Drilling assisted exploration programme for ground water was initiated by CGWB (the then ETO-Exploratory Tubewell Organisation) in 1954. In the initial years, exploratory drilling activities were confined to alluvial tracts. In mid-eighties, Down The Hole Hammer (DTH) drilling rigs were introduced for exploratory drilling in hard rock terrains. Another important development in the early nineties was introduction of open hole drilling technology using percussion drilling rigs for exploratory drilling in boundary/semi-consolidated formations in Himalayan foothills. These exploration programmes formed the background of scientific evaluation of the water bearing properties of various rock formations.
Every year around 750 wells are drilled by CGWB for ground water exploration through in-house resources. CGWB has a fleet of 78 drilling rigs and has capability to construct wells in various types of terrain in the country. In view of enhanced requirements of ground water exploration under the NAQUIM programme, CGWB has also taken up exploratory drilling through outsourcing. The basic concepts and guidelines on ground water exploration can be accessed from Quick Links menu
| Type of Drilling Rig | Number of Drilling Rigs in CGWB |
|---|---|
| Direct Rotary | 24 |
| DTH | 52 |
| Dual Rotary | 2 |
| A high-yielding fracture tapped during exploratory drilling under NAQUIM programme in hard rock areas of Banswara district of Rajasthan with yield of 1100 litre per minute (lpm) | High discharge exploratory well constructed at Puintala village in the drought-prone Bolangir district of Odisha. Drill-time discharge of 600 litres per minute (lpm) recorded in a an otherwise low discharge region. |
- Major activities involved in exploratory drilling are as follows:
- Site Selection
- Selection of Suitable Drilling Technique
- Data Collection During Drilling
- Well Construction
- Well Development
- Pumping Test
- Data Analysis
- Report Preparation
Pumping Test/Aquifer Test is an important activity in ground water exploration, which is performed to find out the behaviour of aquifer as well as the well in response to the stress applied in the form of pumping. The well is pumped at known discharges and the effect of this pumping on the aquifer’s hydraulic head (water level) is measured in the well itself, and/or in a number of nearby piezometers or observation wells. The change in water level induced by the pumping is known as drawdown. The pumping tests are generally conducted to determine:
- Yield and sustainability of well (Yield Tests)
- Performance and efficiency of the well (Well Performance Tests)
- Hydraulic properties of the aquifer (Aquifer Performance Tests)
