Composition and Function of Drill String-Drill Pipe

1. Composition and function of drill string

(1) Composition of drill string

Drilling String is the geDrill Pipeneral name for the steel pipe string above the drill bit and below the faucet.

It includes downhole tools such as Square Kelly, DrillPipe, Drill Collar, various joints and stabilizers.

(2) Function of drill string

(1) Provide drilling fluid flow channels;

(2) Provide drilling weight to the drill bit;

(3)Transmit torque;

(4) Tripping drill bit;

(5) Measuring well depth;

(6) Observe and understand the underground conditions (drill bit working conditions, wellbore conditions, formation conditions);

(7) Carry out other special operations (coring, cement squeezing, salvage, etc.);

(8) Drill-Stem Testing, also known as mid-course testing.

1. Drill pipe

(1) Function: transmit torque and transport drilling fluid, and extend the drill string.

(2) Structure: pipe body + joint

(3) Specifications:

Wall thickness: 9 ~ 11mm, usually 9.19mm.

Outer diameter: Depends on various drill pipe conditions, such as commonly used 127, 140, etc.

Length: Generally around 9.5m.

Common drill pipe specifications (inner diameter, outer diameter, wall thickness, linear density, etc.)

  (2) Connectors and threads

Thread connection conditions: equal size, same thread type, male and female threads matching.

Drill pipe joint features: larger wall thickness, larger outer diameter, and higher strength.

Drill pipe joint type:

Internal Flat (IF), Full Hole (FH), regular (REG); NC series

Internal flat type: mainly used for externally thickened drill pipe. The characteristic is that the inner diameter of the drill pipe is the same, and the drilling fluid flow resistance is small; but the outer diameter is larger and easy to wear.

Full-hole type: mainly used for internal thickening of drill pipe. Its characteristic is that the drill pipe has two inner diameters. The drilling fluid flow resistance is greater than the inner flat type, but its outer diameter is smaller than the inner flat type.

Regular type: Mainly used for internal thickening of drill pipes, drill bits, and fishing tools. Its characteristic is that the inner diameter of the joint <the inner diameter of the thickened part <the inner diameter of the pipe, the drilling fluid flow resistance is large, but the outer diameter is the smallest and the strength is high.

This type of joints all use V-shaped threads, but the buckle type, buckle pitch, taper and size are very different.

NC type series connector

NC23, NC26, NC31, NC35, NC38, NC40, NC44, NC46, NC50, NC56, NC61, NC70, NC77, etc.

NC—National Coarse Thread, (U.S.) national standard coarse thread.

xx—Indicates the base thread pitch circle diameter, the first two digits expressed in inches are multiplied by 10.

For example: NC26 represents a pitch circle diameter of 2.668 inches.

NC threads are also V-type threads. Several NC-type joints listed in Table 2-17 have the same pitch diameter, taper, pitch and thread length as the old API standard joints and can be used interchangeably.

The difference between digital connectors and old API connections: