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Computer Modelling of Electromagnetics for Brine Layer Detection near Potash Mines

Date

2020-04-16

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

0000-0002-4096-1506

Type

Thesis

Degree Level

Masters

Abstract

Safe mine expansion has been a reoccurring issue for potash mines in Saskatchewan over the years. One of the key issues facing mining operations is the potential for water inflow; this concern is even more serious specifically for potash mines due to the solubility of halite and sylvite minerals of which potash mines are largely comprised. The source of water in-flows are porous sedimentary formations above the mine. In this project we are proposing, through computer modelling, the possibility of remotely detecting the presence of these zones of water bearing strata, specifically water bearing carbonates, specifically using geophysical electromagnetic methods. Normally the sedimentary layers near potash mines in Saskatchewan are considered low-hazard for having porous water-bearing characteristics. However, under certain conditions there is the potential for unsaturated water to have been introduced both into the carbonates above the mine, and even into the salt of the prairie evaporate formation itself, enhancing and even creating porosity in the lithology. Areas of higher porosity have been identified in core samples and have been spatially tied to areas of absent overlying salt layers. Historically, several different geophysical techniques have been proposed to determine the presence of water-bearing anomalies near mine. The techniques that have been tested for this purpose include 3D resistivity, frequency-domain electromagnetics, and time-domain electromagnetics. In many cases these efforts have produced effective results. This project sought to investigate the potential of using time-domain electromagnetics to determine the presence of water-bearing anomalies within the carbonates of the Dawson Bay Formation which lie above the Prairie Evaporite Formation. This project consisted of two principal components. One is computer modelling of time-domain electromagnetics in a full-space or mine environment performed in COMSOL Multiphysics, the other, as part of a Mitacs Accelerate internship that the student author participated in concert with Nutrien, under the joint supervision of Dr. Samuel Butler of the University of Saskatchewan and Randy Brehm of Nutrien, is an in-mine time-domain electromagnetics survey conducted in an area of suspected Dawson Bay water-bearing anomalies. The survey found a decisive conductive zone in the vicinity of the suspected carbonate anomaly. Subsequent computer modelling, both forward and inverse, has been performed to attempt to constrain the location of this anomaly relative to the Prairie Evaporite salt.

Description

Keywords

applied geophysics, mining, electromagnetics, environmental, Dawson Bay formation, potash, brine detection

Citation

Degree

Master of Science (M.Sc.)

Department

Geological Sciences

Program

Geology

Citation

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DOI

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