Kelly: The Steel Pipe in Rotary Drilling

August 31, 2024 4 min read Engineering Oil and Gas Kelly Rotary Drilling Oil Industry Drilling Equipment Petroleum Engineering

Kelly, the steel pipe used to transfer rotary motion from the rotary table to the drill string, plays a crucial role in rotary drilling operations in the oil and gas industry.

Introduction

The Kelly is a key component in rotary drilling operations in the oil and gas industry. It is a steel pipe that plays a critical role in transferring rotary motion from the rotary table to the drill string. This motion is essential for the drilling process, ensuring that the drill bit penetrates the Earth’s subsurface to reach oil and gas reservoirs.

Historical Context

The concept of rotary drilling has been around since the early 20th century. The development of the Kelly was a significant milestone in improving drilling efficiency. Early drilling techniques were rudimentary, but the introduction of rotary drilling and the Kelly revolutionized the process, allowing for deeper and more controlled drilling.

Types/Categories

Kellys can be categorized based on their shape and application:

Square Kelly: Features a square cross-section. Preferred for its simplicity and ease of manufacturing.
Hexagonal Kelly: Features a hexagonal cross-section, offering better grip and less wear.

Key Events

1920s: Introduction of the rotary drilling method and the use of Kellys.
1940s-1950s: Advancements in metallurgy improved the durability of Kellys.
1980s: The development of automated drilling rigs led to the integration of more advanced Kelly designs.

Detailed Explanations

The Kelly is connected to the rotary table via the swivel and is crucial for the following reasons:

Torque Transfer: It effectively transfers the rotary motion to the drill string, which is essential for the drill bit’s cutting action.
Vertical Movement: The Kelly moves vertically through the Kelly bushing, accommodating the drill string’s length as drilling progresses.

Mathematical Formulas/Models

The torque (\(T\)) transferred by the Kelly can be represented as:

T = F \cdot r

where:

\( F \) is the force applied by the rotary table.
\( r \) is the radius of the Kelly cross-section.

Charts and Diagrams

    graph TD
	    A[Rotary Table] --> B[Kelly]
	    B --> C[Drill String]
	    C --> D[Drill Bit]
	    style B fill:#f9f,stroke:#333,stroke-width:2px
	    style D fill:#6f9,stroke:#333,stroke-width:2px

Importance and Applicability

Critical Component: The Kelly is essential for efficient drilling operations, allowing for deeper and more precise drilling.
Durability and Strength: It must withstand significant stress and strain, making material choice and design crucial.

Examples

Onshore Drilling: Commonly used in conventional oil and gas drilling rigs.
Offshore Drilling: Adapted for use in offshore rigs with specific modifications to handle environmental conditions.

Considerations

Material Selection: High-strength alloys are preferred for durability.
Maintenance: Regular inspection and maintenance are vital to prevent wear and failure.

Drill String: The assembly of drill pipes that transmits rotary motion and weight to the drill bit.
Rotary Table: A drilling rig component that provides rotational force.

Comparisons

Kelly vs. Top Drive: The Kelly is a traditional component, while the top drive system is a more modern technology that provides rotary motion from the top of the drill string.

Interesting Facts

The name “Kelly” is believed to have originated from early drilling crews who referred to the square section as “square kelly” after a common name.

Inspirational Stories

The development of the Kelly was instrumental in the oil boom of the early 20th century, enabling the discovery of vast oil reserves that powered industrial growth.

Famous Quotes

“Oil is a finite resource, but the ingenuity of man is infinite.” - Anonymous

Proverbs and Clichés

“Strike while the iron is hot.” - Relevant to the immediate response needed in drilling operations.

Expressions, Jargon, and Slang

“Kelly Down”: Refers to lowering the Kelly into the rotary table.

FAQs

What is the main function of a Kelly in drilling?

The main function of a Kelly is to transfer rotary motion from the rotary table to the drill string, enabling the drill bit to cut through the Earth’s subsurface.

What materials are Kellys made of?

Kellys are typically made of high-strength steel alloys to withstand the high torque and stress during drilling operations.

How often should Kellys be inspected?

Regular inspections are recommended, ideally before and after each drilling operation, to ensure there are no signs of wear or damage.

References

“Petroleum Engineering Handbook” by Howard B. Bradley
“Drilling Engineering” by J.J. Azar and G. Robello Samuel

Summary

The Kelly is a fundamental component in rotary drilling, essential for transferring rotary motion to the drill string. Its design and material are crucial for its performance and longevity. Understanding the function and maintenance of the Kelly can significantly impact the efficiency and success of drilling operations.