As global energy markets evolve, AIM-listed small caps are emerging with bold, strategic plays across conventional hydrocarbons, helium, and transitional energy storage. From deepwater gas fields in Indonesia and offshore Jamaica to low-carbon infrastructure in the UK and high-impact helium exploration in the U.S., these companies are navigating regulatory shifts, funding hurdles, and commodity price swings to unlock substantial value. In this update, we examine five standout juniors—Empyrean Energy, EnergyPathways, Mosman Oil & Gas, Prospex Energy, and United Oil & Gas—each at pivotal stages in their respective journeys, and each presenting a distinctive mix of risk, reward, and relevance to the energy transition narrative.
Empyrean Energy
Empyrean Energy PLC (EME) is an oil and gas exploration company listed on AIM, with key assets spanning Southeast Asia and the U.S. Its flagship project is a 8.5% interest in the Duyung PSC, which contains the Mako gas field—one of the largest undeveloped gas fields in the West Natuna Basin, offshore Indonesia. Mako represents a highly strategic asset with significant monetisation potential amid Southeast Asia’s growing energy demand. In addition, the company has an interest in the Sacramento Basin in California and is actively exploring new onshore gas opportunities in the U.S.
Recent developments in 2025 have centred around the Wilson River-1 well, a high-impact vertical oil exploration target located in Southwest Queensland, Australia. Following the execution of key land access and heritage agreements, Empyrean entered a definitive farm-in agreement, securing a 52.8% working interest in the well alongside Condor Energy (27.2%) and Chi Oil (20%). Drilling commenced on 14 March and reached total depth of 1,464m within six days. Preliminary quad combo logs indicate approximately 6 metres of potential gross oil-bearing zone in one of the main target formations. The well has been cased and suspended pending final petrophysical analysis to define the optimal testing and completion strategy. The project has been fully funded through two placings totalling £1.3 million, supported by strong director participation and a salary sacrifice arrangement to preserve working capital.
Meanwhile, at the Duyung PSC, Empyrean and its partners reached a major milestone by signing revised gas sales arrangements with Indonesian authorities. This agreement paves the way for the long-anticipated Mako field development and potentially fast-tracks commercialisation, aligning with Indonesia’s energy security goals. The revised GSA framework could unlock significant near-term value, and management is working toward a final investment decision (FID) once regulatory and partner approvals are finalised. With strong regional demand for gas and proximity to existing infrastructure, the Mako project remains the company’s cornerstone long-term asset.
Looking forward, Empyrean Energy is entering a crucial phase. The outcome of Wilson River-1 could materially impact short-term valuation, while progress on the Mako gas field will determine the company’s medium-term growth. Investors should be aware of typical junior oil & gas risks—drilling outcomes, regulatory delays, and funding gaps—but also note the recent momentum across Empyrean’s portfolio. With a diversified strategy, active operational program, and access to transformational gas assets, Empyrean presents a speculative yet intriguing opportunity in the junior energy sector as it seeks to deliver value through both exploration success and strategic gas monetisation in Asia and North America.
EnergyPathways
EnergyPathways PLC (EPP) is an energy transition company focused on developing large-scale, low-carbon energy storage infrastructure in the UK. Its flagship project, the Marram Energy Storage Hub (MESH), is located offshore in the UK Irish Sea and is designed to integrate natural gas, hydrogen, and long-duration energy storage technologies. The project aims to deliver up to 20 TWh of total storage capacity, with the initial phase targeting 17 TWh of gas storage using the depleted Marram gas field. Strategically positioned near major energy infrastructure, MESH is set to play a critical role in addressing the UK’s growing need for energy security and flexible, home-grown power sources.
In early 2025, EnergyPathways made notable progress on MESH. Concept engineering studies for hydrogen storage using salt caverns were completed, and the company submitted licence applications to the regulator for development approval. The project also aligns closely with UK government energy policy, including goals around offshore wind integration, hydrogen markets, and net-zero emissions. As highlighted in recent statements by government officials, energy storage is expected to become a key pillar of the UK’s future energy mix, with allocation rounds for hydrogen storage anticipated later in 2025—potentially unlocking material value for EPP.
Operationally, EnergyPathways has remained focused on building the business around a just, secure, and integrated transition model. March updates confirmed the company is refining technical and commercial frameworks to accelerate MESH’s progress towards the final investment decision (FID). In addition, EnergyPathways is leveraging regional advantages—such as access to 7–8 GW of surrounding offshore wind capacity, existing pipeline infrastructure, and proximity to major industrial hubs in Northwest England—to attract investment interest and secure long-term project viability. The company also recently issued shares in lieu of fees and options, reflecting prudent capital management as it moves toward asset monetisation.
Looking ahead, EnergyPathways is positioned as a unique UK play on energy security and long-duration energy storage. The successful commercialisation of MESH could transform the company into a major player in the future hydrogen and gas storage value chains. However, investors should note that progress remains contingent on securing regulatory approvals, funding, and execution partnerships. With the FID for MESH expected in 2025 and a strong alignment with national policy objectives, EnergyPathways offers a high-risk, high-reward proposition in one of the UK’s most strategic growth sectors.
Mosman Oil & Gas
Mosman Oil and Gas Ltd (MSMN) is an exploration and development company transitioning its focus from conventional oil and gas to high-value helium assets in the United States. The company currently holds interests in three strategic U.S. helium projects—Vecta (20% WI), Sagebrush (82.5% WI), and Coyote Wash (100% WI)—while retaining upside exposure to Australia via royalty interests following the sale of its exploration permits EP 145 and EPA 155. These divestments, along with the sale of U.S.-based Nadsoilco, mark a decisive pivot towards the helium sector, reflecting Mosman’s strategy to reposition itself in a supply-constrained critical gas market.
In 2025, Mosman accelerated its helium strategy, expanding its Colorado lease position and advancing technical evaluations across all three U.S. projects. At Vecta, a c.51,000-acre block with multiple drill-ready leads, the company is preparing for drilling, with well costs estimated at approximately US$259,000 gross. Sagebrush, which already generates modest oil revenue, is being progressed via seismic reprocessing and a planned 3D seismic survey to delineate helium-bearing formations. Coyote Wash also remains a priority, with five helium leads identified and ongoing technical review. These projects are strategically located near infrastructure, including the Four Corners Helium Processing Plant, enhancing their potential for near-term development and offtake.
Mosman has significantly improved its financial position to support these exploration efforts. The company ended 2024 with A$3.48 million in cash and further strengthened its balance sheet via a £1.5 million placing completed in September. Proceeds are earmarked for drilling and seismic activities across the U.S. portfolio. Additionally, the company retains a 5% royalty on EP 145 and a 2.5% royalty on EPA 155, which could deliver future non-dilutive income if the permits are developed by the new owners. These financial and strategic moves reflect a disciplined approach to capital deployment in line with its refocused helium mandate.
Looking ahead, Mosman Oil and Gas is entering a new phase as a dedicated helium explorer in a market experiencing sustained supply shortages and rising prices. With a solid cash balance, upcoming drilling catalysts, and diversified exposure across three distinct U.S. projects, the company is well-positioned to deliver value. Nonetheless, investors should remain mindful of typical early-stage risks, including exploration uncertainty and regulatory timelines. If successful, Mosman’s repositioning could transform it into a niche supplier of helium—an increasingly strategic resource for semiconductors, medical devices, and aerospace applications.
Prospex Energy
Prospex Energy PLC (PXEN) is a debt-free AIM-listed natural gas investment company with core production assets in Spain and Italy, and exploration interests in Spain and Poland. The company’s portfolio includes the Viura gas field in northern Spain, the El Romeral integrated gas and power project in southern Spain, and the Selva Malvezzi onshore gas concession in Italy. Together, these projects deliver over 3.1 million standard cubic feet per day (MMscfd) net production, offering steady cash flow while underpinning future growth through development drilling and infrastructure expansion. With further exploration exposure at the high-impact Tesorillo permit and new licence applications in Poland, Prospex is positioning itself as a focused European gas growth vehicle in a market increasingly driven by energy security.
Recent activity has centred on accelerating development at all three producing assets. At Viura, the Viura-1B development well exceeded expectationsin January 2025, and two additional wells are planned to boost production and reserves. In Italy, Selva Malvezzi continues to perform well, with four new wells targeting 88.2 Bcf of gas now progressing through permitting. Meanwhile, in Spain, Prospex signed a binding agreement in March 2025 to acquire the remaining 50.1% of Tarba Energía from Warrego Energy, making it the sole shareholder. Tarba holds the El Romeral gas-to-power project and the suspended Tesorillo and Ruedalabola exploration permits. This €652,725 all-cash deal gives Prospex 100% indirect ownership of El Romeral and related exploration permits, and positions the company to significantly increase production and revenue once drilling permits for five new wells are approved. The transaction also strengthens Prospex’s operational control and demonstrates continued momentum in executing its European gas strategy.
In parallel with production growth, Prospex is maintaining exposure to material exploration upside. Through its 100% ownership of Tarba Energía, the company now holds full indirect ownership of the suspended Tesorillo and Ruedalabola permits in southern Spain, which include independently certified prospective resources of up to 2.3 Tcf. Prospex retains the option to advance these assets once permit reinstatement occurs. In Poland, the company is targeting shallow, low-cost conventional gas plays and has submitted licence applications expected to be awarded in 2025. These initiatives align with the company’s strategy to grow within stable European jurisdictions and maintain a balance of near-term cash flow and long-term resource potential.
Looking ahead, Prospex is in a strong position to benefit from its existing production base, fully funded growth plans, and the strategic acquisition of Tarba Energia. With key catalysts including Viura field development, Selva permit approvals, and operational control of El Romeral, the company offers a rare combination of yield, upside, and low-risk jurisdictional exposure. While regulatory delays and permitting remain inherent risks, Prospex’s debt-free balance sheet, internally funded development, and focus on European gas markets make it a compelling play on regional energy resilience and security.
United Oil & Gas
United Oil and Gas PLC (UOG) is currently focused on unlocking the multi-billion barrel potential of its flagship asset—the 100%-owned Walton Morant licence offshore Jamaica. Spanning an expansive 22,400km², the block boasts a mean prospective resource estimate of 7 billion barrels, placing it among the largest underexplored offshore oil opportunities in the Caribbean. With over $40 million of historic investment, high-quality 3D seismic data, and favourable fiscal terms, Walton Morant is strategically positioned to replicate the transformational development model seen at Guyana’s prolific Stabroek Block. The block features more than 21 high-graded prospects and leads, with the Colibri prospect singled out as a potential “basin opener.”
Although still referenced on the company’s website, United has effectively exited the Abu Sennan licence as confirmed by multiple RNS announcements in 2024 and early 2025, including updates on well results, operator disputes, and the final receipt of outstanding receivables. This leaves United’s 25% non-operated interest in the Waddock Cross oil field onshore UK, where phased redevelopment could deliver near-term production and cash flow. Together, these assets reflect a refocused approach, balancing high-impact frontier exploration with selective exposure to lower-risk domestic production.
In March 2025, United took a decisive step to strengthen its balance sheet by settling a long-standing liability with Rockhopper Exploration PLC. The agreement resolved all outstanding obligations stemming from United’s 2020 acquisition of Rockhopper Egypt, with United issuing 115 million new ordinary shares as full and final settlement. This move removed a major legacy overhang, improving the company’s financial clarity and investor confidence and allowing United to fully draw a line under its previous Egyptian exposure.
Just days later, United announced a major strategic milestone: the successful extension of the Walton Morant licence through to January 2028. This two-year extension provides valuable runway to complete current technical work, attract a suitable farm-in partner, and prepare for a potential exploration well in 2026 or 2027. Management has reaffirmed its commitment to a low-cost, focused work programme that continues to de-risk the basin while preserving capital. With historic liabilities now resolved, a key licence extension secured, and a clear operational plan in place, United is better positioned to unlock the vast potential of one of the Caribbean’s most exciting frontier oil plays—though investors should remain aware that significant funding, exploration success, and partner alignment are all critical to realising that upside.
Conclusion
Each of these junior energy companies offers a unique lens into the sector’s shifting dynamics—from Empyrean’s dual-hemisphere exploration strategy and EnergyPathways’ role in the UK’s energy resilience, to Mosman’s pivot into helium, Prospex’s European gas production model, and United’s frontier oil ambitions in Jamaica. For investors willing to stomach the inherent risks—ranging from drilling outcomes and funding challenges to regulatory uncertainties—these companies present speculative but potentially transformative opportunities. With key catalysts expected in the months ahead, retail investors should stay alert to operational updates, farm-in activity, and regulatory decisions that could dramatically alter the growth trajectories of these dynamic juniors.
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