OCTG refers to both tubing and casing, which have similar structures but different sizes and functions. Tubing is placed inside the casing during operation. Casing plays a vital role in supporting the wellbore during drilling and ensuring the smooth operation of the entire oil well after completion. On the other hand, tubing is primarily used for oil and gas extraction, transporting underground oil and gas to the surface.
OCTG (casing and tubing) production is typically governed by the American Petroleum Institute (API) specification, specifically API SPECIFICATION 5CT. Casing and tubing are used in oil extraction, hot spring wells, and geothermal wells for cementing and supporting the wellbore.
Types Of Connections For Casing:
Short Round Thread (SC): This thread type is characterized by short, rounded threads that provide a secure connection. It is commonly used for shallow to medium-depth wells.
Long Round Thread (LC): LC threads have longer, rounded threads that provide a more robust connection. They are suitable for deeper wells and higher-pressure environments.
Buttress Thread (BC): BC threads have a unique asymmetrical shape with a larger and stronger load-bearing surface. This thread type is widely used for deep and high-pressure wells where torque resistance is essential.
Extra Clearance (XC): XC threads feature a direct connection without any taper or seal. They are used in applications where quick and easy assembly and disassembly of the casing are required.
Types 0f Connections For Tubing:
Non-Upset (NU): NU casing has a plain end without any thickening. It is typically used for shallow wells or in non-critical applications.
External Upset (EU): EU casing has an externally thickened end for enhanced strength. It is commonly used in deeper wells and more demanding environments.
Integral Joint (IJ): IJ casing consists of a continuous pipe without separate coupling joints. It offers increased strength and is commonly used in challenging well conditions.
Premium connections: Some wells with stringent gas-tight requirements may require premium connection designs to ensure a secure and leak-free connection.
Conclusion:
The choice of connection type depends on factors such as well depth, pressure conditions, and the desired level of torque resistance. By utilizing the right connection type, oil and gas companies can ensure reliable wellbore integrity, optimal performance, and efficient operations in the extraction of oil and gas resources.
