In a drilling rig, a swivel is a crucial component that allows the drill string to rotate while transmitting drilling fluid (also known as drilling mud) to the drill bit. It is located near the top of the rig structure and is attached to the crown block or mast.
Here are the key features and functions of a swivel:
Rotation Capability: The swivel is designed to provide a rotational movement to the drill string. It allows the drill bit to rotate and drill into the rock formations during drilling operations. The swivel is typically connected to the top drive system or rotary table, which provides the necessary torque to rotate the drill string.
Drilling Fluid Flow: The swivel incorporates channels and passages that allow the continuous flow of drilling fluid from the mud pumps, through the swivel, and down the drill string to the drill bit. This flow of drilling fluid serves multiple purposes, including cooling and lubricating the drill bit, carrying drill cuttings to the surface, and maintaining wellbore stability.
Pressure Control: The swivel is designed to withstand the high-pressure environment encountered during drilling operations. It is equipped with seals and packing elements that prevent the escape of drilling fluid and maintain the pressure integrity within the system.
Load Support: The swivel supports the weight of the drill string and the attached bottom hole assembly, including the drill bit. It transfers the weight to the crown block or mast, allowing the drill string to be suspended and rotated.
Connection to the Kelly: The swivel is connected to the kelly, which is a square or hexagonal pipe that transmits rotational torque from the rotary table or top drive system to the drill string. The connection between the swivel and the kelly allows the transfer of rotational motion to the drill string.
Bearing System: The swivel incorporates a bearing system that enables smooth rotation of the drill string. The bearings are designed to withstand the axial and radial loads exerted during drilling operations.
The swivel plays a vital role in the drilling process by enabling the rotation of the drill string while maintaining the flow of drilling fluid. It is an essential component in achieving efficient drilling operations and maintaining wellbore integrity.
It's important to note that swivels may have different designs and configurations based on the specific rig type, drilling techniques, and operational requirements.