Announcement PDF Bass Oil Limited Level 5, 11-19 Bank Place, T + 61 3 9927 3000 admin@bassoil.com.au ACN: 008 694 817 Melbourne 3000 F + 61 3 9614 6533 www.bassoil.com.au Victoria, Australia Release date: 26 March 2026 Reserves and Contingent Resources at 31 December 2025 Bass Oil Limited (ASX:BAS) is an Australian-listed oil producer that holds a majority interest in eight permits in the Cooper Basin (Australia) including the 100% owned Worrior and Padulla oil fields and a 55% interest in a South Sumatra Basin (Indonesia) KSO. The Company is debt free and committed to creating value in both Australia and Indonesia. Highlights • Bass 2P (Proved plus Probable) oil Reserves of 0.796 million barrels, largely unchanged year-on-year. • Bass 2C Contingent Resources of 1.824 million barrels of oil equivalent, with key activities in the Cooper Basin in 2026 to commercialise these resources. Reserves Bass Oil Limited (ASX:BAS) has completed the annual reserves review for its Australian and Indonesian assets (figures 1 and 2). The Company’s 2P oil reserves at 31 December 2025 are assessed to be 0.796 million barrels, largely unchanged year on year and are summarised herein. Table 1 – Reserves at 31 December 2025 Field Reserves, Developed and Undeveloped (MMbbl) 1P (Proved) 2P (Proved & Probable) 3P (Proved, Probable & Possible) Australia 0.162 0.368 0.649 Indonesia 0.212 0.428 0.905 Total Reserves 0.374 0.796 1.554 The key factors contributing to this result: • In Australia, good production performance in key Worrior wells, largely offsetting production • In Indonesia, strong production performance of the Bunian 3 well, largely offsetting production Bass’ producing assets in the Cooper Basin, South Australia, comprise the 100% owned and operated Worrior and Padulla oil fields. The 2P Field Reserves for the Cooper Basin are assessed as at 31 December 2025, to be 0.368 million barrels of oil. Bass’ producing assets in the South Sumatra Basin, Indonesia comprise the 55% owned and operated Bunian and Tangai oil fields in the Tangai-Sukananti KSO. In accordance with ASX reporting requirements for fiscal environments that use production sharing contracts or similar, Bass reports Net Entitlement Reserves for its Indonesian assets. The 2P Entitlement Field Reserves in the Tangai-Sukananti KSO in Indonesia are assessed to be 0.428 million barrels of oil net to Bass as of 31 December 2025. ASX Announcement Net Entitlement Reserves are the share of cost oil and profit oil that Bass is entitled to receive under the KSO signed with the Indonesian government body, PT Pertamina. The Net Entitlement Reserves formula varies with the fiscal environment, cost recovery status, oil price and scheduled contract expiry. Contingent Resources The total Bass share of 2C Field Contingent Resources as of 31 December 2025 are assessed to be 1.824 million barrels of oil, largely unchanged year on year. The Bass share of 2C Field Contingent Resources for the Cooper Basin in Australia are assessed to be 1.760 million barrels of oil equivalent, largely unchanged year on year. In the Cooper Basin, the Field Contingent Resources comprise volumes in the Worrior and Padulla oil fields currently considered uneconomic but that may be converted to reserves under different economic circumstances and/or with future projects aimed at extending the current economic cut-offs, such as acceleration of production or reduced crude fuel consumption. Additionally, the Worrior Field contains significant contingent resources of oil in the Murta reservoir that may be converted to reserves post fracture stimulation. Planning to assess this potential, with workover and fracture stimulation of 1-2 wells has commenced. The Kiwi high liquids gas contingent resources are unchanged year on year, with raw gas 1C, 2C and 3C contingent resources of 1.1, 3.6 and 11.5 Bcf respectively. These contingent resources are expected to convert to reserves at a later date, pending the planned FEED work in 2026 and continued assessment of the economics of a pipeline connection and associated infrastructure to bring the gas to market. The Bass share of 2C Field Contingent resources for the Tangai-Sukananti KSO are assessed to be 0.064 million barrels of oil. The Field Contingent Resources comprise volumes attributed to currently producing or future planned wells in the Bunian Field that might be accessed if an acceleration in the drilling and production can bring their exploitation forward. Table 2 – Contingent Resources at 31 December 2025 Field Contingent Resources (MMboe) 1C 2C 3C Worrior Oil 0.221 0.582 1.340 Kiwi Gas 0.360 1.178 3.763 Sub-total Australia 0.581 1.760 5.103 Bunian Oil 0.015 0.064 0.740 Sub-total Indonesia 0.015 0.064 0.740 Total Contingent Resources 0.596 1.824 5.843 Year-On-Year Movements in Reserves and Contingent Resources In the Cooper Basin, there is a small decrease in year-on-year Reserves. This is due to continued strong production performance in key Worrior wells largely offsetting the yearly production actuals and lower oil price assumptions. The Contingent Resources are largely unchanged year on year. In the Tangai-Sukananti KSO, there is a small increase in year-on-year 2P Reserves with production largely offset by the strong performance of the Bunian 3 well. There is a small increase in 2C Contingent Resources resulting from a delay in the development drilling program due to rig availability. Table 3 – Movements in Reserves & Resources at 31 December 2025 Field Reserves (MMbbl) 1P (Proved) 2P (Proved & Probable) 3P (Proved, Probable & Possible) Total Reserves 31/12/24 0.357 0.789 1.528 CY 2025 Production (0.065) (0.065) (0.065) Revisions 0.082 0.072 0.091 Total Reserves 31/12/25 0.374 0.796 1.554 Field Contingent Resources (MMboe) 1C 2C 3C Total Contingent Resources 31/12/24 0.563 1.792 5.881 Revisions 0.033 0.032 (0.038) Total Contingent Resources 31/12/25 0.596 1.824 5.843 Notes on Calculation of Reserves and Resources All reserves and resources are estimated by deterministic estimation methodologies consistent with the definitions and guidelines in the Society of Petroleum Engineers (SPE) 2018 Petroleum Resources Management System (PRMS). Under the SPE PRMS guidelines, “Reserves are those quantities of petroleum anticipated to be commercially recoverable by application of development projects to known accumulations from a given date forward under defined conditions”. Net Entitlement Reserves are the reserves that Bass has a net economic entitlement to. That is, a share of cost oil and profit oil that Bass is entitled to receive under the KSO signed with the Indonesian government body, PT Pertamina. Contingent Resources are “those quantities of petroleum estimated, as of a given date, to be potentially recoverable from known accumulations by application of development projects, but which are not currently considered to be commercially recoverable owing to one or more contingencies”. For the Worrior and Padulla oil fields in the Cooper Basin, decline curve analysis (DCA) was used to determine the remaining technically recoverable volumes with an economic model overlay to determine the economically recoverable reserves. The reserves are net of crude oil lease fuel. The Dynamic Model for the TS-KSO in Indonesia was revised following the successful drilling of Tangai-5 and has updated the oil volumetrics and development scenarios and drilling locations used in this report. Additionally, a decline curve analysis (DCA) was conducted on the current wells. The 1P, 2P and 3P cases are a combination of the forecasts from both the Dynamic Model and the DCA as deemed to best represent the field reserves. Qualified Petroleum Reserves and Resources Evaluator Statement The information contained in this report regarding the Bass Oil Limited reserves and contingent resources is based on and fairly represents information and supporting documentation reviewed by Mr Giustino Guglielmo who is an employee of Bass Oil Limited and holds a Bachelor of Engineering (Mech). He is a member of the Society of Petroleum Engineers (SPE) and a Fellow of the Institution of Engineers Australia (FIEAust) and as such is qualified in accordance with ASX listing rule 5.4.1 and has consented to the inclusion of this information in the form and context in which it appears. Authorised for release by the Board of Directors of Bass Oil Limited. For further information please contact: Tino Guglielmo Managing Director Bass Oil Limited Ph: +61 3 9927 3000 Email: tino.guglielmo@bassoil.com.au About Bass Oil Limited: Bass Oil Limited (ASX:BAS) is an Australian-listed oil producer that holds a majority interest in eight permits in the Cooper Basin (Australia) including the 100% owned Worrior and Padulla oil fields and a 55% interest in a South Sumatra Basin (Indonesia) KSO. The Company is debt free and committed to creating value by leveraging the competitive strengths of its team, operating capability, reputation, and relationships in both Australia and Indonesia. Bass is building towards a substantial onshore Australian and Indonesian oil & gas business with a clear focus on expanding production in the Cooper Basin and in South Sumatra. Bass has a strong and committed shareholder base with the Board and management holding over 10% of the issued capital. Figure 1 Cooper Basin, Australia Location Map Figure 2 Tangai-Sukananti KSO, Indonesia Location Map