Drill pipe is a steel pipe with a threaded end that is used to connect the surface equipment of the drilling rig to the drilling. And grinding equipment or bottom hole device locating at the bottom of the drilling rig. The purpose of the drill pipe is to transport drilling mud to the bit and to raise, lower, or rotate the bottom hole device with the bit. The drill pipe must be able to withstand tremendous internal and external pressure, distortion, bending and vibration. In the process of oil and gas extraction and refining, drill pipe can be using many times. Drill pipe is dividing into three categories: kelly pipe, drill pipe and weighted drill pipe. The connection sequence is kelly pipe (1 piece)+ drill pipe (n pieces, determined by the well depth)+ weighted drill pipe (n pieces, determined by the drill assembly design).
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The common components of the drill string are: drill bit, drill collar, drill pipe, stabilizer, special joint and kelly pipe.
API standard E75 to S135 steel grades from 2 3/8 “to 6 5/8” outside diameter series of oil drill pipe as well as high torsional resistance double shoulder joint drill pipe. And special steel grade BNK C95S drill pipe for sulfur Wells. It is mainly appliing to the construction of deep Wells. Horizontal Wells and extending reach Wells in the process of oil and gas exploration and development.
Drill pipe is dividing into three categories: kelly pipe, drill pipe and weighting drill pipe. The connection sequence is kelly pipe (1 piece)+ drill pipe (n pieces, determined by the well depth)+ weighted drill pipe (n pieces, determined by the drill assembly design).
The kelly pipe is located at the top of the drill string. And has two kinds of square and six square.
Effect:
1.When drilling, the kelly is matching with the bushing. And the turntable bushing to transmit the ground rotating torque to the drill pipe to drive the drill string and bit rotation;
2.Bear the full weight of the drill string;
3.Channel for drilling fluid circulation.
Kelly pipe consists of upper and lower joints and pipe body parts. The pipe body part is of two kinds of structure (most of the oil drilling is of four square structure). The upper connector is the left female thread (reverse button), connecting with the faucet, in the rotation process of the left female thread to prevent reverse. The lower joint is right-handing male thread and is connecting with the drill pipe. When working, the upper end of the kelly is always above the turntable surface. And the lower part is below the turntable surface.
Drill pipe
Effect：
Drill pipe is the basic component of drill string. Its main function is to transfer torque and transport drilling fluid, and by gradually lengthening the drill pipe to deepen the hole. Therefore, drill pipe plays a very important role in oil drilling.
Structure：
Drill pipe structure Drill pipe is made of random steel pipe, the wall thickness is generally 9 ~ 11mm; The drill pipe body. And the drill pipe joint are composing of two parts. The pipe body and the joint are welding together by friction welding.
The weighted drill pipe is similar to the oil drill pipe, which is also a hollow steel column with a length of about 10 meters. However, the single weight is heavier than the oil drill pipe. The wall thickness is 2 to 3 times that of the drill pipe. And the drill pipe is connecting between the drill pipe and the drill collar, the purpose is to prevent the fatigue damage when the drill string cross-section changes, and it can also replace the role of a part of the drill collar, but its suspension is simple, the operation is convenient, and the drilling trip time can be saving.
Drill pipe connections play a critical role in the drilling industry. They are the link between the drill string components and provide the necessary strength, sealing, and transmit torque to the drill bit.
These connections withstand the demanding conditions encountered during drilling operations, including high pressures and stresses, different loads, and corrosive environments.
Various types of drill pipe connections have been developed to meet specific operational requirements and challenges, offering different features, strengths, and limitations. That is why it is essential to know the type of drill pipe connection needed, which is what this post is about. Read on!
Selecting the right drill pipe connection type is crucial for the success and safety of drilling operations. The choice of connection or drill pipe joint can significantly impact the efficiency and even more importantly, the safety of drilling projects, such as by preventing unfortunate accidents.
A compatible connection will remain intact during operation, enhancing drilling performance, minimizing downtime due to failures, and reducing the risk of environmental hazards such as oil spills or gas leaks.
Additionally, the right connection type can go a long way in prolonging the life of the drill string and drill collar, reducing the frequency of replacements, which can result in cost savings for drilling companies.
There are various types of drill pipe connections. They are primarily divided into API threads and premium connections.
While both are rotary shouldered connections, API connections are standard connections with a single shoulder compared to a premium thread.
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Premium threads are proprietary connections with a double shoulder and are available in multiple sizes. They offer enhanced performance with better metal sealing, torque shoulders, and durability and longevity compared to standardized API connections, making them a better choice for more demanding drilling scenarios
Below is each API spec connection explained in detail:
The regular style connection (REG) is specifically designed to connect inner upset drill pipes. This connection features the smallest outer diameter and results in the inner drill pipe diameter being lesser than the thickened part of the drill pipe, and the internal diameter of the thickened portion of the drill pipe is smaller than the inside diameter. The REG connection is used for bit connections in drilling operations.
The American Petroleum Institute (API 5CT) has retained all specifications for the REG connection, due to its specialized application and suitability for bit connections.
Its design suits the unique requirements and challenges associated with bit connections, making it a preferred choice for many drilling professionals.
As the drill bit is located at the end of the drilling string, the REG connection experiences reduced stress concentration in the drill pipe thread compared to other connection types. That reduces the risk of fatigue failure and enhances its overall reliability.
The REG connection is primarily for bit connections, so it may not be suitable for other drilling applications or equipment configurations. Its specialized design limits its versatility compared to some other connection types.
When using REG connections, the drilling pipe diameter is smaller than the inner diameter of the thickened portion due to the connection configuration. While this may not be a significant issue for bit connections, it can impact fluid flow rates and pressure ratings in particular drilling scenarios.
The internal flush (IF) connection has a larger outer diameter and connects external upset or internal and external thickened drill pipe. This connection forms a drill pipe joint with an inner diameter that is identical to or almost equal to the diameter of the pipe body.
One of the key advantages of the IF connection is the consistent inner diameter, which ensures a higher fluid flow rate and reduces the risk of restrictions or blockages during drilling operations, increasing efficiency.
However, a notable disadvantage of the IF connection is the potential for stress concentration. The design of the connection, particularly the triangular tooth design, can lead to localized areas of high stress. That may increase the risk of fatigue failure over time, compromising the integrity and reliability of the connection.
Because of the stress concentration issues associated with the IF connection and the development of newer, improved connection designs, the American Petroleum Institute (API) has replaced IF connections.
The full-hole (FH) connection connects the inner and outer thickened drill pipe, forming a drill pipe joint with an inner diameter that matches the thickened end diameter. Both the inner and outer diameters of the connection are smaller than the inside diameter of the drill pipe.
The FH connection offers three different thread specifications, namely V-0.065, V-0.05, and V-0.040, providing options for different drilling requirements and conditions. This versatility makes it widely used across various drilling operations, allowing flexibility and adaptability, such as with drill collars and bits.
One of the limitations of the FH connection is its smaller inner diameter compared to the inner diameter of the pipe. While this may not be a major issue in many drilling operations, it can impact drilling fluid flow rates.
Also, despite offering three different models, the FH connection has fewer thread specifications compared to other drill pipe connections. That may limit its adaptability to certain drilling conditions or equipment configurations, requiring careful selection to ensure compatibility and performance.
The numbered connection (NC) is made for drill pipes with a yield strength of at least 75,000 PSI or more, often referred to as high-strength drill pipes. The API recommends using NC connections for high-strength drill pipes due to their robust design and compatibility requirements.
NCs are engineered to join pins and boxes with equal thread designations, ensuring a secure and reliable connection. They are interchangeable if the grade codes match, meaning if the thread pitch is similar and the different threads are compatible.
The NC connections offer a variety of sizes and configurations to suit different drilling requirements and conditions, ranging from NC10 to NC77. They are suited to bear torsion, pressures, and various drilling rig motions, ensuring durability and reliability in demanding drilling operations.
However, mismatched thread types or pitches can lead to connection issues, compromising the integrity and reliability of the connection. So, it is essential to check with the tool joint manufacturer to ensure the compatibility of NC connections and thread types.
While NC connections are versatile and widely used, they are designed for high-strength drill pipes with a minimum yield strength of 75,000 PSI or above. That limits their application to specific drilling operations requiring high-strength equipment.
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Contact us today to receive a customized estimate for our drill pipe solutions. Experience unparalleled durability and reliability tailored to meet all your drilling operation needs with SOSSUSA!
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