The search for very deep deposits is becoming more and more important in mineral exploration. Due to the absence of surface indicators and the prohibitive cost of deep drilling, indirect methods, such as geophysical surveys, are essential in such context. For deep targets (300 to 2000m), reflection seismic is the geophysical technique having the best compromise between resolution and depth of investigation. Seismic methods remain, however, underutilized in mineral exploration. The main reason is the poor performance of traditional seismic imagery algorithms for metamorphosed and highly folded geological environments. Modern processing algorithms, namely Reverse Time Migration (RTM) and Full Waveform Inversion (FWI), can theoretically image any kinds of structures, regardless of their complexity, dips or material variability. This capability comes from adopting the most complete physical model of wave propagation, or the full-wave equation. To date, RTM and FWI have not been fully developed or tested for mining seismic applications.
We are looking for two PhDs and a postdoctoral fellow to work on the development of FWI and RTM algorithms optimized for mining seismic. Applying full waveform processing in the context of mineral exploration remains a major scientific and technical challenge. Indeed, land seismic data are complex and contain several seismic phases. This complexity requires a complete physical models of wave propagation. One of the main objectives of the research projects will be the development of the viscoelastic formulation of FWI and RTM, which is better adapted to land data than the usual acoustic approximation. Such a formulation has the added advantage of allowing the estimation of the geomechanical properties of rocks. However, convergence of viscoelastic FWI remains problematic. Another principal objective of the research projects will be to regularize FWI in the context of mineral exploration. This will be achieved by the integration of drilling information and petrophysical relationships as constrains to the inversion. FWI will generate high resolution models of the geomechanical properties or rocks and RTM will provide better resolved seismic images. A final objective of the research projects is to fully integrates those high-resolution models within an interpretation workflow adapted to the context of mineral exploration.
The research projects will be conducted in collaboration with key industrial partners. The Geophysics group at Polytechnique Montreal has a solid expertise with seismic inversion and high-performance computing. The successful candidates will work directly with the Mineral Exploration Research Center (MERC) and the mining company Canadian Royalties. The MERC provides high-resolution FWI-optimized seismic lines acquired for the Metal Earth project. The objective of these surveys is to improve our understanding of the formation of VMS deposits in the Green Rocks belt of Abitibi (Canada). For the past two years, Canadian Royalties have been acquiring high-resolution seismic lines for the exploration of Ni-CU-PGE type deposits in the Cape Smith belt (northern Quebec, Canada). These partnerships will allow us to test the new inversion and imaging algorithms as well as improve our scientific understanding of key geologic formations in Northern Quebec.
Financial support
Competitive financial support is offered for the duration of the projects. The postdoctoral internship has a maximum duration of 3 years.
Qualifications
The PhD applicants should have a completed or nearly complete first-class honours degree or a Master degree in Geophysics, Physics, Applied Mathematics, Earth sciences or related majors. The candidates should have a working knowledge of a programming language. Candidates for the postdoctoral fellowship must have extensive experience in seismic data processing, and preferably a good understanding of FWI and RTM.
Application
Interested candidates should send an up-to-date CV and a motivation letter to Pr. Gabriel Fabien-Ouellet at
[email protected].
