Oil Casing Pipe and Factors Affecting Threaded Connection Quality:
Oil casing pipe, also known as special oil pipe, is crucial for drilling oil and gas wells and transporting oil and gas. It encompasses oil drilling pipes, oil casings, and oil suction pipes. Each component has a specific role: oil drill pipes transmit drilling power, oil casings support the well wall during and after drilling, and oil pipes transport oil and gas from the bottom of the well to the surface.
Importance Of Downhole Casing String Quality:
The downhole casing string serves as the permanent channel for oil and gas resource exploitation, playing a vital role in protecting the borehole wall and separating different pressure layers. It is essential to ensure the quality of the downhole casing string to enhance its service life.
Challenges With Threaded Connection:
The threaded connection is a critical aspect of casing strings, and its strength and sealing performance are crucial. The round threaded casing, meeting API standards, has a connection strength of only 80% of the body strength, and the thread's sealing performance is prone to damage. Approximately 86% of casing string failures occur at threaded connections, emphasizing the need to improve connection quality.
Factors Affecting Threaded Connection Quality:
Torque Influence:
Torque affects threaded connection strength and thread sealing.
Excessive torque generates high circumferential stress between the threaded coupling and pin, leading to stress damage or strain cracks, reducing overall pipe string strength and risking breakage at the casing thread.
Different steel grades (J55, K55, N80, L80, C90, T95, P110, Q125, V150) are used based on well conditions and depths.
Corrosion resistance is crucial, especially in corrosive environments.
Environmental Conditions:
Complex geological conditions necessitate casing with anti-collapse properties.
Thread Tightening Torque:
Proper tightening torque is essential for maintaining thread integrity and preventing slip.
Too much torque can lead to stress damage, while too little torque reduces axial load capacity.
Ensuring the quality of threaded connections is paramount in maintaining the integrity and performance of the casing string, ultimately contributing to the overall efficiency and longevity of oil wells.
