Horizon Oil Faces Production Decline but Eyes Growth with Maari Extension and Thai Deal
Horizon Oil reports a 9% decline in net Proved and Probable reserves to 9.0 million barrels of oil equivalent, offset partially by a life extension at Maari. A significant acquisition in Thailand is set to materially increase reserves in the near term.
- 9% decrease in net 2P reserves to 9.0 MMboe as of June 2025
- Maari field life extension adds 0.8 MMboe to reserves
- Net production falls to 1.6 MMboe, mainly due to decline in China assets
- 2C Contingent Resources down 8% to 12.3 MMboe from transfers to reserves
- Pending acquisition of Thai gas and oil fields to materially boost reserves
Overview of Reserve Changes
Horizon Oil Limited’s latest reserves and resources statement, released on 28 July 2025, reveals a 9% decline in its net Proved plus Probable (2P) reserves, falling from 9.9 million barrels of oil equivalent (MMboe) at mid-2024 to 9.0 MMboe as of 30 June 2025. This reduction primarily reflects production depletion of 1.6 MMboe over the year, partially offset by a notable life extension project at the Maari field in New Zealand, which added 0.8 MMboe.
The Maari life extension is a bright spot, driven by stable output from eight production wells and the maturation of infrastructure extension studies. This has allowed Horizon to transfer contingent resources into reserves for the first three years of the Maari licence extension, covering December 2027 to December 2030, marking these volumes as economically viable.
Production Performance and Regional Highlights
Horizon’s total net production for the year was 1.6 MMboe, down from 1.9 MMboe the previous year. The decline is mainly attributed to natural production decreases in its China assets, which fell by 0.2 MMboe to 0.7 MMboe. Meanwhile, production in New Zealand and Australia remained relatively stable, supported by the Maari water injection project and successful infill drilling at the Mereenie field, which continues to produce predominantly gas (93%).
Contingent Resources (2C) also saw an 8% decrease to 12.3 MMboe, primarily due to the transfer of volumes to reserves following the Maari life extension and smaller projects in China, including water injection and infill wells. Prospective Resources remain modest at 2.6 MMboe, unchanged from the previous year.
Strategic Acquisition in Thailand
Significantly, Horizon announced a pending acquisition of a 7.5% interest in the Sinphuhorm gas and oil field and a 60% interest in the Nam Phong gas field, both onshore Thailand. Effective from 1 January 2025, this acquisition is expected to materially increase Horizon’s reserves beyond the current 9.0 MMboe reported but will only be formally booked in the next reserves report. This move signals Horizon’s strategic intent to diversify and grow its asset base in Southeast Asia.
Governance and Reporting Standards
All estimates in the report adhere to the Society of Petroleum Engineers’ Petroleum Resources Management System (PRMS) 2018 standards and have been reviewed internally and externally to ensure accuracy. The reserves and resources are reported net of royalties and lease fuel, reflecting Horizon’s net economic interest across its China, New Zealand, and Australian assets.
Chief Operating Officer Gavin Douglas, a seasoned industry expert with over 25 years of experience, supervised the preparation of the estimates, lending further credibility to the report.
Bottom Line?
Horizon’s reserves decline underscores production challenges but the Maari extension and Thai acquisition set the stage for renewed growth.
Questions in the middle?
- How will the pending Thai acquisition reshape Horizon’s production and reserves profile?
- What are the long-term prospects for China assets amid ongoing production decline?
- Can further life extension projects replicate Maari’s success across Horizon’s portfolio?
