1.1 Sales revenue in respect of Crude Oil is based on the pricing
 formula agreed with the customers for the period from 01.04.2002 to
 31.03.2004. Pending finalization of fresh Memorandum of Understanding
 (MOU)/Crude Oil Sale Agreement (COSA) with the customers, the same
 pricing formula has been provisionally adopted from 01.04.2004 onwards.
 However, for Crude Oil produced in Assam, benchmark price revised by
 MoP&NG w.e.f 01.04.2008 has been adopted. Adjustments, if any, on
 account of this shall be carried out on finalization of agreements/
 receipt of Government directives. However, the Company does not
 envisage any material impact on current year’s results on finalization.
 
 1.2 Sales revenue of Natural Gas under Administrative Price Mechanism
 (APM) was based on the gas prices fixed on provisional basis as per
 directives dated 20.06.2005 and 05.06.2006 of MoP&NG, GoI upto
 31.052010 GoI, vide letter dated 31.05.2010, decided to fix the
 producer price of APM gas produced by National Oil Companies (NOCs) at
 US$ 4.2/mmbtu inclusive of royalty effective from 01.06 2010. For APM
 consumers except for consumers in North Eastern states, the consumer
 price would be same as producer price, i.e. US$ 4.2/ mmbtu inclusive of
 royalty. For APM consumers in North-East, consumer price is 60% of the
 producer price, i.e., US$ 2.52/ mmbtu inclusive of royalty. In
 North-East, the difference between producer price and consumer price is
 paid to the company through GoI Budget.
 
 2 The company is supplying Natural Gas to GAIL (India) Limited (GAIL)
 which also purchases gas from other sources and sells to APM and non
 APM consumers. In case GAIL generates surplus in Gas Pool Account
 during the financial year, same is transferred to ONGC/ Oil India
 Limited (OIL) at the end of financial year in accordance with their
 contribution. Accordingly, an amount ofRs.21,914.90 million (Previous
 yeaW4,415.79 million) is accounted as Surplus from Gas Pool Account
 under ‘Other Income’ in Schedule -18.
 
 3 In Ravva Joint Venture, the demand towards additional profit
 petroleum raised by GoI, based on the decision of the Malaysian High
 Court, was disputed by the Operator M/s Cairn Energy India Limited, due
 to difference in interpretation of provision of Production Sharing
 Contract (PSC) in respect of computation of Post Tax Rate of Return
 (PTRR). The Company is not a party to the dispute but agreed to abide
 by the decision applicable to the Operator. As the dispute between the
 Operator and GoI was not resolved, the Company made a provision in
 Financial Year 2008-09 amounting to Rs. 5,771.14 million (USD 113.82
 million) on account of additional profit petroleum and Rs. 2,829.86
 million (USD 54.88 Million) towards interest thereon totaling
 toRs.8,601.00 million (USD 168.70 Million) as an abundant precaution. GoI
 had recovered such amount subsequently.
 
 The appellate authority of Honorable Malaysian High Court of Kuala
 Lumpur, Malaysia had set aside the decision of the Malaysian High Court
 and the decision of arbitral tribunal in favour of Operator was
 restored on 15th September 2009. GoI has filed an appeal in the Federal
 Court of Malaysia against such restoration.
 
 Pending final outcome of this appeal, the provision is maintained as on
 31st March, 2011 amounting toRs.5,090.17 Million (USD 113.82 Million) on
 account of additional Profit Petroleum and Rs. 2,415.83 Million (USD
 54.02 Million) towards interest thereon totaling toRs. 7,506.00 million
 (USD 167.84 million) as per the demand of DGH after reversal for
 interest ofRs. 103.42 million (USD 2 31 million) against provision of
 interest Rs. 65.41 million (USD 1.45 million) in 2009-10 and adjustment
 of exchange gain ofRs.69.78 million (Previous yearRs.987.20 million).
 
 4 The Company acquired 90% Participating Interest in Exploration Block
 KG-DWN-98/2 from M/s Cairn Energy India Ltd. in 2004-05 for a lump sum
 consideration ofRs.3,711.22 million which was capitalized under
 Exploratory Wells in Progress Accounting Policy No.  6.3. Subsequent
 exploratory drilling costs of wells in this block were capitalized as
 Exploratory Wells in Progress.  Initial-in-Place-Reserves have been
 established in this block and a conceptual development plan as part of
 the proposal for Declaration of Commerciality has been submitted to
 Management Committee (MC) for review on 15 07.2010.  However, the
 Company as an abundant precaution made a provision ofRs. 6,104.80
 million, k 2,360.39 million and Rs. 918.48 million in respect of above
 costs in 2007-08, 2008-09 and 2009-10 respectively. Since there is no
 significant change in status of this block during the current year, the
 expenditure amounting to Rs. 17.67 million on the wells completed upto
 31st March 2009, being more than two years old is provided for in the
 current year.
 
 5 As per the Production Sharing Contracts signed by the Company with
 the GoI, the Company is required to complete Minimum Work Programme
 (MWP) within stipulated time. In case of delay in completion of the
 MWP, Liquidated Damages (LD) is payable for extension of time to
 complete without completing the MWP, the estimated cost of completing
 balance work programme is pl equired to be paid to the GoI. LD amounting 
 to Rs. 113.72 million (Previous yearRs.(-)78.41 million) net of 
 reversal and cost of unfinished MWPRs. 919.81 million (Previous year
 Rs.3,148.58 million) paid/payable to the GoI is included in survey and 
 wells written off expenditure in Sched
 
 6 The Finance (No.2) Act, 2009, has specified the definition of
 “undertaking” for the purpose of claiming tax holiday under section
 80-IB9) of Income Tax Act, 1961 to be ‘all blocks licensed under a
 single contract’ retrospectively whereas the company had earlier
 considered each ‘Well’ as an undertaking. Since the amendment still
 requires clarity on various issues and also considering the advice of
 legal experts, the company continued to make provision for tax without
 considering the benefit u/s 80-IB(9).
 
 7 Capital Works in Progress (CWIP) includes an amount of Rs. 7841.69
 million in respect of C2 C3 plant which is mechanically complete and
 will be capitalized on completion of test run.
 
 8 During the year, the Oil Marketing Companies, nominees of GoI had
 recovered Rs. 1,432.34 million (USD 32.07 million) ONGC’s share as per
 directives of GoI in respect Jointly Controlled Assets - Panna Mukta &
 Tapti. The recovery is towards certain observations raised by auditors
 appointed by Director General Hydrocarbon (DGH) under Production
 Sharing Contract for the period 2002-03 to 2005-06 in respect of cost
 and profit petroleum share payable to GoI. BGEPIL along with RIL
 (“Claimants”) have served a notice of arbitration on the GOI in respect
 of dispute differences and claims arisen in connection with the term of
 Panna, Mukta & Tapti PSCs. Since the company is not a party to the
 arbitration proceedings, it has requested MoP&NG that in case of an
 arbitral award, the same be made applicable to ONGC also, as a
 constituent of contractor for both the PSCs. Pending final arbitral
 award, the same has been shown as ‘Receivable from GoI’.
 
 9 The Company has been charging depreciation on all Trunk Pipelines
 and Onshore Flow Lines (assets below ground) @ 100% based on technical
 assessment by the management.
 
 10 The Company has a system of physical verification of Inventory,
 Fixed Assets and Capital Stores in a phased manner at regular
 intervals. Adjustment of differences, if any, is carried out on
 completion of onciliation.
 
 11 Some balances of Debtors, Creditors and Loans & Advances are subject
 to confirmation/ reconciliation. Adjustments, if any, will be accounted
 for on confirmation/ reconciliation of the same, which will not have a
 material impact.
 
 12 Disclosure under the Revised Accounting Standard -15 on “Employee
 Benefits”
 
 12.1 Brief Description: A general description of the type of Defined
 Benefit Plans is as follows:
 
 12.1.1 Earned Leave (EL) Benefit
 
 Accrual - 30 days per year
 
 Encashment while in service - 75% of Earned Leave balance subject to a
 maximum of 90 days per calendar year
 
 Encashment on retirement - maximum 300 days
 
 12.1.2 Good Health Reward (Half pay leave)
 
 Accrual - 20 days per year
 
 Encashment while in service - Nil
 
 Encashment on retirement - 50% of Half Pay Leave balance.
 
 12.1.3 Gratuity
 
 15 days salary for every completed year of service. Vesting period is 5
 years and the payment is restricted toRs. 1.00 million.
 
 12.1.4 Post Retirement Medical Benefits -
 
 Upon payment of one time prescribed contribution by the employees, full
 medical benefits on superannuation and on voluntary retirement subject
 to the completion of minimum 20 years of service and 50 years of age.
 
 12.1.5 Terminal Benefits
 
 At the time of superannuation, employees are entitled to settle at a
 place of their choice and they are eligible for Transfer Travelling
 Allowance. Employees are gifted a silver plaque also, depending upon
 their level.
 
 13.0 The amounts included in the fair value of plan assets of gratuity
 fund in respect of Reporting Enterprise’s own financial instruments and
 any property occupied by, or other assets used by the reporting
 enterprise are X Nil (Previous Year Nil)
 
 14 Disclosure under Accounting Standard-16 on “Borrowing Costs”
 
 The Company did not incur any borrowing cost for any qualifying asset.
 No borrowing cost is capitalized during the year (previous year Nil).
 
 15 Disclosure under Accounting Standard -17 on “Segment Reporting”
 
 The segment information is presented under the notes to accounts of the
 Consolidated Financial Statements as required under the standard.
 
 16 Disclosure under Accounting Standard -18 on “Related Party
 Disclosure”
 
 16.1 Name of related parties and description of relationship:
 
 A) Joint Venture
 
 Ravva 
 
 CY-OS-90/1( PY3) 
 
 Panna, Mukta & Tapti
 
 CB-OS-2
 
 GK-OSJ-3
 
 RJ-ON-90/1
 
 RJ-ONN-2003/1
 
 PR-OSN-2004/1
 
 RJ-ON/6
 
 B) Jointly Controlled Entity
 
 ONGC Mangalore Petrochemicals Limited Petronet LNG Limited 
 
 ONGC Teri Biotech Limited
 
 Mangalore SEZ Limited
 
 ONGC Petro-additions Limited
 
 ONGC Tripura Power Co. Limited
 
 Dahej SEZ Limited
 
 17.2 Key Management Personnel:
 
 Whole-time Functional Directors:
 
 i)     Shri R.S. Sharma, Chairman and Managing Director up to 31.01.2011
 
 ii) Shri A.K. Hazarika holding additional charge of Chairman and
 Managing Director from 01.02.2011
 
 iii) Dr. A. K. Balyan up to 15.07.2010
 
 iv) Shri U. N. Bose
 
 v) Shri D.K. Pande up to 31.01.2011
 
 vi) Shri D.K.Sarraf
 
 vii) Shri Sudhir Vasudeva
 
 viii) Shri S.V Rao from 25.02.2011
 
 17 Disclosure under Accounting Standard - 19 on ‘Leases’
 
 The company has certain office/residential premises on Operating Lease
 which are cancellable by giving appropriate notice as per the
 respective agreements. During the year Rs. 749.63 million (Previous year
 Rs. 713.47 million) had been paid towards cancellable Operating Lease.
 
 Abbreviations:- BGEPIL- British Gas Exploration & Production India
 Ltd., BPRL-Bharat Petroleum Refinery Ltd., MBN- BMN Investment Ltd,
 CEIL-Cairn Energy India Ltd, CIL-Coal India Ltd., ENI- ENI India Ltd.,
 GAIL -Gail India Ltd., GSPC-Gujarat State Petroleum Corporation Ltd.
 HOEC- Hindustan Oil Exploration Co. Ltd., HPCL- Hindustan Petroleum
 Corporation Ltd, HOEC- Hindustan Oil Exploration Company Ltd., HMEL-
 HPCL-Mittal Energy Ltd., OIL -Oil India Ltd., IOC- Indian Oil
 Corporation Ltd., RIL- Reliance Industries Ltd , TPL-Tata Petrodyne
 Ltd. HEPI Hardy Exploration & Production (India) Inc., PIL- Petrocon
 India Ltd. ROPL-Ravva Oil (Singapore) Pte. Ltd CEIPL- Cairn Energy
 India Pty Ltd, CEHL- Cairn Energy Hydrocarbons Ltd, TIOL - Tullow India
 Operations Ltd, SRL - Suntera Resources Ltd. NTPC- National Thermal
 Power Corporation Ltd. AWEL-Adani welspur Exploration ltd, APGIC-Andra
 Pradesh Gas Infrastructure Corporation Ltd, PIBBV- Petrobras
 International Braspero BV, HEIBV-Hydro Oil & Energy India BV,
 ROPL-Ravva Oil (Sigapur) Ltd, HEPI-hrady Exploration & Production
 (India), PIL-Petrocon India Ltd.
 
 18.0 The financial statements of 128 (Previous year 117) out of 135
 (Previous year 124) JVs/NELP as per para no. 20.3 have been
 incorporated in the accounts to the extent of Company’s participating
 interest in assets, liabilities, income, expenditure and profit/(loss)
 before tax on the basis of statements certified in accordance with
 production sharing contract and the same has been adjusted for changes
 as per accounting policy No. 9.1 in Schedule-26.
 
 18.1 In respect of balance 7 (Previous year 7) JVs/NELP assets,
 liabilities, income and expenditure amounting to Rs. 47.51 Million
 (Previous year Rs. 69.80 Million), Rs. 782.66 million (Previous year Rs.
 143.98 million), Rs. 55.28 million (Previous year Rs. 152.55 million) and Rs.
 943.31 million (Previous year Rs. 812.85 million) respectively have been
 incorporated on the basis of uncertified statements prepared under the
 production sharing contracts and the same has been adjusted for changes
 as per accounting policy No. 9.1 in Schedule-26.
 
 18.2 The Company has given an undertaking to Power Finance
 Corporation (PFC), for an additional funding up to Rs. 2,234.00 million
 in respect of ONGC Tripura Power Co. Limited (OTPC) for cost overrun,
 if any.
 
 19 Disclosure under Accounting Standard - 28 on “Impairment of Assets”
 
 19.1 The Company is engaged mainly in the business of oil and gas
 exploration and production where each cost centre used for depreciation
 depletion) purposes is identified as independent Cash Generating Unit
 (CGU) for assessing the impairment in Producing Properties and fixed
 assets etc. on the basi of ‘value in use’. The Company''has tested all
 its CGUs for impairment as on 31 03.2011 by applying discount rates of
 17.16% (Previous year 17.31%) for Rupee transactions and 12.80 %
 (Previous year 13.07 %) for crude oil and value added products revenue
 measured in USD as on 31.03.2011.
 
 19.2 During the yearRs.1,534.73 million (Previous yearRs.553.45 million)
 was provided as an impairment loss. Out of this,Rs. 600.07 million
 (Previous year Rs. 553.45 million) has been provided as additional
 impairment in respect of Onshore CGUs - Jodhpur and Silchar. Balance of
 Rs. 319.37 million (Previous year Nil) represents impairment provided for
 Kuthalam Value added Plant due to uncertain marketability of its
 products and Rs. 615.29 (Previous year Nil) in respect of certain Onshore
 NELP Blocks due to adjustment of cost recovery from revenue and sharing
 of 100% royalty. Further, impairment loss to Rs.43.76 million (Previous
 yearRs.986.17 million) has been reversed in respect of Onshore Agartala
 and Offshore Ratna CGUs due to increased sale price and Rs. 138.77
 million (Previous year Nil) reversed in Jodhpur onshore due to transfer
 of assets to another CGU.
 
 20 Disclosures under Schedule VI to the Companies Act, 1956:
 
 20.1 Capital Commitment not provided for:
 
 20.1.1 Estimated amount of contracts remaining to be executed on
 capital account:- i) In respect of Company - Rs. 164,076.96 million
 (Previous year Rs. 184,507.29 million).  ii) In respect of Joint Ventures
 - Rs. 145.45 million (Previous year Rs. 194.47 million).
 
 20.1.2 Estimated amount of Minimum Work Programme (MWP) committed under
 various ‘Production Sharing Contracts’ with Government of India/
 Nominated Blocks:
 
 i) In respect of NELP blocks in which the Company has 100%
 participating interest – Rs. 22,558.90 million (Previous year Rs. 33,419.14
 million).
 
 ii) In respect Nominated Blocks Rs. 374.04 million (Previous year Rs.
 1,128.13 million).
 
 iii) In respect of NELP blocks in Joint Ventures - Rs. 92,560.05 million
 (Previous year Rs. 87,076.90 million).
 
 21. Contingent Liabilities:
 
 Claims against the Company/ disputed demands not acknowledged as debt:-
 ( Rs. in million)
 
 Particulars                      As at 31.03.2011    As at 31.03.2010
 
 I In respect of Company
 
 i.  Income Tax                        11,192.71         15,721.36
 
 ii.  Excise Duty                       4,924.11          2,372.44
 
 iii.  Custom Duty                      1,447.47          1,447.47
 
 iv.  Royalty                          19,484.60         18,849.79
 
 v.  Cess                                   6.57             12.76
 
 vi.  AP Mineral Bearing Lands 
      (Infrastructure) Cess             1,470.22          1,171.84
 
 vii.  Sales Tax                       29,465.43         20,135.52
 
 viii.  Service Tax                     1,039.92              -
 
 ix.  Octroi                               66.89             66.89
 
 x.  Specified Land Tax (Assam)         2,526.40          2,274.50
 
 xi.  Claims of contractors in 
      Arbitration / Court              34,199.71         21,262.90
 
 xii.  Others                          17,921.72         17,317.84
 
 Sub Total (A)                        123,745.75        100,633.31
 
 II In respect of Joint Ventures
 
 i.  Income Tax                             8.91              8.91
 
 ii.  Excise Duty                           -               322.42
 
 iii.  Custom Duty                      3,457.81          3,457.89
 
 iv.  Cess                                  -                10.64
 
 v.  Sales Tax and Service Tax          3,116.46          2,959.13
 
 vi.  Claims of contractors in Arbitration 
 / Court                                9,798.45            740.73
 
 vii.  Others                           4,542.00          4,898.72
 
 Sub Total (B)                         20,923.63         12,398.44
 
 TOTAL (A   B)                        144,669.38        113,031.75
 
 The above claims / demands are at various stages of appeal and in the
 opinion of the Company, the same are not tenable.
 
 21. Bank Guarantees given by the Company:
 
 i) Rs. 2,299.97 million (Previous year Rs. 3,426.38 million) including Rs.
 1,330.82 million (Previous year Rs. 1,142.37 million) for NELP Blocks
 where the Company has 100% participating interest.
 
 ii) In respect of Joint Ventures -Rs.5,898.49 million (Previous
 yearRs.7,082.46 million).
 
 iii) Out of total Bank Guarantees of ONGC an amount of Rs. 7,603.35
 million (Previous year Rs. 7,044.00 million) has been provided in respect
 of MWP committed under various ‘Production Sharing Contracts’ with
 Government of India and Nominated Blocks which is also included in
 Capital Commitments under para 23.1.2.
 
 22 Corporate Guarantees executed by the Company on behalf of its
 wholly owned subsidiary, ONGC Videsh Limited (OVL) and ONGC Nile Ganga
 BV (wholly owned subsidiary of OVL):
 
 23 Guarantees executed for financial obligations:
 
 i) Amount of GuaranteeRs.36,371.66 million (Previous yearRs.38,043.51
 million).  ii) Amount OutstandingRs.33,934.69 million (Previous
 yearRs.34,932.70 million).
 
 24. Performance Guarantees executed under the contacts:
 
 Guarantee in respect of Sakhalin Project in favour of Exxonneftgas
 Ltd., M/s. Roseneft-S, SMNG-S and RN-Astra towards performance of
 Company’s obligation under Joint Operating Agreement without any
 financial ceiling.
 
 25 Corporate Guarantees executed by the Company on behalf of its
 subsidiary, MRPL:
 
 i) Amount of GuaranteeRs.7,155.20 million (Previous yearRs.16,246.80
 million).  ii)Amount OutstandingRs.3,442.99 million (Previous
 yearRs.4,828.91 million).
 
 26 Uncalled liability on partly paid shares is Rs. 1,337.19 million
 (Previous Year Rs. 1,337.19 million) against which advance paid Rs.
 1,233.87 million (Previous YearRs. 1,233.87 million).
 
 27 During the financial year 2010-11, the company has incurred
 expenditure on scientific research in in-house R&D centres, which are
 in the process of being approved by the prescribed authority. The Gross
 expenditure incurred by various in house R&D institutes are as under:-
 
 Capital ExpenditureRs. 134.33 million
 
 Revenue ExpenditureRs. 4,329.93 million
 
 28 Previous year''s figures have been regrouped/ reclassified, wherever
 necessary, to confirm to current year''s classification.
 
 29 Figures in parenthesis as given in these Notes to Accounts relate to
 previous year.