1. kelly
The kelly pipe is located at the upper end of the drill string, and its main role is to transfer the torque and withstand the total amount of the drill string. The end face of the drive part of the kelly pipe is divided into square and hexagon, the more square is used in oil drilling, and the water eye is a regular hexagon, because the wall thickness is about three times that of the drill pipe, and is made of high-strength alloy steel, so it has high tensile strength and torsional strength.

2. drill pipe
The drill pipe is the basic component of the drill string, which is mainly used to transfer torsion and transport drilling fluid.

The pipe body and joint of the drill pipe are connected together by butt welding method. In order to increase the strength of the joint, the butt welded part at both ends of the tube body is thickened, and the thickening form has three kinds of internal thickening, external thickening and internal and external thickening.

The inner thickening reduces the inner diameter of both ends of the pipe body to increase the thickness of the pipe wall. The outer diameter of the drill pipe is the same, and the outer diameter of the joint is not too large. When rotating in the well, the contact between the joint and the well wall is small, and the wear is also small.

The inner diameter of the thickened drill pipe is the same, but the outer diameter of both ends of the pipe body is increased, and the outer diameter of the drill pipe joint is larger than that of the same size drill pipe joint, which increases the contact friction between the joint and the wall when rotating in the well, and is easy to wear. Because the inner diameter of the drill pipe is the same as the inner diameter of the pipe, the flow resistance of the circulating drilling fluid is less.

The internal and external thickening drilling is to reduce the inner diameter of the two ends of the pipe and increase the outer diameter to increase the wall thickness of the two ends of the pipe. The drill pipe of this structure combines the advantages of the above two kinds of drill pipe.

3. extra-weight drill pipe

The heavy drill pipe is characterized by more than 2 times the wall thickness than the ordinary drill pipe, the joint body is longer than the ordinary drill pipe, and the middle of the pipe body has a special wear roller. Weighted drill pipe is mainly used in the following aspects:

· 1) Used for the transition zone of drill collar and drill pipe to mitigate the change of bending stress between the two to reduce the damage of drill pipe.
· 2) In small hole drilling instead of drill collar, easy to operate
· 3) Replace most drill collars in directional Wells to reduce the occurrence of twist and stick, etc., thereby reducing costs and helping to maintain the orientation of directional Wells. Due to the large contact area between the drill collar and the tight hole, there is a lot of friction between the drill collar and the wall when rotating, so that the hole has the tendency of deflection. When the heavy drill pipe is used instead of the drill collar, this possibility can be reduced, and it is conducive to maintaining the orientation of the well.

4. drill collar

The drill collar is one of the main components of the drill string, its role is to provide bit weight, while making the BHA have a greater stiffness, so as to make the bit work stable, and help to overcome the hole inclination problem. Drilling classification:

· 1) Cylindrical type: a drill collar made of ordinary alloy steel with round inside and outside the cross section of the tube body
· 2) Spiral type: a drill collar made of ordinary alloy steel with a spiral groove on the surface outside the tube.
· 3) Non-magnetic type: made of stainless alloy steel with very low permeability, the pipe body cross-section inside and outside diameter are round drill collar. The types of drill collars are also square drill collars and non-magnetic spiral drill collars.

spiral dirll collar

The function of the spiral drill collar is to reduce the occurrence of sticking. Three right-handed spiral grooves are processed on the outer cylinder of the round drill collar, and a segment of 305-560mm is left in the outer thread joint part and 475-610mm is left in the inner thread end joint part. The weight of the spiral drill collar is 4% less than that of the same size round drill collar.
Spiral drill collar is not included in the API standard, but there are many manufacturers in foreign countries, and domestic drill collar has been officially put into production, and its specifications and dimensions are the same as foreign products.

6. Drilling tool stabilizer (stablizer)

1) Stabilizer commonly known as centralizer, a certain number of stabilizers are placed in the suitable position of the drill string to form the lower drilling assembly of the drill string, which can prevent the inclination of the well when drilling a straight well and control the trajectory of the hole when drilling a directional well.
2) The use of stabilizers can play a role in improving the stability of the bit, so as to extend the service life of the bit, which is particularly important for diamond bits.
Commonly used stabilizers are divided into three roller stabilizers, replaceable sleeve stabilizers, integral spiral stabilizers, and integral straight edge stabilizers.

7. non-magnetic drill collar
The structure of non-magnetic drill collars is the same as that of ordinary drill collars, but the chemical composition and mechanical properties are different from ordinary drill collars. Non-magnetic drill collar is a kind of drilling tool with special function in directional well engineering. When the magnetic clinometer is used to measure the inclination Angle and azimuth Angle of the hole in a directional well, in order to prevent the compass from being affected by the magnetic field of the drill string, the drill string must be equipped with a certain length of non-magnetic drill collar, so that the magnetic clinometer can be located in a suitable position in the non-magnetic drill collar to measure the inclination, otherwise the correct measurement results cannot be obtained.