representing the Investor or such representative, underwriter
         or accountant; and

                  (o) otherwise use its reasonable best efforts to comply with
         all applicable rules and regulations of the SEC, and make generally
         available to its security holders, earnings statements no later than 45
         days after the end of any 12-month period (or 90 days, if such period
         is a fiscal year) commencing at the end of any fiscal quarter in which
         Eligible Common Stock is sold to underwriters in an Underwritten
         Offering, which statements shall cover said 12-month period.

         The Company may require the Investor (i) to furnish to the Company such
information regarding the distribution of the Eligible Common Stock as the
Company may from time to time reasonably request in writing and (ii) to enter
into an underwriting agreement in the form contemplated by Section 6(m).

         The Investor agrees that, upon receipt of any notice from the Company
of the happening of any event of the kind described in Section 6(c)(v) hereof,
the Investor will forthwith discontinue the offering and disposition of Eligible
Common Stock until the Investor's receipt of the copies of the supplemented or
amended Prospectus contemplated by Section 6(j) hereof, or until it is advised
in writing (the "ADVICE") by the Company that the use of the Prospectus may be
resumed, and has received copies of any additional or supplemental filings which
are incorporated by reference in the Prospectus, and, if so directed by the
Company, the Investor will deliver to the Company (at the Company's expense) all
copies, other than permanent file copies then in the Investor's possession, of
the Prospectus covering such Eligible Common Stock current at the time of
receipt of such notice. In the event the Company shall give any such notice to
suspend the offering and disposition of the Eligible Common Stock, the time
periods regarding the maintenance of the applicable Registration Statement shall
be extended by the number of days during the period from and including the date
of the giving of such notice pursuant to Section 6(c)(v) hereof to and including
the date when the Investor shall have received the copies of the supplemented or
amended Prospectus contemplated by Section 6(j) hereof or the Advice.

         Notwithstanding the foregoing, (a) the Company may delay the filing of
any Registration Statement, any amendment thereof or any supplement to the
related Prospectus, and may withhold efforts to cause any Registration Statement
to become effective, and (b) in the case of an effective Registration Statement,
upon the request of the Company each Investor shall refrain from selling any
shares pursuant to such Registration Statement, if the Company reasonably
determines in good faith that (i) such registration or sale would interfere with
or affect the

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negotiation or completion of any transaction that is being contemplated by the
Company (whether or not a final decision has been made to undertake such
transaction) at the time the right to delay is exercised, (ii) such registration
or sale would involve initial or continuing disclosure obligations with respect
to material non-public information not otherwise required by law or the rules
and regulations of the SEC which disclosure would not be in the best interest of
the Company's stockholders, or (iii), in the case of an Underwritten Offering,
the Investors would be unable to consummate such Underwritten Offering on
reasonable terms due to then currently prevailing market conditions as advised
by the Investor's underwriters; provided, however, that the duration of all such
delays or periods in which shares of Eligible Common Stock may not be sold
pursuant to an effective Registration Statement shall not exceed 180 days in the
aggregate.

         SECTION 7. REGISTRATION EXPENSES.

         All expenses incident to the Company's performance of or compliance
with this Agreement, including without limitation SEC registration and filing
fees, fees with respect to filings required to be made with the National
Association of Securities Dealers, Inc., fees and expenses in compliance with
state securities, or blue sky, laws (including fees and disbursements of counsel
for the underwriters in connection with blue sky qualifications of the Eligible
Common Stock), printing expenses, and fees and disbursements of counsel for the
Company and of all independent certified public accountants of the Company
(including the expenses of any special audit and "cold comfort" letters required
by or incident to such performance) and the fees and expenses incurred in
connection with the listing of the securities to be registered on each
securities exchange on which similar securities issued by the Company are then
listed in connection with the Demand Registration will be borne by the Company,
provided, that all underwriting discounts and selling commissions applicable to
the sale of the Eligible Common Stock and all other expenses of the Investors
incurred in connection with the distribution of Eligible Common Stock (including
all fees and expenses of the consultants, advisors, attorneys, special experts
and other Persons engaged by the Investors, and all relevant taxes, including
transfer taxes) will be borne by the Investors.

         SECTION 8. INDEMNIFICATION; CONTRIBUTION.

         (a) INDEMNIFICATION BY THE COMPANY. The Company agrees to indemnify and
hold harmless the Investors, each Person who participates as an underwriter (any
such Person being an "UNDERWRITER"), and each Person, if any, who controls any
Underwriter within the meaning of the Securities Act as follows: (i) against any
and all loss, claim, damage and expense whatsoever, as incurred, arising out of
any untrue statement or alleged untrue statement of a material fact contained in
any Registration Statement (or any amendment thereto) pursuant to which Eligible
Common Stock was registered under the Securities Act, including all documents
incorporated therein by reference, or the omission or alleged omission therefrom
of a material fact required to be stated therein or necessary to make the
statements therein not misleading or arising out of any untrue statement or
alleged untrue statement of a material fact contained in any Prospectus (or any
amendment or supplement thereto), including all documents incorporated therein
by reference, or the omission or alleged omission therefrom of a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading; (ii) against any and
all loss, liability, claim, damage and expense whatsoever, as

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incurred, to the extent of the aggregate amount paid in settlement of any
litigation, or investigation or proceeding by any governmental agency or body,
commenced or threatened, or of any claim whatsoever based upon any such untrue
statement or omission, or any such alleged untrue statement or omission, if such
settlement is effected with the written consent of the Company; and (iii)
against any and all expense whatsoever, as incurred (including, subject to the
provisions of subsection (c), fees and disbursements of counsel), reasonably
incurred in investigating, preparing or defending against any litigation, or
investigation or proceeding by any governmental agency or body, commenced or
threatened, in each case whether or not a party, or any claim whatsoever based
upon any such untrue statement or omission, or any such alleged untrue statement
or omission, to the extent that any such expense is not paid under (i) or (ii)
above; provided, however, that the Company shall not be liable in any such case
to the extent that any such loss, claim, damage, liability or expense arises out
of or is based upon an untrue statement or omission, or alleged untrue statement
or omission, in a Prospectus, if such untrue statement or omission, or alleged
untrue statement or omission, is corrected in an amendment or supplement to such
Prospectus and if the Investors or the Underwriter, as the case may be,
thereafter fails to deliver such Prospectus as so amended or supplemented prior
to or concurrently with the sale by the Investors or the Underwriter, as the
case may be, of the Eligible Common Stock to the Person asserting such loss,
claim, damage, liability or expense and if the Company has furnished the
Investors or the Underwriter, as the case may be, within a reasonable period of
time prior to such sale with the number of copies of such amended or
supplemented Prospectus reasonably required by the Investors or the Underwriter,
as the case may be; and provided, further, that this indemnity agreement does
not apply to the Investors or any Underwriter with respect to any loss,
liability, claim, damage or expense to the extent arising out of any untrue
statement or omission, or alleged untrue statement or omission, made in reliance
upon and in conformity with information furnished to the Company by the
Investors or any Underwriter expressly for use in a Registration Statement (or
any amendment thereto) or any Prospectus (or any amendment or supplement
thereto).

         (b) INDEMNIFICATION BY THE INVESTORS. In connection with the applicable
Registration Statement, each Investor will furnish promptly to the Company in
writing such information and affidavits as the Company reasonably requests for
use in connection with the Registration Statement or Prospectus and agrees to
indemnify and hold harmless the Company and each Underwriter, if any, and each
of their respective directors and officers (including each officer of the
Company who signed the Registration Statement), and each Person, if any, who
controls the Company or any Underwriter within the meaning of the Securities
Act, against any and all loss, liability, claim, damage and expense described in
the indemnity contained in Section 8(a) hereof, as incurred, but only with
respect to untrue statements or omissions, or alleged untrue statements or
omissions, made in a Registration Statement (or any amendment thereto) or any
Prospectus (or any amendment or supplement thereto) in reliance upon and in
conformity with written information furnished to the Company by such Investor
expressly for use in such Registration Statement (or any amendment thereto) or
such Prospectus (or any amendment or supplement thereto).

         (c) CONDUCT OF INDEMNIFICATION PROCEEDINGS. Each indemnified party
shall give reasonably prompt notice to each indemnifying party of any action or
proceeding commenced against it in respect of which indemnity may be sought
hereunder, provided, that failure to so notify an indemnifying party shall not
relieve it from any liability which it may have under this

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indemnity agreement.If the indemnifying party so elects within a reasonable time
after receipt of such notice, the indemnifying party may assume the defense of
such action or proceeding at such indemnifying party's own expense with counsel
chosen by the indemnifying party and approved by the indemnified parties
defendant in such action or proceeding, which approval shall not be unreasonably
withheld; provided, however, that, if such indemnified party or parties
reasonably determine that a conflict of interest exists where it is advisable
for such indemnified party or parties to be represented by separate counsel or
that, upon advice of counsel, there may be legal defenses available to them
which are different from or in addition to those available to the indemnifying
party, then the indemnifying party shall not be entitled to assume the defense
and the indemnified party or parties shall be entitled to one separate counsel
at the indemnifying party's expense. If an indemnifying party is not entitled to
assume the defense of such action or proceeding as a result of the proviso to
the preceding sentence, such indemnifying party's counsel shall be entitled to
conduct such indemnifying party's defense and counsel for the indemnified party
or parties shall be entitled to conduct the defense of such indemnified party or
parties, it being understood that both such counsel will cooperate with each
other to conduct the defense of such action or proceeding as efficiently as
possible. If an indemnifying party is not so entitled to assume the defense of
such action or does not assume such defense, after having received the notice
referred to in the first sentence of this Section 8(c), the indemnifying party
or parties will pay the reasonable fees and expenses of counsel for the
indemnified party or parties. In such event, however, no indemnifying party will
be liable for any settlement effected without the written consent of such
indemnifying party. If an indemnifying party is entitled to assume, and assumes,
the defense of such action or proceeding in accordance with this Section 8(c),
such indemnifying party shall not be liable for any fees and expenses of counsel
for the indemnified parties incurred thereafter in connection with such action
or proceeding.

         (d) CONTRIBUTION. If for any reason the indemnification provided for in
the preceding subsections (a) and (b) of this Section 8 is unavailable to an
indemnified party or insufficient to hold it harmless as contemplated by such
preceding subsections, then the indemnifying party shall contribute to the
amount paid or payable by the indemnified party as a result of such
unavailability or insufficiency in proportion as is appropriate to reflect not
only the relative benefits received by the indemnified party and the
indemnifying party, but also the relative fault of the indemnified party and the
indemnifying party, as well as any other relevant equitable considerations,
provided, that the Investors shall not be required to contribute in any amount
greater than the dollar amount of the proceeds received by the Investors with
respect to the sale of any Eligible Common Stock. No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.

         SECTION 9. RULE 144.

                  With a view to making available the benefits of certain rules
and regulations of the SEC which may permit the sale of restricted securities to
the public without registration, the Company agrees to:

         (a) make and keep public information available as those terms are
understood and defined in Rule 144 under the Securities Act, or any successor
rule ("RULE 144"), at all times;

<PAGE>   11

                                                                              11

         (b) use its reasonable best efforts to file with the SEC in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act at all times; and

         (c) so long as either Investor owns any Eligible Common Stock, furnish
to such Investor upon request, a written statement by the Company as to its
compliance with the reporting requirements of Rule 144, and of the Securities
Act and the Exchange Act, a copy of the most recent annual or quarterly report
of the Company, and such other reports and documents so filed as the Investor
may reasonably request in availing itself of any rule or regulation of the SEC
allowing the Investor to sell any such securities without registration.

         SECTION 10. PARTICIPATION IN UNDERWRITTEN REGISTRATIONS.

         Merrill Lynch & Co. will serve as the investment banker, manager and
underwriter that will administer the registration of the Eligible Common Stock
pursuant to a Demand unless it requires compensation in excess of prevailing
market rates or unless a different firm is otherwise selected by the Company;
provided, that such other investment banker, manager, or underwriter must be
reasonably satisfactory to the Investor and the Company. Investors acknowledge
to the Company that they will comply with their obligations in the letter to
Merrill Lynch dated the date hereof.

         No person may participate in any Underwritten Registration hereunder
unless such Person (a) agrees to sell such Person's securities on the basis
provided in any underwriting arrangements approved by the Persons entitled
hereunder to approve such arrangements and (b) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents required under the terms of such underwriting arrangements.
Nothing in this Section 10 shall be construed to create any additional rights
regarding the registration of Eligible Common Stock in any Person otherwise than
as set forth herein.

         SECTION 11. MISCELLANEOUS.

         (a) AMENDMENTS AND WAIVERS. The provisions of this Agreement, including
the provisions of this sentence, may not be amended, modified or supplemented,
and waivers or consents to departures from the provisions hereof may not be
given unless the Company has obtained the written consent of the Investor.

         (b) NOTICES. All notices and other communications provided for or
permitted hereunder shall be made in writing by hand-delivery, registered
first-class mail, telex, telecopier, or air courier guaranteeing overnight
delivery:

                  (i) if to the Trust Investor, initially at 24106 Bay Hill
         Blvd., Katy, Texas 77494, Attention: Garlin R. Rhymes, and thereafter
         at such other address, notice of which is given in accordance with this
         Section 11(b).

                  (ii) If to the Individual Investor, initially at 5319 N.
         Liberty Drive, Traverse City, MI 49684, and thereafter at such other
         address, notice of which is given in accordance with this Section
         11(b).

<PAGE>   12

                                                                              12

                  (iii) if to the Company, initially at 4440 Brittmoore Road,
         Houston, Texas 77041, Attention: President, Stephen A. Snider, and
         thereafter at such other address, notice of which is given in
         accordance with the provisions of this Section 11(b), with copies to
         4440 Brittmoore Road, Houston, Texas 77041, Attention: Valerie L.
         Banner, Esq., Senior Vice President and General Counsel, and King &
         Spalding, 1100 Louisiana, Suite 3300, Houston, Texas 77002-5219,
         Attention: Christine B. LaFollette, Esq.

         All such notices and communications shall be deemed to have been duly
given: at the time delivered by hand, if personally delivered; five business
days after being deposited in the mail, postage prepaid, if mailed; when
answered back, if telexed; when receipt acknowledged, if telecopied; and on the
next business day, if timely delivered to any air courier guaranteeing overnight
delivery.

         (c) ASSIGNMENT OF REGISTRATION RIGHTS. Except as otherwise provided
below, neither party may assign this Agreement or any of the rights and
obligations of the parties hereunder without the prior written consent of the
other party; provided, that (i) the Individual Investor may assign this
Agreement and all of his rights and obligations hereunder to one Permitted
Transferee, (ii) the Trust Investor may assign this Agreement and (x) all of its
rights and obligations hereunder, other than pursuant to Section 4, to one
Permitted Transferee and (y) the rights and obligations hereunder, other than
pursuant to Section 4, to Permitted Transferees that are beneficiaries of the
Trust Investor as to shares of Eligible Common Stock owned by the Trust Investor
and (iii) the Company may assign this Agreement and all of its rights and
obligations hereunder to any entity that succeeds to all or substantially all of
the assets of the Company, whether by merger, sale or otherwise. This Agreement
shall inure to the benefit of and be binding upon the successors and permitted
assigns of each of the parties. If the Company shall so request, any such
successor or assign shall agree in writing to acquire and hold the Eligible
Common Stock subject to all of the terms hereof. In the event of any assignment
by the Trust Investor to a Permitted Transferee: (i) such Permitted Transferee
shall participate in all rights of the Trust Investor, and shall be bound by all
obligations of the Trust Investor, as provided in this Agreement, in each case
proportionately based on the relative number of shares of Eligible Common Stock
held by such Permitted Transferee; and (ii) all notices, decisions and elections
provided in this Agreement to be given to or made by the Trust Investor shall be
so given to or made by (and shall be for all purposes conclusively deemed to
have been adequately given or made if so given to or made by) the Trustee of The
Reuben James Helton Trust Dated January 24, 2000 for and on behalf of such
Permitted Transferee.

         (d) COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

         (e) HEADINGS. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

         (f) GOVERNING LAW. This Agreement shall be governed by and construed in
accordance with the laws of the State of Texas, without giving effect to such
jurisdiction's conflicts of law provisions.

<PAGE>   13

                                                                              13

         (g) SEVERABILITY. In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability of
such provision in every other respect and of the remaining provisions contained
herein shall not be affected or impaired thereby.

         (h) ENTIRE AGREEMENT. This Agreement is intended by the parties as a
final expression of their agreement and intended to be complete and exclusive
statement of the agreement and understanding of the parties hereto in respect of
the subject matter contained herein. This Agreement supersedes all prior
agreements and understandings between the parties with respect to such subject
matter.

         (i) CONFIDENTIALITY. The parties hereto agree, and will cause all
Persons under their control to agree, to maintain the confidentiality of any
material, non-public information with respect to the Company that they may
obtain pursuant to the terms of this Agreement, and not to use, or permit the
use of, such information for any improper purpose or in any manner that might be
detrimental to the Company.

         (j) TERMINATION. This Agreement shall terminate on the second
anniversary of the date hereof or, if earlier, when there is no Eligible Common
Stock.

<PAGE>   14

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first written above.

                                     UNIVERSAL COMPRESSION HOLDINGS, INC.

                                     By: /s/ ERNIE L. DANNER
                                         -------------------
                                         Name:  Ernie L. Danner
                                         Title: Executive Vice President

                                     TRUST INVESTOR:

                                        THE REUBEN JAMES HELTON TRUST
                                        DATED JANUARY 24, 2000

                                     By: /s/ GARLIN R. RHYMES
                                         --------------------
                                         Name:  Garlin R. Rhymes
                                         Title: Trustee

                                     INDIVIDUAL INVESTOR:

                                     /s/ MICHAEL PAHL
                                     -----------------
                                         Michael Pahl

<PAGE>   15

                                    EXHIBIT A

                          ADDITIONAL PARTY COUNTERPART

         The undersigned, after having received and reviewed to its satisfaction
a copy of the Registration Agreement, dated as of _________ __, 2000 (the
"Registration Agreement"), by and between Universal Compression Holdings, Inc.
(the "Company") and the Investor, does hereby agree to become party to the
Registration Agreement thereby accepting all the rights, benefits and
obligations of a holder of Eligible Common Stock thereunder. The Company may
attach this page as a counterpart to the Registration Agreement and the
undersigned agrees that such attachment shall be deemed conclusive evidence of
its acknowledgment and acceptance of the terms thereof.

         Defined terms used herein and not otherwise defined herein shall have
the meaning given such terms in the Registration Agreement.

Dated:

                                                     [NAME]
                                                     [ADDRESS FOR NOTICES]

                                                     By:
                                                        -----------------------
                                                        Name:
                                                        Title:

Acknowledged and Accepted By:

UNIVERSAL COMPRESSION HOLDINGS, INC.

By:
   ---------------------------
   Name:
   Title:<PAGE>   1

                                                                     EXHIBIT 4.2

                          FIRST SUPPLEMENTAL INDENTURE

                  This FIRST SUPPLEMENTAL INDENTURE, dated as of September 14,
2000 (the "First Supplemental Indenture"), to the Indenture, dated as of June 2,
2000 (the "Indenture"), is by and among NORTHERN BORDER PARTNERS, L.P., a
Delaware limited partnership (hereinafter called the "Partnership"), NORTHERN
BORDER INTERMEDIATE LIMITED PARTNERSHIP, a Delaware limited partnership (the
"Guarantor"), and BANK ONE TRUST COMPANY, N.A., as Trustee.

                          RECITALS OF THE PARTNERSHIP:

                  WHEREAS, pursuant to the Indenture the Partnership established
and provided for the issuance by the Partnership of a series of Notes designated
as its 8-7/8% Senior Notes due June 15, 2010 (the "Notes") in the aggregate
principal amount of $150,000,000;

                  WHEREAS, Section 2.02 of the Indenture expressly provides the
series of Notes may be reopened for issuances of additional Notes of such series
without the consent of the Holders, provided that no additional Notes may be
issued if an Event of Default has occurred and is continuing with respect to the
Notes;

                  WHEREAS, no Event of Default has occurred and is continuing
with respect to the Notes;

                  WHEREAS, the Partnership desires to reopen the series of Notes
and issue $100,000,000 principal amount of additional Notes which will be part
of the same series as the Notes and rank equally with the Notes in all respects;

                  WHEREAS, in connection with the reopening of the series, the
Partnership desires to amend the Notes in certain respects pursuant to Section
9.01(a) of the Indenture;

                  WHEREAS, the conditions set forth in the Indenture for the
execution and delivery of this First Supplemental Indenture have been complied
with; and

                  WHEREAS, all things necessary to make this First Supplemental
Indenture a valid agreement of the Partnership and the Trustee, in accordance
with its terms, and a valid amendment of, and supplement to, the Indenture have
been done.

                  NOW THEREFORE:

                  Pursuant to Section 2.02 of the Indenture, the series of Notes
established by the Indenture is hereby reopened and there is hereby authorized
for issuance, authentication and delivery $100,000,000 principal amount of
additional Notes (the "Additional Notes") of the same series as the Notes, and
in consideration of the premises and the purchase and acceptance of the
Additional Notes by the Holders thereof, the Partnership mutually covenants and
agrees with the Trustee, for the equal and proportionate benefit of all Holders
of the Notes and the Additional Notes, that the Indenture is hereby supplemented
and amended, to the extent and for the purposes expressed herein, as follows:

<PAGE>   2

                                   ARTICLE ONE
                           AMENDMENTS TO THE INDENTURE

         Section 1.1 Amendments to Indenture. The Indenture is hereby amended
and supplemented as follows:

                  (a) The series of Notes established by the Indenture is hereby
         reopened for the issuance of Additional Notes in an aggregate principal
         amount of $100,000,000 which shall rank equally with the Notes in all
         respects, shall form a single series of $250,000,000 principal amount
         with the Notes, with the same CUSIP number, and shall have the same
         terms as the Notes, except that the Additional Notes initially will be
         dated September 14, 2000. Interest on the Additional Notes shall accrue
         from June 2, 2000. A copy of the form of Additional Note to be issued
         on September 14, 2000 shall be identical to the form of Note included
         as Exhibit A to the Indenture except that the date of original issuance
         will be September 14, 2000 and references to the Registration Rights
         Agreement dated as of June 2, 2000 shall instead refer to the
         Registration Rights Agreement dated as of September 14, 2000.

                  (b) All references in the Indenture and the form of Note
         attached thereto as Exhibit A to the series of Notes established by the
         Indenture and in the outstanding Notes shall be amended, supplemented
         and deemed to include the Additional Notes issued hereunder.

                  (c) The Additional Notes shall be subject to the Indenture, as
         amended hereby.

                  (d) The last sentence of Section 4 of the form of Note
         included as Exhibit A to the Indenture, and of the outstanding Notes,
         shall be deleted in its entirety and the following shall be substituted
         in place thereof:

                  This series of Notes may be reopened for issuances of
                  additional Notes without the consent of Holders, provided that
                  no additional Notes may be issued if an Event of Default has
                  occurred and is continuing with respect to the Notes.

                                   ARTICLE TWO
                                  MISCELLANEOUS

         Section 2.1 Defined Terms. Unless otherwise provided in this First
Supplemental Indenture, all defined terms used in this First Supplemental
Indenture shall have the meanings assigned to them in the Indenture.

         Section 2.2 Conflict of Any Provision of Indenture with Trust Indenture
Act of 1939. If and to the extent that any provision of this First Supplemental
Indenture limits, qualifies or conflicts with another provision included in this
First Supplemental Indenture or in the Indenture which is required to be
included herein or therein by any of Sections 310 to 317, inclusive, of the
Trust Indenture Act of 1939, as amended, such required provision shall control.

                                        2

<PAGE>   3

         Section 2.3 New York Law to Govern. THIS FIRST SUPPLEMENTAL INDENTURE
AND THE NOTES (INCLUDING THE ADDITIONAL NOTES) SHALL BE DEEMED TO BE CONTRACTS
MADE AND TO BE PERFORMED ENTIRELY IN THE STATE OF NEW YORK, AND FOR ALL PURPOSES
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF SAID STATE.

         Section 2.4 Counterparts. This First Supplemental Indenture may be
executed in any number of counterparts, each of which shall be an original, but
such counterparts shall together constitute but one and the same instrument.

         Section 2.5 Effect of Headings. The Article and Section headings herein
are for convenience only and shall not affect the construction hereof.

         Section 2.6 Severability of Provisions. In case any provision in this
First Supplemental Indenture or in the Notes (including the Additional Notes)
shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

         Section 2.7 Successors and Assigns. All covenants and agreements in
this First Supplemental Indenture by the parties hereto shall bind their
respective successors and assigns and inure to the benefit of their respective
successors and assigns, whether so expressed or not.

         Section 2.8 Benefit of First Supplemental Indenture. Nothing in this
First Supplemental Indenture, express or implied, shall give to any Person,
other than the parties hereto, any Registrar, any Paying Agent and their
successors hereunder, and the Holders of the Notes, any benefit or any legal or
equitable right, remedy or claim under this First Supplemental Indenture.

         Section 2.9 Acceptance by Trustee. The Trustee accepts the amendments
to the Indenture effected by this First Supplemental Indenture and agrees to
execute the trusts created by the Indenture as hereby amended, but only upon the
terms and conditions set forth in the Indenture. Without limiting the generality
of the foregoing, the Trustee assumes no responsibility for the correctness of
the recitals contained herein, which shall be taken as the statements of the
Partnership and except as provided in the Indenture the Trustee shall not be
responsible or accountable in any way whatsoever for or with respect to the
validity or execution or sufficiency of this First Supplemental Indenture and
the Trustee makes no representation with respect thereto.

                                        3

<PAGE>   4

                  IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed, all as of the day and year first
above written.

                                   ISSUER:

                                   NORTHERN BORDER PARTNERS, L.P.

                                   By:    /s/ Jerry L. Peters
                                      ------------------------------------------
                                   Name: Jerry L. Peters
                                        ----------------------------------------
                                   Title: Chief Financial & Accounting Officer
                                         ---------------------------------------

                                   GUARANTOR:

                                   NORTHERN BORDER INTERMEDIATE LIMITED
                                   PARTNERSHIP

                                   By:    /s/ Jerry L. Peters
                                      ------------------------------------------
                                   Name: Jerry L. Peters
                                        ----------------------------------------
                                   Title: Chief Financial & Accounting Officer
                                         ---------------------------------------

                                   TRUSTEE:

                                   BANK ONE TRUST COMPANY, N.A.,
                                   as Trustee

                                   By:    /s/ Sharon McGrath
                                      ------------------------------------------
                                   Name: Sharon McGrath
                                        ----------------------------------------
                                   Title: Vice President
                                         ---------------------------------------

                                       4

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