The Lugeon test, or Lugeon test, is a test that is done in the field to estimate soil permeability. It is mainly applied in fractured rocks. It consists of measuring the volume of water "" that can be injected into the ground during a certain time "", in other words the flow is measured, in a section of a certain length "", at a constant pressure.[1][2]​.

In a waterproofed borehole up to a certain depth, from this point the chamber to be tested is drilled, then a pneumatic or hydraulic plug is fixed in the upper part of this section and pressurized water is injected with a pump. At the wellhead the pressure is controlled with a manometer. A water meter and a discharge valve allow the injected flows to be measured at a given pressure kept constant.

The measurements are carried out at 5 pressure levels, in which the water is injected. Before starting, the maximum pressure that will be used is defined; this should not exceed the confining pressure expected from the depth of the drilling; We work on this maximum pressure during the test to avoid generating fractures in the rock due to the pressure generated by the water.

The maximum pressure is related to the objective of the test, for example to evaluate infiltration losses in a reservoir to be created.

For each pressure level, the test consists of pumping the amount of water necessary to maintain a constant pressure in the test area. This pressure is increased at each subsequent level, until reaching the maximum pressure already established. Once this is reached, the water pressure must be reduced, passing through the same pressures of the previous states.

The five states are:.

PMAX being the maximum defined pressure at which the water must be injected.

The permeability is determined with the formula:.

Permeability is usually measured in "Lugeons", a unit named in honor of the geologist Maurice Lugeon.