Geology Reference
In-Depth Information
Field Procedure
A slug test cycle comprises two pulses: the injection pulse and the pumping
pulse (Fig. 3).
Injection pulse:
The rapid insertion of the slug in the bore-well causes a
sudden increase in water level and it is followed by a gradual fall in order
to reach the static water level.
Pumping pulse:
Similarly when the slug is removed suddenly there is a
sudden fall in the water level and then gradually the water level tries to
regain its initial position.
The time taken to reach the initial water level during the injection and
pumping pulses is a direct function of the permeability of the formation.
Data have been recorded using Madofil (automatic water table recorders)
and is coupled with manual measurements which help in calibration and
checking of Madofil data.
Figure 3.
Madofil slug test data.
Data Processing and Interpretation
The recording of the drawdown and the recovery were verified to ensure the
quality of data acquisition. Each test is a cycle of rise and fall in the water
level and in the ideal condition, the water level should come back to its
original position (making
y
= 0). Also the drawdown and recovery curves
should be smooth without any noise.
The field records of water level through Madofil (the automatic water
level recorder) have not shown any noise in recording but in a few cases, a
definite trend of water level decline/increase (of the order of 10 cm) was
observed which is much beyond the accuracy of Madofil (1 cm). This trend
phenomenon is the consequence of pumping in farmer bore-wells or recovery
in wells close to observation wells.
