Rotary drilling, a widely used method in the drilling industry, employs a rotating drill bit to penetrate the Earth’s crust. This technique, with its origins dating back to ancient civilizations, gained prominence in the early 20th century, particularly in the petroleum industry. The rotary table, a crucial component of a rotary drilling rig, plays a pivotal role in the drilling process. This article delves into the functions, components, and operation of the rotary table, drawing upon reputable sources such as Wikipedia, Penn State University’s online course on Petroleum and Natural Gas Engineering, and The Driller magazine.
Key Facts
- Function: The rotary table provides clockwise rotational force to the drill string, which helps in the process of drilling a borehole.
- Rotational Speed: The rotary speed is measured in revolutions per minute (rpm) and indicates the number of times the rotary table completes one full revolution in one minute.
- Components: The rotary system on a drilling rig consists of various components, including the swivel, kelly, kelly bushing, master bushing, rotary table, mousehole, rat hole, rotary hose, drill string, bottom-hole assembly, and drill bit.
- Swivel: The swivel is responsible for allowing the drill string to rotate while providing a passage for drilling mud to flow down the drill string.
- Kelly: The kelly is a square or hexagonal-shaped pipe that connects the swivel to the drill string. It transmits the rotational force from the rotary table to the drill string.
- Kelly Bushing: The kelly bushing is a device that supports the kelly and provides a seal to prevent drilling mud from escaping.
- Master Bushing: The master bushing is a large cylindrical device that holds the kelly bushing and provides a connection point for the rotary table.
- Rotary Table: The rotary table is the main component responsible for providing the rotational force to the drill string. It is typically driven by an electric motor or an engine.
- Mousehole and Rat Hole: The mousehole and rat hole are used to connect single joints of the drill string on a rotary table rig.
- Drill String: The drill string is a series of connected drill pipes that transmit the rotational force from the rotary table to the drill bit.
- Bottom-Hole Assembly: The bottom-hole assembly consists of various tools and equipment required for drilling the current section of the well, including drilling collars, jars, downhole directional steering equipment, and the drill bit.
- Drill Bit: The drill bit is the cutting tool at the bottom of the drill string. There are different types of drill bits, such as tri-cone (roller cone) bits and fixed-cutter bits, which are used based on the rock formations being drilled.
Function of the Rotary Table
The primary function of the rotary table is to impart clockwise rotational force to the drill string, facilitating the drilling of a borehole. The rotational speed, measured in revolutions per minute (rpm), determines the number of times the rotary table completes one full revolution in a minute.
Components of the Rotary System
The rotary system on a drilling rig comprises various components that work in tandem to enable the drilling process. These components include:
- SwivelThe swivel allows the drill string to rotate while providing a passage for drilling mud to flow down the drill string.
- KellyThe kelly, a square or hexagonal-shaped pipe, connects the swivel to the drill string. It transmits the rotational force from the rotary table to the drill string.
- Kelly BushingThe kelly bushing supports the kelly and provides a seal to prevent drilling mud from escaping.
- Master BushingThe master bushing is a large cylindrical device that holds the kelly bushing and provides a connection point for the rotary table.
- Rotary TableThe rotary table is the primary component responsible for providing rotational force to the drill string. It is typically driven by an electric motor or an engine.
- Mousehole and Rat HoleThe mousehole and rat hole are used to connect single joints of the drill string on a rotary table rig.
- Drill StringThe drill string is a series of connected drill pipes that transmit the rotational force from the rotary table to the drill bit.
- Bottom-Hole AssemblyThe bottom-hole assembly consists of various tools and equipment required for drilling the current section of the well, including drilling collars, jars, downhole directional steering equipment, and the drill bit.
- Drill BitThe drill bit is the cutting tool at the bottom of the drill string. Different types of drill bits, such as tri-cone (roller cone) bits and fixed-cutter bits, are used based on the rock formations being drilled.
Basic Operation of the Rotary Table
The rotary table is driven by an electric motor or an engine, which provides the necessary torque to rotate the drill string. The drill string, in turn, transmits this rotational force to the drill bit at the bottom of the wellbore. As the drill bit rotates, it penetrates the rock formation, creating a borehole. Drilling mud is continuously pumped down the drill string and through the drill bit, carrying cuttings to the surface and cooling and lubricating the drill bit.
Conclusion
The rotary table is an essential component of a rotary drilling rig, enabling the drilling of boreholes by imparting rotational force to the drill string. Its operation, in conjunction with other components of the rotary system, facilitates the drilling process and the extraction of valuable resources from the Earth’s crust.
References
- Rotary table (drilling rig). (2022, November 8). Wikipedia. https://en.wikipedia.org/wiki/Rotary_table_(drilling_rig)
- King, G. (n.d.). 9.2.4: The Rotary System. PNG 301: Introduction to Petroleum and Natural Gas Engineering. https://www.e-education.psu.edu/png301/node/727
- Rotary Drilling – An Overview. (2011, November 1). The Driller. https://www.thedriller.com/articles/88669-rotary-drilling-an-overview
FAQs
What is the function of a rotary table in a drilling rig?
The primary function of a rotary table is to provide clockwise rotational force to the drill string, facilitating the drilling of a borehole.
How is the rotary table driven?
The rotary table is typically driven by an electric motor or an engine, which provides the necessary torque to rotate the drill string.
What are the main components of the rotary system?
The main components of the rotary system include the swivel, kelly, kelly bushing, master bushing, rotary table, mousehole, rat hole, rotary hose, drill string, bottom-hole assembly, and drill bit.
What is the role of the drill string in the rotary drilling process?
The drill string transmits the rotational force from the rotary table to the drill bit at the bottom of the wellbore.
What is the purpose of drilling mud in rotary drilling?
Drilling mud is continuously pumped down the drill string and through the drill bit to carry cuttings to the surface, cool and lubricate the drill bit, and maintain the stability of the borehole.
What are the different types of drill bits used in rotary drilling?
Common types of drill bits used in rotary drilling include tri-cone (roller cone) bits and fixed-cutter bits, each designed for specific rock formations.
How is the rotary table connected to the drill string?
The rotary table is connected to the drill string through the kelly, a square or hexagonal-shaped pipe that transmits the rotational force from the rotary table to the drill string.
What safety precautions are taken when operating a rotary table?
Proper safety precautions include wearing appropriate personal protective equipment, ensuring the rotary table is securely fastened, and maintaining a safe working environment around the drilling rig.