Development of water wells

WATER WELLS
DEVELOPMENT OF WELL

To avoid damages and failures of well, well development matters a lot. The main objectives are

1. To clear mud cake formed on bore well wall against permeable zone
2. To clear invaded permeable zone and to remove material which give problem to yield
3. To minimize the skin effect and maximize well efficiency and specific discharge (Q) of the well.

Development Methods

Following two methods does the development of wells

1. Dispersed technique in which development forces allowed to act on the entire screen length at one time

2. Concentrated method in which the force is opposed on a reduced section of the screen at one time


The general dispersed methods are over pumping backwashing, mechanical surging and air development by surging and pumping. The concentrated methods are air surging and lifting and high velocity water jetting and airlifting.

Use of Chemicals

Using chemicals for well development in another efficient process. Most commonly used chemicals are polyphosphate- act as deflocculates and dispersion agent for clays and removal of mud cake. Acids which dissolve acid soluble parts of the formation, permits higher flow rate of water in to the borehole.

Development of Hard Rock Wells

The best technique in chemical treatment followed by air surging and lifting. These are aquifer development techniques in hard rock area where acids are used. Explosives are used hydro fracturing is also most effective to the aquifer yield.

Maintenance And Rehabilitation

The major components of a well maintenance are maintenance of the well and pump for that logbook and history book should be properly maintained to respective wells.

Pump Maintenance

Following points should be taken care of in pump maintenance. If yield falls about 10-15%, pumped should be examined. Any defect in pump observed, intermediate rectification should be done. Well bottom should be clear from filling well.

Well Sickness

The general types of well sickness are,

1. Sand pumping
2. Decrease in yield
3. Deterioration of quality.

Sand pumping due to various reasons like bridging of gravels, improper design, improper selection of gravel, inadequate development high rate of pumping, rapture in screen existence of gases in aquifer zone etc so for this proper understanding of the problem and proper remedies should be taken like lowering proper screen, proper gravel size etc if the problem is due to improper selection of screen and gravel.

Decrease in Yield

In some case, after the proper development, the yield of the well will be very low this is because of the change in regional hydro-geological parameters, for example, in cretaceous growth of bacteria, erosion structural failures or interference of another well nearby. For this hydro fracturing and chemical treatment, mechanical brushing, etc., needed.

Deterioration of Quality

Due to the contamination in surface water, inadequate flushing of aquifer, growth of bacteria etc. For this prevention measures like prevention of seepage of surface contamination and promotion of sufficient recharge should be done.