1. Deptt. of Irrigation and Drainage Engineering, Dr. PDKV, Akola
Development of Well
M. U. Kale
Assistant Professor
Deptt. of Irrigation and Drainage
Engineering, Dr. PDKV, Akola

2. Development of well – to obtain efficient and long lasting well
Development involves – removal of fine material around the well screen, enlarging the passage for entry of water
Development of well increases the effective radius of well and its yield.

3. Objectives of Development of well
To correct any clogging of water bearing formation.
To increase the porosity and permeability of the water bearing formation in the vicinity of the well.
To stabilize the formations around the well screen so that the well will yield sand-free water.

4. Methods of Well Development

5. Over Pumping
To remove fine particles in case of shallow tube wells
Not effective as compared to other methods.
Operate the well at discharge higher than its capacity, except the well in hard rock which is developed at normal discharge.
Over pumping may be continuous.

6. Over pumping means pumping the well continuously at a rate not less than 50 % in excess of its normal discharge except in hard rock.
The development is carried out in at least five steps.
The steps include pumping rates of 1/4, 1/2. 1, 1.5 and 2 times the design capacity, without using foot valve.
Pumping may be conducted in 5 minute cycles and should continue for minimum of 2 hours.

7. Surging with surge block and bailing
Surging consist of working a block or plunger up and down in the tube well so that the water is alternatively forced into the surrounding formation and then allowed to flow back into the well.
Surging action loosens fine sand or gravel particles near the well screen and carries the finer particles into the well from where they can be removed.

8. Adaptability
Does not work effectively in wells tapping low-yielding aquifers.
It is useful for the development of strainer wells or wells with a limited thickness of gravel pack.

9. Surging with pumping and compressed air
Surging with pumping and compressed air is combination of surging and pumping.
A large volume of air is released into the well casing pipe, which produces a strong surge.
Pumping is done with ordinary air-lift pump.
For effective development of well submergence ratio is important.
Submergence ratio is the ratio of length of airline in water divided by its total length.

10. Adaptability Limitations
For development of drilled wells in alluvium formations.
Limitations
Not used for shallow tube wells with coir strainer.
Not suitable for wells where yield is low, drawdown rapid or where submergence is low.

11. Back-washing Water under pressure is forced into the well screen.
Agitates the formation in the vicinity of well screen, which causes the breakdown of bridging sand particles and washes out fine particles.
It is effective method of well development.

12. Back-washing by pumping
Also known as rawhiding.
Consists of starting and stopping the pump intermittently to produce relatively rapid changes in the water level in the well.
Most effective when turbine pump without foot valve is used.

13. Back-washing under pressure
Water is fed into the well under pressure
After some time of feeding water, the well is pumped out vigorously.

14. Back-washing with compressed air
Water is forced back into the formation by means of compressed air.
Similar to back washing under pressure except that instead of water, air is used.
Suitable for wells drilled by direct rotary rigs.
This method is useful for wells having excessive thickness of gravel pack.
If stratum above the aquifer comprises of sandy clay, silt or similar material, back washing method is not suitable

15. High Velocity Jetting
Jetting with water at high velocity is an effective method of development of tube wells.
The high velocity jet working through screen openings agitates and rearrange the sand and gravel particles of the formation surrounding the screen.

16. Dynamiting and Acid Treatment
Not much development work is needed in consolidated formations.
Wells drilled in limestone aquifers are developed by using acid which dissolves limestone.
The dissolution of limestone results in opening the fractures and crevices in the formation.
In granite and genesis formations, water flows through cracks, crevices and joints. They can be opened by shooting a charge of dynamite opposite the flow zone.

17. Dispersing Agent
Adding small quantity of suitable polyphosphate to drilling mud or the water used in back washing, jetting and to the water standing in the well helps considerably in the removal of mud while developing a well.
The phosphate disperse the clay particles in the drilling mud and breaks its gel properties.

18. The polyphosphate that work effectively in helping and removal of mud are tetra-sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and sodium septa-phosphate.
About 2 kg of the chemical is added to 400 lit water

19. Well Interference
If the spacing between the wells is not adequate, the discharge of both wells will be reduced.
Discharge reduces due to increase in drawdown.
In confined aquifer the yield of each of three wells forming equilateral triangle spaced at distance 2a is given as
Assignment - Example 2.9, Book No. 01

20. Multiple-well System
A multiple well system is a group of closely installed shallow tube wells, usually connected to a common header pipe or manifold and pumped by a suction lift of a centrifugal pump.
Such system is also known as well-point system or battery of wells.
The individual wells in a well battery may be strainer well or cavity well depending upon the characteristic of water bearing formation.

21. Battery of wells is adapted under following conditions
Shallow water table
Installation of medium or deep tube well is not economical.
Poor hydraulic characteristics
Salts are present in deeper layers of water bearing formations
Waterlogging problem
To lower down the water table.
Mostly adopted in deltaic region.

22. Thank you