washover string

Fishing for Success: The Washover String in Drilling and Well Completion

In the challenging world of oil and gas drilling, encountering unexpected obstacles is a common occurrence. When a drill string, casing, or other equipment becomes stuck or lost in the wellbore, a specialized operation known as fishing is required to retrieve it. One of the tools used in fishing operations is the washover string, a critical component for recovering lost or damaged equipment by bypassing the obstruction.

What is a Washover String?

A washover string is a specialized assembly of tools designed to be run into the wellbore during fishing operations. Its primary purpose is to create a new passage around a stuck or lost piece of equipment, allowing for retrieval of the obstruction or continuation of drilling.

Assembly of a Typical Washover String:

A typical washover string consists of the following components:

• Washover Back-off Connector: This connector is designed to connect the washover string to the drill pipe or fishing tools. It allows for easy disconnection and retrieval of the string once the washover operation is complete.
• Washover Pipe: Several joints of heavy-duty pipe are used to make up the majority of the washover string. These pipes are typically made of high-strength steel to withstand the rigors of drilling and fishing operations.
• Rotary Shoe: This specialized shoe is attached to the bottom of the washover string. It is designed to be rotated while drilling, which helps to create a new passage through the formation.

How a Washover String Works:

1. Running the String: The washover string is run into the wellbore below the stuck or lost equipment.
2. Drilling a New Passage: The rotary shoe at the bottom of the string is used to drill a new passage through the formation, effectively bypassing the obstruction.
3. Retrieving the Obstruction: Once the new passage is drilled, the washover string is retracted. This allows access to the original wellbore, where the stuck or lost equipment can be retrieved.
4. Continuing Operations: After retrieval, the wellbore can be re-entered through the newly drilled passage, allowing drilling operations to resume.

Advantages of Using a Washover String:

• Bypass Obstructions: A washover string provides a reliable method for bypassing stuck or lost equipment in the wellbore.
• Minimize Downtime: By allowing drilling operations to resume quickly, a washover string minimizes downtime and potential financial losses.
• Efficient Recovery: It offers a practical and efficient way to recover valuable equipment.

Conclusion:

The washover string is an essential tool in the arsenal of fishing operations. Its ability to create a new passage through formations allows for efficient recovery of lost or damaged equipment, minimizing downtime and maximizing wellbore productivity. While utilizing a washover string requires expertise and careful planning, it often proves to be a valuable solution in challenging drilling scenarios.