SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K/A

Report of Foreign Private Issuer
Pursuant to Rule 13a-16 or 15d-16 of the

Securities Exchange Act of 1934

For the month of March 2014

Commission File Number 1-15106

PETRÓLEO BRASILEIRO S.A. - PETROBRAS

(Exact name of registrant as specified in its charter)

Brazilian Petroleum Corporation - PETROBRAS

(Translation of Registrant's name into English)

Avenida República do Chile, 65 
20031-912 - Rio de Janeiro, RJ
Federative Republic of Brazil

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F. 

Form 20-F ___X___ Form 40-F _______

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes _______ No___X____

.

REASON FOR AMENDMENT

The reason for this amendment is to include Management’s Report on Internal Control over Financial Reporting and the report of KPMG Auditores Independentes with our consolidated financial statements that were furnished to the SEC in a report on Form 6-K on February 26, 2014, and  to implement minor typographical corrections.

Management’s Report on Internal Control over Financial Reporting

Petróleo Brasileiro S.A. – Petrobras announces that its management is responsible for establishing and maintaining effective internal control over financial reporting and for its assessments of the effectiveness of internal control over financial reporting.

Our internal control over financial reporting is a process designed by, or under the supervision of our Audit Committee and our Chief Executive Officer and Chief Financial Officer, and effected by our board of directors, management and other personnel to provide reasonable assurance regarding the reliability of financial reporting and the preparation of consolidated financial statements for external purposes in accordance with IFRS, as issued by the IASB.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements on a timely basis.  Therefore even those systems determined to be effective can provide only reasonable assurance with respect to financial statement preparation and presentation.  Also, projections of any evaluation of the effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Our management has assessed the effectiveness of our internal control over financial reporting as of December 31, 2013, based on the criteria established in Internal Control—Integrated Framework (1992) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).  Based on such assessment and criteria, the Company’s management has concluded that Company’s internal control over financial reporting was effective as of December 31, 2013.

On May 14, 2013, COSO published an updated Internal Control - Integrated Framework (2013) and related illustrative documents. As of  December 31, 2013, the company is utilizing the original framework published in 1992. The transition period for adoption of the updated framework ends December 15, 2014. 

The effectiveness of our internal control over financial reporting as of December 31, 2013, has been audited by PricewaterhouseCoopers Auditores Independentes, an independent registered public accounting firm, as stated in their report dated February 25, 2014 included in our 2013 Audited Financial Statements.

Petróleo Brasileiro S.A. – Petrobras

Consolidated financial statements at

December 31, 2013, 2012 and 2011 with

report of independent registered
public accounting firm

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Shareholders of

Petróleo Brasileiro S.A. - Petrobras

In our opinion, the accompanying consolidated statement of financial position and the related consolidated statements of income and comprehensive income, changes in equity and cash flows present fairly, in all material respects, the financial position of Petróleo Brasileiro S.A. - Petrobras and its subsidiaries (the “Company”) at December 31, 2013, and December 31, 2012, and the results of their operations and their cash flows for the years ended December 31, 2013, and December 31, 2012, in conformity with International Financial Reporting Standards as issued by the International Accounting Standards Board. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2013 based on criteria established in Internal Control - Integrated Framework  (1992) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). The Company's management is responsible for these financial statements, for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express opinions on these financial statements and on the Company's internal control over financial reporting based on our integrated audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement and whether effective internal control over financial reporting was maintained in all material respects. Our audits of the financial statements included examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

We also have audited the adjustments to the 2011 financial statements to retrospectively apply the change in accounting for employee benefit plans for the revisions to IAS 19 Employee Benefits as described in Note 2.3. In our opinion, such adjustments are appropriate and have been properly applied. We were not engaged to audit, review, or apply any procedures to the 2011 consolidated financial statements of the Company other than with respect to the adjustments and, accordingly, we do not express an opinion or any other form of assurance on the 2011 consolidated financial statements taken as a whole.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Rio de Janeiro, February 25, 2014

/s/ PricewaterhouseCoopers

Auditores Independentes

CRC 2SP000160/O-5 “F” RJ

/s/ Marcos Donizete Panassol

Contador CRC 1SP155975

Report of Independent Registered Public Accounting Firm

The Board of Directors and Shareholders of

Petróleo Brasileiro S.A. – Petrobras

Rio de Janeiro - RJ

We have audited, before the effects of the adjustments to retrospectively apply the change in accounting described in Note 2.3, the accompanying consolidated statements of income, comprehensive income, changes in shareholders’ equity and cash flows of Petróleo Brasileiro S.A. – Petrobras and subsidiaries for the year ended  December 31, 2011. The 2011 financial statements before the effects of the adjustments discussed in note 2.3 are not presented herein. The 2011 consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on these consolidated financial statements based on our audit.

We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion.

In our opinion, the 2011 financial statements, before the effects of the adjustments to retrospectively apply the change in accounting described in note 2.3, present fairly, in all material respects, the consolidated results of Petrobras and its subsidiaries’ operations and their cash flows for the year ended December 31, 2011, in conformity with International Financial Reporting Standards (IFRS) issued by the International Accounting Standards Board (IASB).

We were not engaged to audit, review, or apply any procedures to the adjustments to retrospectively apply the change in accounting described in note 2.3 and, accordingly, we do not express an opinion or any other form of assurance about whether such adjustments are appropriate and have been properly applied. Those adjustments were audited by a successor auditor.

/s/ KPMG Auditores Independentes  

KPMG Auditores Independentes

Rio de Janeiro, Brazil

March 30, 2012

4

Consolidated Statement of Financial Position

December 31, 2013, 2012 and January 1, 2012 (In millions of US Dollars)

Consolidated Statement of Income

December 31, 2013, 2012 and 2011 (In millions of US Dollars, unless otherwise indicated)

Consolidated Statement of Comprehensive Income

December 31, 2013, 2012 and 2011 (In millions of US Dollars)

Consolidated Statement of Cash Flows

December 31, 2013, 2012 and 2011 (In millions of US Dollars)

Consolidated Statement of Changes in Shareholders’ Equity

December 31, 2013, 2012 and 2011 (In millions of US Dollars)

Notes to the financial statements

December 31, 2013 and 2012 (Expressed in millions of US Dollars, unless otherwise indicated)

1.            The Company and its operations

Petróleo Brasileiro S.A. - Petrobras is dedicated, directly or through its subsidiaries  (referred to jointly as “Petrobras” or “the Company”) to prospecting, drilling, refining, processing, trading and transporting crude oil from producing onshore and offshore oil fields and from shale or other rocks, as well as oil products, natural gas and other liquid hydrocarbons. In addition, Petrobras carries out energy related activities, such as research, development, production, transport, distribution and trading of all forms of energy, as well as any other correlated or similar activities. The Company’s head office is located in Rio de Janeiro – RJ, Brazil.

2.            Basis of preparation

2.1.       Statement of compliance and authorization of financial statements

The consolidated financial information has been prepared and is being presented in accordance with the International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB). The information is presented in U.S. dollars.

The financial statements have been prepared under the historical cost convention, as modified by available-for-sale financial assets, financial assets and financial liabilities measured at fair value and certain current and non-current assets and liabilities, as detailed in the accounting policies set out below.

The annual consolidated financial information was approved and authorized for issue by the Company’s Board of Directors in a meeting held on February 25, 2014.

2.2.       Functional and presentation currency

The functional currency of Petrobras and all Brazilian subsidiaries is the Brazilian Real. The functional currency of most of the entities that operate outside Brazil is the U.S. dollar. The functional currency of Petrobras Argentina is the Argentine Peso.

Petrobras has selected the U.S. Dollar as its presentation currency. The financial statements have been translated into the presentation currency in accordance with IAS 21 - The effects of changes in foreign exchange rates. All assets and liabilities are translated into U.S. dollars at the closing rate at the date of the financial statements; income and expenses, as well as the cash flows are translated into U.S. dollars using the average exchange rates prevailing during the year. Equity items are translated using the exchange rates prevailing at the dates of the transactions or valuation where items are remeasured. All exchange rate differences arising from the translation of the consolidated financial statements from the functional currency into the presentation currency are recognized as cumulative translation adjustments (CTA) within accumulated other comprehensive income in the consolidated statements of changes in shareholders’ equity.

The cumulative translation adjustments were set to nil at January 1, 2009 (the date of transition to IFRS).

2.3.       Prior period restatements

The Statements of Financial Position as of December 31, 2012 and January 1, 2012 have been restated for comparative purposes, including the following effects:

a)             Amendments to IAS 19 – “Employee benefits”

Effective for annual periods beginning on January 1, 2013, amendments to IAS 19 – “Employee benefits” eliminated the option to defer actuarial gains and losses (corridor approach) and requires net interest to be calculated by applying the discount rate used for measuring the obligation to the net benefit asset or liability.

The impact of such amendments, for the year ended December 31, 2012 is: an increase in the Company’s net actuarial liability of US$10,161 (US$6,179 at January 1, 2012), as well as a corresponding decrease in deferred tax liabilities of US$2,988 (US$1,657 at January 1, 2012) and a decrease of US$7,173 in the shareholders’ equity (US$4,522 at January 1, 2012).

b)             Offsetting deferred income taxes

Deferred income tax assets were offset against deferred income tax liabilities by the Company, considering the balance of deferred income taxes of each of the consolidated subsidiaries. The impact of such change for the year ended December 31, 2012 was a decrease of US$ 4,249 in noncurrent assets and liabilities (US$ 3,500 at January 1, 2012).

Those restatements had no significant impact on the Company’s profit or loss or cash flows.

The effects of such changes in the statement of financial position, statement of changes in shareholders’ equity and statement of comprehensive income, for comparative purposes, are set out following:

3.            Summary of significant accounting policies

The accounting policies set out below have been consistently applied to all periods presented in these consolidated financial statements.

3.1.       Basis of consolidation

 The consolidated financial statements include the financial information of Petrobras and the entities it controls (its subsidiaries). Control is achieved when Petrobras: i) has power over the investee; ii) is exposed, or has rights, to variable returns from involvement with the investee; and iii) has the ability to use its power to affect its returns.

Subsidiaries are consolidated from the date on which control is obtained until the date that such control no longer exists. Accounting policies of subsidiaries have been changed, where necessary, to ensure consistency with the policies adopted by the Company.

The consolidation procedures involve combining assets, liabilities, income and expenses, according to their function and eliminating all intragroup balances and transactions, including unrealized profits arising from intragroup transactions.

The entities and structured entities set out following are consolidated:

Petrobras has no equity interest in the structured entities above, and control is not determined by voting rights, but by the power the Company has over the relevant operating activities of such entities.

3.2.       Business segment reporting

The information related to the operating segments (business areas) of the Company is prepared based on items directly attributable to each segment, as well as items that can be allocated to each segment on a reasonable basis.

The measurement of segment results includes transactions carried out with third parties and transactions between business areas, which are charged at internal transfer prices defined between the areas using methods based on market parameters.

Information for each business area is presented as defined by the current organizational structure. The Company operates under the following segments:

a) Exploration and Production (E&P): this segment covers the activities of exploration, development and production of crude oil, NGL (natural gas liquid) and natural gas in Brazil for the purpose of supplying, primarily, our domestic refineries; and also selling the crude oil surplus and oil products produced in the natural gas processing plants to the domestic and foreign markets. The exploration and production segment also operates through partnerships with other companies.

b) Refining, Transportation and Marketing (RT&M): this segment covers the refining, logistics, transport and trading of crude oil and oil products activities, exporting of ethanol, extraction and processing of shale, as well as holding interests in petrochemical companies in Brazil.

c) Gas and Power: this segment covers the activities of transportation and trading of natural gas produced in Brazil and imported natural gas, transportation and trading of LNG (liquid natural gas), generation and trading of electricity, as well as holding interests in transporters and distributors of natural gas and in thermoelectric power stations in Brazil, in addition to being responsible for the fertilizer business.

d) Biofuels: this segment covers the activities of production of biodiesel and its co-products, as well as the ethanol-related activities: equity investments, production and trading of ethanol, sugar and the surplus electric power generated from sugarcane bagasse.

e) Distribution: this segment includes mainly the activities of Petrobras Distribuidora, which operates through its own retail network and wholesale channels to sell oil products, ethanol and vehicle natural gas in Brazil to retail, commercial and industrial customers, as well as other fuel wholesalers.

f) International: this segment covers the activities of exploration and production of oil and gas, refining, transportation and marketing, gas and power, and distribution, carried out outside of Brazil in a number of countries in the Americas, Africa, Europe and Asia.

The corporate segment comprises the items that cannot be attributed to the other segments, notably those related to corporate financial management, corporate overhead and other expenses, including actuarial expenses related to the pension and medical benefits for retired employees and their dependents.

3.3.       Financial instruments

3.3.1. Cash and cash equivalents

Cash and cash equivalents comprise cash in hand, term deposits with banks and short-term highly liquid financial investments that are readily convertible to known amounts of cash, are subject to insignificant risk of changes in value and have a maturity of three months or less from the date of acquisition.

3.3.2. Marketable securities

Marketable securities comprise investments in debt or equity securities. These instruments are initially measured at fair value and are classified and subsequently measured as set out below:

-       Fair value through profit or loss - includes securities purchased and held for trading in the short term. These instruments are subsequently measured at fair value with changes recognized in profit or loss.

-       Held-to-maturity - includes securities with fixed or determinable payments, for which management has the ability and intent to hold until maturity. These instruments are subsequently measured at amortized cost using the effective interest rate method.

-       Available-for-sale – includes securities that are either designated in this category or not classified as fair value through profit or loss or held-to-maturity securities. These instruments are subsequently measured at fair value. Subsequent changes in fair value are recognized within other comprehensive income, in the shareholders’ equity and reclassified to profit or loss when securities are derecognized.

Subsequent changes attributable to interest, foreign exchange, and inflation are recognized in profit or loss for all categories, when applicable.

3.3.3. Trade receivables

Trade receivables are initially measured at the fair value of the consideration to be received and, subsequently, at amortized cost using the effective interest rate method and adjusted for allowances for credit losses and impairment.

The Company recognizes a provision for impairment of trade receivables when there is objective evidence that a loss event occurred after the initial recognition of the receivable and has an impact on the estimated future cash flows, which can be reliably estimated. Such evidence includes insolvency, defaults or a significant probability of a debtor filing for bankruptcy.

3.3.4. Loans and financing (Debt)

Loans and financing are initially recognized at fair value less transaction costs incurred and, after initial recognition, are measured at amortized cost using the effective interest rate method.

3.3.5. Derivative financial instruments

Derivative financial instruments are recognized in the statement of financial position as assets or liabilities and are initially and subsequently measured at fair value.

Gains or losses arising from changes in fair value are recognized in profit or loss as finance income (finance expense), unless the derivative is qualified and designated for hedge accounting.

3.3.6. Hedge accounting

Hedge accounting is formally documented at inception in terms of the hedging relationship and the Company’s risk management objective and strategy for undertaking the hedge.

Hedging relationships which qualify for hedge accounting are classified as:  (i) fair value hedge, when they involve a hedge of the exposure to changes in fair value of a recognized asset or liability, unrecognized firm commitments, or an identifiable portion of such assets, liabilities or firm commitments; and (ii) cash flow hedges when they involve a hedging of the exposure to variability in cash flows that is attributable to a particular risk associated with a recognized asset or liability or a highly probable forecast transaction.

In hedging relationships which qualify for fair value hedge accounting, the gain or loss from remeasuring the hedging instrument at fair value is recognized in profit or loss.

In hedging relationships which qualify for cash flow hedge accounting, the Company designates derivative financial instruments and long-term debt (non-derivative financial instruments) and gains or losses relating to the effective portion of the hedge are recognized within other comprehensive income, in the shareholders’ equity and recycled to profit or loss in the periods when the hedged item affects profit or loss. The gains or losses relating to the ineffective portion are recognized in profit or loss.

When, the hedging instrument expires or is sold, terminated or exercised or no longer meets the criteria for hedge accounting or the Company revokes the designation, the cumulative gain or loss on the hedging instrument that has been recognized in other comprehensive income from the period when the hedge was effective remains separate in equity until the forecast transaction occurs. When, the forecast transaction is no longer expected to occur, the cumulative gain or loss on the hedging instrument that has been recognized in other comprehensive income is immediately reclassified from equity to profit or loss.

3.4.       Inventories 

Inventories are determined by the weighted average cost flow method and mainly comprise crude oil, intermediate products and oil products, as well as natural gas, liquid natural gas (LNG), fertilizers and biofuels, stated at the lower of the average cost, and their net realizable value.

Crude oil and liquid natural gas (LNG) inventories can be traded or used for production of oil products and/or electricity generation, respectively.

Intermediate products are those product streams that have been through at least one of the refining processes, but still need further treatment, processing or converting to be available for sale.

Biofuels mainly include ethanol and biodiesel inventories.

Maintenance materials, supplies, and others, other than raw material, are mainly comprised of production supplies and operating and consumption materials used in the operations of the Company, stated at the average purchase cost, not exceeding replacement cost.

Net realizable value is the estimated selling price of inventory in the ordinary course of business, less estimated cost of completion and estimated expenses to complete its sale.

The amounts presented in the categories above include imports in transit, which are stated at the identified cost.

3.5.       Investments in other companies

An associate is an entity over which the Company has significant influence. Significant influence is the power to participate in the financial and operating policy decisions of the investee but is not control or joint control over those polices.

A joint arrangement is an arrangement over which two or more parties have joint control. A joint arrangement is classified either as a joint operation or as a joint venture depending on the rights and obligations of the parties to the arrangement.

In a joint operation the parties have rights to the assets, and obligations for the liabilities, relating to the arrangement and in a joint venture, the parties have rights to the net assets of the arrangement.

Profit or loss, assets and liabilities related to joint ventures and associates are accounted for by the equity method.

In a joint operation the Company recognizes the amount of its assets, liabilities and related income and expenses. In addition, the Company recognizes its share of the sales revenue and expenses and the joint assets and joint liabilities.

3.6.       Business combinations and goodwill

Acquisitions of businesses are accounted for using the acquisition method when control is obtained. Combinations of entities under common control are not accounted for as business combinations.

The acquisition method requires that the identifiable assets acquired and the liabilities assumed be measured at the acquisition-date fair value. Amounts paid in excess of the fair value are recognized as goodwill. In the case of a bargain purchase, a gain is recognized in profit or loss when the acquisition cost is lower than the acquisition-date fair value of the net assets acquired.

Changes in ownership interest in subsidiaries that do not result in loss of control of the subsidiary are equity transactions. Any excess of the amounts paid/received over the carrying value of the ownership interest acquired/disposed is recognized in shareholders’ equity as an additional paid-in capital.

Goodwill arising from investments in associates and joint ventures without change of control is accounted for as part of these investments. It is measured by the excess of the consideration transferred over the interest in the fair value of the net assets.

3.7.       Oil and Gas exploration and development expenditures

The costs incurred in connection with the exploration, appraisal, development and production of oil and gas are accounted for using the successful efforts method of accounting, as set out below:

-Costs related to geological and geophysical activities are expensed when incurred.

-Amounts paid for obtaining concessions for exploration of oil and natural gas (capitalized acquisition costs) are initially capitalized.

-Costs directly associated with exploratory wells pending determination of proved reserves are capitalized within property, plant and equipment. Exploratory wells that have found oil and gas reserves, but those reserves cannot be classified as proved, continue to be capitalized if the well has found a sufficient quantity of reserves to justify its completion as a producing well and progress on assessing the reserves and the economic and operating viability of the project is under way. An internal commission of technical executives of Petrobras reviews these conditions monthly for each well, by analysis of geoscience and engineering data, existing economic conditions, operating methods and government regulations.

-Costs related to exploratory wells drilled in areas of unproved reserves are expensed when determined to be dry or non-economical (did not encounter potentially economic oil and gas quantities).

-Costs related to the construction, installation and completion of infrastructure facilities, such as platforms, pipelines, drilling of development wells and other related costs incurred in connection with the development of proved reserve areas and successful exploratory wells are capitalized within property, plant and equipment.

3.8.       Property, plant and equipment

Property, plant and equipment are measured at the cost to acquire or construct, including all costs necessary to bring the asset to working condition for its intended use, adjusted during hyperinflationary periods, as well as by the present value of the estimated cost of dismantling and removing the asset and restoring the site and reduced by accumulated depreciation and impairment losses.

Expenditures on major maintenance of industrial units and vessels are capitalized if the recognition criteria are met. Expenditures comprise: replacement of certain assets or parts of assets, equipment assembly services, as well as other related costs. Such maintenance occurs, on average, every four years. Capitalized expenditures are depreciated on a straight line basis based on the estimated time of the maintenance cycle.

General and specific borrowing costs directly attributable to the acquisition or construction of qualifying assets are capitalized as part of the costs of these assets. General borrowing costs are capitalized based on the Company’s weighted average of the cost of borrowings outstanding applied over the balance of assets under construction. Borrowing costs are amortized during the useful life or by applying the unit-of-production method to the related assets.

Except for assets with a useful life shorter than the life of the field, which are depreciated based on the straight line method, depreciation, depletion and amortization of proved oil and gas producing properties are accounted for pursuant to the unit-of-production method, as set out below:

i) Depreciation (amortization) of oil and gas producing properties, including related equipment and facilities is computed based on a unit-of-production basis over the proved developed oil and gas reserves, applied on a field by field basis; and

ii) Amortization of amounts paid for obtaining concessions for exploration of oil and natural gas of producing properties, such as signature bonus (capitalized acquisition costs) is recognized using the unit-of-production method, computed based on the units of production over the total proved oil and gas reserves, applied on a field by field basis.

Except for land, which is not depreciated, other property, plant and equipment is depreciated on a straight line basis. See note 12 for further information about the estimated useful life by class of assets.

3.9.       Intangible assets

Intangible assets are measured at the acquisition cost, less accumulated amortization and impairment losses and comprise rights and concessions, including the signature bonus paid for obtaining concessions for exploration of oil and natural gas (capitalized acquisition costs) and the Assignment Agreement, referring to the right to carry out prospection and drilling activities for oil, natural gas and other liquid hydrocarbons located in blocks in the pre-salt area (“Cessão Onerosa”); public service concessions; trademarks; patents; software and goodwill.

Signature bonuses paid for obtaining concessions for exploration of oil and natural gas and amounts related to the Assignment Agreement are initially capitalized within intangible assets and are transferred to property, plant and equipment upon the declaration of commerciality.

Signature bonuses and amounts related to the Assignment Agreement are not amortized until they are transferred to property, plant and equipment. Intangible assets with a finite useful life, other than amounts paid for obtaining concessions for exploration of oil and natural gas of producing properties, are amortized over the useful life of the asset on a straight-line basis.

Internally-generated intangible assets are not capitalized and are expensed as incurred, except for development costs that meet the recognition criteria related to completion and use of assets, probable future economic benefits, and others.

Intangible assets with an indefinite useful life are not amortized but are tested annually for impairment considering individual assets or cash-generating units. Their useful lives are reviewed annually to determine whether events and circumstances continue to support an indefinite useful life assessment for those assets. If they do not, the change in the useful life assessment from indefinite to finite is accounted for on a prospective basis.

3.10.   Impairment 

Property, plant and equipment and intangible assets with definite useful lives are tested for impairment when there is an indication that the carrying amount may not be recoverable. Assets related to exploration and development of oil and gas and assets that have indefinite useful lives, such as goodwill acquired in business combinations are tested for impairment annually, irrespective of whether there is any indication of impairment.

The impairment test comprises a comparison of the carrying amount of an individual asset or a cash-generating unit with its recoverable amount. Whenever the recoverable amount of the unit is less than the carrying amount of the unit, an impairment loss is recognized to reduce the carrying amount to the recoverable amount. The recoverable amount of an asset or a cash-generating unit is the higher of its fair value less costs of disposal and its value in use. Considering the specificity of the Company’s assets, value in use is generally used by the Company for impairment testing purposes, except when specifically indicated.

Value in use is estimated based on the present value of the risk-adjusted (for specific risks) future cash flows expected to arise from the continuing use of an asset or cash-generating unit (based on assumptions that represent the Company’s best estimates), discounted at a pre-tax discount rate. This rate is obtained from the Company’s weighted average cost of capital post-tax (WACC). Cash flow projections are mainly based on the following assumptions: prices based on the Company’s most recent strategic plan; production curves associated with existing projects in the Company's portfolio, operating costs reflecting current market conditions, and investments required for carrying out the projects.

For the impairment test, assets are grouped at the smallest identifiable group that generates largely independent cash inflows from other assets or groups of assets (the cash-generating unit). Assets related to exploration and development of oil and gas are tested annually for impairment on a field by field basis.

Reversal of previously recognized impairment losses is permitted for assets other than goodwill.

3.11.   Leases 

Leases that transfer substantially all the risks and rewards incidental to ownership of the leased item are recognized as finance leases.

For finance leases, when the Company is the lessee, assets and liabilities are recognized at amounts equal to the fair value of the lease property or, if lower, to the present value of the minimum lease payments, each determined at the inception of the lease.

Capitalized lease assets are depreciated on a systematic basis consistent with the depreciation policy the Company adopts for property, plant and equipment that are owned. Where there is no reasonable certainty that the Company will obtain ownership by the end of the lease term, capitalized lease assets are depreciated over the shorter of the lease term or the estimated useful life of the asset.

When the Company is the lessor, a receivable is recognized at the amount of the net investment in the lease.

If a lease does not transfer all the risks and rewards, it is classified as an operating lease. Operating leases are recognized as expenses over the period of the lease.

Contingent rents are recognized as expenses when incurred.

3.12.   Assets classified as held for sale

Assets, disposal groups and liabilities directly associated with those assets are classified as held for sale if their carrying amounts will principally be recovered through a sale transaction rather than through continuing use. This condition is regarded as met only when the sale is approved by the Company’s management and the asset or disposal group is available for immediate sale in its present condition subject only to terms that are usual and customary for sales of such assets. In addition, the sale should be expected to qualify for recognition as a completed sale within one year from the date of classification as held for sale.

However, events or circumstances may extend past the period to complete the sale by more than one year if the delay is caused by events or circumstances beyond the entity’s control and there is sufficient evidence of the commitment to the plan to sell the asset.

Assets (or disposal groups) classified as held for sale and the associated liabilities are measured at the lower of their carrying amount and fair value less costs to sell. Assets and liabilities are presented separately in the statement of financial position.

3.13.   Decommissioning costs

Decommissioning costs are future obligations to perform environmental restoration, dismantle and remove a facility as it terminates operations due to the exhaustion of the area or economic conditions.

Costs related to the abandonment and dismantling of areas are recognized as part of the cost of an asset (associated with the obligation) based on the present value of the expected future cash outflows, discounted at a risk-adjusted rate when a future legal obligation exists and can be reliably measured.

A corresponding provision is recognized as a liability. Unwinding of the discount is recognized as a financial expense, when incurred. The asset is depreciated similarly to property, plant and equipment, based on the class of the asset.

Future decommissioning costs for oil and natural gas producing properties are initially recognized when a field is declared to be commercial, on a field by field basis, and are revised annually.

Decommissioning costs related to proved developed oil and gas reserves are depreciated by applying the unit-of-production method, computed based on a unit-of-production basis over the proved developed oil and gas reserves, applied on a field by field basis.

3.14.   Provisions and contingent liabilities

Provisions are recognized when there is a present obligation (legal or constructive) that arises from past events and for which it is probable that an outflow of resources embodying economic benefits will be required to settle the obligation, which must be reasonably estimable.

Contingent liabilities for which the likelihood of loss is considered to be possible or which are not reasonably estimable are not recognized in the financial statements but are disclosed unless the expected outflow of resources embodying economic benefits is considered remote.

3.15.   Income taxes

Income tax expense for the period comprises current and deferred tax.

The Company has adopted the Transition Tax Regime in Brazil (RTT) in order to exclude potential tax impacts from the adoption of IFRS in the determination of taxable profit. RTT is based on Brazilian tax/corporate regulations as of December 31, 2007.

a)    Current income taxes

The tax currently payable is computed based on taxable profit for the year, calculated using tax rates that have been enacted or substantively enacted by the end of the reporting period.

Taxable profit differs from accounting profit due to certain adjustments required by tax regulations.

b)   Deferred income taxes

Deferred tax is recognized on temporary differences between the tax base of an asset or liability and its carrying amount. Deferred income tax liabilities are generally recognized for all taxable temporary differences. Deferred tax assets are generally recognized for all temporary deductible differences to the extent that it is probable that taxable profit will be available against which those deductible temporary differences can be utilized.

Deferred tax assets and liabilities shall be measured at the tax rates that are expected to apply to the period when the asset is realized or the liability is settled, based on tax rates (and tax laws) that have been enacted or substantively enacted by the end of the reporting period.

3.16.   Employee benefits (Post-Employment)

Actuarial commitments related to post-employment defined benefit plans and health-care plans are recognized as liabilities in the statement of financial position based on actuarial calculations which are revised annually by an independent actuary, using the projected unit credit method, net of the fair value of plan assets, when applicable, out of which the obligations are to be directly settled.

Under the projected credit unit method, each period of service gives rise to an additional unit of benefit entitlement and each unit is measured separately to determine the final obligation.

Changes in the net defined benefit liability (asset) are recognized when they occur, as follows: i) service cost and net interest cost in profit or loss; and ii) remeasurements in other comprehensive income.

Service cost comprises: (i) current service cost, which is the increase in the present value of the defined benefit obligation resulting from employee service in the current period; (ii) past service cost, which is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting from a plan amendment (the introduction, changes to, or withdraw of a defined benefit plan) or a curtailment (a significant reduction by the entity in the number of employees covered by a plan); and (iii) any gain or loss on settlement.

Net interest on the net defined benefit liability (asset) is the change during the period in the net  defined benefit liability (asset) that arises from the passage of time.

Remeasurements of the net defined benefit liability (asset), recognized in other comprehensive income, comprise: (i) actuarial gains and losses; (ii) the return on plan assets, excluding amounts included in net interest on the net defined benefit liability (asset); and (iii) any change in the effect of the asset ceiling, excluding amounts included in net interest on the net defined benefit liability (asset).

Actuarial assumptions include demographical and financial assumptions, medical costs estimates, as well as historical data related to expenses incurred and employee contributions.

The Company also contributes amounts to defined contribution plans, that are expensed when incurred and are computed based on a percentage over salaries.

3.17.   Share Capital and Stockholders’ Compensation

Share capital comprises common shares and preferred shares. Incremental costs directly attributable to the issue of new shares are classified as additional paid in capital and shown (net of tax) in shareholders’ equity as a deduction from the proceeds.

Preferred shares have priority on returns of capital and dividends, which are based on the higher amount of 3% over the net book value of shareholders equity for preferred shares, or 5% of the share capital for preferred shares. Preferred shares do not grant any voting rights; are non-convertible into common shares and participate under the same terms as common shares, in capital increases resulting from the capitalization of reserves and profits.

Dividend distribution comprises dividends and interest on capital determined in accordance with the limits defined in the Company’s bylaws.

Interest on capital is a form of dividend distribution which is deductible for tax purposes in Brazil.  Tax benefits from the deduction of interest on capital are recognized in profit or loss.

3.18.   Government grants

A government grant is recognized when there is reasonable assurance that the grant will be received and the Company will comply with the conditions attached to the grant.

Government grants are recognized as revenue in profit or loss on a systematic basis over the periods in which the Company recognizes as expenses the related costs for which the grants are intended to compensate. Government grants related to assets are initially recognized as deferred income and thereafter are transferred to profit or loss over the useful life of the asset on a straight-line basis.

3.19.   Recognition of revenue, costs and expenses

Revenue is recognized when it is probable that the economic benefits associated with the transaction will flow to the Company and the amount of revenue and the costs incurred or to be incurred in the transaction can be reliably measured. Revenue is measured at the fair value of the consideration received or receivable for products sold and services provided in the normal course of business, net of returns, discounts and sales taxes.

Revenues from the sale of crude oil and oil products, petrochemical products, natural gas, biofuels and other related products are recognized when the Company retains neither continuing managerial involvement nor effective control over the products sold and the significant risks and rewards of ownership have been transferred to the customer, which is usually when legal title passes to the customer, pursuant to the terms of the sales contract. Sales revenues from freight and other services provided are recognized based on the stage of completion of the transaction.

Finance income and expense mainly comprise interest income on financial investments and government bonds, interest expense on debt, gains and losses on marketable securities measured at fair value, as well as net foreign exchange and inflation indexation charges. Finance expense does not include borrowing costs directly attributable to the construction of assets that necessarily take a substantial period of time to become operational, which are capitalized as part of the costs of these assets. 

Revenue, costs and expenses are recognized on the accrual basis.

4.            Critical accounting policies: key estimates and judgments

The preparation of the consolidated financial information requires the use of estimates and judgments for certain transactions and their impacts on assets, liabilities, revenues and expenses. The assumptions are based on past transactions and other relevant information and are periodically reviewed by Management, although the actual results could differ from these estimates.

Information about those areas that require the most judgment or involve a higher degree of complexity in the application of the accounting practices and that could materially affect the Company’s financial condition and results of operations are set out following.

4.1.       Oil and gas reserves

Oil and gas reserves are estimated based on economic, geological and engineering information, such as well logs, pressure data and fluid sample core data and are used as the basis for calculating unit-of-production depreciation rates and for impairment assessments.

These estimates require the application of judgment and are reviewed at least annually and on an interim basis if objective evidence of significant changes becomes available based on a re-evaluation of already available geological, reservoir or production data and  new geological, reservoir or production data, as well as changes in prices and costs that are used in the estimation of reserves. Revisions can also result from significant changes in development strategy or production equipment and facility capacity.

Oil and gas reserves include both proved and unproved reserves. According to the definitions prescribed by the SEC proved oil and gas reserves are the estimated quantities which geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions (i.e., prices and costs as of the date the estimate is made). Proved reserves can be further subdivided into developed and undeveloped reserves.

Proved developed oil and gas reserves are reserves that can be expected to be recovered through existing wells with existing equipment and operating methods and represented 59.9% of the total proved reserves of the Company as of December 31, 2013.

Although the Company is reasonably certain that proved reserves will be produced, the timing and amount recovered can be affected by a number of factors including completion of development projects, reservoir performance, regulatory aspects and significant changes in long-term oil and gas price levels.

Other information about reserves is presented as supplementary information.

a)             Oil and gas reserves: depreciation, amortization and depletion

Depreciation, amortization and depletion are measured based on estimates of reserves prepared by the Company’s technicians in a manner consistent with SEC definitions. Revisions to the Company’s proved developed and undeveloped reserves impact prospectively the amounts of depreciation and depletion recognized in profit or loss and the carrying amounts of oil and gas properties assets.

Therefore all other variables being equal, a decrease in estimated proved reserves would increase, prospectively, depreciation expense, while an increase in reserves would reduce depreciation.

See notes 3.8 and 12 for more detailed information about depreciation, amortization and depletion.

b)            Oil and gas reserves: impairment testing

The Company assesses the recoverability of the carrying amounts of oil and gas exploration and development assets based on their value in use, as defined in note 3.10. In general, analyses are based on proved reserves and probable reserves. The percentage of probable reserves that the Company includes in cash flows does not exceed the Company’s past success ratios in developing probable reserves.

The Company performs asset valuation analyses on an ongoing basis as a part of its management program by reviewing the recoverability of their carrying amounts based on estimated volumes of oil and gas reserves, as well as estimated future oil and natural gas prices.

The Company, typically, does not view temporarily low oil prices as a trigger event for conducting impairment tests. The markets for crude oil and natural gas have a history of significant price volatility and although prices will occasionally drop precipitously, industry prices over the long term will continue to be driven by market supply and demand fundamentals. Accordingly, any impairment tests that the Company performs make use of its long-term price assumptions used in its planning and budgeting processes and its capital investment decisions, which are considered reasonable estimates, given market indicators and experience.

Lower future oil and gas prices, considered long-term trends, as well as negative impacts of significant changes in reserve volumes, production curve expectations, lifting costs or discount rates could trigger the need for impairment assessment.

See notes 3.8, 12 and 14 for more detailed information about oil and natural gas exploration and development assets.

4.2.       Identifying cash-generating units for impairment testing

Identifying cash-generating units (CGU’s) requires management assumptions and judgment, based on the Company’s business and management model, and may significantly impact the results of the impairment tests of long-lived assets. The assumptions set out following have been consistently applied by the Company:

-       Exploration and Production CGU’s: producing properties: oil and natural gas producing properties comprised of a group of exploration and development assets.

-       Downstream CGU’s: i) Refining assets CGU: a single CGU comprised of all refineries and associated assets, terminals and pipelines, as well as logistics assets operated by Transpetro. This CGU was identified based on the concept of integrated optimization and performance management, which focus on the global performance of the CGU, allowing a shift of margins from one refinery to another. Pipelines and terminals complement and are an interdependent portion of the refining assets, to supply the market; ii) Petrochemical CGU: petrochemical plants from PetroquímicaSuape and Citepe; iii) Transportation CGU: the transportation CGU is comprised of the vessel fleet of Transpetro.

-       Gas & Power CGU’s: i) Natural gas CGU: comprised of natural gas pipelines, natural gas processing plants and fertilizers and nitrogen products plants; and ii) Power CGU: thermoelectric power generation plants.

-       Distribution CGU: comprised of the distribution assets related to the operations of Petrobras Distribuidora S.A. and Liquigás Distribuidora S.A..

-       Biofuels CGU’s: i) Biodiesel CGU: group of assets that compose the biodiesel plants. The CGU reflects an integrated view of the biodiesel plants and is defined based on the production planning and operation process, considering domestic market conditions, the capacity of each plant, as well as the results of biofuels auctions and raw materials supply; ii) Ethanol CGU: comprised of investments in associates and joint ventures in the ethanol sector.

-       International CGU: i) International Exploration and production CGU: oil and natural gas producing properties comprised of a group of exploration and development assets outside of Brazil; ii) Other operations of the international business segment: smallest identifiable group of assets that generates largely independent cash inflows.

Investments in associates and joint ventures including goodwill are individually tested for impairment.

See notes 3.10 and 14 for more detailed information about impairment.

4.3.         Pension and other post-retirement benefits

The actuarial obligations and net expenses related to defined benefit pension and health care post-retirement plans are computed based on several financial and demographic assumptions, of which the most significant are:

-       Discount rate: comprises the projected future inflation rate curve and an equivalent real interest rate that matches the duration of the pension and health care obligations with the yield curve of long-term Brazilian government bonds; and

-       Medical costs: comprise several projected annual growth rates based on per capita health care benefits paid for the last five years, which are used to set a starting point for the curve, which decreases gradually in 30 years, converging to a general inflation index.

These and other estimates are reviewed at least annually and may differ materially from actual results due to changing market and financial conditions, as well as actual results of actuarial assumptions.

The sensitivity analysis of discount rates and changes in medical costs as well as additional information about actuarial assumptions are set out in note 22.

4.4.       Estimates related to contingencies and legal proceedings

The Company is a defendant in numerous legal proceedings involving tax, civil, labor, corporate and environmental issues arising from the normal course of its business for which estimates are made by Petrobras of the amounts of the obligations and the probability that an outflow of resources will be required, based on legal advice and management’s best estimates.

See note 31 for more detailed information about contingencies and legal proceedings.

4.5.       Dismantling of areas and environmental remediation

The Company has legal and constructive obligations to remove equipment and restore onshore and offshore areas at the end of operations at production sites. Its most significant asset removal obligations involve removal and disposal of offshore oil and gas production facilities in Brazil and abroad. Estimates of costs for future environmental cleanup and remediation activities are based on current information about costs and expected plans for remediation.

These estimates require performing complex calculations that involve significant judgment because the obligations are long-term; the contracts and regulation have subjective descriptions of what removal and remediation practices and criteria will have to be met when the events actually occur; and asset removal technologies and costs are constantly changing, along with political, environmental, safety and public relations considerations.

The Company is constantly conducting studies to incorporate technologies and procedures seeking to optimize the operations of abandonment, considering industry best practices. Notwithstanding, the timing and amounts of future cash flows are subject to significant uncertainty.

See notes 3.14 and 20 for more detailed information about the decommissioning provisions.

4.6.       Derivative financial instruments

Derivative financial instruments are measured at fair value in the financial statements. Fair value measurement requires judgment related to the availability of identical or similar assets quoted in active markets or otherwise the use of alternate measurement models that can become increasingly complex and depend on the use of estimates such as future prices, long-term interest rates and inflation indices.

See notes 3.3.5 and 34 for more detailed information about derivative financial instruments.

4.7.       Hedge accounting

Identifying hedging relationships between hedged items and hedging instruments (derivative financial instruments and long-term debt) requires critical judgments related to the existence of the hedging relationship and its effectiveness. In addition, the Company continuously assesses the alignment between the hedging relationships identified and the objectives and strategy of its risk management policy.

See notes 3.3.6 and 34 for more detailed information about hedge accounting.

5.            New standards and interpretations

a)             IASB – International Accounting Standards Board

During 2013, new standards and amendments to standards and interpretations were issued by the International Accounting Standards Board (IASB) effective for annual periods beginning on January 1, 2013, none of which had a significant effect on the consolidated financial statements for 2013, except for amendments to IAS 19 - Employee Benefits (CPC 33 - R1):

·      The effects of the adoption of amendments to IAS 19 – “Employee benefits” are set out in note 2.3.

·      Amendment to IAS 1 - ‘Presentation of financial statements’, regarding other comprehensive income requires for entities to group items presented in ‘other comprehensive income’ (OCI) on the basis of whether they are potentially recycled to profit or loss subsequently.

·      IFRS 10 "Consolidated Financial Statements" - defines principles and requirements for the preparation and presentation of consolidated financial statements when an entity controls one or more entities. Establishes the concept of control as the basis for consolidation and sets out how to apply the principle of control to identify whether an investor controls an investee and therefore must consolidate the investee.

·      IFRS 11 - “Joint Arrangements” - establishes principles for disclosure of financial statements of entities that are parties of joint agreements. There are two types of joint arrangement: joint operations and joint ventures. Joint operations arise where a joint operator has rights to the assets and obligations relating to the arrangement and hence accounts for its interest in assets, liabilities, revenue and expenses. Joint ventures arise where the joint operator has rights to the net assets of the arrangement and hence equity accounts for its interest. Proportional consolidation of joint ventures is no longer allowed.

·      IFRS 12 - “Disclosure of Interests in Other Entities” - Consolidates all the requirements of disclosures that an entity should carry out when participating in one or more entities, including joint arrangements, associates and structured entities.

·      IFRS 13 - “Fair Value Measurement” – provides a precise definition of fair value, as well as a source of fair value measurement and disclosure. Does not extend the use of fair value accounting but provides guidance on how it should be applied where its use is already required or permitted by other standards.

·      Amendments to IFRS 7- “Financial Instruments: Disclosures” – regarding offsetting financial assets and financial liabilities - establishes disclosure requirements for compensation agreements of financial assets and liabilities.

·      IAS 28 (revised 2011) - "Associates and joint ventures" - Includes the requirements for joint ventures, as well as associates, to be accounted for by the equity method, following the issue of IFRS 11.

A number of new standards and amendments to standards and interpretations issued by the International Accounting Standards Board (IASB) are not effective for 2013, as set out below. They have not been adopted in preparing these financial statements at December 31, 2013.