Oman's offshore Block 50 poised for growth with updated reserves

Zawya

25-06-2025

MUSCAT: Masirah Oil Ltd, with its primary owner Rex International Holding Ltd (87.5%), is set to unlock further value from its Yumna Field in Block 50 Offshore Oman, following a comprehensive independent reserves estimation report by Exceed Torridon Ltd (XCD). The summary report, issued on June 23, 2025, highlights updated reserves figures as of December 31, 2024, and outlines an ambitious development strategy that includes several new wells aimed at enhancing recovery and extending the field's life.
The Yumna Field, the first discovery in Oman's Block 50, has been a significant asset for Masirah Oil since its initial discovery in 2013 and the spudding of the first development well, Yumna-1, in December 2019. The field has shown robust performance, with production transferred to a Mobile Offshore Production Unit (MOPU) in April 2020, and subsequent wells, Yumna-2, Yumna-3, Yumna-4, and Yumna-5, contributing to its output.
According to the XCD report, which was prepared in line with the Petroleum Resource Management System (PRMS) standards, the Yumna Field had produced approximately 9 million stock tank barrels (MMstb) by December 31, 2024. The updated assessment reveals significant changes in the remaining reserves, attributed to continued production, improved terms, and further optimization of the depletion plan.
For the "Base 2P" category, the current report estimates gross attributable reserves to the license at 6.0 MMstb, a notable increase from the previous report's 3.7 MMstb. This 27% change underscores the positive impact of ongoing field optimization. Similarly, the "High 3P" category shows an increase to 7.0 MMstb from 4.1 MMstb, representing a 34% change. The "Low 1P" reserves also saw a slight increase to 0.5 MMstb from 0.4 MMstb. These figures are based on new assumptions for economic cut-off, with the economic limit for 1P, 2P, and 3P reserves set at December 2025, November 2030, and June 2031, respectively.
A key factor in the updated reserves is the continuous refinement of the reservoir model. XCD provided Masirah Oil with an updated static and dynamic reservoir model in late 2023, which informed the drilling of the Yumna-5 well. The field exceeded initial production forecasts, prompting a further model update in October 2024 to better reflect the production trends. The report notes that this updated forecast has been accurate.
The forward plan for the Yumna Field is focused on continued production optimization from the existing wells and the phased introduction of new development wells.
Yumna-6 is slated to begin in the second half of 2025 as a sidetrack from the existing Yumna-2 well, targeting reserves in the northwest. Following this, a new well, Yumna-7, will be a step-out to the northeast, and Yumna-8, featuring a horizontal completion, will target reserves in the far northern part of the field, north of Yumna-2 and Yumna-6. These three wells (Yumna-6, Yumna-7, and Yumna-8) are included in the 2P development plan. Beyond these, the 3P scenario includes the drilling of Yumna-9, Yumna-10, and Yumna-11, further expanding the field's drainage.
The technical review within the report indicates a positive development of the estimated in-place resource. Well data, including from the recently drilled Yumna-5, has identified additional reserves and reduced uncertainty in the volume estimations between 2020 and 2024. The field continues to experience a strong water drive from a very large aquifer, and based on production data, a recovery factor of approximately 45% is considered appropriate. The reservoir properties observed in Yumna-5 align with predictions, with effective sweep and residual oil saturations in the lowermost part of the reservoir.
In 2024, the Yumna Field produced 0.864 MMstb gross oil from four wells: Yumna-2, Yumna-3, Yumna-4, and Yumna-5. While Yumna-1 was shut-in due to Electrical Submersible Pump (ESP) issues and Yumna-2 was temporarily shut-in for gas lift optimization, the field's oil rate peaked at 4,300 stb/d on April 26, 2024, before slowly declining to 2,700 stb/d. A constant Brent price of $65/bbl was used for economic calculations to determine the cut-off limit for production in this report.
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