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                                LIMITED GUARANTY


                  THIS LIMITED GUARANTY ("Guaranty"), is made and entered into
as of September 24, 1998 by PAUL B. LOYD, JR. ("Guarantor"), for the benefit of
COMPASS BANK, a Texas state chartered banking institution ("Bank").


                              W I T N E S S E T H:


                  WHEREAS, on the date hereof, Bank has advanced or will advance
certain funds to CARRIZO OIL & GAS, INC., a Texas corporation ("Borrower")
pursuant to the Fourth Amendment of even date herewith to that certain First
Amended and Restated Loan Agreement dated August 28, 1997, as amended by the
First Amendment thereto dated December 23, 1997, the Second Amendment thereto
dated December 30, 1997 and the Third Amendment thereto dated July 30, 1998 (the
"Loan Agreement"), specifically including the indebtedness evidenced by that
certain term promissory note dated of even date herewith, executed by Borrower
and payable to Bank, in the principal amount of $7,000,000.00 and all other
notes given in substitution therefor or in modification, renewal or extension
thereof in whole or in part (the "Second Term Note");

                  WHEREAS, as a condition to Bank's entry into said Fourth
Amendment and its advance of funds to Borrower thereunder, Guarantor has agreed
to enter into this Guaranty of certain indebtedness owed or to be owed by
Borrower to Bank; and

                  WHEREAS, Guarantor will directly and indirectly benefit from
the Second Term Loan, as defined in the Loan Agreement, as amended by the Fourth
Amendment and evidenced by the Second Term Note.

                  NOW, THEREFORE, for and in consideration of the premises and
the extension of credit by Bank to Borrower pursuant to the Loan Agreement, and
for TEN AND NO/100 DOLLARS ($10.00) and other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, and to induce Bank
to execute the Fourth Amendment, Bank and Guarantor hereby agree as follows:

                  1. Guarantor unconditionally guarantees the prompt payment to
Bank of the following (the "Guaranteed Indebtedness"):

         (a)      Any and all indebtedness, obligations (including reimbursement
                  obligations) and liabilities of Borrower to Bank now existing
                  or hereafter incurred in connection with or incident to the
                  Second Term Loan, under or arising out of or in connection
                  with any documents executed in connection with any
                  indebtedness of Borrower to Bank in connection with the Second
                  Term Loan 





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                  or any promissory note or notes executed by Borrower at any
                  time in connection with the Second Term Loan, whether for
                  principal, interest, penalty interest, fees, expenses or
                  otherwise, including, without limitation, all sums, principal,
                  accrued interest and other amounts owing with respect to the
                  Second Term Note, together with any and all renewals,
                  extensions and/or rearrangements thereof, whether with or
                  without notice to Guarantor;

         (b)      All interest, charges, expenses, attorneys' or other fees and
                  any other sums payable to or incurred by the Bank in
                  connection with the execution, administration or enforcement
                  of the Bank's rights and remedies under the Second Term Note;
                  and

         (c)      All post-petition interest on the Guaranteed Indebtedness in
                  the event of a bankruptcy or insolvency of the Borrower.

Provided, however, that Guarantor's obligation hereunder shall never exceed
$3,500,000.00. Guarantor shall at all times maintain at least $4,000,000 in
Liquid Assets. To evidence such maintenance of Liquid Assets, Guarantor shall
deliver to Bank, on or before the forty-fifth (45th) day after the end of each
calendar quarter, a Certificate of Liquidity in the form attached hereto as
Exhibit "A", certifying the value of such Guarantor's Liquid Assets effective as
of the end of each calendar quarter. "Liquid Assets" shall mean Cash on hand and
balances in checking accounts available for immediate withdrawal, the value,
from time to time, of short-term, highly liquid investments that are readily
convertible to Cash, such as treasury bills, commercial paper and money market
funds, and the value, from time to time, of unrestricted shares of stock that
are publicly traded on the New York Stock Exchange, the American Stock Exchange,
or NASDAQ, and otherwise acceptable to the Bank, but only to the extent the
foregoing are free from all liens, claims and encumbrances, including liens or
security interests in favor of the Bank. "Cash" shall mean legal tender of the
United States of America.

                  2. If the Guaranteed Indebtedness is not paid by Guarantor
when due, as required herein, and this Guaranty is placed in the hands of an
attorney for collection, or if this Guaranty is enforced by suit or through the
Bankruptcy Court or through any judicial proceedings, Guarantor shall pay to
Bank an amount equal to its reasonable attorneys' fees and collection costs
incurred by Bank in the collection of the Guaranteed Indebtedness.

                  3. This is an absolute, complete and continuing Guaranty, and
no notice of the Guaranteed Indebtedness or any extension of credit already or
hereafter contracted by or extended to Borrower need be given to Guarantor, nor
shall anything herein contained be a limitation upon the amount of credit which
may be extended to Borrower, the numbers of transactions with Borrower,
repayments by Borrower to Bank, or the allocation by Bank of repayment by
Borrower, it being the understanding of the Guarantor that Guarantor's liability
shall continue hereunder so long as any of the Guaranteed Indebtedness remains
unpaid. Borrower and Bank may rearrange, increase, decrease, extend and/or renew
the Guaranteed Indebtedness without notice to Guarantor and in such 




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event Guarantor will remain fully bound hereunder on the Guaranteed
Indebtedness. The obligations of Guarantor hereunder shall not be released,
impaired or diminished by any amendment, modification or alteration of the Loan
Agreement or the Second Term Note. Guarantor expressly waives all notices of any
kind, presentment for payment, demand for payment, protest, notice of protest,
notice of intent to accelerate, notice of acceleration, dishonor, diligence,
notice of any amendment of the Loan Agreement, notice of any adverse change in
the financial condition of Borrower, notice of any adjustment, indulgence,
forbearance or compromise that might be granted or given by Bank to Borrower,
and also notice of acceptance of this Guaranty, acceptance on the part of Bank
being conclusively presumed by its request for this Guaranty and delivery of the
same to it. The liability and obligations of Guarantor hereunder shall not be
affected or impaired by any action or inaction by Bank in regard to any matter
waived or notice of which is waived by Guarantor in this paragraph or in any
other paragraph of this Guaranty.

                  4. Guarantor authorizes Bank, without notice or demand and
without affecting Guarantor's liability hereunder, (a) to take and hold security
for the payment of this Guaranty and/or the Guaranteed Indebtedness, and to
exchange, enforce, waive and/or release any such security; (b) to apply such
security and direct the order or manner of sale thereof as Bank in its
discretion may determine; (c) to obtain a guaranty of the Guaranteed
Indebtedness from any one or more other persons, corporations or entities
whomsoever and to enforce, waive, rearrange, modify, limit or release at any
time or times such other persons, corporations or entities from their
obligations under such guaranties; (d) to waive or delay the exercise of any of
its rights or remedies against the Borrower or any other person or entity; (e)
to renew, extend, or modify the terms of any of the Guaranteed Indebtedness or
any instrument or agreement evidencing the same; and (f) to fully or partially
release at any time any Guarantor which executes this Guaranty whether with or
without consideration.

                  5. Guarantor waives any right to require Bank to (a) proceed
against, or make any effort at the collection of the Guaranteed Indebtedness
from Borrower or any other guarantor or party liable for the Guaranteed
Indebtedness; (b) proceed against or exhaust any collateral held by Bank; or (c)
pursue any other remedy in Bank's power whatsoever. Guarantor further waives any
and all rights and remedies which Guarantor may have or be able to assert by
reason of the provisions of Chapter 34 of the Texas Business and Commerce Code.
Guarantor waives any defense arising by reason of any disability, lack of
corporate authority or power, or other defense of Borrower or any other
guarantor of the Guaranteed Indebtedness, and Guarantor shall remain liable
under this Guaranty regardless of whether Borrower or any other guarantor be
found not liable on the Guaranteed Indebtedness for any reason including,
without limitation, insanity, minority, disability, bankruptcy, insolvency,
death or corporate dissolution, even though rendering the Guaranteed
Indebtedness void or unenforceable or uncollectible as against Borrower or any
other guarantor. This Guaranty shall continue to be effective or be reinstated,
as the case may be, if at any time any payment of any of the Guaranteed
Indebtedness is rescinded or must otherwise be returned by Bank upon the
insolvency, bankruptcy or reorganization of Borrower or otherwise, all as though
such payment had not been made and will, thereupon, guarantee payment of such
amount as to which refund or restitution has been made, together with interest
accruing thereon subsequent to the 




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date of refund or restitution at the applicable rate under the Loan Agreement
and collection costs and fees (including, without limitation, attorneys' fees)
applicable thereto, subject to the limitations set forth in Sections 1 and 10
hereof.

                  6. The liability and obligations of Guarantor hereunder shall
not be affected or impaired by (a) the failure of Bank or any other party to
exercise diligence or reasonable care in the preservation, protection or other
handling or treatment of all or any part of the collateral securing payment of
all or any part of the Guaranteed Indebtedness, (b) the failure of any security
interest or lien intended to be granted or created to secure the Guaranteed
Indebtedness to be properly perfected or created or the unenforceability of any
security interest or lien for any other reason, or (c) the subordination of any
such security interest or lien to any other security interest or lien.

                  7. Bank may pursue any remedy without altering the obligations
of Guarantor hereunder and without liability to Guarantor, even though Bank's
pursuit of such remedy may result in Guarantor's loss of rights of subrogation
or to proceed against others for reimbursement or contribution or any other
right. In no event shall any payment by Guarantor entitle it, by subrogation or
otherwise, to any rights against Borrower or any right to participate in any
security now or hereafter held by Bank prior to payment in full of all of the
Guaranteed Indebtedness and, in any event, not until 367 days after the making
of any payment and/or the granting of any security interest by Borrower or any
other guarantor to Bank in connection with the Guaranteed Indebtedness.

                  8. Should the status of Borrower change in any way, including,
without limitation, as a result of any dissolution of Borrower, any sale, lease
or transfer of any or all of the assets of Borrower, any changes in the
shareholders of Borrower, or any reorganization of Borrower, this Guaranty shall
continue, and shall cover the Guaranteed Indebtedness under the new status.

                  9. The liability of Guarantor for the payment of the
Guaranteed Indebtedness shall be primary and not secondary.

                  10. Guarantor is familiar with and has independently reviewed
the books and records regarding the financial condition of Borrower and is
familiar with the value of any and all collateral intended to be granted as
security for the payment of the Guaranteed Indebtedness; Guarantor is not,
however, relying on such financial condition or such collateral as an inducement
to enter into this Guaranty. As of the date hereof, and after giving effect to
this Guaranty and the contingent obligations evidenced hereby, Guarantor is, and
will be, solvent, and has and will have assets and property which, valued
fairly, exceed such Guarantor's obligations, debts and liabilities, and has and
will have assets and property sufficient to satisfy, repay and discharge the
same. Notwithstanding the definition of Guaranteed Indebtedness herein, the
liability of Guarantor hereunder is limited to (a) the lowest amount that would
render this Guaranty void against creditors or creditors' representatives under
any fraudulent conveyance or similar law or under Sections 544 or 548 of the
Bankruptcy Code of 1978, as revised, minus (b) $1.00.





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                  11. If Borrower shall at any time or times be or become
obligated to Bank for payment of any indebtedness other than the Guaranteed
Indebtedness, Bank (without in anywise impairing its rights hereunder or
diminishing Guarantor's liability) shall be at liberty at any time or times to
apply to such other indebtedness any amounts paid to or received by or coming
into the hands of Bank from or attributable to Borrower or any other person or
party liable for any of such other indebtedness or from or attributable to or
representing proceeds of any property or security held by Bank securing payment
of such other indebtedness or any credits, deposits or offsets due Borrower or
other party liable on any of such other indebtedness (whether or not the
Guaranteed Indebtedness or such other indebtedness are then due), it being
intended to give Bank the right to apply all payments, credits and offsets and
amounts becoming available for application on or credit against the indebtedness
of Borrower to Bank (now or hereafter existing) first toward payment and
satisfaction of the Borrower's indebtedness not hereby guaranteed, before making
application thereof on or against the Guaranteed Indebtedness.

                  12. Guarantor represents and warrants that this Guaranty
accurately and completely embodies the entire agreement between Guarantor and
Bank with respect to the respective rights, obligations and liabilities of
Guarantor and Bank hereunder, and supersedes all prior agreements and
understandings, if any, relating to the subject matter hereof. Guarantor
acknowledges that Guarantor is not relying on any representations (oral or
otherwise) of Bank, or any other party, other than as expressly described in
this Guaranty.

                  13. This Guaranty was reviewed by Guarantor, and Guarantor
acknowledges and agrees that Guarantor (a) understands fully all of the terms of
this Guaranty and the consequences and implications of Guarantor's execution of
this Guaranty, and (b) has been afforded an opportunity to have this Guaranty
reviewed by, and to discuss the terms, consequences and implications of this
Guaranty with an attorney or other such persons as Guarantor may have desired.

                  14. This Guaranty is and shall be in every particular
available to the successors and assigns of Bank and is and shall always be fully
binding upon the heirs, executors, administrators, successors and assigns of
Guarantor. This Guaranty is intended for and shall inure to the benefit of Bank
and each and every other person who shall from time to time be or become the
owner or holder of any of the Guaranteed Indebtedness, and each and every
reference herein to "Bank" shall also include and refer to each and every
successor or assignee of Bank at any time holding or owning any part of or
interest in any part of the Guaranteed Indebtedness. This Guaranty shall be
transferable and negotiable, with the same force and effect and to the same
extent that the Guaranteed Indebtedness is transferable, it being understood and
stipulated that upon the assignment or transfer by Bank of any of the Guaranteed
Indebtedness the legal or beneficial owner of the Guaranteed Indebtedness (or
part thereof or interest therein thus transferred or assigned by Bank) shall
also, unless provided otherwise by Bank in its assignment, have and may exercise
all of the rights granted to Bank under this Guaranty to the extent of the part
of or interest in the Guaranteed Indebtedness thus assigned or transferred to
such person or entity. Guarantor expressly waives notice of transfer or
assignment of the Guaranteed Indebtedness, or any part thereof, or of the rights
of Bank hereunder.


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                  15. All amounts becoming payable by Guarantor to Bank under
this Guaranty shall be payable at Bank's offices in the City of Houston, Harris
County, Texas.

                  16. Any notice hereunder to Guarantor shall be in writing,
duly stamped and addressed to Guarantor at the address shown below Guarantor's
signature hereto, or at such other address as Guarantor may by written notice,
received by Bank, have designated as Guarantor's address for such purpose. Any
notice provided for herein shall become effective upon the earlier of (a) the
first business day of Bank following the deposit in a regularly maintained
postal deposit box of the United States Postal Service, or (b) the day of its
receipt by Guarantor; but actual notice, however given or received, shall always
be effective. The preceding sentence shall not be construed in anywise to affect
or impair any waiver of notice or demand herein provided or to require giving of
notice or demand to or upon Guarantor in any situation or for any reason.

                  17. It is the intention of the parties hereto to comply
strictly with all applicable usury laws; accordingly, it is agreed that
notwithstanding any provisions to the contrary in this Guaranty, or in any
documents securing payment hereof or otherwise relating hereto, in no event
shall this Guaranty or such documents require the payment or permit the
collection of an aggregate amount of interest in excess of the maximum amount
permitted by such laws, including the laws of the State of Texas and the laws of
the United States of America. If any such excess of interest is contracted for,
charged or received under this Guaranty or under the terms of any documents
securing payment hereof or otherwise relating hereto, or if under any
circumstances, the amount of interest (including all amounts payable hereunder
which are not denominated as interest but which constitute interest under the
applicable laws) contracted for, charged or received under this Guaranty shall
exceed the maximum amount of interest permitted by the applicable usury laws,
then in any such event (a) the provisions of this paragraph shall govern and
control, (b) Guarantor shall not be obligated to pay the amount of such interest
to the extent that it is in excess of the maximum amount of interest permitted
by the applicable usury laws, (c) any such excess interest which may have been
collected shall be either applied as a credit against the then unpaid Guaranteed
Indebtedness or, if the Guaranteed Indebtedness shall have been paid in full,
refunded to Guarantor, and (d) the effective rate of interest shall be
automatically reduced to the maximum lawful contract rate allowed under the
applicable usury laws as now or hereafter construed by the courts having
jurisdiction thereof. It is further agreed that without limitation of the
foregoing, all calculations of the rate of interest contracted for, charged or
received under this Guaranty or under such other documents which are made for
the purpose of determining whether such rate exceeds the maximum lawful contract
rate, shall be made, to the extent permitted by applicable usury laws, by
amortizing, prorating, allocating and spreading in equal parts during the full
period during which this Guaranty is to be in effect, all interest at any time
contracted for, charged or received from Guarantor or otherwise by the holder or
holders hereof in connection with this Guaranty.

                  18. In case any of the provisions of this Guaranty shall for
any reason be held to be invalid, illegal, or unenforceable, such invalidity,
illegality, or unenforceability shall not affect 



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any other provisions hereof, and this Guaranty shall be construed as if such
invalid, illegal, or unenforceable provision had never been contained herein.

                  19. In all instances herein, the singular shall be construed
to include the plural and the masculine to include the feminine.

                  20. This Guaranty may be executed in multiple counterparts
each of which shall constitute an original, but all of which when taken together
shall constitute one and the same Guaranty.

                  21. THIS GUARANTY SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS AND THE UNITED STATES OF AMERICA.
All actions or proceedings with respect to the Guaranteed Indebtedness or this
Guaranty may be instituted in the Courts of the State of Texas located in Harris
County, Texas, or the United States District Court for the Southern District of
Texas, and by execution and delivery of this Guaranty, Guarantor irrevocably and
unconditionally submits to the jurisdiction (both subject matter and personal)
of each such Court, and irrevocably and unconditionally waives (a) any objection
Guarantor may now or hereafter have to the laying of venue in any such Courts,
(b) any claim that any action or proceeding brought in any of such Courts has
been brought in an inconvenient forum, and (c) any right to bring any action or
proceeding with respect to the Guaranteed Indebtedness or this Guaranty in any
forum other than the courts of the State of Texas located in Harris County,
Texas, or the United States District Court for the Southern District of Texas.

                  22. Guarantor represents and warrants to Bank that this
Guaranty is a valid, binding and enforceable obligation of Guarantor and does
not violate any provisions of any law, rule, regulation, contract or agreement
enforceable against Guarantor.

                  23. Guarantor hereby agrees that a counterpart of this
Guaranty bearing the signature of Guarantor may be effectively delivered to the
Bank by the delivery of an electronic facsimile sent via telecopier; and that
Guarantor shall be bound by his facsimile signature thereon.

                  EXECUTED this 24th day of September, 1998.

                                   GUARANTOR:



                                         --------------------------------------
                                         PAUL B. LOYD, JR.

                                         Address: 901 Threadneedle #200
                                                  Houston, TX 77079




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STATE OF TEXAS

COUNTY OF HARRIS



                  We,________ and ________, sign our names to this instrument as
witnesses to the signature of PAUL B. LOYD, JR., (the "Signor"), and being duly
sworn, do hereby declare to the undersigned authority that we are personally
acquainted with the Signor, that we know the Signor to be the person that he
purports to be through his signature, that he has signed this instrument
willingly, and that each of us, in the presence and hearing of the Signor, the
undersigned authority, and each other, hereby execute this instrument as
witnesses to the Signor's signing, and that to the best of our knowledge, the
Signor is twenty-one years of age or older, of sound mind, and under no
constraint or undue influence.


                                         WITNESSES:


                                         -------------------------------------
                                         Printed Name:


                                         --------------------------------------
                                         Printed Name:


STATE OF TEXAS

COUNTY OF HARRIS


                  The foregoing instrument was subscribed, sworn to and
acknowledged before me by PAUL B. LOYD, JR., the Signor, and was also subscribed
and sworn to before me by and, as witnesses, this day of September, 1996.




                                         -------------------------------------
                                         Notary Public in and for
                                         The State of


[Notarial Seal or Stamp]



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