Rost 1-26, Rost 2-26 and Brobee Operations Update

Mendell Helium plc

("Mendell Helium" or the "Company")

Rost 1-26, Rost 2-26 and Brobee Operations Update

Mendell Helium (LON: MDH), the helium production company with operations in Kansas, is pleased to report that operational activity continues to advance as scheduled across the Rost lease in Fort Dodge. Recent site upgrades have led to enhanced performance  from the Brobee saltwater disposal asset, high-capacity infrastructure upgrades at Rost 2-26, and targeted well intervention work to optimise and accelerate long-term production at Rost 1-26.

Operational Highlights:

·    Brobee Disposal Well Success: Operating under a maximum surface vacuum (30 inHg) during testing, indicating superior Arbuckle formation permeability and pure gravity-driven intake. Permitted for up to 10,000 bpd, providing low-OpEx disposal for the Rost wells and potential future wells as part of planned regional expansion.

·    Rost 1-26 Perforated Interval Doubled: Perforations doubled to 4ft and surface pumping unit acquired and scheduled to be upgraded from a 320 to a significantly larger 640 unit, increasing fluid handling capacity up to 900 bpd to accelerate gas liberation

·    Capital Efficiency: Sand-tolerant pump installed at Rost 1-26 to extend operational life by 6-12 months, with all workovers completed using on-site rig infrastructure to eliminate extra mobilisation costs.

·    Rost 2-26 ESP: Optimised Halliburton Electrical Submersible Pump (ESP) and VFD unit with 24/7 remote digital telemetry delivered to site.

·    Infrastructure: High-capacity electrical supply and transformer currently being installed to power the ESP, surface processing, and helium purification facilities prior to de-watering and gas production initiation.

·    Stable High-Grade Helium: Wellhead helium concentrations remain at approximately 5.1%.

Rost 2-26 ESP and Infrastructure Update

ESP Sizing and Optimisation

Following extensive consultations with the Halliburton engineering team, an optimised Electrical Submersible Pump (ESP) design has been finalised, approved, and delivered to site, alongside a high-specification Halliburton Variable Frequency Drive (VFD) unit. The optimised ESP has been specifically engineered to handle the downhole production conditions present in Rost 2-26, whilst maximising water handling rates to accelerate the de-watering process required to initiate gas production.

The accompanying Halliburton VFD unit features advanced digital telemetry and remote-control capabilities, allowing the engineering team to monitor real-time downhole conditions (including pressure, temperature, and motor performance) and adjust operating parameters remotely without requiring site intervention. This 24/7 digital tracking provides continuous oversight during de-watering, enabling dynamic pump optimisation and enhancing subsurface reservoir characterisation.

Site Power Upgrade and Timeline

To accommodate the increased power requirements of this upgraded ESP system, alongside planned surface processing and helium purification upgrades required to handle expected volumes from Rost 2-26, a new high-capacity electrical supply and transformer are currently being installed on-site by the local utility provider. With all surface and downhole equipment already delivered and ready for deployment, downhole installation and de-watering operations are scheduled to commence immediately following final grid connection and energisation of the upgraded power supply.

Brobee exceeded expectations during operational testing

The Brobee saltwater disposal well has exceeded expectations during recent operational testing, demonstrating exceptional natural fluid acceptance into the targeted Arbuckle formation. Results confirmed that the well is currently operating under a full surface vacuum (30 inHg), indicating superior reservoir permeability and sub-hydrostatic formation pressure.

This strong performance allows fluid to be drawn down seamlessly into the formation using pure gravity flow, eliminating the need for active surface pumping pressure (which the Company previously required). Operating without surface pumping is expected to deliver significant commercial and operational advantages, including reduced power consumption, lower equipment wear, and lower operating costs (OpEx) per barrel.

Permitted for a capacity of up to 10,000 barrels of water per day (bpd), the Brobee saltwater disposal well is expected to comfortably accommodate wastewater disposal from both Rost wells, whilst providing scalable capacity to support future development wells across the area.

Rost 1-26 Operational Upgrade and Perforation Update

Downhole Optimisation and Scale Prevention

To address historical pump wear caused by formation sand and low-lubrication fluids, the standard tubing pump at Rost 1-26 has been replaced with a specialised, sand-tolerant pump assembly. This upgraded unit is designed to resist abrasion, significantly extending operational pump life and reducing ongoing workover frequency.

In tandem, a full chemical analysis of downhole scale deposits was performed by a specialist firm, resulting in a customised chemical treatment program to prevent future scale accumulation and preserve optimal fluid flow.

Perforation Expansion and Beam Pump Upgrade

To maximise gas production from the asset, the technical team added an additional 2 feet of perforations at Rost 1-26, doubling the open interval to 4 feet. As water removal has been shown to be linked with gas liberation in this reservoir, the increased perforation density is expected to deliver higher fluid production and subsequently drive increased gas flow.

To handle these higher expected fluid volumes, the surface pumping unit has been significantly upgraded:

·   The previous 320 pumping unit (capable of handling 400-500 barrels of water per day) has been demobilised and can be reused at future wells.

·    A substantially larger 640 pumping unit has been acquired and is scheduled for installation over the coming days, increasing total surface water handling capacity to up to 900 barrels of water per day.

Helium Stability and Cost Synergies

Direct wellhead testing at Rost 1-26 continues to demonstrate stable, high-grade helium concentrations of approximately 5.1%, matching initial well test results.

As the workover rig was already deployed on-site following operations at Brobee and Rost 2-26, these perforation and pump upgrades were completed cost-efficiently without incurring additional rig mobilisation or demobilisation expenses.

Nick Tulloch, Chief Executive Officer of Mendell Helium, said: "Following extensive upgrades to the Brobee disposal well and the Rost 1-26 production well, alongside drilling and completing, the Rost 2-26 production well, we are now poised to commence production from both wells.  Subject to completion of the utility connection, we expect de-watering operations at both Rost wells to commence by mid-August 2026.

"With a high helium content and an operating approach already demonstrated at Rost 1-26, we are optimistic about the Rost wells' combined performance.  A particular highlight is the Brobee disposal well where water intake exceeds expectations.  As well as servicing the Rost wells, we believe that Brobee is a valuable asset for the Company, capable of supporting our ongoing production plans in the Fort Dodge region.

"As production develops, we are continuing to assess improvements and increased scale in our surface operations where we seek to remove waste products, primarily nitrogen and hydrocarbons from the gas stream and therefore deliver a more purified helium gas content to our offtaker.  This work will be ongoing for several months and will be necessarily carried out in conjunction with the Rost wells' production."

This announcement contains inside information for the purposes of the UK Market Abuse Regulation and the Directors of the Company are responsible for the release of this announcement.

ENDS

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Overview of Mendell Helium

Mendell Helium is a helium producer in Kansas, USA where it operates through its wholly owned subsidiary M3 Helium.

M3 Helium's flagship well, Rost 1-26, is in Fort Dodge, just to the east of Dodge City, Kansas. It has been tested as containing 5.1% helium composition and a drill stem test yielded a maximum flow rate of approximately 2,900 Mcf per day. Water removed from Rost 1-26 is delivered to Brobee, a nearby disposal well that has been permitted at 10,000 barrels of water per day at 1,200 psi.  Production at Rost 1-26 commenced in early November 2025 and the most recently recorded flow rate in December 2025 was 250 Mcf per day equating to approximately $1.4 million of helium per year (at $300/Mcf helium).

M3 Helium has subsequently drilled and completed a second well, Rost 2-26, which is being prepared for de-watering and gas production. It also owns additional leases in the Fort Dodge area capable of supporting up to eight new production wells. It has also agreed a joint venture with Ritchie Exploration, Inc. to recomplete the Schneweis Ventures 13A, a well with a drill stem test of over 10,000 Mcf per day and a historic flow rate of 300 Mcf per day.

At the Rost wells in Fort Dodge, M3 Helium treats the raw gas on site to concentrate the helium and has leased two tube trailers which it uses for deliveries to its offtaker.

M3 Helium also has interests in five producing wells (Peyton, Smith, Nilson, Bearman and Dimmitt) within the Hugoton gas field in South-Western Kansas, one of the largest natural gas fields in North America. Significantly these wells are in the proximity of a gathering network and the Jayhawk gas processing plant meaning that producing wells are all tied into the infrastructure.

Forward Looking Statements

These forward-looking statements are not historical facts but rather are based on the Company's current expectations, estimates, and projections about its industry; its beliefs; and assumptions. Words such as 'anticipates,' 'expects,' 'intends,' 'plans,' 'believes,' 'seeks,' 'estimates,' and similar expressions are intended to identify forward-looking statements. These statements are not a guarantee of future performance and are subject to known and unknown risks, uncertainties, and other factors, some of which are beyond the Company's control, are difficult to predict, and could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements. The Company cautions security holders and prospective security holders not to place undue reliance on these forward-looking statements, which reflect the view of the Company only as of the date of this announcement. The forward-looking statements made in this announcement relate only to events as of the date on which the statements are made. The Company will not undertake any obligation to release publicly any revisions or updates to these forward-looking statements to reflect events, circumstances, or unanticipated events occurring after the date of this announcement except as required by law or by any appropriate regulatory authority.