Features of Different Types of Casing Pup Joints

Ordinary connection type casing pup joints

1. Structural features:

Both ends have standard casing pipe connection threads, which usually match the casing pipe threads of the same specification, and the thread precision requirements are high to ensure the tightness and sealing of the connection. For example, the API standard casing pup joint thread meets the API specification, and the parameters such as tooth type and pitch are precisely controlled, so that the pup joint can be smoothly connected with other casing pipes to form a complete casing string.

The shape of the pipe body is a simple cylinder, and its outer diameter and wall thickness are the same as the connected casing pipe, which ensures the structural consistency of the entire casing string and the smoothness of fluid passage.

2. Application scenarios:

It is mainly used to connect casing pipes of the same specification when the length of the casing string is adjusted. For example, in conventional oil drilling, when the total length of the casing string deviates slightly from the designed well depth, the length can be accurately adjusted by inserting the ordinary connection type casing pup joint, so that the casing pipe can be accurately lowered to the predetermined depth.

Variable diameter casing pup joint

1. Structural features:

The outer diameters of the two ends are different, showing a gradient shape. This pup joint is designed to connect casing pipes of different outer diameters. In the transition section, the outer diameter of the pup joint gradually changes from one specification to another to ensure that the fluid can smoothly transition between different pipe diameters and reduce pressure loss and turbulence.

Its internal structure will also be optimized according to the difference in the inner diameters of the connecting casing pipes at both ends. For example, there may be a certain taper design inside so that the fluid will not generate greater resistance when flowing through the pup joint due to the sudden change in pipe diameter.

2. Application scenarios:

Used to integrate casing strings with different outer diameters. In complex oil well structures, due to changes in formation conditions or drilling design, casing pipes of different outer diameters may need to be used to adapt to the pressure and stability requirements of different formations. The variable diameter casing pup joint can effectively connect these casing pipes of different outer diameters to build a complete casing pipe system. For example, when drilling in soft and hard alternating formations, the upper softer formation may use a larger outer diameter casing pipe to provide better support, and the lower harder formation may use a smaller outer diameter casing pipe to reduce costs. The variable diameter casing pup joint is used to connect these two different outer diameter casing pipes.

Special function casing pup joints

1. Structural features:

With special auxiliary structures or functional components. For example, the position, size and number of the side holes of the casing pup joints with side holes are designed according to specific functional requirements. These side holes can be used for diversion, injection or installation of special downhole monitoring equipment for downhole fluids.

Some special function casing pup joints may have special coatings or linings inside. If it is used for corrosion prevention, there may be corrosion-resistant coatings, such as epoxy coatings, whose thickness and uniformity will be strictly controlled to ensure effective anti-corrosion performance; if it is used for heat insulation, there may be insulation material linings, whose materials and structures can effectively isolate heat transfer.

2. Application scenarios:

Used to achieve specific downhole operation functions. When performing oil well stimulation measures such as acidizing and fracturing, the casing pup joints with side holes can accurately inject acid or fracturing fluid into specific formation positions. In terms of downhole monitoring, special function casing pup joints equipped with sensor interfaces can monitor downhole pressure, temperature, flow and other parameters in real time, providing important data support for oil well production management. For example, in some high-temperature and high-pressure oil wells, special-function casing pup joints equipped with temperature sensors can timely feedback the temperature changes downhole, helping operators to determine whether the production status of the oil well is normal.

Summary

The above is a detailed introduction to the structural characteristics and application scenarios of different casing pup joints. When purchasing or using casing pup joints, it is necessary to select appropriate casing pup joints according to the operating environment and functional requirements to play their correct role and improve work efficiency.