EX-4.8




 Exhibit 4.8 
 DeGolyer and MacNaughton 
 5001 Spring Valley Road 

Suite 800 East 

Dallas, Texas 75244 
 January 13, 2012 
 Petrobras Argentina S.A. 

Maipú 1, 21st Floor 

(C1084ABA) Buenos Aires 
 Argentina 

Gentlemen: 
 Pursuant to your
request, we have conducted a reserves evaluation of the net proved crude oil, condensate, natural gas liquids (NGL), and natural gas reserves, as of December 31, 2011, of certain selected properties in Argentina owned by Petrobras Argentina
S.A. This evaluation was completed on January 13, 2012. Petrobras Argentina S.A. has represented that these properties account for 73 percent on a net equivalent barrel basis of Petrobras Argentina S.A.’s net proved reserves as of
December 31, 2011. These reserves represent 100 percent of properties operated by Petrobras Argentina S.A. The net proved 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. This report was prepared in accordance with guidelines specified in Items 1202 (a)(8) of Regulation S-K and is to be used for inclusion
in certain SEC filings by Petrobras Argentina S.A. 
 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, 2011. Net reserves are defined as that portion of the gross reserves attributable to the interests owned by Petrobras Argentina S.A. after
deducting all interests owned by others. 
 Estimates of oil, condensate, NGL, and natural gas reserves should be regarded only
as estimates that may change as further production history and additional information become available. Not only are such reserves 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. 
 Data used in this
evaluation were obtained from reviews with Petrobras Argentina S.A. personnel, Petrobras Argentina S.A. 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 Petrobras Argentina S.A. 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 the 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. 

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 estimated by us included in this report are classified as proved. Only proved reserves have been evaluated for this
report. Reserves classifications used by us 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 geosciences 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 geosciences 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 geosciences, 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 geosciences, engineering, or performance data and reliable technology establish the higher contact with reasonable certainty. 

  
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 (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.

 (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. 

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. 
 Primary Economic
Assumptions 
 The following economic assumptions were used for estimating existing and future prices and costs: 

Oil, Condensate, and Natural Gas Liquids Prices 
 Petrobras Argentina S.A. has represented that the oil, condensate, and NGL prices were based on a 12-month average 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. Petrobras Argentina S.A. provided these 12-month average prices by field, each including differentials
to the West Texas Intermediate reference price of U.S.$96.23 per barrel. The 12-month average adjusted product prices were U.S.$61.70 per barrel for crude oil and condensate and U.S.$30.49 per barrel or NGL. These prices were not escalated for
inflation. 

  
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 Natural Gas Prices 

Petrobras Argentina S.A. has represented that the natural gas prices were defined by contractual arrangements. The average adjusted
product price, provided by Petrobras Argentina S.A., was U.S.$2.32 per thousand cubic feet. These prices were not escalated for inflation. 
 Operating Expenses and Capital Costs 
 Operating expenses and capital costs,
based on information provided by Petrobras Argentina S.A., 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. 
 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, 2011,
estimated proved oil, condensate, NGL and gas reserves. The reserves estimated in this report can be produced under current regulatory guidelines. 
 Our estimates of Petrobras Argentina S.A.’s net proved reserves attributable to the reviewed properties are based on the definitions of proved reserves of the SEC and are as follows, expressed in
millions of barrels (MMbbl), millions of cubic feet (MMcf), and millions of barrels of oil equivalent (MMboe): 
  

													
	 	  	Estimated by DeGolyer and MacNaughton
Net Proved Reserves
as of
December 31, 2011	 
	 	  	Oil
Condensate,
and NGL
(MMbbl)	 	  	Natural
Gas
(MMcf)	 	  	Oil
Equivalent
(MMboe)	 
	 Proved Developed
	  	 	35,263	  	  	 	331,430	  	  	 	90,501	  
	 Proved Undeveloped
	  	 	11,411	  	  	 	364,568	  	  	 	72,172	  
				
	 Total Proved
	  	 	46,674	  	  	 	695,998	  	  	 	162,673	  

 Note: Gas is converted to oil equivalent using a factor of 6,000 cubic feet of gas per 1 barrel of oil equivalent.

 In our opinion, the information relating to estimated 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, and 932-235-50-9 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), (8), and 1203(a) of Regulation
S–K of the Securities and Exchange Commission; provided, however, that estimates of proved developed and proved undeveloped reserves are not presented at the beginning of the year. 

  
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 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. 

  
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 DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has
been providing petroleum consulting services throughout the world since 1936. DeGolyer and MacNaughton does not have any financial interest, including stock ownership, in Petrobras Argentina S.A. Our fees were not contingent on the results of our
evaluation. This letter report has been prepared at the request of Petrobras Argentina S.A. DeGolyer and MacNaughton has used all assumptions, data, procedures, and methods that it considers necessary and appropriate to prepare this report.

  

			
	 	 	Submitted,
		
		 	/s/ DeGolyer and MacNaughton
		 	DeGOLYER and MacNAUGHTON
		 	Texas Registered Engineering Firm F-716
		
		 	 /s/Julian P. Garcia, P.E.

		 	Julian P. Garcia, P.E.
		 	Vice President
		 	DeGolyer and MacNaughton


  
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 CERTIFICATE of QUALIFICATION 

I, Julian P. Garcia, 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 Vice President with DeGolyer and MacNaughton, which company did prepare the report addressed to Petrobras Argentina S.A. dated January 13, 2012, and
that I, as 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 1982 and a Master of Science degree in 1988 in Petroleum
Engineering; 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 that I have in excess of 28 years of experience in the oil and gas reservoir studies
and reserves evaluations. 

  

			
	 	 	 /s/Julian P. Garcia, P.E.

		 	Julian P. Garcia, P.E.
		 	Vice President
		 	DeGolyer and MacNaughton


  
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