EXHIBIT 99.1

March 31, 1998

Carrizo Oil & Gas, Inc.
14811 St. Mary's Lane, Suite 148
Houston, Texas 77079

Gentlemen:

At your request, we have prepared an estimate of the reserves,
future production, and income attributable to certain leasehold interests of
Carrizo Oil & Gas, Inc. (Carrizo) as of December 31, 1997. The subject
properties are located in the states of Louisiana and Texas. The income data
were estimated using the Securities and Exchange Commission (SEC) guidelines for
future price and cost parameters.

The estimated reserves and future income amounts presented in
this report are related to hydrocarbon prices. December 1997 hydrocarbon prices
were used in the preparation of this report as required by SEC guidelines;
however, actual future prices may vary significantly from December 1997 prices.
Therefore, volumes of reserves actually recovered and amounts of income actually
received may differ significantly from the estimated quantities presented in
this report. The results of this study are summarized below.

SEC PARAMETERS
Estimated Net Reserves and Income Data
Certain Leasehold Interests of
CARRIZO OIL & GAS, INC.
As of December 31, 1997
- --------------------------------------------------------------------------------

Proved
----------------------------------------------------
Developed Total
---------------------------------------
Producing Non-Producing Undeveloped Proved
----------- ----------- ----------- -----------

NET REMAINING RESERVES
Oil/Condensate - Barrels 205,067 39,185 228,081 472,333
Plant Products - Barrels 74,769 119,012 0 193,781
Gas - MMCF 4,330 3,806 2,843 10,979

INCOME DATA
Future Gross Revenue $14,218,979 $10,638,011 $9,763,906 $34,620,896
Deductions 3,205,343 2,112,227 2,846,179 8,163,749
----------- ----------- ---------- -----------
Future Net Income (FNI) $11,013,636 $ 8,525,784 $6,917,727 $26,457,147

Discounted FNI @ 10% $ 9,221,567 $ 5,373,375 $4,437,984 $19,032,926

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Liquid hydrocarbons are expressed in standard 42 gallon
barrels. All gas volumes are sales gas expressed in millions of cubic feet
(MMCF) at the official temperature and pressure bases of the areas in which the
gas reserves are located.

The future gross revenue is after the deduction of production
taxes. The deductions are comprised of the normal direct costs of operating the
wells, ad valorem taxes, recompletion costs, development costs, and certain
abandonment costs net of salvage. The future net income is before the deduction
of state and federal income taxes and general administrative overhead, and has
not been adjusted for outstanding loans that may exist nor does it include any
adjustment for cash on hand or undistributed income. No attempt was made to
quantify or otherwise account for any accumulated gas production imbalances that
may exist. Gas reserves account for approximately 73 percent and liquid
hydrocarbon reserves account for the remaining 27 percent of total future gross
revenue from proved reserves.

RESERVES INCLUDED IN THIS REPORT

The proved reserves included herein conform to the definition
as set forth in the Securities and Exchange Commission's Regulation S-X Part
210.4-10 (a) as clarified by subsequent Commission Staff Accounting Bulletins.
The definition of proved reserves is included in the section entitled
"Definitions of Reserves" which is attached with this report.

The proved developed non-producing reserves included herein
are comprised of shut-in and behind pipe categories. The various reserve status
categories are defined in the section entitled "Reserve Status Categories (SEC)"
which is attached with this report.

ESTIMATES OF RESERVES

In general, the reserves included herein were predominantly
estimated by the volumetric method due to the limited production history of the
wells considered in this study. However, performance methods were used in
certain cases where characteristics of the data indicated this method was more
appropriate in our opinion. The reserves estimated by the performance method
utilized extrapolations of various historical data in those cases where such
data were definitive. Reserves were estimated by the volumetric method in those
cases where there were inadequate historical performance data to establish a
definitive trend or where the use of production performance data as a basis for
the reserve estimates was considered to be inappropriate.

The reserves included in this report are estimates only and
should not be construed as being exact quantities. They may or may not be
actually recovered, and if recovered, the revenues therefrom and the actual
costs related thereto could be more or less than the estimated amounts.
Moreover, estimates of reserves may increase or decrease as a result of future
operations.

FUTURE PRODUCTION RATES

Initial production rates are based on the current producing
rates for those wells now on production. Test data and other related information
were used to estimate the anticipated initial production rates for those wells
or locations which are not currently producing. If no production decline trend
has been established, future production rates were held constant, or adjusted
for the effects of curtailment where appropriate, until a decline in ability to
produce was anticipated. An estimated rate of decline was then applied to
depletion of the reserves. If a decline trend has been established, this

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March 31, 1998
Page 3

trend was used as the basis for estimating future production rates. For reserves
not yet on production, sales were estimated to commence at an anticipated date
furnished by Carrizo.

In general, we estimate that future gas production rates
limited by allowables or marketing conditions will continue to be the same as
the average rate for the latest available 12 months of actual production until
such time that the well or wells are incapable of producing at this rate. The
well or wells were then projected to decline at their decreasing delivery
capacity rate. Our general policy on estimates of future gas production rates is
adjusted when necessary to reflect actual gas market conditions in specific
cases.

The future production rates from wells now on production may
be more or less than estimated because of changes in market demand or allowables
set by regulatory bodies. Wells or locations which are not currently producing
may start producing earlier or later than anticipated in our estimates of their
future production rates.

HYDROCARBON PRICES

Carrizo furnished us with prices in effect at December 31,
1997 and these prices were held constant except for known and determinable
escalations. In accordance with Securities and Exchange Commission guidelines,
changes in liquid and gas prices subsequent to December 31, 1997 were not taken
into account in this report. Future prices used in this report are discussed in
more detail in the section entitled "Hydrocarbon Pricing Parameters" which is
attached with this report.

COSTS

Operating costs for the leases and wells in this report are
based on the operating expense reports of Carrizo and include only those costs
directly applicable to the leases or wells. When applicable, the operating costs
include a portion of general and administrative costs allocated directly to the
leases and wells under terms of operating agreements. No deduction was made for
indirect costs such as general administration and overhead expenses, loan
repayments, interest expenses, and exploration and development prepayments that
are not charged directly to the leases or wells.

Development costs were furnished to us by Carrizo and are
based on authorizations for expenditure for the proposed work or actual costs
for similar projects. The estimated net cost of abandonment after salvage was
included for properties where abandonment costs net of salvage are significant.
At the request of Carrizo, their estimate of zero abandonment costs after
salvage value for onshore properties was used in this report. Ryder Scott has
not performed a detailed study of the abandonment costs nor the salvage value
and makes no warranty for Carrizo's estimate.

Current costs were held constant throughout the life of the
properties.

GENERAL

While it may reasonably be anticipated that the future prices
received for the sale of production and the operating costs and other costs
relating to such production may also increase or decrease from existing levels,
such changes were, in accordance with rules adopted by the SEC, omitted from
consideration in making this evaluation.

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The estimates of reserves presented herein were based upon a
detailed study of the properties in which Carrizo owns an interest; however, we
have not made any field examination of the properties. No consideration was
given in this report to potential environmental liabilities which may exist nor
were any costs included for potential liability to restore and clean up damages,
if any, caused by past operating practices. Carrizo has informed us that they
have furnished us all of the accounts, records, geological and engineering data,
and reports and other data required for this investigation. The ownership
interests, prices, and other factual data furnished by Carrizo were accepted
without independent verification. The estimates presented in this report are
based on data available through November 1997.

Neither we nor any of our employees have any interest in the
subject properties and neither the employment to make this study nor the
compensation is contingent on our estimates of reserves and future income for
the subject properties.

This report was prepared for the exclusive use and sole
benefit of Carrizo Oil & Gas, Inc. The data, work papers, and maps used in this
report are available for examination by authorized parties in our offices.
Please contact us if we can be of further service.

Very truly yours,

RYDER SCOTT COMPANY
PETROLEUM ENGINEERS

Michael F. Stell, P.E.
Vice President
MFS/ag

DEFINITIONS OF RESERVES

PROVED RESERVES (SEC DEFINITION)

Proved reserves of crude oil, condensate, natural gas, and natural gas
liquids are estimated quantities that geological and engineering data
demonstrate with reasonable certainty to be recoverable in the future from known
reservoirs under existing 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 escalation based on
future conditions.

Reservoirs are considered proved if economic producibility is supported
by either actual production or conclusive formation test. In certain instances,
proved reserves are assigned on the basis of a combination of core analysis and
electrical and other type logs which indicate the reservoirs are analogous to
reservoirs in the same field which are producing or have demonstrated the
ability to produce on a formation test. The area of a reservoir considered
proved includes (1) that portion delineated by drilling and defined by fluid
contacts, if any, and (2) the adjoining portions not yet drilled that can be
reasonably judged as economically productive on the basis of available
geological and engineering data. In the absence of data on fluid contacts, the
lowest known structural occurrence of hydrocarbons controls the lower proved
limit of the reservoir.

Reserves that can be produced economically through the application of
improved recovery techniques are included in the proved classification when
these qualifications are met: (1) 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, and (2) it is
reasonably certain the project will proceed. Improved recovery includes all
methods for supplementing natural reservoir forces and energy, or otherwise
increasing ultimate recovery from a reservoir, including (1) pressure
maintenance, (2) cycling, and (3) secondary recovery in its original sense.
Improved recovery also includes the enhanced recovery methods of thermal,
chemical flooding, and the use of miscible and immiscible displacement fluids.

Proved natural gas reserves are comprised of non-associated, associated
and dissolved gas. An appropriate reduction in gas reserves has been made for
the expected removal of natural gas liquids, for lease and plant fuel, and for
the exclusion of non-hydrocarbon gases if they occur in significant quantities
and are removed prior to sale. Estimates of proved reserves do not include crude
oil, natural gas, or natural gas liquids being held in underground or surface
storage.

Proved reserves are estimates of hydrocarbons to be recovered from a
given date forward. They may be revised as hydrocarbons are produced and
additional data become available.

RESERVE STATUS CATEGORIES (SEC)

Reserve status categories define the development and producing status
of wells and/or reservoirs.

PROVED DEVELOPED

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.

Developed reserves may be subcategorized as producing or non-producing
using the SPE/WPC Definitions:

Producing
Reserves sub-categorized as producing are expected to be recovered from
completion intervals which are open and producing at the time of the
estimate. Improved recovery reserves are considered producing only after
the improved recovery project is in operation.

Non-Producing
Reserves sub-categorized as non-producing include shut-in and behind pipe
reserves. Shut-in reserves are expected to be recovered from (1)
completion intervals which are open at the time of the estimate but which
have not started producing, (2) wells which were shut-in for market
conditions or pipeline connections, or (3) wells not capable of
production for mechanical reasons. Behind pipe reserves are expected to
be recovered from zones in existing wells, which will require additional
completion work or future recompletion prior to the start of production.

PROVED UNDEVELOPED

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
reasonable certainty that there is continuity of production from the existing
productive formation. Estimates for proved undeveloped reserves are attributable
to any acreage for which an application of fluid injection or other improved
technique is contemplated, only when such techniques have been proved effective
by actual tests in the area and in the same reservoir.

HYDROCARBON PRICING PARAMETERS

SECURITIES AND EXCHANGE COMMISSION PARAMETERS

OIL AND CONDENSATE

Carrizo furnished us with oil and condensate prices in effect
at December 31, 1997 and these prices were held constant to depletion of the
properties. In accordance with Securities and Exchange Commission guidelines,
changes in liquid prices subsequent to December 31, 1997 were not considered in
this report.

PLANT PRODUCTS

Carrizo furnished us with plant product prices in effect at
December 31, 1997 and these prices were held constant to depletion of the
properties.

GAS

Carrizo furnished us with gas prices in effect at December 31,
1997 and with its forecasts of future gas prices which take into account SEC
guidelines, current spot market prices, contract prices, and fixed and
determinable price escalations where applicable. In accordance with SEC
guidelines, the future gas prices used in this report make no allowances for
future gas price increases which may occur as a result of inflation nor do they
make any allowance for seasonal variations in gas prices which may cause future
yearly average gas prices to be somewhat lower than December 31, 1997 gas
prices. For gas sold under contract, the contract gas price including fixed and
determinable escalations, exclusive of inflation adjustments, was used until the
contract expires and then was adjusted to the current market price for the area
and held at this adjusted price to depletion of the reserves.