Maintenance and Use of Drill Pipes

**Maintenance and Use of Drill Pipes**

**Abstract:**
The main forms of drill pipe damage include grooves and dents on the shoulder surface of the joints, as well as corrosion and erosion on the pipe body. This article analyzes the causes of drill pipe damage during drilling operations, as well as the methods for maintenance and proper usage. The goal is to provide guidance for drilling operations, extend the service life of drill pipes, and prevent drill pipe accidents.

**Keywords:** Drill Pipe; Maintenance; Usage; Prevention

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### 1. Introduction

The drill pipe is a crucial component of drilling machinery. The drill string, composed of drill pipes, is used to transmit torque and drilling pressure. It also serves as a channel for drilling fluid, and is essential for bit replacement and accident management. Moreover, it is the part most prone to damage.

### 2. Stress and Operating Conditions of Drill Pipes

The drill string is an elastic system, subjected to varying loads in both magnitude and direction during drilling. The load distribution across different sections of the drill string is uneven. Additionally, friction between the drill string and the borehole wall, as well as occasional sticking, further complicates the stress conditions.

During various drilling operations, the drill string experiences different types of stress, including tensile, compressive, torsional, and bending stresses. The drill string also undergoes longitudinal and lateral vibrations due to bending and twisting deformations, which cause vibrational loads on both the drill string and surface equipment.

### 3. Drill Pipe Damage and Mechanism Analysis

According to inspection records from the Zhongyuan project in 2018, the following damage statistics were observed:
– Thread galling accounted for 66% of drill pipe replacements.
– Pipe bending accounted for 2.3%.
– Grooves on the shoulder surface accounted for 35.2%.
– Severe thread wear accounted for 13.2%.
– Damage to internal and external threads and shoulder surfaces accounted for 9.6%.
– Thread shoulder scratches accounted for 5.7%.
– Eccentric wear and external diameter reduction accounted for 9.8%.
– Wall thinning or punctures due to erosion accounted for 17.6%.

The main causes of drill pipe damage are as follows:

1. **Early Joint Damage:**
– Thread quality issues during manufacturing (e.g., improper thread fit, surface finish, and hardness) lead to thread galling.
– Inferior thread compound fails to form a protective film, causing thread wear or galling under pressure.
– Inadequate or uneven application of thread compound and improper cleaning of internal and external threads result in thread wear or damage to the shoulder surface.
– Misalignment during make-up causes accelerated thread wear, insufficient or excessive make-up torque, leading to thread damage.

2. **Friction between the rotating or tripping drill pipe and the borehole or casing causes external diameter wear or eccentric wear.**

3. **Corrosion and erosion of the pipe body:**
– High-pressure, high-velocity drilling fluids cause erosion, thinning, or punctures in the pipe wall.
– Long-term storage of new drill pipes leads to CO2 absorption and electrochemical corrosion.

4. **Impact Damage:**
– Improper handling during tripping, causing pipe bending or damage to the thread shoulder.
– Damage during transport or from rough handling on the rig floor.

### 4. Maintenance and Use of Drill Pipes

1. **Thread and Joint Maintenance:**
– **Protection during use:**
– Clean the threads thoroughly before drilling and use thread protectors.
– Apply high-quality thread compound that meets standards.
– Evenly apply thread compound to both internal and external threads, including the shoulder surface.
– Avoid forcing misaligned threads during make-up, and ensure proper torque according to API RP7G standards.
– **Welded Hardbanding Technology:**
– Applying welded hardbanding on joints can significantly reduce wear and extend the service life of both the drill pipe and casing.

2. **Maintenance of the Pipe Body:**
– Inspect the pipe before use, and do not use pipes with significant damage or wear.
– Avoid hitting the pipe with heavy hammers, and use wooden boards on the rig floor to protect the pipe.
– Follow the designed parameters and avoid overloading the drill pipe.
– Apply thread compound and use thread protectors during transport.
– Regularly inspect for cracks or erosion to prevent failures.

3. **Use of Internal Coatings:**
– Internal coatings can protect the pipe from erosion and corrosion, extending the service life.

### 5. Conclusion and Recommendations

To prevent drill pipe failure, the following preventative measures are recommended:

1. **Strengthen Pre-Drilling Inspections:**
– Inspect the quality of the drill pipe, including material, hardness, threads, and heat treatment.
– Regularly inspect and repair drill pipes during storage.

2. **Standardize Drill Pipe Operations:**
– Evenly apply thread compound and ensure proper make-up torque.
– Avoid damaging the pipe surface, especially the sealing surfaces.

3. **Use Drill Pipes Scientifically:**
– Ensure smooth transition in the stiffness of the drill string to avoid localized stress concentrations.
– Use larger diameter drill pipes whenever possible.
– Carefully select drilling parameters to avoid drill string resonance and buckling.

4. **Routine Maintenance:**
– Regularly clean the internal and external surfaces of the drill pipe to reduce corrosion.
– Strengthen non-destructive testing, especially for high-stress areas.

By following these recommendations, the service life of drill pipes can be extended, and the risk of accidents can be minimized.

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This is a comprehensive analysis of the causes of drill pipe damage and the maintenance methods needed to prevent premature failure.