6 June 2023

                                                      Mosman Oil and Gas Limited

("Mosman" or the "Company")

USA Operations Update

Mosman Oil and Gas Limited (AIM: MSMN), the oil exploration, development, and production company, announces an update in respect to its USA Operations.

USA Production (Various interests)

Production at all sites continues with current internal estimates indicating that production in April 2023 was 6,951 BOE gross (232 boepd), 2,936 BOE (101 boepd) net to Mosman.

The April net production daily average of 101 boepd is lower than the previous quarter's (March 2023 quarter) daily average of circa 133 boepd, primarily due to workovers at Cinnabar-1 (details below).

These interim production numbers are subject to change upon receipt of final sales invoices from the purchasers of products and other adjustments. At this time these are internal estimates only and accordingly final numbers may vary. Mosman will release the normal full quarterly production numbers after the end of the June quarter.

Major Project Updates

Cinnabar (75% Working Interest)

Having established production and the Reserves at Cinnabar, the current phase of operations is to establish production rates from several of the prospective reservoir zones to facilitate development plans to produce the 1.646 million boe of Reserves.

The workover on 25 April 2023 isolated the First and Second Wilcox zones with a cement retainer (a form of bridge plug). Since then, the First Wilcox has flowed intermittently. The First Wilcox zone was re-perforated to see if that increased production, and the well has been swabbed. Whilst well pressure builds when the well is shut in, production remains intermittent. Further workovers are planned to optimize production, and these may include a frac that has been successful in nearby independently operated wells (not yet tried on this lease).

At Cinnabar, a key reason for first focusing on the First Wilcox zone, and then other Wilcox sands to follow, is to determine the optimal production methodology for each zone. This data collected will be used in the setting of the development plan for the wider lease with a view to building longer term value from the asset.

In due course, the well may then be recompleted in other Wilcox sands, including the Eight Wilcox that has a good response on electric logs, but has not been flow tested.

At the historic G-1 well, the well is producing oil at varying rates up to 12 bopd following commencement of gas injection.

A workover of the G-2 well is also being considered.

As previously announced ongoing technical work is being undertaken in order to prepare a Development Plan for the Cinnabar lease. This work will include updates of the 3D seismic interpretation on the lease and the geological model and result in the identification of drilling targets and locations. The Development Plan is expected to take several months to complete.

Stanley (34.85% to 38.5% Working Interest)

Stanley has benefitted from the completion of gas infrastructure and workovers to optimise production, and the installation of Jet pumps has increased production at Stanley 4 and 5.

Stanley 3 has been off-line to enable installation of a jet pump and this well will be back on production once surface equipment installation is completed.

Production from the shallower Stanley 1 and 2 wells was impacted by a lightning strike on 9^th May 2023 that caused a small fire and required some equipment to be replaced. This resulted in minor loss of production.

Winters (23% Winters-2 Working Interest)

Winters-2 continues to produce at rates exhibiting natural decline.

Winters-1 has been recompleted as a water injection well.

Arkoma

The project remains for sale.

Cash position

As at 31 May 2023, Mosman had cash at bank of circa AU$1.2 million, which is after the payment for the Cinnabar gas connection of USD110,000 (gross).

John W Barr, Chairman, said: "I am pleased that production continues with various operational issues being managed effectively. I look forward to reporting on further progress on the development plan for the Cinnabar Reserves in due course."

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.

Updates on the Company's activities are regularly posted on its website:

www.mosmanoilandgas.com

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