Mosman Oil and Gas Limited (AIM: MSMN), the helium, hydrogen and hydrocarbon exploration, development and production company, which holds a 100% working interest in the Coyote Wash Project in Colorado, USA ("Coyote Wash Project"), is pleased to announce the first internal estimate of prospective helium resources for the project.
Highlights
- Best estimate 2U gross prospective helium resources of 1,072 MMcf (million cubic feet) calculated across six identified prospects at Coyote Wash, using parameters consistent with the recent independent evaluation of the nearby Sagebrush Project prepared by Sproule ERCE and announced on 18 September 2025.
- Resource model incorporates known reservoir properties from the Coyote Wash 30-12 well and helium concentration data of 2.7% He measured at Mosman's Sagebrush-1 well, located 5 miles to the southwest.
- Coyote Wash lies in an established helium-producing region with proven reservoir deliverability in the Middle and Lower Leadville formations.
Coyote Wash Project
The Coyote Wash Project is located in the Four Corners region of Colorado and lies within an area of established helium production from the Leadville Formation carbonates, including the Doe Creek field approximately 50 miles to the north.
Technical evaluations by Mosman and its partner Four Corners Helium (FCH) have focused on reinterpretation of vintage well data and reprocessed 3D seismic to understand the resource potential within the project area. The Coyote Wash 30-12 well, drilled by Wintershall in 1985, encountered 258 feet of Leadville carbonates within the Coyote Wash North closure. Three DST's were performed in the middle and lower Leadville flowing non-flammable gas. Test data indicates the well flowed 173mcf/d from 14ft of stacked dolomite units in the middle Leadville. Although the gas composition was not analysed at the time, the well confirmed good reservoir properties and deliverability from the Leadville sequence before being plugged and abandoned.
A detailed petrophysical interpretation of Coyote Wash 30-12 and nearby offset wells was subsequently undertaken by FCH to determine key reservoir parameters for resource calculations. Interpretation of the reprocessed 3D seismic has defined six individual prospects at the Leadville level within the project area. Coyote Wash North (CN-1) is located in the upthrown fault block, while the remaining five prospects lie in the southern downthrown block. These structures have been mapped from high-quality seismic data and form the basis of Mosman's initial prospective resource estimates.
Helium was confirmed at Mosman's Sagebrush-1 well, located five miles southwest of Coyote Wash 30-12, with measured concentrations of 2.7% He. Regional gas and production data indicate that similar commercial helium concentrations are likely to be present at Coyote Wash, and this value has been used to calculate the prospective helium resources across the six defined structures.
In determining reservoir parameters, Mosman adopted a 5% porosity value for the southern Coyote Wash prospects, consistent with the conservative "most likely" porosity used by Sproule ERCE in their recent independent analysis of the Sagebrush resource. A higher 8% porosity was applied to the Coyote Wash North prospect, reflecting its proximity to the Coyote Wash 30-12 well and the high reservoir quality observed there.
Next Steps
Mosman will now formally engage Sproule ERCE, the independent consultant who recently verified helium prospective resources at Sagebrush, to conduct a detailed assessment and certification of the Coyote Wash prospective resources.
This work will provide a third-party validation of Mosman's internal estimates and form the basis for future drilling and development planning.
Howard McLaughlin, Chief Executive Officer of Mosman, commented:
Coyote Wash represents another exciting step in Mosman's US helium growth strategy. With six mapped Leadville prospects and best-estimate helium prospective resources exceeding one billion cubic feet, the project has clear scale and upside potential. The combination of strong reservoir characteristics, proven regional helium charge, and proximity to our Sagebrush discovery provides confidence that Coyote Wash could become a significant addition to Mosman's portfolio. Following Sproule ERCE's successful independent verification at Sagebrush, we look forward to engaging them again to confirm and refine these results as we advance towards drilling and development."