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                                   MESA INC.
 
                                RIGHTS OFFERING
 
                     DTC PARTICIPANT OVERSUBSCRIPTION FORM
 
THIS FORM IS TO BE USED ONLY BY DEPOSITORY TRUST COMPANY PARTICIPANTS TO
EXERCISE THE OVERSUBSCRIPTION PRIVILEGE IN RESPECT OF RIGHTS WITH RESPECT TO
WHICH THE BASIC SUBSCRIPTION PRIVILEGE WAS EXERCISED AND DELIVERED THROUGH THE
FACILITIES OF THE DEPOSITORY TRUST COMPANY. ALL OTHER EXERCISES OF
OVERSUBSCRIPTION PRIVILEGES MUST BE EFFECTED BY THE DELIVERY OF THE SUBSCRIPTION
FORMS.

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THE TERMS AND CONDITIONS OF THE RIGHTS OFFERING ARE SET FORTH IN THE PROSPECTUS
OF MESA INC. ("MESA") DATED JULY   , 1996 (THE "PROSPECTUS") AND ARE
INCORPORATED HEREIN BY REFERENCE. COPIES OF THE PROSPECTUS ARE AVAILABLE UPON
REQUEST FROM MESA, THE INFORMATION AGENT, THE DEALER MANAGER AND THE
SUBSCRIPTION AGENT.

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VOID UNLESS RECEIVED BY THE SUBSCRIPTION AGENT WITH PAYMENT IN FULL BY 5:00
P.M., NEW YORK CITY TIME, ON JULY 26, 1996 (THE "EXPIRATION DATE").

                             ---------------------
 
     1. The undersigned hereby certifies to Mesa and the Subscription Agent that
it is a participant in The Depository Trust Company ("DTC") and that it has
either (i) exercised the Basic Subscription Privilege in respect of Rights and
delivered such exercised Rights to the Subscription Agent by means of transfer
to the DTC account of the Subscription Agent or (ii) delivered to the
Subscription Agent a Notice of Guaranteed Delivery in respect of the exercise of
the Basic Subscription Privilege and will deliver the Rights called for in such
Notice of Guaranteed Delivery to the Subscription Agent by means of transfer to
such DTC account of the Subscription Agent. The undersigned hereby certifies to
Mesa and the Subscription Agent that it owned           Shares of Common Stock
on July 3, 1996 (the "Record Date").
 
     2. The undersigned hereby exercises the Oversubscription Privilege to
purchase, to the extent available,           shares of Series A 8% Cumulative
Convertible Preferred Stock and certifies to Mesa and the Subscription Agent
that such Oversubscription Privilege is being exercised for the account or
accounts of persons (which may include the undersigned) on whose behalf all
basic subscription privilege rights have been exercised.
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     3. The undersigned understands that payment of the Subscription Price of
$2.26 per share for each share of Series A 8% Cumulative Convertible Preferred
Stock subscribed for pursuant to the Oversubscription Privilege must be received
by the Subscription Agent at or before 5:00 p.m. New York City time on the
Expiration Date and represents that such payment, in the aggregate amount of
$          either (check appropriate box):
 
     / /  has been or is being delivered to the Subscription Agent pursuant to
          the Notice of Guaranteed Delivery referred to above
 
                                       or
 
     / /  is being delivered to the Subscription Agent herewith
 
                                       or
 
     / /  has been delivered separately to the Subscription Agent;
 
and, in the case of funds not delivered pursuant to a Notice of Guaranteed
Delivery, is or was delivered in the manner set forth below (check appropriate
box and complete information relating thereto):
 
     / /  uncertified check
 
     / /  certified check
 
     / /  bank draft
 
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Basic Subscription Confirmation Number
 
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          DTC Participant
 
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      Name of DTC Participant
 
By:
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   Name:
   Title:
 
Contact Name:
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Phone Number:                             
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Dated:                            1996         
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