Impeller flow log - Borehole geophysical Logging

[BRIS]

I have a specification for drilling and testing water well boreholes. The specification calls for the contractor to undertake “impeller flow log” but it gives no details.

What is this and how is it carried out??

Thanks

 

[BigHarvey]

It looks like a french test called "micro-moulinet" which was invented by Cambefort and Barrée. It allows to measure the vertical speed of water in a borehole. The main purpose is to identify permeability contrasts in a hole ( which is interesting in a water well ). Results can be processed to determine horizontal permeability of the soil.
The measuring device consists in an impeller and an optical counter. It works in an uncased borehole ( over the length to be tested ) in a slotted tube ( diameters 42 mm or 72 mm