Investor Presentaiton

Resources Segment (Gas and Oil E&P) Business Overview 1. Producing and selling crude oil/gas in Vietnam and Norway 2. Exploration and development of gas in Vietnam and other parts of Southeast Asia to shift to production of natural gas, which will become an important energy source in a decarbonized society Rights owned in oil/gas fields and sales Business Overview Production Oil/Gas Reserves Reserves *2,3 150 100 [million BOE] 2020 2021 *2 Total reserves in Norwegian oil fields and Vietnamese gas fields *3 Reserves reflect Idemitsu's rights and ownership ratios 50 destinations as of the end of March 2023 Rights owned Destination (%)*1 0 Sao Vang and Dai Nguyet gas field (Vietnam) 43.08 Asia Snorre 9.60 Tordis/Vigdis 9.60 Statfiord/East 4.80 Sygna 4.32 Norway Fram 15.00 Europe H-Nord 28.80 Byrding 15.00 Vega 3.30 Duva 30.00 *1 Companies in which Idemitsu owns rights Norway INPEX Idemitsu Norge AS Vietnam Idemitsu Gas Production (Vietnam) Co., Ltd. Reserve Estimation Standards 2022 •Idemitsu's reserves estimation is conducted based on PRMS (Petroleum Resources Management System) standards ⚫PRMS standards were established jointly by the Society of Petroleum Engineers (SPE), the World Petroleum Congress (WPC), the American Association of Petroleum Geologists (AAPG), and the Society of Petroleum Evaluation Engineers (SPEE) and is recognized as an international standard ⚫Reserves defined by PRMS standards are categorized into 1) proved, 2) probable, and 3) possible reserves. Idemitsu's reserves estimate is calculated as the total of proved and probable reserves (1+2) Proved Reserves ⚫The definition of proved reserves is recognized as the most conservative among definitions used widely in the petroleum/gas industry • Proved reserves are those quantities of petroleum/gas which, by analysis of geological and engineering data, can be estimated with reasonable certainty to be commercially recoverable under current economic conditions and operating methods ⚫When probabilistic methods are used, there should be at least a 90% probability of recovery that the quantities actually recovered will equal or exceed proved reserves Probable Reserves ⚫Probable reserves are those unproved reserves which analysis of geological and engineering data suggests are more likely than not to be recoverable •When probabilistic methods are used, there should be at least a 50% probability that the quantities actually recovered will equal or exceed the sum of estimated proved plus probable reserves idemitsu Copyright Idemitsu Kosan Co., Ltd. All Rights Reserved. 63 63

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