The Lugeon test (or Packer Test)

Background

The Lugeon test (or Packer Test) is an in-situ testing method widely used to estimate the average hydraulic conductivity of rock formations. The test is named after Maurice Lugeon (1933), a Swiss geologist who first formulated the test. The test is also referred to as a Water Pressure Test. The Lugeon test is a constant rate injection test carried out in a portion of a borehole isolated by inflated packers. Water is injected into the isolated portion of the borehole using a slotted pipe. Water is injected at specific pressure “steps” and the resulting pressure is recorded when the flow has reached a quasi-steady state condition. A pressure transducer is also located in that portion of the borehole to measure the pressure with a help of reading station on the surface. The results provide information about hydraulic conductivity of the rock mass including the rock matrix and the discontinuities. (Royle, 2010)

Test Description

The following is a general description of the test. There are several variations and interpretations of the Lugeon test.  Readers are encouraged to consult the supporting materials in the References section.  A more thorough description of the field procedure can be found in ISO 22282-3. (Geotechnical investigation and testing -- Geohydraulic testing -- Part 3: Water Pressure Tests in Rock)

Based on the drill core, an assessment of the expected injection rates and pressure can be made. The tester will need to have an idea of the pressures to be tested. The expected pressure range will be based on the estimated permeability of the rock and the expected intake of injected water. These will have to be assessed based on previous experience in the borehole(s), and correlated to the pumping equipment available. A maximum test pressure (Pmax) is defined so that it does not exceed the in-situ minimum stress, thus avoiding hydraulic fracturing.

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