An Introduction to Semi-Premium Connections

This is a USS-CDC which is a semi-premium connection from US Steel

What are semi-premium connections? 

Similar to premium connections, semi-premium connections entered development in the 1960s and 1970s in response to more rigorous and complex needs amongst end-users. These users required higher-performing and more reliable connections than what traditional API connections were able to provide. Semi-premium connections are generally proprietary designs that sit between API and premium connections in terms of both function and price. Semi-premium connections come in hundreds of varieties from dozens of manufacturers, including OCTG industry leaders, US Steel and Hunting

Using semi-premium connections

Most semi-premium connections feature metal-to-metal seals and torque shoulders to aid in make up and compression resistance, while also reducing undesirable hoop stresses in couplings. Certain semi-premium connections also offer limited gas-tight sealability, a feature not offered by API connections. 

There are no specific standards for semi-premium connections, however, the standards for premium connections are often used as a reference point when evaluating their performance and durability. 

Learn more about the industry standards for premium connections

OCTG industry applications

The Traditional API Buttress Connection

One common way in which semi-premium connections are optimized is by taking the traditional API buttress connection and using this as a base to which modifications are then applied. In a standard buttress connection, the pin noses do not make contact with each other or shoulder at the final assembled position. This means that torque energy is stored radially in the coupling, potentially leading to high levels of hoop stress, which could in turn contribute to environmental cracking conditions. Additionally, with no positive stop at the make up during well installation, the high-rotational forces could further rotate the pins inside the coupling, again increasing the risk of hoop stress. 

The Semi-Premium Buttress Connection

However, by shortening the buttress coupling and controlling certain manufacturing tolerances, semi-premium connection manufacturers have developed connections with pin-to-pin or pin-to-shoulder contact at make up to allow for higher rotational torques while limiting hoop stress. This positive stop contact now also allows buttress-compatible semi-premium connections to achieve 100% compression efficiencies.

Further Optimising the Semi-Premium Buttress Connection 

A significant portion of the semi-premium market is devoted to these buttress-compatible semi-premium connections. This has led to further innovations, including the development of proprietary thread forms, such as Marubeni Itochu Steel’s PANTHER connection. The PANTHER connection takes the semi-premium buttress connection and further optimizes it by modifying the thread taper and pitch in order to minimize the thread length and increase ease of running. The PANTHER connection is also able to stab deeper and make up in fewer turns, allowing running crews to save up to 20% of their run time, per connection. 

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