--> Helium in Southwestern Saskatchewan: Accumulation and Geological Setting

AAPG ACE 2018

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Helium in Southwestern Saskatchewan: Accumulation and Geological Setting

Abstract

Saskatchewan is experiencing renewed interest in potential helium production due to increasing commodity prices. Helium was reported in gas analyses from wells in southwestern Saskatchewan as early as the 1950s, with anomalous values of helium up to 2%. Helium was produced in the early 1970s from four wells and recently three wells have produced in southwest Saskatchewan, with another 8 wells that have recently been drilled for helium targets.

With the mounting interest in helium, a study was initiated to better understand the generation, accumulation and geological setting of helium resources in the province. This included an examination of close to 1900 analyses from 1412 wells analyses in Ministry of the Economy well files from southwestern Saskatchewan, which identified anomalous helium concentrations in stratigraphic intervals ranging from the Cambrian to the Cretaceous, but in particular the lower Paleozoic. From these wells, 55 gas analyses have helium values of greater than 0.3% and of those, 13 are greater than 1%. The results of this study have been published and work is now being done to include the wells in the southeast corner of the province.

Understanding the source, migration and trapping of the helium is critical in understanding where the economic accumulations occur. Although the physical processes required to trap economic amounts of helium (source, migration, carrier beds and trap with seal) are similar to hydrocarbon natural gas traps, it requires a more robust seal for its reservoir than hydrocarbons. The two likely models for the development of helium plays in southwest Saskatchewan are:

1) generation of helium by radioactive decay of uranium and thorium in Precambrian granitic basement rocks; migration along fracture/fault systems developed throughout the Phanerozoic by the numerous tectonic elements in this part of the province (e.g. the Great Falls Tectonic Zone); and pooling/entrapment in sediments draping structural highs with effective seals such as silicified siltstone; and

2) generation of helium by radioactive decay of uranium and thorium naturally occurring in the shales of the lower Paleozoic rocks (primarily Deadwood Formation shales) with migration into stagnant pore water, partitioning of the helium from the water into gas, and pooling/entrapment as noted above.

Based on current understanding, the most viable exploration models seem to be closed structures created by Lower Paleozoic sediments draped over Precambrian highs.