Carrizo Oil & Gas, Inc. Announces 2012 U.S. Proved Reserves Including Record Proved Oil Reserves and Record PV-10 Proved Reserves Value of $1.4 Billion, Record 2012 Production, and Fourth Quarter 2012 Capital Expenditures

HOUSTON, TX -- (Marketwire) -- 02/25/13 -- Carrizo Oil & Gas, Inc. (NASDAQ: CRZO) today announced 2012 U.S. proved reserves of 115.1 MMboe, including record proved oil reserves of 39.1 MMbbls (a 58% increase year on year) and record PV-10 proved reserves value of $1.4 billion (a 64% increase year on year), and record 2012 production of 9.4 MMboe (a 26% increase year on year), including fourth quarter production above guidance for both oil and gas. All comparisons of 2012 to the prior year are based on 2011 proved reserves of 95.9 MMboe, which are adjusted to exclude 53.8 MMboe of reserves (97% natural gas) associated with 2012 U.S. property sales.

2012 U.S. Proved Reserves, Production and Reserve Replacement
2012 proved reserves in the U.S., as determined by the Company's third-party reserve engineers, were 115.1 MMboe, an increase of 20% from year-end 2011, and are comprised of 39.1 MMbbls of oil, a 58% increase over 2011, 5.4 MMboe of NGLs, a 71% increase over 2011, and 423.7 Bcf of natural gas, a 4% increase over 2011.

Additional reserve highlights include:

• Reserve Replacement of 303%
• Eagle Ford proved reserves increased to 49.0 MMboe, 72% above the 28.5 MMboe at year-end 2011
• 46% of total proved reserves classified as proved developed

At year-end 2012, the pre-tax value of these reserves, using a discount rate of 10% and SEC price assumptions ("PV-10 value") was $1.412 billion, a 64% increase over Carrizo's reserve value of $860 million at the end of 2011. Oil reserves represent 80% of the Company's 2012 PV-10 value compared to 61% at the end of 2011.

The average realized prices used to calculate our 2012 proved reserves and PV-10 value were $101.35 per barrel of oil, $32.12 per barrel of NGLs, and $1.95 per Mcf of natural gas, using the trailing 12-month average of the first of month price in accordance with SEC requirements. These prices are 9% higher, 29% lower, and 39% lower than the prices used at the end of 2011 for oil, NGLs, and natural gas, respectively. The increase in the average realized oil price is largely due to the premium over NYMEX received for our Eagle Ford oil.

The following table provides details about the distribution of the Company's 2012 U.S. proved reserves:

      Region                Total       Oil        NGLs   Natural Gas
      ------------------ --------------------------------------------
                           (MMboe)    (MMbbls)   (MMboe)     (Bcf)
      Eagle Ford                49.0      36.6         5.2       43.5
      Barnett                   50.6          -          -      303.5
      Marcellus                 12.5          -          -       74.7
      Niobrara and Other         3.0        2.5        0.2        2.0
      ---------------------------------------------------------------
      Total                   115.1       39.1        5.4      423.7

Carrizo successfully replaced 303% of its 2012 record production of 9.4 MMboe.

Record full year 2012 production included:

• 2.9 MMboe from the Eagle Ford, 352% above 2011
• 7.9 Bcf of natural gas from the Marcellus, compared to 0.3 Bcf in 2011

Fourth quarter 2012 production of 2.379 MMboe consisted of:

• 831 Mbbls of oil or 9,033 Bbls/day, 4% above the third quarter of 2012 and 4% above the high end of guidance
• 9,285 MMcfe of natural gas and NGLs or 100,924 Mcfe/day, essentially flat as compared to the third quarter of 2012 and 2% above the high end of guidance

Fourth Quarter 2012 U.S. Capital Expenditures
The Company's U.S. capital expenditures for the fourth quarter were $145.3 million, comprised of $130.7 million for drilling and completions and $14.6 million for leasehold and seismic. The drilling and completion costs by region for the fourth quarter were $115.8 million, $8.4 million, $4.8 million and $1.7 million for Eagle Ford, Marcellus, Niobrara and Barnett/Other, respectively.

2012 U.K. North Sea Proved Reserves
An agreement to sell Carrizo's interest in the Huntington Field Development Project in the U.K. North Sea to Iona Energy Inc. was announced prior to the end of 2012. Because the sale closed subsequent to year end, the U.K. reserves will be presented in Carrizo's 2012 financial statements, but have been excluded from the 2012 reserves and PV-10 values discussed above. The 2012 proved reserves in the U.K. North Sea, as determined by the Company's third-party reserve engineers, were 6.0 MMboe, comprised of 5.2 MMbbls of oil and 4.7 Bcf of natural gas.

Carrizo President and CEO S.P. "Chip" Johnson, IV commented, "By selling lower return natural gas reserves and reinvesting the proceeds in drilling higher return, high value oil properties, we increased the present value of our 2012 U.S. reserve base by over 64%, largely due to the 58% increase in our proved oil reserves, all through the drill bit and performance driven revisions. We think this is an exceptional result and believe it to be proof that our strategy to grow the oil component of our reserves has significantly increased the intrinsic value of Carrizo.

"Our operations staff has done an outstanding job making our transition a reality, replacing over 300% of our record production, keeping our drilling and completion activities on schedule, reducing our capital costs in the second half, and exceeding our production guidance every quarter this year. As we announced previously, our 2013 activities are planned to move at an intentionally constrained pace in order to keep our spending near the level of our cash flow and available cash. The oil component of our production is expected to grow at a much higher rate than our gas component and our internal forecast projects our EBITDA to grow approximately three times our overall production growth. The projected growth in our EBITDA along with our previously announced reduction in planned 2013 capital expenditures should lead to a reduction in our debt to EBITDA ratio over the course of the year.

"Although our Niobrara oil play doesn't receive the attention or the capital of our Eagle Ford play, drilling results there have been contributing to our better than expected oil production rates. The last ten Niobrara wells that we brought on production had an average 24 hour oil production test rate of 736 barrels per day (gross). Two of these wells, the Bringelson 1-20 and the Castor 2-36, both flowed over 1,000 barrels per day (gross). We continue to view our Niobrara operations very favorably and now have 2 rigs drilling in the play.

"The recent acquisition of some key Utica leases in a very competitive area has caused us to revise our Utica drilling plans. Carrizo and our partner, Avista Capital Partners, now plan to spud our first Utica horizontal well this summer in the Richland Township of Guernsey County, Ohio. We hope to have production test results to announce from this well in the fourth quarter of this year."

Conference Call Reminder
Carrizo will hold a conference call to discuss 2012 fourth quarter and full year financial results on Tuesday, February 26, 2013 at 10:00 AM Central Standard Time. Carrizo plans to issue a financial results press release prior to the market opening on Tuesday, February 26, 2013.

Conference Call

Date & Time:
Tuesday, February 26 at 10:00 AM CST

Dial-In Number:
(800) 670 - 5957 (U.S. & Canada)
+1 (303) 223 - 2680 (Intl./Local)

Telephone Replay Number:
(800) 633 - 8284 (U.S. & Canada)

+1 (402) 977 - 9140 (Intl./Local)

Enter Replay Reservation #: 21647863 for U.S., Canadian and International callers.

The replay will be available through Tuesday, March 5, 2013 at 11:59 AM CST.

A simultaneous webcast of the call may be accessed over the internet at http://www.investorcalendar.com/IC/CEPage.asp?ID=170543 or by visiting our website at http://www.crzo.net clicking on "Investor Relations" and then clicking on "2012 Fourth Quarter Conference Call Webcast". To listen, please go to either website in time to register and install any necessary software. The webcast will be archived for replay on the Carrizo website for 15 days.

About the Company
Carrizo Oil & Gas, Inc. is a Houston-based energy company actively engaged in the exploration, development, and production of oil and gas from resource plays located in the United States. Our current operations are principally focused in proven, producing oil and gas plays primarily in the Eagle Ford Shale in South Texas, the Niobrara Formation in Colorado, the Barnett Shale in North Texas, the Marcellus Shale in Pennsylvania, and the Utica Shale in Ohio.

Statements in this release, including but not limited to those relating to reserves, our ability to develop, explore for, acquire and replace oil and gas reserves and sustain production, timing and levels of production, the uncertainties inherent in projecting future rates of production for our wells and the extent to which actual production differs from estimated proved oil and gas reserves, sales transactions (including effects thereof), the volatility of commodity prices for oil, NGLs and natural gas, our ability to sell the production at reasonable prices, our ability to generate profits or achieve targeted reserves in our development and exploratory drilling activities, our ability to contract for drilling rigs, supplies and services at reasonable costs, development and capital spending plans, drilling and completion schedules, plans for development in emerging resource plays, guidance, funding sources, the Company's or management's intentions, beliefs, expectations, hopes, projections, assessment of risks, estimations, plans or predictions for the future, results of the Company's strategies, timing of completion and drilling of wells, location and manner of drilling, completion and pipeline connections and other statements that are not historical facts are forward looking statements that are based on current expectations. Although the Company believes that its expectations are based on reasonable assumptions, it can give no assurance that these expectations will prove correct. Important factors that could cause actual results to differ materially from those in the forward looking statements include market and other conditions, capital needs and uses, regulatory changes, permitting, commodity price changes, effects of the global economy on exploration activity, dependence on exploratory drilling activities, operating risks, land issues, availability of capital and equipment, actions by governmental authorities, industry partners and other third parties, weather and other risks described in the Company's Form 10-K for the year ended December 31, 2011 and its other filings with the U.S. Securities and Exchange Commission.

Information about PV-10 Values
This release contains references to the PV-10 value of the Company's U.S. proved reserves, which is equal to the standardized measure of discounted future net cash flows from proved reserves, before deducting future income taxes, discounted at 10 percent. Carrizo believes that the presentation of PV-10 values provides relevant and useful information because it is widely used by investors, analysts and creditors as a basis for comparing the relative size and value of the Company's proved reserves to other oil and gas companies. Because many factors that are unique to each individual company may impact the amount and timing of future income taxes, the use of a pre-tax measure provides greater comparability when evaluating oil and gas companies. Carrizo also uses PV-10 values when assessing the potential return on investment related to its oil and gas properties and in evaluating acquisitions. The PV-10 value is not a measure of financial or operating performance under U.S. GAAP, nor is it intended to represent the current market value of proved oil and gas reserves. PV-10 value should not be considered in isolation or as a substitute for the standardized measure of discounted future net cash flows as defined under U.S. GAAP. The PV-10 value of the Company's U.S. proved reserves may be reconciled to its standardized measure of discounted future net cash flows, by reducing the Company's PV-10 value by the discounted future income taxes associated with such reserves as shown below.

Reconciliation of PV-10 Value (Non-GAAP) to Standardized Measure of Discounted Future Net Cash Flows (GAAP) as of December 31, 2012 ($ in billions)

PV-10 Value                                                 $1.412
Future Income Taxes (discounted at 10%)                     ($0.233)
                                                            --------
Standardized Measure of Discounted Future Net Cash Flows    $1.179
                                                            ========

Information About Reserve Replacement Ratios
Carrizo uses the reserve replacement ratio as an indicator of its ability to replenish annual production volumes and grow its reserves, thereby providing some information on the sources of future production. Management believes reserve replacement information is frequently used by analysts, investors and others in the industry to evaluate the performance of companies like Carrizo. The reserve replacement ratio is calculated by dividing the sum of reserve additions from all sources (revisions, extensions, discoveries, and other additions and acquisitions) by the actual production for the corresponding period. This calculation is adjusted for the effect of property sales as appropriate. The Company does not use unproved reserve quantities in calculating the reserve replacement ratio. It should be noted that the reserve replacement ratio is a statistical indicator that has limitations. As an annual measure, the ratio is limited because it typically varies widely based on the extent and timing of new discoveries and property acquisitions. Its predictive and comparative value is also limited for the same reasons. The ratio does not distinguish between changes in reserve quantities that are producing and those that will require additional time and capital to begin producing. In addition, since the ratio does not take into consideration the cost or timing of future production of new reserves, it cannot be used as a measure of value creation.