At present, there are four main series designed and developed by all countries in the world: VM series, Hydrir series, Hunting series, Tenaris series.  

Special buckle characteristics

Although different countries and companies have different designs for the special fasteners of oil casing, the basic forms are basically the same, mainly to improve the connection strength and sealing performance of the string.  

On the other hand, most casing special connections are divided into three parts: the connection thread part, the torsion-resistant table shoulder part and the sealing surface part.  

Most use API trapezoidal threads to improve interchangeability of threaded sections.  

Advantages of special buckle:  

In the early use of oil well pipe, special buckle is designed for different oil fields, different blocks and different well conditions, with strong personalized color.  However, as well conditions become more complex, the use of pipelines becomes more stringent.  Through the comparison, screening and practical test of various foreign special buckles, more than 10 typical products have been gradually formed, which can basically meet the special needs of current oil fields.  Although a variety of special buckle products can meet drilling and production needs under different simultaneous conditions, they all share the following common advantages:  

1. The connection strength of the joint can match the strength of the pipe body, and even the joint strength higher than the pipe body is suitable for deep and ultra-deep Wells;  

2. Good sealing performance, suitable for high pressure gas Wells, oil Wells and thermal recovery Wells  

3. Strong bending resistance, suitable for matching Wells, large displacement Wells and horizontal Wells;  

4. It is easy to fix, can be fastened quickly, and is not easy to drill in harsh environment such as desert and ocean;  

5. Good anti-viscosity, can be removed repeatedly without damaging the thread;  

6. Strong torque resistance;  

7. Good corrosion resistance.