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                                                                     EXHIBIT 4.7

                                     FORM OF
                  CERTIFICATE OF DESIGNATION, VOTING POWERS AND
                        RIGHTS OF SERIES A 6% CONVERTIBLE
                 PREFERRED STOCK OF VISTA ENERGY RESOURCES, INC.


         Vista Energy Resources, Inc., a corporation organized and existing
under the laws of the State of Delaware (the "CORPORATION"), DOES HEREBY
CERTIFY:

         That, pursuant to authority conferred upon the Board of Directors by
the Corporation's Certificate of Incorporation, as amended, and pursuant to the
provisions of Section 151 of the Delaware General Corporation Law, as amended,
the Board of Directors, by written consent dated _______, ____, unanimously
adopted the following resolution providing for the creation and issuance of a
series of shares of the Corporation's authorized preferred stock designated as
"Series A 6% Convertible Preferred Stock":

         RESOLVED, that a new series of the Corporation's authorized but
unissued preferred stock be, and the same hereby is, established and designated,
and that the designation and amount thereof, and the relative rights,
preferences, qualifications, limitations and restrictions thereof, are as
follows:


         SECTION 1. DESIGNATION, NUMBER OF SHARES AND STATED VALUE OF SERIES A
PREFERRED STOCK. There is hereby authorized and established a series of the
Corporation's preferred stock, par value $0.01 per share, that shall be
designated as "Series A 6% Convertible Preferred Stock" ("SERIES A PREFERRED"),
and the number of shares constituting such series shall be 5,000,000. Such
number of shares may be increased, but not decreased, by resolution adopted by
the Board of Directors of the Corporation. The "STATED VALUE" per share of
Series A Preferred initially shall be equal to $_________ (which amount shall be
proportionately adjusted in the case of recapitalizations, stock splits, stock
dividends, combinations of shares or similar matters directly affecting the
Series A Preferred).


         SECTION 2. DEFINITIONS. In addition to the definitions set forth
elsewhere herein, the following terms shall have the meanings indicated:

         "BUSINESS DAY" shall mean any day other than a Saturday, Sunday or a
day on which banking institutions in New York, New York, are authorized or
obligated by law or executive order to close.

         "CLOSING PRICE" with respect to a particular security on any Trading
Day shall mean the last reported sales price, regular way, for such security on
such Trading Day, or, in case no sale takes place on such day, the average of
the closing bid and ask prices, regular way, on such Trading Day, in either case
as reported in the principal consolidated transaction reporting system with
respect to securities listed or admitted to trading on the American Stock
Exchange or the New York Stock Exchange or, if not listed or admitted to trading
on the American Stock Exchange or the New York Stock Exchange, as reported in
the principal consolidated transaction reporting system with respect




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to securities listed on the principal national securities exchange on which such
security is listed or admitted to trading or, if such security is not listed or
admitted to trading on any national securities exchange, the last quoted price
as reported by The Nasdaq Stock Market or such other system then in use.

         "COMMON STOCK" shall mean the common stock, par value $0.01 per share,
of the Corporation.


         "CONVERSION PRICE" shall mean the conversion price per share of Common
Stock into which Series A Preferred is convertible, as such conversion price may
be adjusted pursuant to Section 9 hereof. The initial Conversion Price shall be
$_____________.


         "JUNIOR SECURITIES" means the Common Stock or any other series of stock
issued by the Corporation ranking junior to the Series A Preferred in payment of
dividends or distributions or upon liquidation, dissolution or winding-up of the
Corporation.

         "MARKET PRICE" per share of Common Stock as of any date shall mean (i)
if the Common Stock is listed or admitted to trading on a national securities
exchange or The Nasdaq Stock Market, the average of the daily Closing Prices for
a period of 30 consecutive Trading Days ending on such date, or (ii) if the
Common Stock is not then so listed or admitted, the fair market value per share
of the Common Stock as reasonably determined by an investment banking firm
mutually acceptable to the Corporation and the holders of shares of Series A
Preferred.

         "ORIGINAL ISSUE DATE" shall mean the date on which shares of Series A
Preferred are first issued.

         "PARITY SECURITY" means any class or series of stock issued by the
Corporation ranking on a parity with the Series A Preferred in payment of
dividends or distributions or upon liquidation, dissolution or winding-up of the
Corporation.

         "PAYABLE-IN-KIND" or "PAID-IN-KIND" when used in reference to any
dividend payable on the shares of Series A Preferred means payment of the
dividend by issuance of that number of additional shares of Series A Preferred
that has an aggregate Stated Value equal to the dollar amount of such dividend
then payable. In lieu of any fractional share of Series A Preferred Stock to
which a holder of Series A Preferred Stock would otherwise be entitled, such
holder shall receive the nearest whole share of Series A Preferred Stock (i.e.
if less than .5 rounded down, and if .5 or more rounded up). Shares of Series A
Preferred issued as dividends Payable-in-Kind shall be duly authorized, validly
issued and nonassessable and, upon issuance, shall have rights (including
without limitation dividend, voting, conversion and redemption rights) identical
to the outstanding shares of Series A Preferred in respect of which they are
issued.


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         "PERSON" means any individual, corporation, association, partnership,
joint venture, limited liability company, trust, estate, or other entity or
organization.

         "SENIOR SECURITIES" means any class or series of stock, or any class or
series of debt or debt security convertible or exchangeable into any class or
series of stock, issued by the Corporation ranking senior to the Series A
Preferred in payment of dividends or distributions or upon liquidation,
dissolution or winding-up of the Corporation.

         "TRADING DAY" with respect to any security means (i) if such security
is listed or admitted for trading on any national securities exchange, a day on
which such national securities exchange is open for trading, or (ii) if such
security is not listed or admitted to trading on any national securities
exchange, a Business Day.

         "UNDERLYING COMMON STOCK" means at any time, with respect to any share
of Series A Preferred, the aggregate number of shares of Common Stock into which
such share is then convertible pursuant to Section 9 hereof.

         SECTION 3. DIVIDENDS AND DISTRIBUTIONS.

                  (a) The holders of outstanding shares of Series A Preferred
         shall be entitled to receive, as and when declared by the Corporation,
         out of funds of the Corporation legally available for the payment of
         dividends, preferential quarterly dividends at the times and at the
         rates provided for in this Section 3. Dividends on shares of the Series
         A Preferred shall be cumulative and shall accrue whether or not there
         shall be (at the time such dividend becomes payable or at any other
         time) profits, surplus or other funds of the Corporation legally
         available for the payment of dividends.


                  (b) Dividends shall accrue on each outstanding share of Series
         A Preferred at the rate of six percent (6%) per annum of the Stated
         Value (the "DIVIDEND RATE") of such share. Dividends shall be payable
         quarterly, in arrears, as of the last Business Day of each December,
         March, June and September, commencing with ____________ (each, a
         "REGULAR DIVIDEND PAYMENT DATE"). Dividends shall also be payable on
         any Redemption Date and on the final distribution date relating to the
         dissolution, liquidating or winding up of the Corporation (each such
         date, together with each Regular Dividend Payment Date, is a "DIVIDEND
         PAYMENT DATE").


                  (c) Dividends on outstanding shares of Series A Preferred
         shall be Payable-in-Kind during the period (the "EXCLUSIVE PIK PERIOD")
         beginning on the Original Issue Date and ending on the earlier of (i)
         the Dividend Payment Date on December 31, 2001, and (ii) the
         liquidation, dissolution or winding up of the Corporation (in
         connection with the bankruptcy or insolvency of the Corporation or
         otherwise). After the Exclusive PIK Period, dividends on the shares of
         Series A Preferred shall be Payable-in-Kind or, at the Corporation's
         option, payable in cash.


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                  (d) The amount of dividends payable on each Dividend Payment
         Date shall be determined by applying the Dividend Rate from but
         excluding the immediately preceding Dividend Payment Date (or from but
         excluding the date of issuance of shares of Series A Preferred, with
         respect to the first dividend period) to and including the Dividend
         Payment Date.

                  (e) Notwithstanding the foregoing or anything else herein to
         the contrary, however, dividends payable on any Redemption Date (as
         defined in Section 6(c) hereof) or the final distribution date relating
         to the dissolution, liquidation or winding up of the Corporation, shall
         be payable in cash only. If a Dividend Payment Date does not occur on a
         Regular Dividend Payment Date, dividends shall be calculated on the
         basis of the actual number of days elapsed from but excluding the
         immediately preceding Regular Dividend Payment Date to and including
         such non-Regular Dividend Payment Date. Dividends payable on the shares
         of Series A Preferred for any period of less than a full quarterly
         dividend period shall be computed on the basis of a 360-day year
         comprised of twelve 30-day months.

                  (f) Dividends payable on each Dividend Payment Date shall be
         paid to record holders of the shares of Series A Preferred as they
         appear on the books of the Corporation at the close of business on the
         10th Business Day immediately preceding the respective Dividend Payment
         Date or on such other record date as may be fixed by the Board of
         Directors of the Corporation in advance of a Dividend Payment Date,
         provided that no such record date shall be less than 10 nor more than
         60 calendar days preceding such Dividend Payment Date.

                  (g) So long as any shares of Series A Preferred are
         outstanding:

                           (i) No dividend or other distribution shall be
                  declared or paid, or set apart for payment, on or in respect
                  of, any Junior Securities (other than dividends or
                  distributions payable in shares of Junior Securities or in
                  rights to purchase Junior Securities), nor shall any Junior
                  Securities be redeemed, purchased or otherwise acquired for
                  any consideration (or any money be paid to a sinking fund or
                  otherwise set apart for the purchase or redemption of any such
                  Junior Securities) unless full cumulative dividends on all
                  outstanding shares of Series A Preferred and any Parity
                  Securities have been or contemporaneously are declared and
                  paid for all dividend periods terminating on or prior to the
                  date set for payment of such dividend.

                           (ii) No dividend or other distribution, except as
                  described in the next succeeding sentence, shall be declared
                  or paid, or set apart for payment, on or in respect of, Series
                  A Preferred or any Parity Securities for any period unless
                  full cumulative dividends on all outstanding shares of Series
                  A Preferred and any Parity Securities have been or
                  contemporaneously are declared and paid for all dividend
                  periods terminating on or prior to the date set for payment of
                  such dividend. When dividends are not paid in full, as
                  aforesaid, on the shares of Series A Preferred and any Parity
                  Securities, all dividends declared upon such Parity Securities
                  shall be declared and paid pro rata so that the amounts of
                  dividends per share declared and paid on the


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                  shares of Series A Preferred and such Parity Securities shall
                  in all cases bear to each other the same ratio that unpaid
                  dividends per share on the Series A Preferred and on such
                  Parity Securities bear to each other.

                           (iii) No shares of Series A Preferred or any Parity
                  Securities shall be redeemed, purchased or otherwise acquired
                  for any consideration (or any money be paid to a sinking fund
                  or otherwise set apart for the purchase or redemption of any
                  such Parity Security) by the Corporation unless the full
                  cumulative dividends on all outstanding shares of Series A
                  Preferred shall have been or contemporaneously are declared
                  and paid for all dividend periods terminating on or prior to
                  the date on which such redemption, purchase or other payment
                  is to occur.

                           (iv) No dividend or other distribution of cash or
                  debt shall be declared or paid, or set apart for payment, on
                  or in respect of, any Junior Securities, nor shall any Junior
                  Securities be redeemed, purchased or otherwise acquired for
                  any cash or debt consideration (or any money or debt paid to a
                  sinking fund or otherwise set apart for the purchase or
                  redemption of any Junior Securities) unless full cumulative
                  dividends on all outstanding shares of Series A Preferred have
                  been or contemporaneously are declared and paid in cash for
                  all dividend periods terminating on or prior to the date set
                  for payment of such dividend or distribution.

                           (v) No dividend or other distribution of cash or debt
                  shall be declared or paid, or set apart for payment, on or in
                  respect of, any Parity Securities unless full cumulative
                  dividends on all outstanding shares of Series A Preferred have
                  been or contemporaneously are declared and paid in cash for
                  all dividend periods terminating on or prior to the date set
                  for payment of such dividend or distribution. No Parity
                  Securities be redeemed, purchased or otherwise acquired for
                  any cash or debt consideration (or any money or debt paid to a
                  sinking fund or otherwise set apart for the purchase or
                  redemption of any Parity Securities) unless the Series A
                  Preferred shall have been called for redemption pursuant to
                  Section 6 hereof and the full Redemption Price (as defined in
                  Section 6(b) hereof) shall have been or contemporaneously is
                  paid in cash on or prior to the date set for payment of such
                  dividend or distribution.

         SECTION 4. CERTAIN COVENANTS AND RESTRICTIONS. So long as any shares of
Series A Preferred are outstanding:

                  (a) The Corporation shall at all times reserve and keep
         available for issuance upon the conversion of the shares of Series A
         Preferred as provided in Section 6 and Section 9 hereof, respectively,
         such number of its authorized but unissued shares of Common Stock as
         will be sufficient to permit the conversion of all outstanding shares
         of Series A Preferred and all other securities and instruments
         convertible into shares of Common Stock, and shall take all reasonable
         action within its power required to increase the authorized number of
         shares of Common Stock necessary to permit the conversion of all
         outstanding shares of Series A


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         Preferred and all such other securities and instruments convertible
         into shares of Common Stock.

                  (b) The Corporation covenants and agrees that all shares of
         Common Stock that may be issued upon exercise of the conversion rights
         of shares of Series A Preferred will, upon issuance, be duly
         authorized, valid issued, fully-paid and nonassessable.

                  (c) Prior to the delivery of any securities which the
         Corporation shall be obligated to deliver upon payment of dividends
         Payable-in-Kind or conversion of the Series A Preferred, the
         Corporation will endeavor to comply with all federal and state
         securities laws and regulations thereunder requiring the registration
         of such securities with, or any approval of or consent to the delivery
         of such securities by, any governmental authority.

                  (d) The Corporation shall pay all taxes and other governmental
         charges (other than any income or franchise taxes), documentary stamp
         or similar issue or transfer taxes that may be imposed with respect to
         the issue or delivery of the Series A Preferred (or any other
         securities issued on account of the Series A Preferred pursuant hereto)
         or shares of Common Stock upon conversion of Series A Preferred or
         payment of dividends Payable-in-Kind as provided herein or otherwise.
         The Corporation shall not be required, however, to pay any tax or other
         charge imposed in connection with any transfer involved in the issue of
         any certificate for shares of Common Stock in any name other than that
         of the registered holder of the shares of the Series A Preferred
         surrendered in connection with the conversion thereof or otherwise,
         and, in such case, the Corporation shall not be required to issue or
         deliver any stock certificate until such tax or other charge has been
         paid, or it has been established to the Corporation's satisfaction that
         no tax or other charge is due.

         SECTION 5. LIQUIDATION PREFERENCE.

                  (a) In the event of any liquidation, dissolution or winding-up
         of the Corporation (in connection with the bankruptcy or insolvency of
         the Corporation or otherwise), whether voluntary or involuntary, before
         any payment or distribution of the assets of the Corporation (whether
         capital or surplus) shall be made to or set apart for the holders of
         shares of any Junior Securities, the holders of the shares of Series A
         Preferred shall be entitled to receive an amount per share in cash
         equal to the Stated Value per share held by them, plus an amount in
         cash equal to the full cumulative dividends accrued and unpaid thereon,
         to the date of such payment, whether or not declared. No payment on
         account of any such liquidation, dissolution or winding-up of the
         Corporation shall be paid to the holders of the shares of Series A
         Preferred or the holders of any Parity Securities unless there shall be
         paid at the same time to the holders of the shares of Series A
         Preferred and the holders of any Parity Securities proportionate
         amounts determined ratably in proportion to the full preferential
         amounts to which the holders of all outstanding shares of Series A
         Preferred and the holders of all such outstanding Parity Securities are
         respectively entitled with respect to such distribution (but only to
         the extent of such preferential amounts). For purposes of this Section
         5, neither a consolidation or merger of the Corporation with one or
         more partnerships, corporations or other entities nor a sale, lease,
         exchange or transfer of all or any substantial part of the


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         Corporation's assets for cash, securities or other property shall be
         deemed to be a liquidation, dissolution or winding-up of the
         Corporation, whether voluntary or involuntary.

                  (b) After payment of the full amount of the liquidation
         preference to which the holders of shares of Series A Preferred are
         entitled, such holders will not be entitled to any further
         participation in any distribution of assets of the Corporation.

                  (c) Written notice of any liquidation, dissolution or
         winding-up of the Corporation, stating the payment date or dates when
         and the place or places where the amounts distributable in such
         circumstances shall be payable, shall be given by first class mail,
         postage prepaid, not less than 15 days prior to any payment date stated
         therein, to the holders of record of the shares of Series A Preferred
         at their respective addresses as the same shall appear in the records
         of the Corporation.

         SECTION 6. REDEMPTION. The outstanding shares of Series A Preferred are
subject to redemption in accordance with the following provisions:

                  (a) Subject to the terms hereof, the Corporation may at its
         option elect to redeem outstanding shares of Series A Preferred, in
         whole or in part (pro-rata among the outstanding shares), on any
         Business Day if both (i) the average of the Closing Prices of the
         Corporation's Common Stock during any period of at least 30 consecutive
         Trading Days during the preceding 60 Trading Days shall have exceeded
         120% of the Conversion Price, and (ii) the Closing Price per share of
         the Corporation's Common Stock on the Trading Day immediately preceding
         the day on which such notice is given shall have equaled or exceeded
         110% of the Conversion Price.

                  (b) The redemption price per share for Series A Preferred (the
         "REDEMPTION PRICE") shall be equal to the Stated Value plus an amount
         equal to the aggregate dollar amount of all accrued and unpaid
         dividends through the Redemption Date. The Redemption Price shall be
         paid in cash from any source of funds legally available therefor.

                  (c) The Business Day designated by the Corporation for the
         redemption of shares of Series A Preferred is referred to herein as the
         "REDEMPTION DATE." Not less than 60 days nor more than 75 days prior to
         the Redemption Date, a notice specifying the time and place of such
         redemption shall be given by first class mail, postage prepaid, to the
         holders of record of the shares of Series A Preferred to be redeemed at
         their respective addresses as the same shall appear on the books of the
         Corporation (but no failure to mail such notice or any defect therein
         shall affect the validity of the proceedings for redemption except as
         to the holder to whom the Corporation has failed to mail such notice or
         except as to the holder whose notice was defective), calling upon each
         such holder of record to surrender to the Corporation on the Redemption
         Date at the place designated in such notice such holder's certificate
         or certificates representing the then outstanding shares of Series A
         Preferred held by such holder. Each such notice of redemption shall
         specify the Redemption Date, the Redemption Price, the place or places
         of payment, that payment will be made upon presentation and surrender
         of the shares of Series A Preferred, that dividends will cease to
         accrue on such shares on and after


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         the Redemption Date, the then-effective Conversion Price pursuant to
         Section 9 hereof, and that the right of holders to convert shares of
         Series A Preferred will terminate at the close of business on the
         Business Day immediately preceding the Redemption Date (unless the
         Corporation defaults in the payment of the Redemption Price). On or
         after the Redemption Date, each holder of shares of Series A Preferred
         called for redemption shall surrender such holder's certificate or
         certificates for such shares to the Corporation at the place designated
         in the redemption notice and shall thereupon be entitled to receive
         payment of the Redemption Price in the manner set forth in Section 6(b)
         above. If the redemption is delayed for any reason, dividends shall
         continue to accrue on the shares of Series A Preferred outstanding, and
         shall be added to and become a part of the Redemption Price of such
         shares, until the Redemption Price, as so adjusted, for such shares is
         paid in full.

                  (d) Notwithstanding the foregoing, if notice of redemption has
         been given pursuant to Sections 6(a) and 6(c) hereof and any holder of
         the Series A Preferred shall, before the close of business on the
         Business Day immediately preceding the Redemption Date, give notice to
         the Corporation pursuant to Section 9(b) hereof of the conversion of
         any or all of the shares to be redeemed held by that holder, then (i)
         the Corporation shall not have the right to redeem those shares for
         which the conversion notice has been given, (ii) the holder shall not
         be entitled to payment of the Redemption Price with respect to those
         shares, (iii) the conversion of those shares shall become effective as
         provided in Section 9 hereof, and (iv) any funds that have been
         deposited for the payment of the Redemption Price of those shares shall
         be returned to the Corporation immediately after such conversion.

         SECTION 7. SHARES TO BE RETIRED. All shares of Series A Preferred
repurchased, redeemed, converted or otherwise acquired by the Corporation shall
be retired and cancelled and shall be restored to the status of authorized but
unissued shares of Preferred Stock, without designation as to series, and may
thereafter be reissued (subject to the provisions of Section 8 hereof).

         SECTION 8. VOTING RIGHTS.

                  (a) Except as otherwise provided in this Section 8 or required
         by law or any provision of the Certificate of Incorporation of the
         Corporation, the holders of the shares of Series A Preferred shall vote
         together with the shares of Common Stock as a single class at any
         annual or special meeting of stockholders of the Corporation upon the
         following basis: each holder of shares of Series A Preferred shall be
         entitled to such number of votes for the shares of Series A Preferred
         held by such holder on the record date fixed for such meeting as shall
         be equal to the whole number of shares of Underlying Common Stock with
         respect to such shares of Series A Preferred immediately after the
         close of business on the record date fixed for such meeting. In all
         cases where the holders of separate classes or series of the
         Corporation's capital stock have the right to vote separately as a
         class, the holders of Series A Preferred shall be entitled to one vote
         for each such share held by them.

                  (b) For so long as any shares of Series A Preferred remain
         outstanding, the Corporation shall not, without the affirmative vote or
         consent of the holders of a majority of the shares of Series A
         Preferred voting together as a single class, authorize, create or
         issue,


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         or increase the authorized or issued amount of, any class or series of
         stock of Senior Securities, Parity Securities or Series A Preferred
         (except through payment of dividends Payable-in-Kind on the Series A
         Preferred), or any security convertible into or exchangeable for Senior
         Securities or Parity Securities or reclassify or modify any Junior
         Securities so as to become Parity Securities or Senior Securities.

                  (c) Shares of Series A Preferred acquired by a subsidiary of
         the Corporation shall have no voting rights.

                  (d) For so long as any shares of Series A Preferred remain
         outstanding, the Corporation shall not, without the affirmative vote or
         consent of the majority (unless a higher percentage shall then be
         specified by law) of the shares of Series A Preferred voting together
         as a single class, merge or consolidate with or into any other Person
         or permit any other Person to merge with or into the Corporation,
         unless each share of Series A Preferred shall remain outstanding and
         unaffected or shall be converted into or exchanged for convertible
         preferred stock of the surviving entity (and, in the case of triangular
         mergers, with conversion rights into the common equity of the ultimate
         parent entity) having powers, preferences and relative participating,
         optional and other rights, and qualifications, limitations and
         restrictions thereof identical to a share of Series A Preferred, and
         unless the affirmative vote or consent of the holders of all the shares
         of Series A Preferred voting together as a single class shall have been
         obtained if such exchange, merger or consolidation shall result in the
         existence of Senior Securities or Parity Securities (treating
         securities issued by the surviving entity as having been issued by the
         Corporation) other than those previously approved pursuant to Section
         8(b) hereof; provided, however, that the voting rights with respect to
         this Section 8(d) shall be exercisable only by the original holder of
         the Series A Preferred and such voting rights shall terminate on the
         first date on which such original holder no longer owns shares of
         Series A Preferred which constitute at least 14.03% of the total issued
         and outstanding shares of Common Stock of the Corporation (based upon
         the number of shares of Common Stock into which the shares of Series A
         Preferred are then convertible and deeming the shares of Series A
         Preferred to be converted into issued and outstanding shares of Common
         Stock for the purpose of such computation).

         SECTION 9. CONVERSION RIGHTS. Holders of shares of Series A Preferred
shall have the right to convert all or a portion of such shares into shares of
Common Stock, as follows:

                  (a) Subject to and upon compliance with the provisions of this
         Section 9, shares of Series A Preferred shall be convertible at the
         option of the holder thereof into duly authorized, validly issued,
         fully paid and non-assessable shares of Common Stock. The number of
         shares of Common Stock deliverable upon conversion of one share of
         Series A Preferred shall be determined by dividing the Stated Value of
         such share of Series A Preferred by the Conversion Price then in effect
         (i.e., prior to any adjustment of the Conversion Price, one share of
         Common Stock will be issued for each share of Series A Preferred
         surrendered for conversion). In lieu of any fractional share of Common
         Stock to which a holder of Series A Preferred Stock would otherwise be
         entitled, such holder shall receive the nearest whole share of Common
         Stock (i.e., if less than .5 rounded down, and if .5 or more rounded
         up).


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         A holder of Series A Preferred may provisionally convert any shares of
         Series A Preferred that are the subject of a pending registration with
         the Securities and Exchange Commission. Unless the holder states an
         earlier time in the conversion notice to the Corporation, a provisional
         conversion will be effective only as of the closing of the holder's
         sale of Common Stock issuable upon conversion of Series A Preferred
         made pursuant to such an effective registration statement (and only
         with respect to the shares so sold); otherwise, such shares of Series A
         Preferred shall be outstanding as Series A Preferred for all purposes
         hereunder (including accrual and payment of dividends) during any
         period in which a provisional conversion is pending.

                  (b) The conversion of shares of Series A Preferred may be
         effected by the holder thereof by the surrender of the certificate for
         such shares to the Corporation at the principal office of the
         Corporation. If the conversion is to be provisional as provided in
         Section 9(a) above, the holder shall also deliver a notice to the
         Corporation with a statement to that effect. If any shares of Series A
         Preferred are called for redemption pursuant to Section 6 hereof, such
         right of conversion shall cease and terminate as to the shares called
         for redemption at the close of business on the Business Day immediately
         preceding the Redemption Date, unless the Corporation shall default in
         the payment of the Redemption Price, in which event such conversion
         right shall remain in effect until full payment of the Redemption Price
         has been made.

                  (c) As promptly as practicable after the surrender of shares
         of Series A Preferred for conversion (unless the shares are surrendered
         in a provisional conversion as provided in Section 9(a) hereof), the
         Corporation shall issue and deliver or cause to be issued and delivered
         to the holder of such shares certificates representing the number of
         fully paid and non-assessable shares of Common Stock into which such
         shares of Series A Preferred have been converted in accordance with the
         provisions of this Section 9. In lieu of any fractional share of Common
         Stock to which a holder of Series A Preferred Stock would otherwise be
         entitled, such holder shall receive the nearest whole share of Common
         Stock (i.e., if less than .5 rounded down, and if .5 or more rounded
         up). Subject to the following provisions of this Section 9, and, except
         with respect to provisional conversions, such conversion shall be
         deemed to have been made as of the close of business on the date on
         which the shares of Series A Preferred shall have been surrendered for
         conversion in the manner herein provided, so that all rights of the
         holder of the shares of Series A Preferred so surrendered shall cease
         at such time, and the person or persons entitled to receive the shares
         of Common Stock upon conversion thereof shall be treated for all
         purposes as having become the record holder or holders of such shares
         of Common Stock at such time; provided, however, that any such
         surrender (other than for provisional conversion) on any date when the
         stock transfer books of the Corporation are closed shall be deemed to
         have been made, and shall be effective to terminate the rights of the
         holder or holders of the shares of Series A Preferred so surrendered
         for conversion and to constitute the person or persons entitled to
         receive such shares of Common Stock as the record holder or holders
         thereof for all purposes, at the opening of business on the next
         succeeding day on which such transfer books are open and such
         conversion shall be at the Conversion Price in effect at such time. If
         shares are surrendered for provisional conversion, the Corporation
         shall either (i) reissue certificates for the number


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<PAGE>   11

         of shares of Series A Preferred surrendered for provisional conversion,
         if the sale of the underlying Common Stock (as provided in Section 9(a)
         above) does not occur, or (ii) issue certificates for the number of
         shares of Common Stock into which the shares provisionally surrendered
         have been converted to the order of the purchaser thereof, if the sale
         of the underlying Common Stock (as provided in Section 9(a) above) does
         occur. If, following the delivery of a notice of redemption by the
         Corporation pursuant to Section 6 hereof, but not otherwise, a holder
         of shares of Series A Preferred elects to exercise its rights of
         conversion under this Section 9, such holders of shares of Series A
         Preferred who surrender their shares of Series A Preferred for
         conversion shall be entitled to payment in cash by the Corporation of
         all accrued and unpaid dividends to the date the Series A Preferred are
         surrendered for conversion (or deemed to have been converted, in the
         case of shares provisionally converted), prorated for any portion of
         the then current dividend period during which the Series A Preferred
         are surrendered for conversion, whether or not any dividend in respect
         of the then-current dividend period has been declared or set aside. The
         Corporation shall make that payment as promptly as practicable
         following the surrender of certificates for shares of Series A
         Preferred for conversion as provided herein (or following the sale of
         the underlying Common Stock, in the case of shares that are
         provisionally converted and subsequently sold as provided in Section
         9(a) hereof) and, when applicable, shall accompany the certificates for
         Common Stock into which such shares of Series A Preferred have been
         converted.

                  (d) Before taking any action which would cause an adjustment
         reducing the Conversion Price below the then par value of the shares of
         Common Stock deliverable upon conversion of the shares of Series A
         Preferred, the Corporation will take any corporate action which may, in
         the opinion of its counsel, be necessary in order that the Corporation
         may validly and legally issue fully paid and non-assessable shares of
         Common Stock at such adjusted Conversion Price.

                  (e) The Conversion Price shall be subject to adjustment from
         time to time as follows:

                           (i) In case at any time the Corporation shall (A)
                  subdivide the outstanding shares of Common Stock into a
                  greater number of shares, or (B) combine the outstanding
                  shares of Common Stock into a smaller number of shares, the
                  Conversion Price in effect immediately prior thereto shall be
                  adjusted proportionately so that the adjusted Conversion Price
                  shall bear the same relation to the Conversion Price in effect
                  immediately prior to such event as the total number of shares
                  of Common Stock outstanding immediately prior to such event
                  shall bear to the total number of shares of Common Stock
                  outstanding immediately after such event. Such adjustment
                  shall become effective immediately after the effective date of
                  a subdivision or combination.

                           (ii) In case at any time the Corporation shall
                  declare, order, pay or make any dividend or other distribution
                  to holders of the Common Stock payable in shares of Common
                  Stock, then, in each such case, subject to Section 9(e)(v)
                  hereof, the Conversion Price in effect immediately prior to
                  the close of business on the record date fixed for
                  determination of holders of any class of securities entitled
                  to receive


                                       11

<PAGE>   12

                  such dividend or distribution shall be reduced to a price
                  (calculated to the nearest .001 of a cent) determined by
                  multiplying such Conversion Price by a fraction:

                                    (A) the numerator of which shall be the
                           number of shares of Common Stock outstanding
                           immediately prior to such dividend or distribution;
                           and

                                    (B) the denominator of which shall be the
                           number of shares of Common Stock outstanding
                           immediately after such dividend or distribution.

                  Shares of Common Stock owned by or held for the account of the
                  Corporation shall not be deemed outstanding for the purpose of
                  any such computation. Such adjustment shall be made on the
                  date such dividend is paid or such distribution is made and
                  shall become effective retroactive to the record date for the
                  determination of stockholders entitled to receive such
                  dividend or distribution.

                           (iii) In case at any time the Corporation shall
                  declare, order, pay or make any dividend or other distribution
                  to all holders of the Common Stock, other than a dividend
                  payable in shares of Common Stock (including, without
                  limitation, dividends or distributions payable in cash,
                  evidences of indebtedness, rights, options or warrants to
                  subscribe or purchase any Common Stock or other securities, or
                  any other securities or other property, but excluding any
                  rights to purchase any stock or other securities if such
                  rights are not separable from the Common Stock except upon the
                  occurrence of a contingency beyond the control of the
                  Corporation), then, and in each such case, subject to Section
                  9(e)(v) hereof, the Conversion Price in effect immediately
                  prior to the close of business on the record date fixed for
                  the determination of holders of Common Stock entitled to
                  receive such dividend or distribution shall be reduced to a
                  price (calculated to the nearest .001 of a cent) determined by
                  multiplying such Conversion Price by a fraction:

                                    (A) the numerator of which shall be the
                           Market Price per share of Common Stock in effect as
                           of such record date or, if the Common Stock trades on
                           an ex-dividend basis, on the Trading Day immediately
                           prior to the date of commencement of ex-dividend
                           trading, less the value of such dividend or
                           distribution (as determined in good faith by the
                           Board of Directors of the Corporation) applicable to
                           one share of Common Stock; and

                                    (B) the denominator of which shall be such
                           Market Price per share of Common Stock as of such
                           record date or, if the Capital Stock trades on an
                           ex-dividend basis, on the Trading Day immediately
                           prior to the date of commencement of ex-dividend
                           trading.

                  Such adjustment shall be made on the date such dividend is
                  paid or such distribution is made and shall become effective
                  retroactive to the record date for the determination of
                  stockholders entitled to receive such dividend or
                  distribution. In case at any time


                                       12


<PAGE>   13


                  the Corporation shall declare, order, pay or make a dividend
                  or rights to purchase any stock or other securities that are
                  not separable from the Common Stock except upon the occurrence
                  of a contingency beyond the control of the Corporation, the
                  Corporation shall make provision so that the holder of any
                  share of Series A Preferred thereafter surrendered for
                  conversion shall be entitled to receive the number of shares
                  of Common Stock and rights to purchase stock or other
                  securities that such holder would have owned or have been
                  entitled to receive after the occurrence of any of such events
                  had the share of Series A Preferred been surrendered for
                  conversion immediately before the occurrence of such event or
                  the record date therefor, whichever is earlier. If any such
                  rights are redeemed, the holder of Series A Preferred shall
                  have the right to receive, in lieu of any such rights, any
                  cash, property or securities paid in respect of such
                  redemption.

                           (iv) In case at any time the Corporation issues or
                  sells any shares of Common Stock or any rights, options or
                  warrants to subscribe for or purchase shares of Common Stock
                  or shares having the same rights, privileges and preferences
                  as the Common Stock ("EQUIVALENT COMMON STOCK") or securities
                  convertible into Common Stock or equivalent common stock, at a
                  price per share of Common Stock or equivalent common stock (or
                  having a conversion price per share, if a security is
                  convertible into shares of Common Stock or equivalent common
                  stock) less than the Market Price of the Common Stock as of
                  the date of such issue or sale, then upon such issue or sale
                  the Conversion Price shall be reduced to such Conversion Price
                  determined by multiplying the Conversion Price in effect
                  immediately prior to such issue or sale by a fraction, (y) the
                  numerator of which shall be the sum of the number of shares of
                  Common Stock outstanding immediately prior to such issue or
                  sale plus the number of shares of Common Stock which the
                  aggregate offering price of the total number of shares of
                  Common Stock and/or equivalent common stock so to be offered
                  (and/or the aggregate initial conversion price of the
                  convertible securities so to be offered) would purchase at
                  such Market Price and (z) the denominator of which shall be
                  the sum of the number of shares of Common Stock outstanding
                  immediately prior to such issue or sale plus the number of
                  additional shares of Common Stock and/or equivalent common
                  stock to be offered for subscription or purchase (or into
                  which the convertible securities so to be offered are
                  initially convertible). In case such subscription price may be
                  paid in a consideration part of or all of which shall be in a
                  form other than cash, the value of such consideration shall be
                  determined in good faith by the Board of Directors of the
                  Corporation. Shares of Common Stock owned by or held for the
                  account of the Corporation shall not be deemed outstanding for
                  the purpose of any such computation. Such issue or sale
                  adjustment shall be made successively upon the issuance or
                  sale of shares of Common Stock or equivalent common stock or
                  any rights, options or warrants to subscribe for or purchase
                  Common Stock or equivalent common stock or securities
                  convertible into common stock or equivalent common stock.
                  Notwithstanding the foregoing, no adjustment of the Conversion
                  Price pursuant to this Section 9(e)(iv) shall be made upon (A)
                  the conversion or redemption of shares of Series A Preferred;
                  (B) the payment of any stock dividend on the Series A
                  Preferred; (C) the issuance of options to officers,


                                       13

<PAGE>   14

                  directors and employees of the Corporation and its
                  subsidiaries to purchase shares of Common Stock, including any
                  such options as are issued and outstanding as of the Original
                  Issue Date, provided that, with respect to all such options,
                  the number of shares of Common Stock that may be subject to
                  such options shall be limited to 15% of the Corporation's
                  fully diluted shares of Common Stock based upon securities
                  outstanding as of the Original Issue Date; (D) the issuance
                  and sale of Common Stock upon exercise of any rights or
                  options referenced in the immediately preceding clause (C) or
                  in Section 9(e)(iii) above; or (E) the issuance and sale of
                  Common Stock in an underwritten public offering.

                           (v) If the amount of any adjustment of the Conversion
                  Price required pursuant to this Section 9(e) would be less
                  than 1% of the Conversion Price in effect at the time such
                  adjustment is otherwise so required to be made, such amount
                  shall be carried forward and an adjustment with respect
                  thereto made at the time of and together with any subsequent
                  adjustment which, together with such amount and any other
                  amount or amounts so carried forward, shall aggregate at least
                  1% of such Conversion Price. All calculations under this
                  Section 9(e) shall be made to the nearest .001 of a cent.

                           (vi) Except as herein otherwise expressly provided,
                  for all purposes of this Section 9(e) the term "Common Stock"
                  shall mean the Common Stock and any shares of stock or other
                  class of capital stock of the Corporation which is not
                  preferred as to dividends or assets over any other class of
                  capital stock of the Corporation and which is not subject to
                  redemption, or which is issued to the holders of shares of
                  Common Stock upon any reclassification thereof.

         Notwithstanding anything in this Section 9(e), there will be no
         adjustment hereunder as a result of the reverse stock split
         contemplated in Section 5.17 of the Agreement and Plan of Merger dated
         October 8, 1999, to which the Corporation is a party, which reverse
         stock split shall be deemed to have occurred prior to effectiveness of
         this Certificate.

                  (f) In case at any time after the Original Issue Date, the
         Corporation shall be a party to any transaction (including without
         limitation a merger, consolidation, statutory share exchange, sale of
         all or substantially all of the Corporation's assets or
         recapitalization of the Common Stock), in each case as a result of
         which shares of Common Stock (or any other securities of the
         Corporation then issuable upon conversion of the Series A Preferred)
         shall be converted into the right to receive stock, securities or other
         property (including without limitation cash or any combination thereof)
         (each of the foregoing transactions being referred to as a "FUNDAMENTAL
         CHANGE TRANSACTION"), then the shares of Series A Preferred remaining
         outstanding will thereafter no longer be subject to conversion into
         Common Stock (or such other securities) pursuant to this Section 9, but
         instead each share shall be convertible into the kind and amount of
         stock and other securities and property receivable (including without
         limitation cash) upon the consummation of such Fundamental Change
         Transaction by a holder of that number of shares or fraction thereof of
         Common Stock (or such other securities) into which one share of Series
         A Preferred was convertible immediately


                                       14

<PAGE>   15

         prior to such Fundamental Change Transaction assuming such holder of
         Common Stock failed to exercise any right of election as to the kind of
         consideration to be received in such Fundamental Change Transaction.
         The Corporation shall not be a party to any Fundamental Change
         Transaction after which shares of the Series A Preferred shall remain
         outstanding unless the terms of such Fundamental Change Transaction are
         consistent with the provisions of this Section 9(f), and it shall not
         consent or agree to the occurrence of any such Fundamental Change
         Transaction until the Corporation has entered into an agreement with
         the successor or purchasing entity, as the case may be, for the benefit
         of the holders of the shares of Series A Preferred which will contain
         provisions enabling the holders of shares of the Series A Preferred
         which remain outstanding after such Fundamental Change Transaction to
         convert such shares into the consideration received by holders of
         Common Stock (or any other securities of the Corporation then issuable
         upon conversion of the Series A Preferred) at the Conversion Price
         immediately after such Fundamental Change Transaction. In the event
         that at any time, as a result of an adjustment made pursuant to this
         Section 9, the Series A Preferred shall become subject to conversion
         into any securities other than shares of Common Stock, thereafter the
         number of such other securities so issuable upon conversion of the
         shares of Series A Preferred shall be subject to adjustment from time
         to time in a manner and on terms as nearly equivalent as practicable to
         the provisions with respect to the shares of Series A Preferred
         contained in this Section 9. The provisions of this Section 9(f) shall
         similarly apply to successive Fundamental Change Transactions.

                  (g) Upon the occurrence of any event requiring an adjustment
         of the Conversion Price, then, and in any such case, the Corporation
         shall promptly deliver to the holders of shares of Series A Preferred a
         notice stating the Conversion Price resulting from such adjustment and
         the method of calculation thereof and setting forth a brief statement
         of the facts requiring such adjustment and upon which such adjustment
         is based.

                  (h) In case at any time:

                           (i) the Corporation shall declare or pay to all
                  holders of Common Stock any dividend (whether payable in
                  Common Stock, cash, securities or other property);

                           (ii) there shall be any capital reorganization, or
                  reclassification of the Common Stock of the Corporation or
                  consolidation or merger of the Corporation with, or sale of
                  all or substantially all of its assets to, another corporation
                  or other entity;

                           (iii) there shall be a voluntary or involuntary
                  dissolution, liquidation or winding-up of the Corporation;

                           (iv) there shall be any other Fundamental Change
                  Transaction; or

                           (v) there shall occur any other event that would
                  cause an adjustment to the Conversion Price of the Series A
                  Preferred;


                                       15

<PAGE>   16


         then, in any one or more of such cases, the Corporation shall give to
         the holder of shares of Series A Preferred (A) at least 15 days prior
         to any event referred to in clause (i) or (v) above and at least 30
         days prior to any event referred to in clause (ii), (iii) or (iv)
         above, written notice of the date on which the books of the Corporation
         shall close or records shall be taken for such dividend or distribution
         or for determining rights to vote in respect of any such organization,
         reclassification, consolidation, merger, sale, dissolution,
         liquidation, winding-up or Fundamental Change Transaction, and (B) in
         the case of any such reorganization, reclassification, consolidation,
         merger, sale, dissolution, liquidation, winding-up or Fundamental
         Change Transaction known to the Corporation, at least 30 days prior
         written notice of the date, or if not then known, a reasonable
         approximation thereof by the Corporation) when the same shall take
         place. Such notice in accordance with the foregoing clause (A) shall
         also specify, in the case of any such dividend or distribution, the
         date on which such holders of Common Stock shall be entitled thereto,
         and such notice in accordance with the foregoing clause (B) shall also
         specify the date on which such holders of Common Stock shall be
         entitled to exchange their Common Stock, securities or other property
         deliverable upon such reorganization, reclassification, consolidation,
         merger, sale, dissolution, liquidation, winding-up or Fundamental
         Change Transaction, as the case may be.

                  (i) Whenever the Conversion Price is adjusted as provided
         herein, the Corporation shall prepare and mail to the record holders of
         Series A Preferred an officer's certificate signed by the Chairman of
         the Board, President, or Chief Financial Officer of the Corporation
         setting forth the Conversion Price after the adjustment, the method of
         calculation thereof, and a brief statement of the facts requiring the
         adjustment and upon which the adjustment is based. If the calculation
         of the adjustment requires a determination by the Corporations' Board
         of Directors, the certificate shall attach and certify to the
         resolution of the Board of Directors relating to the determination.

                  (j) All shares of Common Stock issuable upon the conversion
         set forth in this Section 9 shall be duly authorized, validly issued,
         fully-paid and nonassessable.

         SECTION 10. RANKING. Without limiting the definition of Junior
Securities, the following securities and obligations of the Corporation shall
rank junior to the Series A Preferred with respect to the payments required or
permitted to be made to the holders thereof pursuant to their respective
governing instruments and payments required to be made to the holders of the
Series A Preferred pursuant hereto: the shares of Common Stock. No Senior
Securities or Parity Securities are outstanding or authorized on the date hereof
or will be outstanding or authorized on the Original Issue Date.

         SECTION 11. RECORD HOLDERS. The Corporation may deem and treat the
record holder of any shares of Series A Preferred as the true and lawful owner
thereof for all purposes, and the Corporation shall not be affected by any
notice to the contrary.

         SECTION 12. NOTICES. Except as may otherwise be provided by law or
provided for herein, all notices referred to herein shall be in writing, and all
notices hereunder shall be deemed to have been given upon receipt, in the case
of a notice of conversion given to the Corporation as


                                       16

<PAGE>   17

contemplated in Section 9(b) hereof, or, in all other cases, upon the earlier of
receipt of such notice or three Business Days after the mailing of such notices
sent by first-class mail, postage prepaid, addressed: If to the Corporation, to
its principal executive offices (Attention: Corporate Secretary) or to any agent
of the Corporation designated as permitted hereby; or if to a holder of the
Series A Preferred, to such holder at the address of such holder as listed in
the stock record books of the Corporation (which shall include the records of
the Transfer Agent), or to such other address as the Corporation or holder, as
the case may be, shall have designated by notice similarly given.

         SECTION 13. REGISTRATION OF TRANSFER. Upon the surrender of any
certificate representing the Series A Preferred to the Corporation or its
transfer agent, the Corporation shall, or shall cause its transfer agent to, at
the request of the record holder of such certificate, execute and deliver (at
the Corporation's expense) a new certificate or certificates in exchange
therefor, of Series A Preferred representing in the aggregate the number of
shares of Series A Preferred represented by the surrendered certificate. Each
such new certificate shall be registered in such name and shall represent such
number of shares of Series A Preferred as is requested by the holder of the
surrendered certificate and shall be substantially identical in form to the
surrendered certificate, and dividends shall accrue on the Series A Preferred
represented by such new certificate from the date as of which dividends have
been fully paid on the Series A Preferred represented by the surrendered
certificate.

         SECTION 14. REPLACEMENT. Upon receipt of evidence satisfactory to the
Corporation (an affidavit of the registered holder shall be satisfactory) of the
ownership and the loss, theft, destruction or mutilation of any certificate
evidencing shares of Series A Preferred, and, in the case of any such loss,
theft or destruction, upon receipt of indemnity reasonably satisfactory to the
Corporation (provided, that, if the holder is a financial institution or other
institutional investor, its own agreement shall be satisfactory), or, in the
case of any such mutilation, upon surrender of such certificate, the Corporation
shall (at its own expense) execute and deliver in lieu of such certificate a new
certificate of like kind representing the number of shares of Series A Preferred
of such class represented by such lost, stolen, destroyed or mutilated
certificate and dated the date of the lost, stolen, destroyed or mutilated
certificate, and dividends shall accrue on the Series A Preferred represented by
such new certificate from the date to which dividends have been fully paid on
the Series A Preferred represented by the lost, stolen, destroyed or mutilated
certificate.

         SECTION 15. SUCCESSORS AND TRANSFEREES. The provisions applicable to
shares of Series A Preferred shall bind and inure to the benefit of and be
enforceable by the Corporation, the respective successors to the Corporation,
and by any record holder of shares of Series A Preferred.


                                       17

<PAGE>   18

         IN WITNESS WHEREOF, the Corporation has caused this Certificate to be
executed this ____ day of _______, _____.

                                    VISTA ENERGY RESOURCES, INC.



                                    By:
                                       ----------------------------------------
                                       C. Randall Hill
                                       President


                                       18