2 June 2026

Helix Exploration PLC

("Helix Exploration" or "Helix" or the "Company")

Noble Gas Isotope Results from Rudyard

Helix Exploration PLC (AIM: HEX, OTCQB: HEXFF), the helium exploration and development company advancing the Rudyard Helium Project ("Rudyard") in northern Montana, announces the results of independent noble gas isotope analyses conducted across its three producing helium wells and production gas stream at Rudyard. Samples were analyzed by Dr. Peter Barry at Woods Hole Oceanographic Institution (WHOI) using a noble gas mass spectrometry in May 2026.

Highlights

•   Helium-3 to helium-4 ratios (³He/⁴He) ~33× above typical crustal helium values and carries ~1% helium in the raw well gas stream across all three producing wells. He isotopes consistently range from 0.665-0.690 relative to air (Ra) - indicating predominantly crustal gases (92%) and a whiff of mantle (8%).

•   Consistency across all three wells (0.665-0.690 Ra) is a strong geological indicator that the Company is drawing from a single, uniform deep reservoir - a positive attribute for development planning.

•   Production gas stream records 855 parts per billion ("ppb") helium-3, following purification at Helix's Rudyard plant - one of the highest values documented for any producing helium field.

•   Argon isotope signature (⁴⁰Ar/³⁶Ar: 7,950-9,665) is 27-33 times above atmospheric values and carries ~1,500 parts per million ("ppm") argon in the raw well gas stream. The profile is consistent with a potential underground argon source. Direct ³⁹Ar analysis is currently being arranged.

•   Neon isotope ratios confirm crust and mantle noble gas components - further independent evidence of a deep, ancient, and isolated reservoir underpinning Rudyard's helium production.

Helium-3 Isotope Results

Argon Isotopes - Possible Underground Argon Source

The same analyses reveals a potentially significant argon finding. Argon that has been sealed deep underground for millions of years - shielded from cosmic radiation - becomes depleted in a naturally radioactive isotope called argon-39. This "underground argon" is rare and is in high demand from the global physics community for use in ultra-sensitive dark matter detectors, where even trace radioactive contamination must be eliminated. There is currently only one known commercial source of underground argon in the world - a CO₂ field in Cortez, Colorado - where the Global Argon Dark Matter Collaboration (GADMC), a consortium including Princeton University, ETH Zürich, and leading European physics laboratories, is extracting 120 tonnes for the DarkSide-20k dark matter experiment in Italy. There is no established commodity price; its value is defined by its unique scarcity.

Helix's argon isotope results show that the argon in Rudyard's wells has the indications of gas that has been completely sealed underground for a long time, with no mixing with the atmosphere - the same geological characteristic that underpins known underground argon sources. High 40Ar/36Ar values (>8,000) are on par with those measured from Cortez (~11,000), suggesting a similar deep source for the argon at Rudyard. These argon isotope ratios are 27 to 33 times above normal atmospheric values, and the wells carry approximately 1,500 parts per million ("ppm") argon in the raw gas stream. Furthermore, He/Ne values exceeding 60,000 confirm that Rudyard gas streams have experienced very little mixing with the modern atmosphere. These characteristics, together with the crust-mantle mixed helium and neon isotope signatures, paint a consistent picture of a deep, ancient, isolated reservoir.

The Company has not yet carried out the specific test - a direct measurement of argon-39 - needed to confirm whether Rudyard's argon qualifies as underground argon. That measurement requires specialist equipment available at only a small number of laboratories worldwide, and Helix is actively making those arrangements. Until that test is completed, no equivalence to Cortez can be claimed. However, if the result is favorable, it would represent a discovery of considerable scientific and commercial significance and would position Rudyard as a potential second source of underground argon in the world. Notably, the concentration of argon-40 is approximately 3x higher (~1500 ppm) at Rudyard vs reported concentrations at Cortez of ~600 ppm.

The convergence of an exceptional ³He/⁴He signature, elevated mantle neon isotopes, and a highly radiogenic argon profile provides strong geochemical evidence that Rudyard draws from a deep, ancient, and isolated noble gas reservoir. These characteristics directly underpin the field's helium production and - pending ³⁹Ar confirmation - may establish Rudyard as one of the most geochemically significant noble gas accumulations in North America.

Bo Sears, Chief Executive Officer of Helix Exploration, commented:

"These results are remarkable and reinforce what we have believed since day one - Rudyard is not a typical helium field. The isotopic signature across all three wells points to a deep crustal source that has clearly been influenced by the mantle. With primordial helium serving as a tracer for deep magmatic intrusion into the crust and a potential release mechanism for crustally derived helium-4 and argon-40, this radiogenic helium-4 and argon-40, along with a small amount of helium-3 then migrate upward along ancient fault pathways to accumulate in our Souris and Red River formations. Critically, the component of mantle helium-3 independently validates our geological thesis for natural hydrogen at Rudyard - the deep magmatic systems that release primordial helium from the crust are precisely those associated with geological hydrogen generation.

On the argon side, we have more work to do, but the early isotopic data is striking and we look forward to what further analyses may reveal. Rudyard continues to surprise us, and we look forward to keeping shareholders informed as this picture develops."

Qualified Person

In accordance with the AIM Note for Mining and Oil and Gas Companies, Dr. Peter Barry, Associate Scientist with Tenure at WHOI, has reviewed the technical information contained herein. Dr. Barry has a PhD in geochemistry and approximately 20 years of experience working with noble gases. He has worked closely with the oil and gas industry for more than a decade.

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.

Enquiries

Helix Exploration PLC

Cairn - Nominated Adviser

Hannam & Partners - Broker

Camarco - Financial PR

Notes to Editors

Helix Exploration is a helium exploration company focused on the exploration and development of helium deposits within the 'Montana Helium Fairway'. Founded by industry experts with extensive experience of helium systems in the US, the Company listed in April 2024.

Helix is focused on production at its Rudyard Project in northern Montana, taking advantage of existing infrastructure and low-cost processing to target first gas in 2025. The Company has four production wells targeting up to 236ft Helium / Nitrogen gas in the Souris and Red River formations, flowing up to 3,800 Mcf/day at 1.2% helium. Rudyard field can support multiple production wells and has potential to generate net revenue of $115-$220 million over a 12.5-year life of field.

Helix is committed to open and transparent communication with investors and the wider market as the project progresses through development into production.

"Our approach is simple: build scale efficiently, develop resources strategically, and deliver near-term cash flow."

Bo Sears, Chief Executive Officer

The Company's Admission Document, and other information required pursuant to AIM Rule 26, is available on the Company's website at https://www.helixexploration.com/.

Caution Regarding Forward-Looking Statements

Certain statements in this announcement are, or may be deemed to be, forward-looking statements. Forward-looking statements are identified by their use of terms and phrases such as 'believe', 'could', 'should', 'envisage', 'estimate', 'intend', 'may', 'plan', 'potentially', 'expect', 'will' or the negative of those, variations or comparable expressions, including references to assumptions. These forward-looking statements are not based on historical facts but rather on the Directors' current expectations and assumptions regarding the Company's future growth, results of operations, performance, future capital and other expenditures, competitive advantages, business prospects and opportunities. Such forward-looking statements reflect the Directors' current beliefs and assumptions and are based on information currently available to the Directors. In particular, the presence of depleted ³⁹Ar in the Company's argon has not been confirmed and cannot be inferred solely from ⁴⁰Ar/³⁶Ar ratios. Readers are cautioned not to place undue reliance on such forward-looking statements.