Analysis of Fluid Flow Pathways in the Mount Meager Volcanic Complex, Southwestern Canada, Utilizing AMT and Petrophysical Data.

Defining the spatial distribution of geological structures and rock properties is important for understanding how fluid flow is controlled in a geothermal reservoir. Here, we present a procedure to examine the potential fluid pathways. By combining 3‐D resistivity models derived from audio‐magnetotelluric (AMT) data with available rock properties (porosity and permeability) and fluid sample data (fluid resistivity, salinity, and temperature), we investigated the relationship between electrical resistivity and fluid flow in an active volcanic system. Different petrophysical models and empirical relations are evaluated to determine the relationship between the fluid flow system at Mount Meager, British Columbia, and the resistivity model. In addition, we utilized porosity and permeability measured in the laboratory to define the porosity‐permeability relationship. The porosity of the volcanic core samples showed a range of 2.6%–23.2% and the permeability was in a range of 0.001–5,186.57 mD. The results showed the potential of 3‐D inversion of AMT data to map the fluid pathways at Mount Meager. These pathways are correlated with loss circulation zones in boreholes and can account for porosity up to 8.5%, which using the porosity‐permeability relationship translates to permeability of the order 0.249 mD. Not only are the fault and fracture zones important for reservoir exploitation, but they also provide permeability for the circulation of meteoric water. Our studies suggest that a set of fractures with 0.1 m spacing and 20 mm aperture can keep 40% fluid in pores and transmit fluid with possible permeability of 666 mD. Plain Language Summary: Geothermal is the natural heat within the Earth. Heat passes to the near‐surface by the magma intrusion into the crust and circulation of groundwater through fluid flow pathways. This paper evaluates the fluid flow pathways, structure, and physical properties beneath the Mount Meager Volcanic Complex (MMVC; Canada). The audio‐magnetotelluric (AMT) method (natural‐source electromagnetic geophysical technique) was used to produce the 3‐D resistivity model. Moreover, utilizing laboratory experiments, we modified rock‐physical and fluid chemistry relationships to focus on the MMVC rather than using relations adapted to other volcanic settings. The AMT model shows correlations between the locations of conductors and faults and suggests that faults act as flow pathways. A porosity of up to 8.5% is expected in the potential reservoir zone. By combining the resistivity model with rock and fluid properties, we mapped potential flow pathways and rock properties. Results showed that in rocks with low porosity and permeability, fractures provide the primary way of flow with porosity and permeability up to 40% and 666 mD, respectively. This project contributes to the development of conceptual models of the hydrothermal flow, which could be used to reduce the risk of future exploitation of geothermal resources. Key Points: Audio‐magnetotelluric data have been used to model the conductivity distribution beneath an active volcanic system in southwestern CanadaUtilizing 3‐D Inversion, we provide details on the structure, physical properties, and flow pathways of a volcano‐hosted geothermal systemPermeability can increase up to five orders of magnitude in fractured rocks beneath Mount Meager [ABSTRACT FROM AUTHOR]