A Comprehensive Guide To Drill Pipe Steel Grades

Drill pipe is a tool used in oil, gas and geological exploration projects. The rod body is mostly made of medium-carbon alloy structural seamless steel pipes, such as 36Mn2V, 35CrMo, 42MnMo7 and other types of steel, which have high tensile strength and impact toughness. The joint part is made of alloy structural steel, and the overall performance is improved through heat treatment processes (such as hardenability treatment). ‌

Drill pipe is an OCTG pipe. It is a key material for connecting drill bits and drilling tools. With different drilling depths and complexities, it requires drill pipes of different materials and steel grades to meet drilling requirements.

Drill pipe steel grade classification method

The steel grade classification of drill pipe mainly adopts the API specification (American Petroleum Institute) standard. The API specification stipulates the size, hardness, material composition and other standards of drill pipe, so that the drilling team can choose the appropriate drill pipe in different geological environments.

There are many drill pipe steel grades defined in the API standard, mainly including but not limited to the following:

1. E-75

This is a drill pipe steel grade with a minimum yield strength of 75,000 psi.

2. G-105

A drill pipe steel grade with a minimum yield strength of 105,000 psi.

3. S-135

This is a high-strength steel grade with a minimum yield strength of 135,000 psi.

4. V-150

This steel grade of drill pipe has a minimum yield strength of 150,000 psi.

5. X-95

This steel grade of drill pipe has a minimum yield strength of 95,000 psi.

6. Z-140

This steel grade of drill pipe has a minimum yield strength of 140,000 psi.

7. NC50

This is a drill pipe steel grade with special needs, usually used for medium to heavy load applications with non-corrosive or effective corrosion inhibition.

8. HT Series

For example, HT55, this is a heat-treated steel grade that provides extra strength and durability.

9. XT Series

For example, XT54 and XT57, these are extra-strength steel grades used in more demanding applications.

10. GPDS Series

For example, GPDS26 and GPDS46, these are high-strength drill pipe steel grades used in specific applications.

11. IEU (Internal-External Upset) and IF (External Upset)

These refer to the type of drill pipe joints, IEU means internal and external upset, and IF means external upset, which affect the strength and pressure-bearing capacity of the drill pipe.

Differences among the main steel grades

1. D-grade steel

D-grade steel has lower strength and is often used for shallower drilling work. It is mainly composed of ordinary carbon steel and can be used in most geological environments.

2. E-grade steel

E-grade steel is more durable than D-grade and can withstand deeper well depths. Its main component is low alloy steel containing manganese. Due to the high manganese content, the manufacturing cost is relatively high.

3. X-grade steel

X-grade steel can withstand higher pressure and friction and is suitable for deepwater or ultra-deepwater drilling. Its main component is alloy steel containing nickel, chromium and molybdenum, which has higher strength and corrosion resistance.

4. G-grade steel

G-grade steel, also known as high-strength steel, can withstand greater tension and pressure and is suitable for drilling in complex geological environments. Its main component is alloy steel containing chromium, molybdenum and cobalt, which has higher strength and corrosion resistance.

Commonly used drill pipe steel grades

Currently, the commonly used drill pipe steel grades can be divided into the following five types:

1. E75 steel grade

E75 means strength grade 75 ksi (500MPa), which is a relatively common drill pipe steel grade, mainly composed of carbon, manganese, silicon, phosphorus, sulfur, chromium, molybdenum and other elements, with high strength and toughness.

2. X95 steel grade

X95 means strength grade 95 ksi (655MPa), which is a high-strength drill pipe steel grade, mainly composed of chromium, molybdenum, titanium and other elements, with extremely high wear resistance and corrosion resistance, suitable for deep and difficult drilling operations.

3. G105 steel grade

G105 means strength grade 105 ksi (724MPa), which is a drill pipe steel grade with good wear resistance, mainly composed of chromium, molybdenum, nickel and other elements, with high strength and toughness, suitable for deep and ultra-deep wellbore wall drilling machinery.

4. S135 steel grade

S135 means strength grade 135 ksi (931MPa), which is a high-strength, high-toughness, high-wear-resistant drill pipe steel grade, mainly composed of carbon, molybdenum, chromium and other elements, can adapt to extreme downhole environments, and can meet the requirements of ultra-deep and high-strength wells.

5. V150 steel grade

V150 is a new steel grade composed of vanadium, phosphorus, sulfur and other elements. It has high strength, high rigidity and high wear resistance and is widely used in new and difficult drilling fields.

Tips for judging drill pipe steel grade

1. Observe the drill pipe steel grade mark to determine the grade and strength grade of the steel.

2. Infer the steel grade of the drill pipe by testing and analyzing the chemical composition of the drill pipe. For example, a drill pipe with high chromium, high molybdenum and high titanium content may belong to the high-strength G-105 or S-135 grade.

3. Perform mechanical tests on the mechanical properties of the drill pipe, such as tensile tests and impact tests, to determine its strength grade and steel grade.

How to choose the right drill pipe steel grade

When choosing a drill pipe steel grade, the following points need to be considered:

1. Well depth and complexity

Choose the right drill pipe steel grade based on factors such as drilling depth, wellbore size, inclination, and formation state to meet the requirements of drilling construction.

2. Downhole environment

Choose drill pipe materials that can adapt to the downhole environment, including the influence of ambient temperature, pressure, corrosive agents, etc.

3. Cost factors

The performance and price of drill pipe steel grade are positively correlated. Select the appropriate steel grade to reduce costs as much as possible while ensuring safety and operating efficiency.

Summary

The steel grade of drill pipe is one of the key factors affecting drilling operations. Various steel grades have their own characteristics. Choosing the right steel grade is of great significance to drilling construction. When choosing, it is necessary to fully consider the safety, efficiency, economy and other factors of drilling operations. Through the reasonable selection of drill pipe steel grade, the effectiveness and benefits of drilling construction can be improved.