Mise-a-la-Masse

The Mise-a-la-Masse method of surveying is used for examining highly conductive subsurface bodies and the area around them. The continuity, extent, dip and strike of the body can be determined with greater ease if the current is injected directly into the conductive body than by the other resistivity mapping methods. If the body does not extend to the surface, the connection could be made through a drill hole.

One current electrode (C-) is connected to the conductive body and the other current electrode (C+) is placed at a considerable distance. One potential electrode (P-) is located in line with the two current connections and at considerable distance on the opposite side of the conductive body. The survey is then conducted with only one potential electrode (P+) being moved over a square grid of measuring points. The readings from the instrument and the potential electrode (P+) coordinates are recorded. A contour map is then generated from these data.

The distance of the far current electrode (C+) from the potential electrode grid (P+) should be at least 2 or 3 times the maximum dimension of the grid. The same is true for the distance between the grid and the stationary potential electrode (P-).

Appendix P gives an example of a Mise-a-la-Masse survey over a steel pipe.

Beasley, CW and S.W. Ward, 1986, Three dimensional mise-a-la-masse modeling applied to mapping fracture zones, Geophysics, vol. 51, pp.98-111

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