Rotary drillg methods to explore ground water

There are two kind of rotary rigs. They are direct rotary and another one is the reverse rotary rigs. Both of them have advantage one is suitable in case of hard formation and one other one is very suitable in case of loose formation such as gravel, sand and other loose formations Based on the their capacity the direct rotary rigs are classified as  Light rotary rigs, medium rotary rig and heavy rotary rigs. Rotary rigs with the rated maximum hook capacity, up to about 9000kg and capacity of drilling slim hole with 6cm. drill pipes, up to about 400 m may be may be consider light rig . They are suitable for drilling and completion of light- capacity tube well.to depth up to 60-150m or so, in alluvial and semi- consolidated formation. There average preformation may range between 5 to 30 m/day depending on the size and depth of the bore and type of formation. Medium direct rotary drilling rigs have rated maximum hook-load capacity up to 13000-18000 kg and are capable of drilling pilot hole up to depth of 700m.,using 6-7 cm.drill pipes. These rigs are suitable to drilling and completion of medium capacity tube well to a depth of 300m or so, in alluvial or semi consolidated formation. Heavy duty rotary rigs are have a maximum hooked capacity up to 22000to45000kg.. Yhey are capable of drilling pilot hole up to 1000musing 9cm drilling pipes. These rigs are suitable to construct heavy capacity tube well up to a depth of 250m.  Coming to the suitability of direct rotary rig it is quite suitable for drilling deep hole in unconsolidated formation. However it may be not economical for drilling in the formation like boulder and very hard formation, due to slow progress and high cost

of drilling bit it is also not suitable in alanted and fissured formatiom and serious lost circulation zone . Now the reverse rotary drilling is the process of drilling by reverse circulation of rotary drill wprks on the same principalas that of direct rotary method except that the drilling fluid is circulated in the reverse direction to that of direct rotary method.  In this process  the drilled fluid which is generally water is fed from tankdown the annural space between the hole and drilled pipeand is recovered along with the drillcuttingsthrough the drillpipe, generally by means of a centrifugal pump. It is discharged into the setting tank where the cutting are allowed to settle.So the these are the two way of rotary drilling. These method of rotary method are very popular in the terai part of Indo gangatic plain where ther formations are generally allvial and soft. however in the siwalik hill and along the Bhabar zone these method have low performence. There are several companies like Soilmec, Casagrande, Hutte etc.are involve in the construction of these type of drilling rigs. The rotary drilling rigs are used to construct irrigation wells. Rotary drilling methods are also applied in the core drilling where an information about the ubsurface are required. These are generally used to obtain core samples such as to determine the bearing capacity of formation for the construction of heavy building and bridges. In case identifaying mineral deposits it is also used. In this case the diameter of the drilled hole is reletively very small and there is no need of casing installation as in case of water, oil and gas wells. So In conclusion it could be summarised taht these typr of rig is very fruitful and benificial to construct drill hole that are used for verious purpose