(RYDER SCOTT COMPANY LOGO)
    
    FAX (713) 651-08491100 LOUISIANA
    
    SUITE 3800
    
    HOUSTON, TEXAS 77002-5218
    
    TELEPHONE (713) 651-9191
 Exhibit 99.1
  
    SEC PARAMETERS    Carrizo Oil & Gas, Inc.
 
 ProvedDevelopedTotalProducing
    
    
    Non-Producing
    
    
    Undeveloped
    
    
    ProvedNet Remaining ReservesOil/Condensate  Barrels
    
    
    342,738
    
    
    
    148,937
    
    
    
    9,384
    
    
    
    501,059Plant Products  Barrels
    
    
    238,641
    
    
    
    82,709
    
    
    
    28,662
    
    
    
    350,012Gas  MMCF
    
    
    13,353
    
    
    
    2,265
    
    
    
    547
    
    
    
    16,165Income Data ($M)Future Gross Revenue
    
    $
    86,358.0
    
    
    $
    18,823.6
    
    
    $
    3,500.8
    
    
    $
    108,682.4Deductions
    
    
    17,484.6
    
    
    
    4,826.0
    
    
    
    2,599.3
    
    
    
    24,909.9Future Net Income (FNI)
    
    $
    68,873.4
    
    
    $
    13,997.6
    
    
    $
    901.5
    
    
    $
    83,772.5Discounted FNI @ 10%
    
    $
    58,280.9
    
    
    $
    9,830.4
    
    
    $
    509.1
    
    
    $
    68,620.4
 1200, 530 8TH AVENUE, S.W.
    
    CALGARY, ALBERTA T2P 3S8
    
    TEL (403) 262-2799
    
    FAX (403) 262-2790621 17TH STREET, SUITE 1550
    
    DENVER, COLORADO 80293-1501
    
    TEL (303) 623-9147
    
    FAX (303) 623-4258




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Reserves Included in This Report
 proved reserves
   Estimates of Reserves




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Future Production Rates
   Hydrocarbon Prices
    Costs




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General
       RYDER SCOTT COMPANY, L.P.
 
 
 
 MFS/sm




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PETROLEUM RESERVES DEFINITIONS
 SECURITIES AND EXCHANGE COMMISSION
 INTRODUCTION
    PROVED RESERVES (SEC DEFINITIONS)
  Proved oil and gas reserves . Proved oil and gas reserves are the estimated quantities of crude
oil, natural gas, and natural gas liquids which geological and engineering data demonstrate with
reasonable certainty to be recoverable in future years from known reservoirs under existing
economic and operating conditions, i.e., prices and costs as of the date the estimate is made.
Prices include consideration of changes in existing prices provided only by contractual
arrangements, but not on escalations based upon future conditions.
 (i) Reservoirs are considered proved if economic producibility is supported by either actual
production or conclusive formation test. The area of a reservoir considered proved includes:
 (A) that portion delineated by drilling and defined by gas-oil and/or oil-water
contacts, if any; and




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(B) the immediately adjoining portions not yet drilled, but which can be reasonably
judged as economically productive on the basis of available geological and engineering
data. In the absence of information on fluid contacts, the lowest known structural
occurrence of hydrocarbons controls the lower proved limit of the reservoir.
 (ii) Reserves which can be produced economically through application of improved recovery
techniques (such as fluid injection) are included in the proved classification when
successful testing by a pilot project, or the operation of an installed program in the
reservoir, provides support for the engineering analysis on which the project or program was
based.(iii) Estimates of proved reserves do not include the following:
 (A) oil that may become available from known reservoirs but is classified separately as
indicated additional reserves;(B) crude oil, natural gas, and natural gas liquids, the recovery of which is subject to
reasonable doubt because of uncertainty as to geology, reservoir characteristics, or
economic factors;(C) crude oil, natural gas, and natural gas liquids, that may occur in undrilled
prospects; and(D) crude oil, natural gas, and natural gas liquids, that may be recovered from oil
shales, coal, gilsonite and other such sources.
 Proved developed oil and gas reserves . Proved developed oil and gas reserves are reserves that can
be expected to be recovered through existing wells with existing equipment and operating methods.
Additional oil and gas expected to be obtained through the application of fluid injection or other
improved recovery techniques for supplementing the natural forces and mechanisms of primary
recovery should be included as proved developed reserves only after testing by a pilot project or
after the operation of an installed program has confirmed through production response that
increased recovery will be achieved.
 Proved undeveloped reserves . Proved undeveloped oil and gas reserves are reserves that are
expected to be recovered from new wells on undrilled acreage, or from existing wells where a
relatively major expenditure is required for recompletion. Reserves on undrilled acreage shall be
limited to those drilling units offsetting productive units that are reasonably certain of
production when drilled. Proved reserves for other undrilled units can be claimed only where it
can be demonstrated with certainty that there is continuity of production from the existing
productive formation. Under no circumstances should estimates for proved undeveloped reserves be
attributable to any acreage for which an application of fluid injection or other improved recovery
technique is contemplated, unless such techniques have been proved effective by actual tests in the
area and in the same reservoir.




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Economic producibility of estimated proved reserves can be supported to the satisfaction of
the Office of Engineering if geological and engineering data demonstrate with reasonable certainty
that those reserves can be recovered in future years under existing economic and operating
conditions. The relative importance of the many pieces of geological and engineering data which
should be evaluated when classifying reserves cannot be identified in advance. In certain
instances, proved reserves may be assigned to reservoirs on the basis of a combination of
electrical and other type logs and core analyses which indicate the reservoirs are analogous to
similar reservoirs in the same field which are producing or have demonstrated the ability to
produce on a formation test. (extracted from SAB-35)
 In determining whether proved undeveloped reserves encompass acreage on which fluid
injection (or other improved recovery technique) is contemplated, is it appropriate to distinguish
between (i) fluid injection used for pressure maintenance during the early life of a field and (ii)
fluid injection used to effect secondary recovery when a field is in the late stages of depletion?
.... The Office of Engineering believes that the distinction identified in the above question may be
appropriate in a few limited circumstances, such as in the case of certain fields in the North Sea.
The staff will review estimates of proved reserves attributable to fluid injection in the light of
the strength of the evidence presented by the registrant in support of a contention that enhanced
recovery will be achieved. (extracted from SAB-35)
 Companies should report reserves of natural gas liquids which are net to their leasehold
interest, i.e., that portion recovered in a processing plant and allocated to the leasehold
interest. It may be appropriate in the case of natural gas liquids not clearly attributable to
leasehold interests ownership to follow instruction (b) of Item 2(b)(3) of Regulation S-K and
report such reserves separately and describe the nature of the ownership. (extracted from SAB-35)
 The staff believes that since coalbed methane gas can be recovered from coal in its natural
and original location, it should be included in proved reserves, provided that it complies in all
other respects with the definition of proved oil and gas reserves as specified in Rule 4- 10(a)(2) including the requirement that methane production be economical at current prices, costs, (net of
the tax credit) and existing operating conditions. (extracted from SAB-85)
  SUB-CATEGORIZATION OF DEVELOPED RESERVES (SPE/WPC DEFINITIONS)
  Producing .
 Non-Producing.




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