Methods of drilling wells

Methods of drilling wells

Drilling is the process of making holes in the earth crust. Many methods can be used for
drilling wells.
Drilling methods can be classified in accordance with various principles. Any methods of drilling
involves formation disintegration machine which can be used for drilling, disintegrate and
excavate rock by four basic mechanism:-
A - By mechanically induced stresses.
B - By thermally induced stresses.
C - By fusion and vaporization.
D - By chemical reactions.
From all the principles mentioned only mechanical drillings widely used for drilling oil and gas
wells. Drilling methods based on other mechanism of formation disintegration were tested in
laboratories and in the field but not used in the industry.
Industrial methods of mechanical drilling can be further subdivided according to the character
or rock design tools motion.
I. Drilling methods with reciprocating motion of the tool.
II. Drilling methods with rotary motions of the tool.
Mechanical methods of drilling with rotary motion of the working tool are the most
widely used methods in the oil and gas industry.
These methods can be classified in accordance with the position of a mover that drives the
tool:
1- Drilling methods with the mover on the earth surface.
2- Drilling methods with the mover situated near the bottom of the hole.
One of many possible classification of drilling methods is given below:
Now, two drilling methods are widely used:
1- Rotary drilling (about 85 % of total footage in the USA and other countries except the
USSR).
2- Turbo-drilling (about 85 % of the total footage in the USSR).
Cable-tool drilling still being used in the USA and about 10 % of the total footage is drilled
with this method. Drilling with electro drill is under wide field experiment since more than 10
years in the USSR.
Hence rotary drilling is the most important method of making bore holes in petroleum
industry and it is this method that should be mainly Considered in the course of Oil Well
Drilling Technology.