Rotary drill pipe types

The function of drill pipe is to transmit the output torque of power head and pressure to the drilling tool, and to cut, crush, pull or grind the geology. There are three types of drill pipes: friction type, machine lock type and combination type. Among them, the machine lock type is divided into: sectional type and multi-point interlocking type.
1. Friction rod: Through drilling load, friction resistance is formed between drill rods and pressure is transferred.
Advantage:
Drilling depth (friction rod is one section more than machine lock rod).
The speed of lifting up and drilling down is fast.
No locks or unlocks are required.
Therefore, it is easy to operate, saves time and has low probability of carrying rods.

Disadvantages:
When there is no load (slip), the pressure is almost lost.
Not suitable for hard formation.
Low pressure (e.g. 220 rig, torque load 22tm), with diameter 440 drill pipe.
The drill pipe radius is 0.22m, 22/0.22 = 100 (t).
The friction coefficient of steel is 0.11.
100 * 0.11 = 11 (t), in many cases the load can not reach the maximum, so the pressure will be smaller.

2. Machine lock rod
2.1. Segmentation
There are several fixed locking points on the drill pipe, which can transfer pressure without loss through the interlocking machine between the power bit and the drill pipe.

Advantage:
It can be applied to a wider range of strata.
Friction occurs in soft strata.
There is no loss of pressure.

Disadvantages:
Shallow depth (one section shorter than friction rod)
Slow drilling.
Increase the difficulty and time of operation.
Increase the odds of a pole.

2.2. Multipoint Formula

It can be applied to a wider range of strata.
No locks need to be found.
There is no loss of pressure.
Lock point connection increases drill pipe strength.

Disadvantages:
Shallow drilling (one section less than friction rod);
Increase the difficulty of operation;
Increase the odds of a pole.

3. Combination
The outer 3 sections are segmented locks and the inner 3 sections are friction rods, which are suitable for high strength upper sections and soft geology lower sections. It seems that there are only three-in-one configurations, which are seldom used in the market.

Advantage:
It can be drilled into upper hard formation.
The drilling depth of the locking rod is extended.

Disadvantages:
Increase the difficulty of operation.
Stratigraphic limitations.