Document:

Consent letter of DeGolyer and MacNaughton

 Exhibit 10.5 

DEGOLYER AND MACNAUGHTON 

5001 SPRING VALLEY ROAD 

SUITE 800 EAST 

DALLAS, TEXAS 75244 

June 22, 2010 

Dr. Juan José Suárez Coppel 

Director General 
 Petróleos Mexicanos

 Avenida Marina Nacional No. 329 

Colonia Huasteca 
 Torre Ejecutiva, Piso 41

 11311 Mexico, D.F. Mexico 
 Dear
Dr. Suárez Coppel: 
 We hereby consent to the references to DeGolyer and MacNaughton as set forth under the heading
“Exploration and Production (Reserves)” in the Annual Report on Form 20-F of Petróleos Mexicanos for the year ended December 31, 2009, and to the filing as an exhibit to the Form 20-F of our report describing our review of the
estimates of proved oil, condensate, natural gas, and oil equivalent reserves owned by the United Mexican States (“Mexico”) as of January 1, 2010, for 68 fields located offshore of Mexico in the Southwest Marine Region. These
estimates were prepared in accordance with the reserves definitions of Rules 4-10(a) (1)-(32) of Regulation S-X of the United States Securities and Exchange Commission. 

 

	
	Very truly yours,
	
	/s/ DeGolyer and MacNaughton
	
	DeGOLYER and MacNAUGHTON
	Texas Registered Engineering Firm F-716DeGolyer and MacNaughton, Report of Reserves Data

 Exhibit 10.6 

DEGOLYER AND MACNAUGHTON 

5001 SPRING VALLEY ROAD 

SUITE 800 EAST 

DALLAS, TEXAS 75244 

June 22, 2010 
 Pemex
Exploración y Producción 
 Avenida Marina Nacional No. 329 

Colonia Huasteca 
 Torre Ejecutiva, Piso 41

 11311 Mexico, D.F. Mexico 

Gentlemen: 
 Pursuant to your
request, we have conducted a reserves audit of the net proved crude oil, condensate, natural gas liquids (NGL), and sales-gas reserves, as of January 1, 2010, of certain properties owned by Pemex Exploración y Producción (PEP) in
the Región Marina Suroeste of Mexico. PEP has represented that these properties account for 13.5 percent on a net total liquids equivalent barrel basis of PEP’s net proved reserves as of January 1, 2010, and that the net proved
reserves estimates 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. We have reviewed information provided
to us by PEP that it represents to be PEP’s estimates of the net reserves, as of January 1, 2010, for the same properties as those which we evaluated. 

Reserves included herein are expressed as net reserves as represented by PEP. Gross reserves are defined as the total estimated petroleum
to be produced from these properties after December 31, 2009. Net reserves are defined as that portion of the gross reserves attributable to the interests owned by PEP after deducting all interests owned by others. 

Estimates of oil, condensate, NGL, and sales gas 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. 

 
 2
 
 DEGOLYER AND
MACNAUGHTON 
  
 Data
used in this audit were obtained from reviews with PEP personnel and PEP files. In the preparation of this report we have relied, without independent verification, upon such information furnished by PEP 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 standard geological and engineering methods generally accepted by the
petroleum industry. 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. 

 
 3
 
 DEGOLYER AND
MACNAUGHTON 
  
 Definition of
Reserves 
 Petroleum reserves estimated by PEP and by us included in this report are classified by degree of proof as
proved and 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. Proved reserves classifications by PEP and by us 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. 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.

 
 4
 
 DEGOLYER AND
MACNAUGHTON 
  
 (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. 

(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. 

 
 5
 
 DEGOLYER AND
MACNAUGHTON 
  

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 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. 

 
 6
 
 DEGOLYER AND
MACNAUGHTON 
  
 Primary Economic
Assumptions 
  
 The following economic assumptions
were used for estimating existing and future prices and costs: 
 Oil, Condensate, and NGL Prices 

PEP has represented that the oil, condensate, and NGL prices were based on a 12-month average price (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. 

Natural Gas Prices 

PEP 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. 
 Operating
Expenses and Capital Costs 
 Operating expenses and capital costs, based on information provided by PEP, 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 January 1, 2010, estimated oil and gas volumes. The reserves estimated in this
report can be produced under current regulatory guidelines. 

 
 7
 
 DEGOLYER AND
MACNAUGHTON 
  
 PEP has
represented that estimated net proved reserves attributable to the reviewed properties are based on the definitions of proved reserves of the SEC. PEP represents that its estimates of the net proved reserves attributable to these properties which
represent 13.5 percent of PEP’s reserves on a total liquids equivalent basis are as follows, expressed in thousands of barrels (Mbbl), millions of cubic feet (MMcf): 

 

									
	 	  	Estimated by PEP
Net Proved Reserves as of January 1, 2010
	 	  	Oil and
Condensate
(Mbbl)	  	NGL
(Mbbl)	  	Sales
Gas
(MMcf)	  	Total Liquids
Equivalent*
(Mbbl)
	 Properties reviewed by

DeGolyer and MacNaughton
	  		  		  		  	
	 Mexico
	  		  		  		  	
	 Proved Developed
	  	664,471	  	108,007	  	1,027,284	  	969,998
	 Proved Undeveloped
	  	535,099	  	117,876	  	1,398,304	  	921,831
		  	 	  	 	  	 	  	 
	 Total Proved
	  	1,199,570	  	225,883	  	2,425,588	  	1,891,829

 

	 	*	Total liquids equivalent volumes are based on heating values that vary for each field. 

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. 

 
 8
 
 DEGOLYER AND
MACNAUGHTON 
  
 In
comparing the detailed net proved reserves estimates prepared by us and by PEP, we have found differences, both positive and negative. It is our opinion that the net proved reserves estimates prepared by PEP on the properties reviewed by us and
referred to above, when compared on the basis of net total liquids equivalent barrels, in aggregate, differ by 9 percent and are considered to be reasonable. 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 PEP. Our fees were not contingent on the results of our evaluation.
This letter report has been prepared at the request of PEP. DeGolyer and MacNaughton has used all procedures and methods that it considers necessary to prepare this report. 

 

	
	Submitted,
	
	/s/ DeGolyer and MacNaughton
	 DeGOLYER and MacNAUGHTON
 Texas
Registered Engineering Firm F-716

	

	
	
	/s/ R. M. Shuck, P.E.
	R. M. Shuck, P.E.
	Senior Vice President
	DeGolyer and MacNaughton

  

 Jun. 25, 2010 

DEGOLYER AND MACNAUGHTON 

 
 CERTIFICATE of QUALIFICATION 

I, R. Michael Shuck, 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 PEP dated June 22, 2010, and that I, as
Senior Vice President, was responsible for the preparation of this report. 

  

	 	2.	That I attended University of Houston, and that I graduated with a Bachelor of Science degree in Chemical Engineering in the year 1977; 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 32 years of experience in the oil and gas reservoir studies and reserves evaluations.

	
	
	 /s/ R. M. Shuck, P.E.

R. M. Shuck, P.E.

	Senior Vice President
	DeGolyer and MacNaughton

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