Ambient Noise Tomography (ANT) Shear Wave (Vs) Velocity Model for the Topaz prospect. Illustration: Pulsar Helium.
North America
New Gas

A helium reservoir in fractured basement

Most of the world’s helium is produced as a by-product of natural gas extraction or from geological settings similar to classic hydrocarbon plays. However, with the growing demand for helium and dwindling hydrocarbon reserves, helium explorers are expanding their search. One such company is Pulsar Helium, which acquired acreage in Lake County, northern Minnesota, a region historically known for metal ore mining

In 2011, a borehole tar­geting nickel unexpect­edly discovered gas. The gas flowed from the hole with such force that it reportedly ‘screamed like a jet engine’ for four days un­til experts were able to seal the well. Analysis revealed that the gas contained over 10 % helium, along with CO2 and nitrogen.

The targeted rock for­mations are part of the Duluth intrusive complex. The complex consists of lay­ered mafic rocks emplaced 1.1 billion years ago when the Midcontinent Rift be­gan to split apart the North American craton. The rel­atively stable tectonic con­ditions since then have allowed helium to slowly accumulate over time.

Well above the cut-off value

In 2024, Pulsar Helium drilled the Jetstream #1 ap­praisal well, located 20 m from the discovery hole. Laboratory tests revealed up to 14.5 % helium and an average of 9.9 % helium over a 12-day flow test, well above the 0.3 % cut-off val­ue for economic production. Wireline analysis identified discrete zones with produc­tive permeability related to fracture porosity with­in the igneous rock. The well achieved a flow rate of 821,000 ft3 per day under well-head compression.

The passive seismic model shows a significant velocity decrease in the zone that flows helium, while im­permeable igneous rocks cap the helium-rich zone. The shear wave anomaly has a vertical thickness of approx­imately 610 m and covers an aerial extent of 7 km2.

Initially, the Jetstream #1 well only reached the top of the low-velocity zone. Consequently, Pulsar Heli­um decided to deepen the well earlier this year, and it now transects the entire ve­locity anomaly. The compa­ny also drilled the Jetstream #2 appraisal well to further assess reservoir properties, such as porosity, permea­bility and well connectivi­ty. Both wells successfully flowed helium to surface, confirming the geophys­ical interpretation of the shear wave anomaly cor­responding to the helium-bearing zone.

Rock dust

Currently, the company is conducting pressure and flow tests. Wellhead pres­sures are encouraging for both wells, but drilling fines, rock dust generat­ed during air drilling, are hindering the flow tests. Drilling fines partially coat the wellbore walls and lim­it gas flow. A preliminary clean-up of both wells has mobilised part of the drill­ing fines and resulted in im­proved flow; the wells flow naturally and on compres­sion. Further flow testing will resume once clean-up is complete.

In addition to helium, Pulsar plans to capital­ise on the approximately 62 % CO2 present in the gas stream by constructing a dual helium-CO2 produc­tion facility.

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