04 August 2025

Mosman Oil and Gas Limited

("Mosman" or the "Company")

Key Permitting Approvals Imminent For Sagebrush And Coyote Wash Helium Projects

Mosman Oil and Gas Limited (AIM: MSMN), the helium, hydrogen and hydrocarbon exploration, development and production company, is pleased to provide an update on regulatory progress at its flagship helium projects, Sagebrush and Coyote Wash, in Colorado, USA.

Sagebrush Project

At the Sagebrush Project, where Mosman holds an 82.5% working interest, the Company is advancing its 3D seismic acquisition program and planning an extended production test at the previously drilled Sagebrush-1 well. As part of this process, Mosman is working closely with the Ute Mountain Ute Tribe and Bureau of Indian Affairs ("BIA") to finalise permitting.

• 3D Seismic Survey Approval: Following the successful completion of biological and cultural surveys, Mosman anticipates formal Tribal approval for the 3D seismic survey by mid-August 2025. The seismic acquisition programme is anticipated to start in late September through mid October.

• Lease Assignment (Seeley Acreage): Mosman is also progressing the administrative process to secure BIA approval for the assignment of the Seeley (Sagebrush) lease. This is a critical step towards initiating an extended production test at the Sagebrush-1 well. A Reservation-wide bond is currently being finalised to satisfy BIA requirements.

These approvals represent key milestones in the Company's plan to advance the helium potential at Sagebrush, where historic gas analysis has recorded helium concentrations of 2.76% from the Leadville Formation.

Independent Resource Verification Underway

Mosman is pleased to confirm that Sproule, a globally recognised independent energy consulting firm, has commenced work on its independent estimate of helium resources at the Sagebrush project. This verification process includes a comprehensive review of geological and engineering data and is expected to further validate and refine Mosman's internal assessments. Results from Sproule's report are anticipated towards the end of August 2025, supporting the Company's objective to advance Sagebrush towards commercialisation.

Coyote Wash Project

The Coyote Wash Project covers a 4,320-acre area where Mosman holds a 100% working interest. The final Environmental Assessment was completed on 17 July 2025 and is currently undergoing a 30-day public comment period.

Pending the conclusion of this process, BIA approval is expected mid-August 2025. Upon approval, Mosman will hold a fully permitted exploration and development agreement over six drill-ready helium prospects identified via reprocessed 3D seismic data.

These prospective targets lie within the highly promising Leadville Carbonates and McCracken sandstones fairways, and are supported by historical drilling in the area.

Next Steps

The timely receipt of these approvals will enable Mosman to:
• Commence 3D seismic acquisition at Sagebrush as soon as a crew can be available
• Execute an extended flow test of Sagebrush-1 later in the year
• Advance Coyote Wash towards drilling in 2026

Mosman Interim-CEO Howard McLaughlin commented "The pending approvals for both the Sagebrush and Coyote Wash Projects represent pivotal milestones for Mosman. With 3D seismic at Sagebrush ready to proceed and the IMDA (Indian Minerals Development Agreement) at Coyote Wash nearing finalisation, we are well-positioned to unlock the significant helium potential of both projects. These are transformative opportunities for Mosman."

Interview

Interim CEO Howard McLaughlin discusses the latest developments at Sagebrush and Coyote Wash. Link below to view the interview:

https://youtu.be/6VKsDU-D7Tw

Market Abuse Regulation (MAR) Disclosure

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 ('MAR') which has been incorporated into UK law by the European Union (Withdrawal) Act 2018. Upon the publication of this announcement via Regulatory Information Service ('RIS'), this information is now considered to be in the public domain.

Enquiries:

Updates on the Company's activities are regularly posted on its website: www.mosmanoilandgas.com

Notes to editors

Mosman (AIM: MSMN) is a helium, hydrogen and hydrocarbon exploration, development, and production company with projects in the US and Australia. Mosman's strategic objectives remain consistent: to identify opportunities which will provide operating cash flow and have development upside, in conjunction with progressing exploration. The Company has several projects in the US, in addition to royalty interests in Australia.