<PAGE>   1
                                                                    EXHIBIT 10.2


THIS WARRANT AND ANY SHARES ISSUABLE UPON THE EXERCISE OF THIS WARRANT HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), NOR
UNDER ANY STATE SECURITIES LAW AND SUCH SECURITIES MAY NOT BE PLEDGED, SOLD,
ASSIGNED, HYPOTHECATED, OR OTHERWISE TRANSFERRED UNTIL (1) A REGISTRATION
STATEMENT WITH RESPECT THERETO IS EFFECTIVE UNDER THE ACT AND ANY APPLICABLE
STATE SECURITIES LAW OR (2) THE COMPANY RECEIVES AN OPINION OF COUNSEL TO THE
COMPANY OR COUNSEL TO THE HOLDER OF SUCH SECURITIES, WHICH COUNSEL AND OPINION
ARE REASONABLY SATISFACTORY TO THE COMPANY, THAT SUCH SECURITIES MAY BE
PLEDGED, SOLD, ASSIGNED, HYPOTHECATED, OR TRANSFERRED WITHOUT AN EFFECTIVE
REGISTRATION STATEMENT UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS.

THE TRANSFER OF THIS WARRANT AND THE SHARES ISSUABLE UPON THE EXERCISE HEREOF
IS RESTRICTED AS DESCRIBED HEREIN.


                       MARCUM NATURAL GAS SERVICES, INC.

          WARRANT FOR THE PURCHASE OF 200,000 SHARES OF COMMON STOCK,
                            $.01 PAR VALUE PER SHARE


No. 1

                 THIS CERTIFIES that, for good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, National Securities
Corporation (the "Holder") is entitled to subscribe for and purchase from
Marcum Natural Gas Services, Inc., a Delaware corporation (the "Company"), upon
the terms and conditions set forth herein, at any time or from time to time,
during the period commencing on the date hereof (March 13, 1998) (the
"Effective Date") and expiring at 5:00 p.m. New York time on March 13, 2003 or
earlier as described below in Section 1(d) (the "Exercise Period"), 200,000
shares of the Company's common stock, par value $.01 per share (the "Common
Stock"), at a price (the "Exercise Price") per share of Common Stock as
described below.  As used herein, the term "this Warrant" shall mean and
include this Warrant and any Warrant or Warrants hereafter issued as
<PAGE>   2
a consequence of the exercise or transfer of this Warrant in whole or in part.
As used herein, the term "Holder" shall include any transferee to whom this
Warrant has been transferred in accordance with the terms hereof.


                 The number of shares of Common Stock issuable upon exercise of
the Warrants (the "Warrant Shares") and the Exercise Price may be adjusted from
time to time as hereinafter set forth.

                 1.               (a) Subject to the provisions of Section 2,
this Warrant may be exercised during the Exercise Period, as to all or any
portion of the Warrant Shares which have vested pursuant to the schedule set
forth below in Section 1(b), by transmission by telecopy of the Election to
Exercise, followed within three (3) business days by the surrender of this
Warrant (with the Election to Exercise attached hereto duly executed) to the
Company at its office at 1675 Broadway, Suite 2150, Denver, Colorado 80202, or
at such other place as is designated in writing by the Company, together with a
certified or bank cashier's check payable to the order of the Company in an
amount equal to the product of the Exercise Price and the number of Warrant
Shares for which this Warrant is being exercised (the "Aggregate Exercise
Price").  Alternatively, for as long as the Common Stock is publicly traded on
a national stock exchange or listed in a national stock quotation system, this
Warrant may be exercised in the manner set forth in the preceding sentence by
surrendering this Warrant in exchange for the number of Warrant Shares equal to
the product of (x) the number of shares of Common Stock as to which this
Warrant is being exercised, multiplied by (y) a fraction, the numerator of
which is the Market Price (as defined below) of the shares of Common Stock
minus the Exercise Price of the shares of Common Stock and the denominator of
which is the Market Price per share of Common Stock.  Solely for the purposes
of this Section 1, Market Price shall be calculated as the average of the
Market Price for each of the twenty (20) trading days immediately preceding the
date on which the form of election attached hereto is deemed to have been sent
to the Company pursuant to this Section 1 (the "Notice Date").  As used herein,
the phrase "Market Price" at any date shall be deemed to be the last reported
sale price, or, in case no such reported sale takes place on such day, the
average of the last reported sale prices for the last three (3) trading days,
in either case as officially reported by the principal securities exchange on
which the Common Stock is listed or admitted to trading, or, if the Common
Stock is not listed or admitted to trading on any national securities exchange,
the average closing sale price as furnished by the NASD through The Nasdaq
Stock Market, Inc. ("Nasdaq") or similar organization if Nasdaq is no longer
reporting such information, or if the Common Stock is not quoted on Nasdaq, as
determined in good faith by resolution of the Board of Directors of the
Company, based on the best information available to it.

                                  (b)  The warrants shall vest in four 50,000
warrant tranches (each, a "Tranche").  The first Tranche shall vest as of the
Effective Date (March 13, 1998) and shall


                                     -2-
<PAGE>   3
become exercisable six months from the Effective Date (September 13, 1998).
The Exercise Price for the first Tranche shall be $1.107 per share.

                                  (c)  The remaining three Tranches shall vest
based upon the closing price of the Common Stock, as reported on Nasdaq,
achieving or exceeding the stock price trigger (the "Trigger") for each of the
remaining Tranches for at least twenty (20) consecutive trading days (the last
day of which shall be the vesting date for such Tranche) occurring on or after
the Effective Date.  Each of the remaining three Tranches shall become
exercisable six (6) months following the date in which its Trigger is achieved.
Two or more Tranches may vest on the same date.  For each of the remaining
three Tranches, the Exercise Price shall equal the Trigger.  The number of
Warrants vesting and the Exercise Price and Triggers for each of the remaining
three Tranches shall be as follows:

<TABLE>
<CAPTION>
                 Number of Warrants Vested           Exercise Price and Trigger
                 -------------------------           --------------------------
                          <S>                        <C>
                          50,000                     $1.50 per share

                          50,000                     $2.00 per share

                          50,000                     $2.50 per share
</TABLE>


Any Warrants which have not vested as of the earlier of (i) March 13, 2000 and
(ii) the date that the Financial Advisory and Consulting Agreement, dated March
13, 1998, between the Company and the Holder shall be terminated, shall expire
without vesting and shall be unexercisable.

                          (d)  The Warrants shall expire and become
unexercisable on the earlier of the following: (i) March 13, 2003; (ii) six (6)
months following the date upon which the employment with the Holder of both
Gregg D.  Pollack ("Pollack") and Brian Friedman ("Freidman") is terminated
(the "Employment Expiration"); or (iii) six (6) months following the date upon
which both Pollack and Friedman discontinue serving as the Holder's primary
contacts with the Company ("Change of Contact").  The Company, in its sole
discretion, may agree to waive the Employment Expiration or to substitute one
or more of the contacts applicable to the Change of Contacts.

                 2.       Upon each exercise of the Holder's rights to purchase
Warrant Shares, the Holder shall be deemed to be the holder of record of the
Warrant Shares issuable upon such exercise, notwithstanding that the transfer
books of the Company shall then be closed or certificates representing such
Warrant Shares shall not then have been actually delivered to the Holder.
Within five (5) business days after each such exercise of this Warrant and
receipt by the Company of this Warrant, the Election to Exercise and the
Aggregate Exercise Price, the


                                     -3-
<PAGE>   4
Company shall issue and deliver to the Holder a certificate or certificates for
the Warrant Shares issuable upon such exercise, registered in the name of the
Holder or its designee.  If this Warrant should be exercised in part only, the
Company shall, upon surrender of this Warrant for cancellation, execute and
deliver a new Warrant evidencing the right of the Holder to purchase the
balance of the Warrant Shares (or portions thereof) subject to purchase
hereunder.

                 3.       Any Warrants issued upon the transfer or exercise in
part of this Warrant shall be numbered and shall be registered in a warrant
register (the "Warrant Register") as they are issued.  The Company shall be
entitled to treat the registered holder of any Warrant on the Warrant Register
as the owner in fact thereof for all purposes and shall not be bound to
recognize any equitable or other claim to or interest in such Warrant on the
part of any other person, and  shall not be liable for any registration of
transfer of Warrants which are registered or to be registered in the name of a
fiduciary or the nominee of a fiduciary unless made with the actual knowledge
of the general counsel of the Company that a fiduciary or nominee is committing
a breach of trust in requesting such registration of transfer.  In all cases of
transfer by an attorney, executor, administrator, guardian, or other legal
representative, duly authenticated evidence of his or its authority shall be
produced.  Upon any registration of transfer, the Company shall deliver a new
Warrant or Warrants to the person entitled thereto.  This Warrant may be
exchanged, at the option of the Holder thereof, for another Warrant, or other
Warrants of different denominations, of like tenor and representing in the
aggregate the right to purchase a like number of Warrant Shares (or portions
thereof), upon surrender to the Company or its duly authorized agent.
Notwithstanding anything contained herein to the contrary, the Company shall
have no obligation to cause Warrants to be transferred on its books to any
person if, in the opinion of counsel to the Company, such transfer does not
comply with the provisions of the Act and any applicable state securities laws
and the rules and regulations thereunder.

                 4.       The Company shall at all times reserve and keep
available out of its authorized and unissued Common Stock, solely for the
purpose of providing for the exercise of the rights to purchase all Warrant
Shares granted pursuant to the Warrants, such number of shares of Common Stock
as shall, from time to time, be sufficient therefor.  The Company covenants
that all shares of Common Stock issuable upon exercise of this Warrant, upon
receipt by the Company of the required documentation, properly signed, and the
full Exercise Price therefor, shall be validly issued, fully paid,
nonassessable, and free of preemptive rights.

                 5.       The Exercise Price in effect at any time and the
number and kind of securities purchasable upon the exercise of this Warrant
shall be subject to adjustment from time to time upon the happening of certain
events as follows:

                          (a)     In case the Company shall (i) declare a
dividend or make a distribution on its outstanding shares of Common Stock, in
each case, in shares of Common Stock, (ii) subdivide or reclassify its
outstanding shares of Common Stock into a greater number





                                      -4-
<PAGE>   5
of shares, or (iii) combine or reclassify its outstanding shares of Common
Stock into a smaller number of shares, the Exercise Price in effect at the time
of the record date for such dividend or distribution or of the effective date
of such subdivision, combination or reclassification shall be proportionately
adjusted so that after such event the Exercise Price shall equal the price
determined by multiplying the Exercise Price by a fraction, the denominator of
which shall be the number of shares of Common Stock outstanding after giving
effect to such action, and the numerator of which shall be the number of shares
of Common Stock outstanding immediately prior to such action.  Such adjustment
shall be made successively whenever any event listed above shall occur.

                          (b)     Upon each adjustment of the Exercise Price
pursuant to the provisions of this Section 5, the number of Warrant Shares
issuable upon the exercise at the adjusted Exercise Price of each Warrant shall
be adjusted so that after the event necessitating the adjustment to the
Exercise Price, the number of Warrant Shares into which this Warrant shall be
exercisable shall be equal to the nearest number of whole shares of Common
Stock determined by multiplying a number equal to the Exercise Price in effect
immediately prior to such adjustment by the number of Warrant Shares issuable
upon exercise of this Warrant immediately prior to such adjustment and dividing
the product so obtained by the adjusted Exercise Price.

                          (c)     For the purpose of this Warrant, the term
"Common Stock" shall mean (i) the class of stock designated as Common Stock in
the Certificate of Incorporation of the Company as amended as of the date
hereof, or (ii) any other class of stock resulting from successive changes or
reclassifications of such Common Stock consisting solely of changes in par
value, or from par value to no par value, or from no par value to par value.

                          (d)     In case of any consolidation of the Company
with, or merger of the Company into, another corporation (other than a
consolidation or merger which does not result in any reclassification or change
of the outstanding Common Stock), the corporation formed by such consolidation
or merger shall execute and deliver to the Holder a supplemental warrant
agreement providing that the Holder of this Warrant shall have the right
thereafter (until the expiration of such Warrant) to receive, upon exercise of
such Warrant, the kind and amount of shares of stock and other securities and
property receivable upon such consolidation or merger by a holder of the number
of shares of Common Stock for which such Warrant might have been exercised
immediately prior to such consolidation, merger, sale or transfer.  Such
supplemental warrant agreement shall provide for adjustments which shall be
identical to the adjustments provided in this Section 5.  The above provision
of this subsection shall similarly apply to successive consolidations or
mergers.

                          (e)     No adjustment in the Exercise Price or the
number of Warrant Shares shall be required if such adjustment is less than
one-tenth of one percent (0.1%) of such Exercise Price or number of Warrant
Shares; provided, however, that any adjustments which





                                      -5-
<PAGE>   6
by reason of this Section 5(e) are not required to be made shall be carried
forward and taken into account in any subsequent adjustment.  All calculations
under this Section 5 shall be made to the nearest one-tenth of one cent
($0.001) and one-thousandth of one share (.001).

                          (f)     In any case in which this Section 5 shall
require that an adjustment in the number of Warrant Shares be made effective as
of a record date for a specified event, the Company may elect to defer, until
the occurrence of such event, issuing to the Holder, if the Holder exercised
this Warrant after the record date, the Warrant Shares, if any, issuable upon
such exercise over and above the Warrant Shares, if any, issuable upon such
exercise prior to such adjustment; provided, however, that the Company shall
deliver to the Holder a due bill or other appropriate instrument evidencing the
Holder's right to receive  such additional Warrant Shares upon the occurrence
of the event requiring such adjustment.

                          (g)     Whenever there shall be an adjustment as
provided in this Section 5, the Company shall promptly cause written notice
thereof to be sent by certified mail, postage prepaid, to the Holder, at its
address as it shall appear in the Warrant Register, which notice shall be
accompanied by an officer's certificate setting forth the number of Warrant
Shares issuable upon the exercise of this Warrant if such Warrant were
exercisable on the date of such notice, and setting forth a brief statement of
the facts requiring such adjustment and the computation thereof, which
officer's certificate shall be conclusive evidence of the correctness of any
such adjustment absent manifest error.

                 6.       In case at any time the Company shall propose

                          (a)     to pay any dividend or make any distribution
on shares of Common Stock in shares of Common Stock or make any other
distribution in excess of five percent (5%) of the Market Price of the Common
Stock (other than regularly scheduled cash dividends which are not in a greater
amount per share than the most recent such cash dividend) to all holders of
Common Stock; or

                          (b)     to issue any rights, warrants, or other
securities to all holders of Common Stock entitling them to purchase any
additional shares of Common Stock or any other rights, warrants, or other
securities; or

                          (c)     to effect any reclassification or change of
outstanding shares of Common Stock, or any consolidation or merger, described
in Section 7; or

                          (d)     to effect any liquidation, dissolution, or
winding-up of the Company,

then, and in any one or more of such cases, the Company shall give written
notice thereof, by registered mail, postage prepaid, to the Holder at the
Holder's address as it shall appear in the





                                      -6-
<PAGE>   7
Warrant Register, mailed at least 15 days prior to (i) the date as of which the
holders of record of shares of Common Stock to be entitled to receive any such
dividend, distribution, rights, warrants, or other securities are to be
determined, or (ii) the date on which any such reclassification, change of
outstanding shares of Common Stock, consolidation, merger, liquidation,
dissolution, or winding-up is expected to become effective, and the date as of
which it is expected that holders of record of shares of Common Stock shall be
entitled to exchange their shares for securities or other property, if any,
deliverable upon such reclassification, change of outstanding shares,
consolidation, merger, sale, lease, conveyance of property, liquidation,
dissolution, or winding-up.

                 7.       The issuance of any shares or other securities upon
the exercise of this Warrant, and the delivery of certificates or other
instruments representing such shares or other securities, shall be made without
charge to the Holder for any tax or other charge in respect of such issuance,
other than applicable transfer taxes.  The Company shall not, however, be
required to pay any tax which may be payable in respect of any transfer
involved in the issue and delivery of any certificate in a name other than that
of the Holder and the Company shall not be required to issue or deliver any
such certificate unless and until the person or persons requesting the issue
thereof shall have paid to the Company the amount of such tax or shall have
established to the satisfaction of the Company that such tax has been paid.

                 8.       (a)  If, at any time during the Exercise Period on or
after September 13, 1998, the Company proposes to register any of its
securities under the Act (other than on a Form S-4 or a Form S-8 or successor
form thereto), it will give written notice by registered mail, at least fifteen
(15) days prior to the filing of each such registration statement, to the
Holders of this Warrant or the Warrant Shares of its intention to do so.  If
any of the Holders of this Warrant or the Warrant Shares notify the Company
within fifteen (15) days after mailing of any such notice of its or their
desire to include any Warrant Shares in such registration statement, the
Company shall afford such Holders the opportunity to have any such Warrant
Shares registered under such registration statement.  In the event that the
managing underwriter for said offering advises the Company in writing that in
its opinion the number of Warrant Shares requested to be included in such
registration exceeds the number which can be sold in such offering without
causing a diminution in the offering price or otherwise adversely affecting the
offering, the Company will include in such registration (a) first, the
securities the Company proposes to sell, (b) second, the securities held by
persons and entities that have demand registration rights, (c) third, the
Warrant Shares requested to be included in such registration which in the
opinion of such underwriter can be sold, pro rata among those persons having
registration rights similar those set forth in this Section 8 who requested
such registration, and (d) fourth, other securities requested to be included in
such registration.  Notwithstanding the provisions of this Section 8, the
Company shall have the right at any time after it shall have given written
notice pursuant to this Section 8(a) (irrespective of whether a written request
for inclusion of any such securities shall have been made) to elect not to file
any such proposed registration statement or to withdraw the same after the
filing but prior to the effective date thereof.





                                      -7-
<PAGE>   8
                          (b)  At any time during the Exercise Period on or
after September 13, 1998, the Holder shall have the right, exercisable by
written notice to the Company, to have the Company prepare and file with the
Securities and Exchange Commission (the "Commission"), on one occasion, an
appropriate registration statement as selected by the Company and such other
documents, including a prospectus, as may be necessary in the opinion of both
counsel for the Company and counsel for the Holder, in order to comply with the
provisions of the Act, so as to permit a public offering and sale of Warrant
Shares by the Holder.  The Company shall use its commercially reasonable
efforts to have such registration statement filed with and declared effective
by the Commission within one hundred twenty (120) days of receipt of the notice
from the Holder.  If the Holder intends for the public offering covered by its
demand request to occur by means of an underwriting, it shall so advise the
Company as a part of its demand request, and the managing underwriter of such
underwritten public offering shall be selected by the Holder and shall be
reasonably acceptable to the Company.  The Company shall be entitled to include
in any registration statement filed pursuant to this Section 8(b) additional
shares of Common Stock for its own account and for the account of its other
security holders.  If the managing underwriter advises the Company in writing
that the inclusion of any or all such additional shares of Common Stock would
materially adversely affect the marketing of the public offering of the Warrant
Shares, then the Company shall not be entitled to include such additional
shares of Common Stock in any such registration statement to the extent the
managing underwriter advises.  Notwithstanding the provisions of this Section
8(b), the Company shall have the right to delay or suspend the filing of a
registration statement for up to 90 days from the time the filing thereof would
otherwise be required under this Section 8(b) if, in the good faith
determination of the Company's board of directors, such registration would be
seriously detrimental to the Company and its stockholders or would materially
adversely affect the business, affairs, properties, financial condition,
results of operations or prospects of the Company or any pending or proposed
acquisition, merger, reorganization, recapitalization or other transaction or
public offering of the Company's securities, or would require premature
disclosure thereof not in the best interests of the Company; provided, however,
that the Company shall not be entitled to exercise this right more than once.

                          (c)  It shall be a condition precedent to the
obligation of the Company hereunder to register the Warrant Shares under this
Section 8 that the holder thereof furnish to the Company and the managing
underwriter such information regarding itself, the intended method of
disposition of such Warrant Shares and such other information as the Company or
the managing underwriter shall from time to time reasonably request and that
shall be reasonably required to effect the registration of the Warrant Shares.

                          (d)  The holder of the Warrant Shares shall pay all
underwriting and brokerage fees, discounts and commissions related to the sale
of the Warrant Shares in a public offering registered pursuant to the
provisions of this Section 8, together with the fees and expenses of any
separate counsel, accountants and other advisors retained by the Holder in
connection with the offering.  All other fees, costs and expenses incurred in
connection with any





                                      -8-
<PAGE>   9
registration of such public offering including, but not limited to, all federal
and state registration, qualification, filing fees, printing and document
distribution costs and expenses, fees and disbursements of the Company's
counsel, accountants and other experts, Nasdaq additional listing fees,
transfer fees, exchange fees, fees of transfer agents and registrants shall be
borne as follows: (i) if pursuant to a demand registration under Section 8(b),
the Company shall bear the first $10,000 of such costs, fees and expenses, and
the Holder shall bear the difference, except that the Company shall also bear
its proportionate share of any such costs, fees and expenses to the extent it
includes additional shares of Common Stock in such registration, and (ii) if
pursuant to a piggyback registration under Section 8(a), by the Company.

                 9.       Unless registered as contemplated by Section 8
hereof, the Warrant Shares issued upon exercise of the Warrants shall be
subject to a stop transfer order and the certificate or certificates evidencing
such Warrant Shares shall bear the following, or a substantially similar,
legend:

                          "THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE BEEN
                          NOT REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
                          AMENDED.  SUCH SHARES MAY NOT BE OFFERED OR SOLD
                          EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION
                          STATEMENT UNDER SUCH ACT, OR AN EXEMPTION FROM
                          REGISTRATION UNDER SUCH ACT.  SUCH SHARES ARE SUBJECT
                          TO CERTAIN RESTRICTIONS ON TRANSFER CONTAINED IN A
                          WARRANT, DATED MARCH 13, 1998, A COPY OF WHICH ARE ON
                          FILE WITH THE SECRETARY OF THE COMPANY."

                 10.      Upon receipt of evidence satisfactory to the Company
of the loss, theft, destruction, or mutilation of any Warrant (and upon
surrender of any Warrant if mutilated), and upon reimbursement of the Company's
reasonable incidental expenses and, if reasonably requested, an indemnity
reasonably acceptable to the Company, the Company shall execute and  deliver to
the Holder thereof a new Warrant of like date, tenor, and denomination.

                 11.      The Holder of any Warrant shall not have, solely on
account of such status, any rights of a stockholder of the Company, either at
law or in equity, or to any notice of meetings of stockholders or of any other
proceedings of the Company, except as provided in this Warrant.





                                      -9-
<PAGE>   10
                 12.      Neither this Warrant nor, unless registered as
contemplated by Section 8 hereof, the Warrant Shares issuable upon exercise of
this Warrant, may be offered, sold, assigned, hypothecated or otherwise
transferred, in whole or in part, except (i) to the officers, directors,
shareholders or employees of the Holder, (ii) by will or the laws of descent
and distribution as a result of the death of any permitted transferee, or (iii)
to any successor to the business of the Holder.  In addition, neither this
Warrant nor, until registered as contemplated by Section 8 hereof, any Warrant
Shares issued upon exercise of this Warrant, may be pledged, offered, sold,
assigned, hypothecated or otherwise transferred until (i) a registration
statement with respect thereto has been filed and become effective under the
Act and under the applicable state securities laws, or (ii) the Company has
received an opinion of counsel to the Company or counsel to the holder of such
securities, which counsel and opinion are reasonably satisfactory to the
Company, that such securities may be pledged, offered, sold, assigned,
hypothecated or transferred without an effective registration statement under
the Act and applicable state securities laws.  It shall be a condition to the
transfer of this Warrant and any Warrant Shares that any transferee hereof or
thereof deliver to the Company its written agreement to accept and be bound by
all of the terms and conditions of this Warrant.

                 13.      The Holder and each transferee of this Warrant or of
the Warrant Shares issuable upon the exercise of this Warrant, by their
acceptance of this Warrant or of any Warrant Shares, each hereby represents and
warrants that this Warrant and the Warrant Shares issuable upon exercise of
this Warrant are being acquired or will be acquired for investment purposes for
the account of the holder of such securities with no intention of a sale,
transfer or other distribution that is not in compliance with the Act and
applicable state securities laws.

                 14.      The Company shall not be required to issue any
fraction of a share of Common Stock upon the exercise of this Warrant.  If any
fraction of a share of Common Stock would be issuable upon the exercise of this
Warrant, the Company shall, in lieu of issuing such fractional interest, pay to
the Holder an amount of cash equal to such fraction multiplied by the Market
Price of a share of Common Stock as of the trading date preceding the date of
exercise.





                                      -10-
<PAGE>   11
                 15.      This Warrant shall be construed in accordance with
the laws of the State of New York applicable to contracts made and performed
within such State, without regard to principles of conflicts of law.



Dated: March 13, 1998

                                       MARCUM NATURAL GAS SERVICES, INC.


                                       By: /s/ A. BRADLEY GABBARD
                                          ------------------------------------
                                          Name:  A. Bradley Gabbard
                                          Title: Executive Vice President





                                      -11-
<PAGE>   12
                               FORM OF ASSIGNMENT


(To be executed by the registered holder if such holder desires to transfer the
attached Warrant.)

                 FOR VALUE RECEIVED, ____________________________ hereby sells,
assigns, and transfers unto __________________ a Warrant to purchase __________
shares of Common Stock, no par value per share, of Marcum Natural Gas Services,
Inc. (the "Company"), together with all right, title, and interest therein, and
does hereby irrevocably constitute and appoint
______________________________________________ attorney to transfer such
Warrant on the books of the Company, with full power of substitution.

Dated: 
      --------------------

                                        Signature
                                                 ----------------------------


Signature Guaranteed:



                                     NOTICE


                 The signature on the foregoing Assignment must correspond to
the name as written upon the face of this Warrant in every particular, without
alteration or enlargement or any change whatsoever.
<PAGE>   13
To:   Marcum Natural Gas Services, Inc.
      1675 Broadway, Suite 2150
      Denver, Colorado 80202



                              ELECTION TO EXERCISE


                 The undersigned hereby exercises his or its rights to purchase
      _______ Warrant Shares covered by the within Warrant and tenders payment
      herewith [in the amount of $_________] [in the form of ________ number of
      Warrant Shares] in accordance with the terms thereof, certifies that he
      owns this Warrant free and clear of any and all claims, liens and/or
      encumbrances and requests that certificates for such securities be issued
      in the name of, and delivered to:


                  --------------------------------------------

                  --------------------------------------------

                  --------------------------------------------
                    (Print Name, Address and Social Security
                         or Tax Identification Number)

      and, if such number of Warrant Shares shall not be all the Warrant Shares
      covered by the within Warrant, that a new Warrant for the balance of the
      Warrant Shares covered by the within Warrant be registered in the name
      of, and delivered to, the undersigned at the address stated below.


      Dated:                              Name                                
            ---------------                   --------------------------------
                                              (Print)

      Address:                                                                
              ----------------------------------------------------------------



                                          
                                           -----------------------------------
                                           (Signature)