Drilling & Well Completion

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.

Test Your Knowledge

Quiz: Fishing for Success - The Washover String

Instructions: Choose the best answer for each question.

1. What is the primary purpose of a washover string?

a) To clean debris from the wellbore. b) To solidify the wellbore wall. c) To bypass a stuck or lost piece of equipment. d) To increase the diameter of the wellbore.

Answer

c) To bypass a stuck or lost piece of equipment.

2. Which of the following is NOT a typical component of a washover string?

a) Washover Back-off Connector b) Washover Pipe c) Rotary Shoe d) Drill Bit

Answer

d) Drill Bit

3. How does the rotary shoe on a washover string help in bypassing an obstruction?

a) It cuts through the obstruction. b) It pushes the obstruction aside. c) It drills a new passage through the formation. d) It anchors the string to the wellbore.

Answer

c) It drills a new passage through the formation.

4. What is a key advantage of using a washover string?

a) It prevents further drilling complications. b) It minimizes downtime and potential financial losses. c) It allows for easier wellbore completion. d) It increases the wellbore's production capacity.

Answer

b) It minimizes downtime and potential financial losses.

5. When is a washover string typically used?

a) During routine wellbore maintenance. b) Before drilling through a known challenging formation. c) When encountering a stuck or lost piece of equipment. d) After well completion to ensure proper sealing.

Answer

c) When encountering a stuck or lost piece of equipment.

Exercise:

Scenario: A drilling crew encounters a stuck drill pipe while drilling a well. The crew decides to use a washover string to bypass the obstruction.

Task: Describe the steps involved in using a washover string to retrieve the stuck drill pipe and resume drilling operations.

Exercise Correction

Here are the steps involved in using a washover string to retrieve the stuck drill pipe and resume drilling operations:

  1. **Prepare the Washover String:** Assemble the washover string with the back-off connector, washover pipe, and rotary shoe. Ensure all connections are secure and the string is ready for deployment.
  2. **Run the Washover String:** Lower the washover string into the wellbore, carefully passing it below the stuck drill pipe.
  3. **Drill a New Passage:** Rotate the rotary shoe at the bottom of the string, using the drilling rig to drill a new passage through the formation, effectively bypassing the stuck drill pipe.
  4. **Retrieve the Washover String:** Once the new passage is drilled, carefully retract the washover string from the wellbore.
  5. **Retrieve the Stuck Drill Pipe:** With the new passage created, the crew can now access the original wellbore where the stuck drill pipe is located. They can utilize appropriate fishing tools and techniques to retrieve the stuck drill pipe.
  6. **Re-enter the Wellbore:** After retrieving the stuck drill pipe, the wellbore can be re-entered through the newly drilled passage, allowing drilling operations to resume.

Books

  • Petroleum Engineering Handbook: This comprehensive handbook, published by the Society of Petroleum Engineers (SPE), covers a wide range of topics related to oil and gas production, including drilling, well completion, and fishing operations. You will likely find information on washover strings in the sections related to drilling and wellbore intervention.
  • Drilling Engineering: A Comprehensive Approach: This book by John Lee covers various aspects of drilling engineering, including fishing operations. It provides details about different fishing techniques and tools, including the use of washover strings.
  • Well Completion Design and Operations: This book by Jerry J. Reynolds covers the essential principles and techniques involved in well completion, including wellbore recovery operations. It includes sections on fishing and the utilization of washover strings in these operations.

Articles

  • Journal of Petroleum Technology (JPT): This journal published by SPE regularly features articles on various aspects of oil and gas exploration and production. You can find articles on fishing operations, including specific cases where washover strings were successfully employed.
  • Drilling Contractor: This magazine covers drilling industry news, technology, and case studies. You can find articles on fishing operations and specific techniques used in wellbore recovery.
  • Oil & Gas Journal: This publication focuses on global oil and gas industry news, technology, and trends. It features articles on drilling and well completion, including discussions on fishing techniques and the use of washover strings.

Online Resources

  • Society of Petroleum Engineers (SPE): SPE's website contains a vast library of technical papers, presentations, and publications related to various aspects of the oil and gas industry, including drilling and well completion. You can use the search function to find relevant information on washover strings.
  • IADC (International Association of Drilling Contractors): IADC's website provides resources for drilling contractors, including information on drilling technology, safety, and environmental regulations. You may find articles or case studies related to fishing operations and the use of washover strings.
  • Schlumberger: This major oilfield service company has a comprehensive website with information on its drilling and well completion services, including fishing operations. You may find articles and technical documents describing the use of washover strings in their service offerings.

Search Tips

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  • Combine keywords: Combine multiple keywords to refine your search results. For example, you can use "washover string fishing operations" or "washover string wellbore recovery."
  • Include technical terms: If you are familiar with technical terms related to drilling and well completion, include them in your search query to get more specific results. For instance, you can search for "washover string rotary shoe" or "washover string back-off connector."
  • Use quotation marks: Use quotation marks around specific phrases to ensure that Google only returns results containing those exact phrases. For example, "washover string drilling technique" will only return results that include that exact phrase.

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