Ovality Limit (CT)

Ovality Limit (CT): A Critical Parameter for Coiled Tubing Operations

Coiled tubing (CT) is a crucial piece of equipment in the oil and gas industry, used for a wide range of operations from well completions to stimulation and workovers. Its ability to navigate complex wellbores and deliver fluids or tools to specific locations makes it an indispensable tool. However, CT is subject to wear and tear during its operational life, and one of the most important factors affecting its performance and safety is its ovality.

Ovality refers to the degree of deviation from a perfectly circular cross-section of the CT. As the CT is subjected to repeated bending and flexing, its circular shape can become distorted, leading to an elliptical cross-section. This ovality can significantly impact the CT's performance and even pose safety risks.

Ovality limit (CT) refers to a critical threshold of ovality, beyond which the CT may not be suitable for certain operations, particularly in deep wells or in operations involving significant stresses on the tubing. This limit is usually expressed as a percentage of ovality, based on the initial circular diameter of the tubing.

Here's why ovality limits are crucial:

• Increased drag and friction: Ovality increases the contact area between the CT and the wellbore, leading to higher friction and drag. This can hinder the smooth flow of fluids and limit the depth to which the CT can be deployed.
• Reduced burst strength: Ovality weakens the CT's structural integrity, potentially leading to a reduced burst pressure. This can pose a serious safety hazard in high-pressure environments.
• Premature wear and tear: Ovality can accelerate wear and tear on the CT, reducing its lifespan and requiring more frequent replacements.
• Difficulty in navigating complex wellbores: Ovality can make it harder for the CT to navigate complex wellbores, especially those with tight radius bends.

Beyond the ovality limit, the CT may not be suitable for:

• Deep well operations: The high pressures and complex geometries found in deep wells can significantly exacerbate the negative effects of ovality, leading to potential failures and safety concerns.
• Operations outside of completion hangoffs: Certain operations, such as stimulation treatments or workovers, require a higher degree of control and precision. Ovality can hinder the ability to effectively perform these tasks.

Ensuring compliance with ovality limits:

• Regular inspection: CT should be regularly inspected to monitor its ovality levels. This can be done using specialized tools and techniques.
• Replacement or repair: If ovality exceeds the acceptable limit, the CT may need to be replaced or repaired to ensure safety and performance.
• Strict quality control: Manufacturers and operators should maintain strict quality control measures during the manufacturing, handling, and operation of CT to minimize ovality.

Ovality limit (CT) is an important parameter to consider for ensuring safe and efficient CT operations. By closely monitoring ovality levels and adhering to established limits, operators can mitigate risks, optimize performance, and extend the lifespan of their CT assets.