Introduction to BEYOND drilling tools

Time : 2025-06-07

1.The composition and function of the drill string

(I) Composition of drill string

Drilling String is the general term for the steel pipe string above the drill bit and below the tap.

It includes downhole tools such as Square Kelly, Drill Pipe, Drill Collar, various joints, stabilizers, etc.。

(II) Function of drill string

(1) Provide a flow channel for drilling fluid;

(2) Provide drilling pressure to the drill bit;

(3) Transmit torque;

(4) Lift and lower the drill bit;

(5) Measure the well depth;

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

(7) Perform other special operations (coring, cementing, salvage, etc.);

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

图片1.jpg

图片2.jpg

2. Drill pipe

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

(2) Structure: pipe body + joint

(3) Specifications:

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

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

Length: generally around 9.5m.

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

Physical properties		Drill pipe steel grade
Physical properties		D	E	95(X)	105(G)	135(S)
Minimum yield strength	MPa	379.21	517.11	655.00	723.95	930.70
Minimum yield strength	1b/in	55000	75000	95000	105000	135000
Maximum yield strength	MPa	586.05	723.95	861.85	930.79	1137.64
Maximum yield strength	1b/in	85000	105000	125000	135000	165000
Minimum tensile strength	MPa	655.00	689.48	723.95	792.90	999.74
Minimum tensile strength	1b/in	95000	100000	105000	115000	145000

图片4.jpg

Connectors and threads

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

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

Drill pipe joint types:

Flat inside (IF), through hole (FH), regular (REG); NC series

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

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

Regular type: mainly used for internal thickened drill pipe and drill bits, salvage tools. Its characteristic is that the inner diameter of the joint is less than the inner diameter of the thickened part, and the drilling fluid flow resistance is large, but the outer diameter is the smallest and the strength is greater.

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

图片5.jpg

NC series connectors

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

NC—National Coarse Thread, (US) National Standard Coarse Thread.

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

For example: NC26 indicates a pitch diameter of 2.668 inches.

NC thread is also a V-type thread. The NC type connectors in the table have the same pitch diameter, taper, pitch and thread length as the old API standard connectors and can be used interchangeably.

The difference between digital connectors and old API connectors