Exhibit 99_1

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas75244

February14, 2011

Dune Energy,
Inc.

Two Shell Plaza

777 Walker
Street, Suite 2300

Houston, Texas 77002

Gentlemen:

Pursuant to your request, we have prepared estimates of the extent
and value of the net proved, probable, and possible crude oil, condensate, and natural gas reserves, as of December 31, 2010, of certain selected properties owned by Dune Energy, Inc. (Dune).This evaluation was completed on February 14,
2011.Dunehas represented that these properties account for 100 percent of Dunes net proved, probable, and possible reserves as of December 31, 2010. The net proved, probable, and possible reserves estimates prepared by us have been
prepared in accordance with the reserves definitions of Rules 410(a) (1)(32) of Regulation SX of the Securities and Exchange Commission (SEC) of the United States.

Reserves included herein are expressed as net reserves. Gross reserves are defined as the total estimated petroleum to be produced from
these properties after December 31, 2010. Net reserves are defined as that portion of the gross reserves attributable to the interests owned by Dune after deducting all interests owned by others.

Data used in this evaluation were obtained from reviews with Dune personnel, Dune files, from records on file with the appropriate
regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Dune with respect to property interests, production from such properties, current
costs of operation and development, current prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented. A field examination of the
properties was not considered necessary for the purposes of this report.

Methodology and Procedures

Estimates of reserves were prepared by the use of appropriate geologic, petroleum engineering, and evaluation principals and techniques
that are in accordance with practices generally recognized by the petroleum industry as presented in the publication of the Society of Petroleum Engineers entitled Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves
Information (Revision as of February 19, 2007). The method or combination of methods used in the analysis of each reservoir was tempered by experience with similar reservoirs, stage of development, quality and completeness of basic data,
and production history.

When applicable, the volumetric method was used to estimate the original oil in place (OOIP) and
original gas in place (OGIP). Structure and isopach maps were constructed to estimate reservoir volume. Electrical logs, radioactivity logs, core analyses, and other available data were used to prepare these maps as well as to estimate
representative values for porosity and water saturation. When adequate data were available and when circumstances justified, material balance and other engineering methods were used to estimate OOIP or OGIP.



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Estimates of ultimate recovery were obtained after applying recovery factors to OOIP or
OGIP. These recovery factors were based on consideration of the type of energy inherent in the reservoirs, analyses of the petroleum, the structural positions of the properties, and the production histories. When applicable, material balance and
other engineering methods were used to estimate recovery factors. An analysis of reservoir performance, including production rate, reservoir pressure, and gas-oil ratio behavior, was used in the estimation of reserves.

For depletion-type reservoirs or those whose performance disclosed a reliable decline in producing-rate trends or other diagnostic
characteristics, reserves were estimated by the application of appropriate decline curves or other performance relationships. In the analyses of production-decline curves, reserves were estimated only to the limits of economic production or to the
limit of the production licenses as appropriate.

Definition of Reserves

Petroleum reserves included in this report are classified by degree of proof as proved, probable, or possible. Reserves classifications
used in this report are in accordance with the reserves definitions of Rules 410(a) (1)(32) of Regulation SX of the SEC. Reserves are judged to be economically producible in future years from known reservoirs under existing
economic and operating conditions and assuming continuation of current regulatory practices using conventional production methods and equipment. In the analyses of production-decline curves, reserves were estimated only to the limit of economic
rates of production under existing economic and operating conditions using prices and costs consistent with the effective date of this report, including consideration of changes in existing prices provided only by contractual arrangements but not
including escalations based upon future conditions. The petroleum reserves are classified as follows:

Proved oil and gas
reserves  Proved oil and gas reserves are those quantities of oil and gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically produciblefrom a given date forward, from
known reservoirs, and under existing economic conditions, operating methods, and government regulationsprior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain,
regardless of whether deterministic or probabilistic methods are used for the estimation. The project to extract the hydrocarbons must have commenced or the operator must be reasonably certain that it will commence the project within a reasonable
time.

(i) The area of the reservoir considered as proved includes:

(A) The area identified by drilling and limited by fluid contacts, if any, and (B) Adjacent undrilled portions of the reservoir that
can, with reasonable certainty, be judged to be continuous with it and to contain economically producible oil or gas on the basis of available geoscience and engineering data.

(ii) In the absence of data on fluid contacts, proved quantities in a reservoir are limited by the lowest known hydrocarbons (LKH) as seen in a well penetration unless geoscience, engineering, or
performance data and reliable technology establishes a lower contact with reasonable certainty.

(iii) Where direct observation
from well penetrations has defined a highest known oil (HKO) elevation and the potential exists for an associated gas cap, proved oil reserves may be assigned in the structurally higher portions of the reservoir only if geoscience, engineering, or
performance data and reliable technology establish the higher contact with reasonable certainty.

(iv) Reserves which can be
produced economically through application of improved recovery techniques (including, but not limited to, fluid injection) are included in the proved classification when:

(A) Successful testing by a pilot project in an area of the reservoir with properties no more favorable than in the reservoir as a whole, the operation of an installed program in the reservoir or an
analogous reservoir, or other evidence using reliable technology establishes the reasonable certainty of the engineering analysis on which the project or program was based; and (B) The project has been approved for development by all necessary
parties and entities, including governmental entities.



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(v) Existing economic conditions include prices and costs at which economic producibility
from a reservoir is to be determined. The price shall be the average price during the 12-month period prior to the ending date of the period covered by the report, determined as an unweighted arithmetic average of the first-day-of-the-month price
for each month within such period, unless prices are defined by contractual arrangements, excluding escalations based upon future conditions.

Probable reserves  Probable reserves are those additional reserves that are less certain to be recovered than proved reserves but which, together with proved reserves, are as likely as not to
be recovered.

(i) When deterministic methods are used, it is as likely as not that actual remaining quantities recovered will
exceed the sum of estimated proved plus probable reserves. When probabilistic methods are used, there should be at least a 50% probability that the actual quantities recovered will equal or exceed the proved plus probable reserves estimates.

(ii) Probable reserves may be assigned to areas of a reservoir adjacent to proved reserves where data control or
interpretations of available data are less certain, even if the interpreted reservoir continuity of structure or productivity does not meet the reasonable certainty criterion. Probable reserves may be assigned to areas that are structurally higher
than the proved area if these areas are in communication with the proved reservoir.

(iii) Probable reserves estimates also
include potential incremental quantities associated with a greater percentage recovery of the hydrocarbons in place than assumed for proved reserves.

(iv) See also guidelines in paragraphs (iv) and (vi) of the definition of possible reserves.

Possible reserves  Possible reserves are those additional reserves that are less certain to be recovered than probable reserves.

(i) When deterministic methods are used, the total quantities ultimately recovered from a project have a low probability of exceeding
proved plus probable plus possible reserves. When probabilistic methods are used, there should be at least a 10% probability that the total quantities ultimately recovered will equal or exceed the proved plus probable plus possible reserves
estimates.

(ii) Possible reserves may be assigned to areas of a reservoir adjacent to probable reserves where data control and
interpretations of available data are progressively less certain. Frequently, this will be in areas where geoscience and engineering data are unable to define clearly the area and vertical limits of commercial production from the reservoir by a
defined project.

(iii) Possible reserves also include incremental quantities associated with a greater percentage recovery of
the hydrocarbons in place than the recovery quantities assumed for probable reserves.

(iv) The proved plus probable and proved
plus probable plus possible reserves estimates must be based on reasonable alternative technical and commercial interpretations within the reservoir or subject project that are clearly documented, including comparisons to results in successful
similar projects.

(v) Possible reserves may be assigned where geoscience and engineering data identify directly adjacent
portions of a reservoir within the same accumulation that may be separated from proved areas by faults with displacement less than formation thickness or other geological discontinuities and that have not been penetrated by a wellbore, and the
registrant believes that such adjacent portions are in communication with the known (proved) reservoir. Possible reserves may be assigned to areas that are structurally higher or lower than the proved area if these areas are in communication with
the proved reservoir.

(vi) Pursuant to paragraph (iii) of the proved oil and gas definition, where direct observation has
defined a highest known oil (HKO) elevation and the potential exists for an associated gas cap, proved oil reserves should be assigned in the structurally higher portions of the reservoir above the HKO only if the higher contact can be established
with reasonable certainty through reliable technology. Portions of the reservoir that do not meet this reasonable certainty criterion may be assigned as probable and possible oil or gas based on reservoir fluid properties and pressure gradient
interpretations.



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Developed oil and gas reserves  Developed oil and gas reserves are reserves of
any category that can be expected to be recovered:

(i) Through existing wells with existing equipment and operating methods or
in which the cost of the required equipment is relatively minor compared to the cost of a new well; and

(ii) Through installed
extraction equipment and infrastructure operational at the time of the reserves estimate if the extraction is by means not involving a well.

Undeveloped oil and gas reserves Undeveloped oil and gas reserves are reserves of any category 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.

(i) Reserves on undrilled acreage shall be limited to those
directly offsetting development spacing areas that are reasonably certain of production when drilled, unless evidence using reliable technology exists that establishes reasonable certainty of economic producibility at greater distances.

(ii) Undrilled locations can be classified as having undeveloped reserves only if a development plan has been adopted indicating that they
are scheduled to be drilled within five years, unless the specific circumstances justify a longer time.

(iii) Under no
circumstances shall estimates for 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
projects in the same reservoir or an analogous reservoir, as defined in [section 210.410 (a) Definitions], or by other evidence using reliable technology establishing reasonable certainty.

The extent to which probable and possible reserves ultimately may be reclassified as proved reserves is dependent upon future drilling,
testing, and well

performance. The degree of risk to be applied in evaluating probable and possible reserves is influenced by economic and
technological factors as well as the time element. Probable and possible reserves in this report have not been adjusted in consideration of these additional risks and therefore are not comparable with proved reserves.

The development status shown herein represents the status applicable on December 31, 2010. In the preparation of this study, data
available from wells drilled on the appraised properties through December 31, 2010, were used in estimating gross ultimate recovery. When applicable, gross production estimated to December 31, 2010, was deducted from gross ultimate
recovery to arrive at the estimates of gross reserves as of December 31, 2010. Production data through November 2010 were available for most properties.

Our estimates of Dunes net reserves attributable to the reviewed properties are based on the definitions of reserves of the SEC and are as follows, expressed in thousands of barrels (Mbbl) and
millions of cubic feet (MMcf).



|             |  |                         |       |  |           |  |        |                         |  |  |           |  |  |                         |       |  |           |  |   |  |  |  |       | 
|------------ |  | ----------------------- | ----- |  | --------- |  | ------ | ----------------------- |  |  | --------- |  |  | ----------------------- | ----- |  | --------- |  | - |  |  |  | ----- | 
|             |  | Proved                  |       |  | Probable  |  |        | Possible                | 
|             |  | Oil andCondensate(Mbbl) |       |  | Gas(MMcf) |  |        | Oil andCondensate(Mbbl) |  |  | Gas(MMcf) |  |  | Oil andCondensate(Mbbl) |       |  | Gas(MMcf) | 
|             |  |                         |       |  |           | 
|Producing    |  |                         | 2,406 |  |           |  | 15,298 |                         |  |  | 63        |  |  |                         | 645   |  |           |  | 0 |  |  |  | 0     | 
|Nonproducing |  |                         | 1,309 |  |           |  | 16,835 |                         |  |  | 66        |  |  |                         | 1,497 |  |           |  | 0 |  |  |  | 0     | 
|Undeveloped  |  |                         | 1,977 |  |           |  | 16,420 |                         |  |  | 336       |  |  |                         | 582   |  |           |  | 1 |  |  |  | 3,257 | 
|             |  |                         |       |  |           |  |        |                         |  |  |           |  |  |                         |       |  |           |  |   |  |  |  |       | 
|Total        |  |                         | 5,692 |  |           |  | 48,553 |                         |  |  | 465       |  |  |                         | 2,724 |  |           |  | 1 |  |  |  | 3,257 | 

Note: Probable and possible
reserves have not been risk adjusted to make them comparable to proved reserves.



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Primary Economic Assumptions

Revenue values in this report are expressed in terms of estimated future gross revenue, future net revenue, and present worth of future
net revenue. These values are based on the continuation of prices in effect on December 31, 2010.

Future gross revenue
is defined as that revenue to be realized from the production and sale of the estimated net reserves. Future net revenue is calculated by deducting estimated production taxes, ad valorem taxes, operating, gathering, processing expenses, and capital
costs from the future gross revenue. Present worth of future net revenue is calculated by discounting the future net revenue at the arbitrary rate of 10 percent per year compounded monthly over the expected period of realization.

Revenue values in this report were estimated using the initial prices and expenses provided by Dune. Future prices were estimated using
guidelines established by the SEC and the Financial Accounting Standards Board (FASB). The prices used in this report are based on SEC guidelines. The assumptions used for estimating future prices and expenses are as follows:

Oil and Condensate Prices

Dune has represented that the oil and condensate prices were based on a reference price, calculated as the unweighted arithmetic average of the first-day-of-the-month price for each month within the
12-month period prior to the end of the reporting period, unless prices are defined by contractual arrangements. Dune supplied differentials by field to the ConocoPhillips WTI reference price of $76.05 per barrel and the prices were held constant
thereafter. The volume-weighted average price attributable to estimated proved reserves was $78.34 per barrel.

Natural Gas
Prices

Dune has represented that the natural gas prices were based on a reference price, calculated as the unweighted
arithmetic average of the first-day-of-the-month price for each month within the 12-month period prior to the end of the reporting period, unless prices are defined by contractual arrangements. The gas prices were calculated for each property using
differentials and British thermal units factors to the Henry Hub Louisiana Onshore reference price of $4.38 per million British thermal units furnished by Dune and held constant thereafter. The volume-weighted average price attributable to estimated
proved reserves was $4.714 per Mcf.

Operating Expenses and Capital Costs

Operating expenses and capital costs, based on information provided by Dune, were used in estimating future costs required to operate the
properties. In certain cases, future costs, either higher or lower than existing costs, may have been used because of anticipated changes in operating conditions. These costs were not escalated for inflation.



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The estimated future revenue and expenditures attributable to the production and sale of
Dunes net proved reserves of the properties appraised, as of December 31, 2010, is summarized in thousands of dollars (M$), as follows:



|                                    |                    |        |         |                       |             |  |             |  |  |  |         |  |  |  |         | 
|----------------------------------- | ------------------ | ------ | ------- | --------------------- | ----------- |  | ----------- |  |  |  | ------- |  |  |  | ------- | 
|                                    |                    | Proved |         |                       | TotalProved | 
|                                    | DevelopedProducing |        |         | DevelopedNonproducing |             |  | Undeveloped |  | 
|Future Gross Revenue, M$            |                    |        | 259,912 |                       |             |  | 182,050     |  |  |  | 232,794 |  |  |  | 674,756 | 
|Production and Ad Valorem Taxes, M$ |                    |        | 27,027  |                       |             |  | 16,668      |  |  |  | 19,726  |  |  |  | 63,421  | 
|Operating Expenses, M$              |                    |        | 103,328 |                       |             |  | 49,783      |  |  |  | 27,653  |  |  |  | 180,764 | 
|Investment Costs, M$                |                    |        | 0       |                       |             |  | 12,964      |  |  |  | 40,682  |  |  |  | 53,646  | 
|Abandonment Costs, M$               |                    |        | 33,456  |                       |             |  | 0           |  |  |  | 0       |  |  |  | 33,456  | 
|Future Net Revenue, M$              |                    |        | 96,101  |                       |             |  | 102,635     |  |  |  | 144,733 |  |  |  | 343,469 | 
|Present Worth at 10 Percent, M$     |                    |        | 68,404  |                       |             |  | 47,921      |  |  |  | 98,204  |  |  |  | 214,529 | 

Note: Future income taxes have not
been taken into account in the preparation of these estimates.

The estimated future revenue and expenditures attributable to
the production and sale of Dunes net probable reserves of the properties appraised, as of December 31, 2010, is summarized in thousands of dollars (M$) as follows:



|                                    |                    |          |       |                       |               |  |             |  |  |  |        |  |  |  |        | 
|----------------------------------- | ------------------ | -------- | ----- | --------------------- | ------------- |  | ----------- |  |  |  | ------ |  |  |  | ------ | 
|                                    |                    | Probable |       |                       | TotalProbable | 
|                                    | DevelopedProducing |          |       | DevelopedNonproducing |               |  | Undeveloped |  | 
|Future Gross Revenue, M$            |                    |          | 7,995 |                       |               |  | 11,892      |  |  |  | 29,326 |  |  |  | 49,213 | 
|Production and Ad Valorem Taxes, M$ |                    |          | 649   |                       |               |  | 1,249       |  |  |  | 3,504  |  |  |  | 5,402  | 
|Operating Expenses, M$              |                    |          | 26    |                       |               |  | 2,234       |  |  |  | 919    |  |  |  | 3,179  | 
|Investment Costs, M$                |                    |          | 0     |                       |               |  | 1,235       |  |  |  | 864    |  |  |  | 2,099  | 
|Abandonment Costs, M$               |                    |          | 0     |                       |               |  | 0           |  |  |  | 0      |  |  |  | 0      | 
|Future Net Revenue, M$              |                    |          | 7,320 |                       |               |  | 7,174       |  |  |  | 24,039 |  |  |  | 38,533 | 
|Present Worth at 10 Percent, M$     |                    |          | 6,746 |                       |               |  | 3,654       |  |  |  | 11,526 |  |  |  | 21,926 | 

Notes:

1. Future income taxes have not been taken into account in the preparation of these estimates.

2. Values for probable reserves have not been risk adjusted to make them comparable to values for

proved reserves.

The estimated
future revenue and expenditures attributable to the production and sale of Dunes net possible reserves of the properties appraised, as of December 31, 2010, is summarized in thousands of dollars (M$) as follows:



|                                    |  |                    |   |  |                       |  |   |             |  |  |        |  |  |  |        | 
|----------------------------------- |  | ------------------ | - |  | --------------------- |  | - | ----------- |  |  | ------ |  |  |  | ------ | 
|                                    |  | Possible           |   |  | TotalPossible         | 
|                                    |  | DevelopedProducing |   |  | DevelopedNonproducing |  |   | Undeveloped |  | 
|Future Gross Revenue, M$            |  |                    | 0 |  |                       |  | 0 |             |  |  | 16,179 |  |  |  | 16,179 | 
|Production and Ad Valorem Taxes, M$ |  |                    | 0 |  |                       |  | 0 |             |  |  | 1,087  |  |  |  | 1,087  | 
|Operating Expenses, M$              |  |                    | 0 |  |                       |  | 0 |             |  |  | 1,117  |  |  |  | 1,117  | 
|Investment Costs, M$                |  |                    | 0 |  |                       |  | 0 |             |  |  | 8,200  |  |  |  | 8,200  | 
|Abandonment Costs, M$               |  |                    | 0 |  |                       |  | 0 |             |  |  | 0      |  |  |  | 0      | 
|Future Net Revenue, M$              |  |                    | 0 |  |                       |  | 0 |             |  |  | 5,775  |  |  |  | 5,775  | 
|Present Worth at 10 Percent, M$     |  |                    | 0 |  |                       |  | 0 |             |  |  | 2,525  |  |  |  | 2,525  | 

Notes:

1. Future income taxes have not been taken into account in the preparation of these estimates.

2. Values for possible reserves have not been risk adjusted to make them comparable to values for proved reserves.



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Estimates of oil, condensate, and natural gas reserves and future net revenue should be
regarded only as estimates that may change as further production history and additional information become available. Not only are such reserves and revenue estimates based on that information which is currently available, but such estimates are
also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

While
the oil and gas industry may be subject to regulatory changes from time to time that could affect an industry participants ability to recover its oil and gas reserves, we are not aware of any such governmental actions which would restrict the
recovery of the December 31, 2010, estimated oil and gas volumes. The reserves estimated in this report can be produced under current regulatory guidelines.

In our opinion, the information relating to estimated proved, probable, and possible reserves, estimated future net revenue from proved, probable, and possible reserves, and present worth of estimated
future net revenue from proved reserves of oil, condensate, natural gas liquids, and gas contained in this report has been prepared in accordance with Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7, 932-235-50-9,932-235-50-30, and
932-235-50-31(a), (b), and (e) of the Accounting Standards Update 932-235-50, Extractive Industries  Oil and Gas (Topic 932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and
Rules 410(a) (1)(32) of Regulation SX and Rules 302(b), 1201, 1202(a) (1), (2), (3), (4), (5), (8), and 1203(a) of Regulation SK of the Securities and Exchange Commission; provided, however, future income tax expenses
have not been taken into account in estimating the future net revenue and present worth values set forth herein.

To the
extent the above-enumerated rules, regulations, and statements require determinations of an accounting or legal nature, we, as engineers, are necessarily unable to express an opinion as to whether the above-described information is in accordance
therewith or sufficient therefor.

DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has
been providing petroleum consulting services throughout the world for over 70 years. DeGolyer and MacNaughton does not have any financial interest, including stock ownership, in Dune. Our fees were not contingent on the results of our evaluation.
This letter report has been prepared at the request of Dune. DeGolyer and MacNaughton has used all assumptions, data, procedures, and methods that it considers necessary and appropriate to prepare this report.



Submitted,DeGOLYER and MacNAUGHTONTexas Registered Engineering Firm F-716




/s/ Paul J. SzatkowskiPaul J. Szatkowski, P.E.Senior Vice PresidentDeGolyer and MacNaughton




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CERTIFICATE of QUALIFICATION

I, Paul J. Szatkowski, Petroleum Engineer with DeGolyer and MacNaughton, 5001 Spring Valley Road, Suite 800 East, Dallas, Texas, 75244
U.S.A., hereby certify:

1. That I am a Senior Vice President with DeGolyer and MacNaughton, which company did prepare the
letter report addressed to Dune dated February 14, 2011, and that I, as Senior Vice President, was responsible for the preparation of this report.

2. That I attended Texas A&M University, and that I graduated with a Bachelor of Science degree in Petroleum Engineering in the year 1974; that I am a Registered Professional Engineer in the State of
Texas; that I am a member of the International Society of Petroleum Engineers and the American Association of Petroleum Geologists; and that I have in excess of 36 years of experience in oil and gas reservoir studies and reserves evaluations.



/s/ Paul J. SzatkowskiPaul J. Szatkowski, P.E.Senior Vice PresidentDeGolyer and MacNaughton