Borehole Design, Drilling, Construction & Equipment – (A brief insight) A borehole comes in handy to supplement other water sources that may not be having adequate amount s of water as may be the requirement for domestic, agricultural, industrial, communal usage etc. We have over the years undertaken hundreds of boreholes in various sectors. We herein briefly outline the most important basics that one need to know about borehole designs, drilling, construction and Pumping Equipment
A well, be it shallow or deep (borehole) is a hydraulic structure which, when properly designed and constructed, permits the economic abstraction of water from a water-bearing formation. Successful wells are designed and constructed by using materials that will provide an efficient well with a long service life, taking maximum advantage of the hydro geological conditions, and applying the principles of hydraulics in a practical way to the analysis of wells and aquifer performance.
Typical borehole design
Various drilling methods have been developed because geologic conditions range from hard rocks such as granite and dolomite to completely unconsolidated sediments such as alluvial sand and gravel. Particular drilling methods are dominant in certain areas because they are most effective in penetrating the local aquifers and thus offer cost advantages.
The drilling procedure depends on the depth and diameter of the well, type of formation to be penetrated, sanitation requirements and the principal use of the well. No single drilling method is best for all geological conditions and well installation.
Well construction comprises four or five distinct operations: drilling, installation of casings, placing a well screen and filter pack, if required, grouting to provide sanitary protection, and developing the well to ensure sand-free operation at maximum yield.
The driller is expected to report changes or fluctuations in the static water level at various depths during the course of drilling. Whenever possible, pumping tests should be carried out to determine borehole yield.
Common Drilling methods
- In The Cable Tool Percussion, the borehole is stabilized during the entire drilling operation.
Recovery of reliable samples is possible from every depth unless heaving conditions occur. The well can be constructed with little chance of contamination. Because of size, drilling rig can be operated in more rugged, inaccessible terrain or in other areas where space is limited. The well can be drilled in formations where lost circulation is a problem. The well can be bailed at any time to determine the approximate yield at that depth.
- In The direct Rotary Drilling method, penetration rates are relatively high in all types of material. Minimal casing is required during the drilling operation. Rig mobilization and demobilization are rapid. Well screens can be set easily as part of the casing installation. This method has of late been adopted in most drilling operations due to its flexibility in mobilization High penetration rates and overall reduced cost since there is no need of establishing a site camp as tents will serve for the few days (mostly less than a week) that the work will be in progress.
Borehole construction Casing
The casing serves as a housing for the pumping equipment, holds the borehole walls from collapsing and as a vertical conduit for water flowing upward from the aquifer to the pump intake. Selection of casing material is based on water quality, well depth, cost, borehole diameter, and the drilling procedure. Steel is used most commonly, but thermoplastic materials can be used especially in areas where groundwater is highly corrosive and the depth of the well is less than 200 meters.
The choice of gravel pack material used for screens depends on the rock layer and formation, potential presence of iron bacteria and strength requirements. Water quality analysis show whether groundwater is corrosive or incrusting or both. It is therefore important to use a well screen fabricated from corrosion-resistant material. Incrusting water deposits minerals on the screen surface and in the pores of the formation just outside the screen. These deposits plug both the screen openings and the formation.
Gravel Pack permits water to enter the well from the saturated aquifer, prevents sediment from entering the well and serves structurally to support unconsolidated aquifer material. The value of a Gravel Pack depends on how effectively it contributes to the success of a well. The Gravel Pack should not clog at any time and should thus be correctly sized , sufficient column and collapse strength. It should also be easily developed and resistant to corrosion.
Selection of the type of borehole pump to be installed in a productive borehole will depend on a myriad of factors some of which may border to affordability of day to day running expenses and maintenance and/or the quantity of water required. Other factor will be chemical and physical components of the water, available mode of power (Electrical, Fuel, Solar and Manual). There are different types of pumps namely:
The Last is the most commonly used type of pump and installed right at the bottom of the borehole with the only difference being the Power source, which are Mainly Electricity, Diesel Generators and solar power. In spite of all the different type of pumps the basic determinant of the size and the eventual cost of the pumping Equipment is the Depth of the borehole and the sustainable Maximum borehole yield that is usually determined during the test pumping process after completion of drilling.
Water link’s Equipment
We have invested substantially mainly in our drilling department and in our fleet have:
Acker rotary rig, truck mounted complete with a compressor 420 PSI/ 1100 cfm, and 100HP mud pump capable of doing 350 meters of 8 inch hole in all types of formations
prd rotary rig on tow with compressor 300 Psi/900CFM and 10 HP Mud pump capable of 200 mtrs of 8 inch hole in all formation.
A fleet of 4 wheel trucks and vans in our support team Where we may fall short we do hire from our co-operating engineering firms at highly discounted costs and thus maintaining our competitiveness .
We boast of having a team of highly qualified and experienced workforce, which we understand and appreciate as the backbone of every efficient organization, presently in our employment we have highly Qualified managers and project planners, Engineers, Technician