1887

Abstract

Summary

Magnetotelluric (MT) is classically used in geophysical exploration for imaging electrical conductivity structures and is being developped as a monitoring technique. In geothermic during fluid injections and stimulation experiments, MT is used in addition to microseismic observations and can provide critical information to geothermal fluid flows because the electrical conductivity is related with temperature, porosity, water content and minerals of rocks. Some experiments have shown that such MT signals might be difficult to observe because they are at periods of 1–10 s, within the MT dead-band. We show actual data from Northern France then consider the sensitivity of MT monitoring by forward modelling. We use ModEM open source code to build a 3-dimensional model which includes topography and simple sedimentary conductive layers. Modelling allows us to simulate different changes that could be caused by brine and/or acid injection within fractures at depth and show subsequent MT monitoring parameters, particularly the phase tensor. From these models, it seems that MT monitoring in a sedimentary environment at 20 □.m could be sensitive to an increase of conductivity in a fault area at geothermal depths of 2–3 km if the size of the disturbed domain reaches about 10×0.3×2 km3.

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/content/papers/10.3997/2214-4609.201702599
2017-11-05
2019-12-11
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References

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