Document:

<PAGE>
                                                                   EXHIBIT 10.17

June 24, 2002

Natural Gas Services Group, Inc.
2911 S. County Road 1260
Midland, Texas 79706

Gentlemen:

In accordance with recent discussions, Western National Bank ("WNB") is pleased
to make the following commitment to Natural Gas Services Group, Inc., including,
but not limited to, the terms and conditions set forth below.

BORROWER:            Natural Gas Services Group, Inc. ("NGSG")

AMOUNT:              $3,500,000

PURPOSE:             Refinance remaining balance on indebtedness to Dominion
                     after initial public offering and partial paydown.

TERM:                Five Years

RATE:                Wall Street Journal Prime + 1.0%, floating daily.

REPAYMENT:           Monthly payments of $58,333 + accrued interest.

COLLATERAL:          Superior security interest in all A/R, Inventory, and
                     Equipment of borrowing entity and subsidiaries.
                     Cross-collateralized with the with WNB notes # 816559, #
                     816307, # 817093, and # 817092.

                     $1,000,000 life insurance policy on Wayne Vinson.

GUARANTORS:          Unlimited guaranties of: NGE Leasing; Rotary Gas; Hi-Tech
                     Compressor; Flare King; and Great Lakes Compression.

REPRESENTATIONS & WARRANTIES:

                     Usual and customary representations and warranties for
                     transactions of this nature, including but not limited to
                     the following:

                     (1)    No material adverse change in financial condition of
                            Borrower

                     (2)    Absence of litigation or any existing or pending
                            adverse decree orders from a court or environmental
                            agency.

                     (3)    No change in the nature of NGSG's primary business
                            practices.

<PAGE>

CONDITIONS PRECEDENT:

                     (1)    Negotiation and execution of loan documents
                            satisfactory to WNB and Borrower.

                     (2)    Completion of Initial Public Offering with NGSG
                            netting at least $8,000,000 in proceeds.

                     (3)    NGSG shall be in compliance with existing loan
                            agreement at time of funding.

                     (4)    Proceeds from the Initial Public Offering used to
                            reduce Dominion debt to $3,500,000

COVENANTS:

                     This facility is governed by a comprehensive loan agreement
                     containing all of the standard representations, warranties,
                     and events of default including, but not limited to, the
                     following provisions:

                     (1)    NGSG shall provide monthly financial statements
                            (consolidated with all subsidiaries), accounts
                            receivable aging, borrowing base certificate ($750M
                            RLOC), and compliance certificates within 45 days of
                            each month end.

                     (2)    NGSG shall provide a quarterly report listing the
                            physical location of all lease units including any
                            remaining lease terms.

                     (3)    NGSG shall provide annual audited financial
                            statements of borrower and all subsidiaries
                            (combined) within 90 days of fiscal year end.

                     (4)    NGSG shall incur no additional debts, liens, or
                            encumbrances in excess of $100M without prior,
                            written WNB approval.

                     (5)    NGSG shall make no asset sales in excess of $100,000
                            without prior written WNB approval.

                     (6)    NGSG shall make no distributions / dividends (except
                            for stated dividends on existing preferred stock)
                            without prior, written WNB approval.

                     (7)    NGSG shall make no changes in management at the CEO
                            / President level without prior, written WNB
                            approval.

                     (8)    Use of loan proceeds limited to pay off of
                            $3,500,000 Dominion Debt.

                     (9)    NGSG will allow WNB, at borrowers expense, to
                            perform limited visual inspections on a portion of
                            the leased compressors at least semi annually, not
                            to exceed one inspection per quarter.

                     (10)   NGSG shall maintain a three month moving average
                            traditional cash flow coverage of not less than
                            1.25x beginning 9/30/02. Calculated per existing
                            loan agreement.

                     (11)   NGSG shall maintain a minimum current ratio of 1.5x
                            measured monthly beginning 9/30/02.

                     (12)   NGSG shall not exceed a maximum debt less
                            subordinated debt / tangible worth + subordinated
                            debt as equity ratio of 1.0x beginning 9/30/02.

<PAGE>

                     (13)   NGSG shall maintain a minimum tangible net worth of
                            $11.5MM beginning 9/30/02.

CLOSING COSTS:

                     Borrower will pay all necessary fees and expenses incurred
                     by WNB with respect to preparation of loan documents and
                     filing fees.

Thank you for the opportunity to continue to serve your banking needs. If you
are in agreement with the terms and conditions outlined above, please sign this
commitment and return it to me at your earliest convenience. If you should have
any questions, comments, or simply wish to further our discussions pertaining to
your request, please do not hesitate to contact me at 570-4181.

Sincerely,

/s/ Scott Lovett

Scott Lovett
Executive Vice President
Western National Bank

AGREED TO AND ACCEPTED THIS 25TH DAY OF JUNE, 2002.

BORROWER: NATURAL GAS SERVICES GROUP, INC.

BY: WAYNE VINSON, PRESIDENT

/s/ Wayne Vinson

Wayne Vinson
President / Natural Gas Services Group, Inc.<PAGE>
                                                                   EXHIBIT 10.18

                            [THE STATE OF TEXAS SEAL]

                               THE STATE OF TEXAS

                               SECRETARY OF STATE

         IT IS HEREBY CERTIFIED that the attached is a true and correct copy of
the following described document on file in this office:

                        HY BON ROTARY COMPRESSION, L.L.C.
                               FILE NO. 7067346-22

ARTICLES OF ORGANIZATION                                      APRIL 20, 2000

[THE STATE OF TEXAS SEAL]                  IN TESTIMONY WHEREOF, I have hereunto
                                           signed my name officially and
                                           caused to be impressed hereon the
                                           Seal of State at my office in
                                           Austin, Texas on July 16, 2001.

                                                             /s/ HENRY CUELLAR
                                                             -----------------

                                             Henry Cuellar
                                             Secretary of State DAB
<PAGE>
                            ARTICLES OF ORGANIZATION
                                       OF
                        HY-BON ROTARY COMPRESSION, L.L.C.

James P. Boldrick adopts the following Articles of Organization for a limited
liability company under the Texas Limited Liability Company Act.

                                    ARTICLE I

         The name of the limited liability company, referred to in these
Articles as the "Company", is Hy-Bon Rotary Compression, L.L.C.

                                   ARTICLE II

         The period of duration of the Company is perpetual.

                                   ARTICLE III

         The purpose for which the Company is organized is to transact any and
all lawful business for which limited liability companies may be organized under
the Texas Limited Liability Company Act.

                                   ARTICLE IV

         The address of the company's initial registered office is 2404 Commerce
Drive, Midland, Texas 79703. The company's initial registered agent at that
address is James J. Woodcock.

                                    ARTICLE V

         The Company will have five (5) managers. The names and addresses of the
initial managers are:

<PAGE>

<Table>

<S>                                   <C>
1. James J. Woodcock, President       P.O. Box 4185, Midland, TX 79704

2. Wayne Vincent, Vice President      2911 S. County Rd. 1260, Midland, TX 79706

3. James P. Boldrick                  1801 West Wall, Midland, Texas 79701

4. James D. Ross, Treasurer           P.O. Box 4185, Midland, Texas 79704

5. Wallace Sparkman                   P.O. Box 2483, Corpus Christi, TX 78403.
</Table>

                                   ARTICLE VI

         The Company's organizer is James P. Boldrick, whose address is 1801
West Wall, Midland, Texas 79701.

         These Articles of Organization are executed on behalf of the Company on
this 17th day of April, 2000.

                                               /s/ JAMES P. BOLDRICK
                                             ----------------------------------
                                             JAMES P. BOLDRICK, ORGANIZER

SWORN TO on this 17th day of April, 2000, by the above named organizer.

                                               /s/ [ILLEGIBLE]
                                             ----------------------------------
                                             Notary Public, State of Texas

                                        2

<PAGE>

                         HY-BON ROTARY COMPRESSION, LLC

                                UNANIMOUS CONSENT

                              RESOLUTION OF MEMBERS

         The undersigned, being all of the members of Hy-Bozo Rotary
Compression, LLC hereby waive notice of meeting and consent to the following
resolution:

         RESOLVED that the attached "REGULATIONS OF HY-BON ROTARY COMPRESSION,
LLC" are approved and effective as of May 1, 2000; that signatures may be
transmitted by facsimile transmission, and the above described document may be
signed in counterpart by the undersigned.

                                          NGE Leasing, Inc.

                                          By: /s/ Scott Sparkman
                                             -----------------------------

                                          President
                                          --------------------------------
                                          (title)

                                          Hy-Bon Engineering Company, Inc.

                                          By:  /s/ James D. Ross
                                             -----------------------------
                                                    CFO
                                          --------------------------------
                                          (title)

                                        3

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