Stripping (pipe running)

Test Your Knowledge

Stripping (Pipe Running) Quiz:

Instructions: Choose the best answer for each question.

1. What is the primary purpose of stripping in oil and gas operations?

a) To increase the flow rate of drilling fluid. b) To remove debris from the wellbore. c) To hold back the flow of drilling fluid during pipe running. d) To lubricate the pipe as it is lowered into the well.

2. Why is stripping essential for managing fluid pressure?

a) It helps to increase the weight of the pipe. b) It prevents the drilling fluid from becoming contaminated. c) It reduces the risk of blowouts and other dangerous situations. d) It increases the efficiency of the drilling process.

3. What is a stripping valve used for?

a) To control the flow of drilling fluid back to the surface. b) To measure the pressure of the drilling fluid. c) To seal the wellbore during pipe running. d) To lubricate the pipe as it is lowered into the well.

4. Which type of stripping involves removing the entire volume of drilling fluid from the wellbore?

a) Partial stripping b) Full stripping c) Continuous stripping d) Selective stripping

5. What is the main benefit of stripping in terms of wellbore integrity?

a) It reduces the risk of wellbore collapse. b) It prevents the loss of drilling fluid into the formation. c) It increases the rate of drilling. d) It reduces the risk of pipe sticking.

Stripping (Pipe Running) Exercise:

Scenario:

You are a drilling engineer overseeing the pipe running operation in a deep well. During the operation, the drilling crew reports that they are experiencing significant pressure buildup in the wellbore. The drilling fluid is being pushed back up the wellbore, causing a potential risk of a blowout.

Task:

1. Identify the potential problem: What is causing the pressure buildup in the wellbore?
2. Propose a solution: Based on your understanding of stripping, what steps should you take to address this issue and ensure a safe and efficient pipe running process?
3. Explain your reasoning: Clearly explain why your proposed solution will effectively address the problem and ensure the safety of the operation.

Techniques

Chapter 1: Techniques

Stripping Techniques in Pipe Running

This chapter delves into the various techniques employed in stripping operations during pipe running. Understanding these techniques is crucial for optimizing the process and ensuring safe and efficient wellbore operations.

1.1 Stripping Valve Operation:

The heart of stripping lies in the stripping valve. This specialized valve, strategically placed at the wellhead, plays a pivotal role in controlling fluid flow during pipe running. Its operation involves carefully regulating the rate of fluid return to the surface, thereby managing the pressure within the wellbore.

1.2 Full Stripping:

This technique involves the complete removal of drilling fluid from the wellbore as the pipe is lowered. Full stripping is typically employed in shallow wells or when there's a high pressure risk. It guarantees precise pressure control and minimizes the risk of fluid loss.

1.3 Partial Stripping:

In contrast, partial stripping aims to remove only a portion of the drilling fluid from the wellbore. This technique is often preferred in deeper wells where full stripping might be challenging or could cause unwanted pressure fluctuations. Partial stripping allows for a more controlled approach to managing pressure gradients.

1.4 Stripping Methods:

• Manual Stripping: This traditional method involves manually opening and closing the stripping valve to adjust the fluid flow rate. It requires constant monitoring and adjustments to maintain the desired pressure.
• Automated Stripping: Modern automated stripping systems utilize sensors and control mechanisms to automatically regulate the valve based on predefined parameters. This method offers greater precision and efficiency compared to manual stripping.

1.5 Considerations for Selecting Stripping Technique:

The choice of stripping technique depends on several factors, including wellbore depth, formation pressure, expected fluid volume, and the overall risk assessment. Experienced engineers and operators must carefully evaluate these factors to determine the most suitable technique for a given operation.

1.6 Stripping Considerations for Specific Well Conditions:

• High-Pressure Wells: Full stripping may be required to manage the elevated pressure and prevent blowouts.
• Deep Wells: Partial stripping is often preferred to minimize pressure fluctuations and ensure wellbore stability.
• Casing Running: Stripping is particularly crucial during casing running, as the weight of the casing can create significant pressure on the fluid.

1.7 Conclusion:

Stripping techniques are essential for managing pressure and fluid flow during pipe running, ensuring a safe and efficient operation. Understanding the different methods and their applications allows for optimal performance and minimizes risks in the oil and gas industry.

Chapter 2: Models

Modelling Stripping Operations

This chapter explores the use of mathematical models to simulate and optimize stripping operations during pipe running. These models provide valuable insights into pressure dynamics, fluid flow patterns, and the effectiveness of different stripping strategies.

2.1 Mathematical Modelling of Pressure Dynamics:

Stripping models are built upon fundamental fluid mechanics principles, taking into account factors like:

• Wellbore geometry: Wellbore diameter, length, and depth.
• Drilling fluid properties: Density, viscosity, and compressibility.
• Pipe weight and dimensions: Weight per unit length, diameter, and buoyancy.
• Stripping valve characteristics: Flow rate capacity, pressure drop, and valve operation settings.

2.2 Simulation Software for Stripping Operations:

• Drilling Simulator Software: Specialized software packages are available for simulating drilling and completion operations, including stripping scenarios. These programs allow users to input wellbore parameters, fluid properties, and stripping valve settings to predict pressure behavior and optimize stripping strategies.
• Finite Element Analysis (FEA) Software: FEA software is used to model complex fluid flow scenarios in the wellbore. It can simulate pressure distribution, fluid velocities, and interactions between the pipe and the surrounding fluid.

2.3 Application of Stripping Models:

• Predicting Pressure Behavior: Models allow engineers to predict the pressure changes in the wellbore during pipe running under different stripping scenarios.
• Optimizing Stripping Strategies: By running simulations with various stripping techniques, operators can determine the most efficient approach for managing fluid pressure and preventing complications.
• Evaluating Wellbore Stability: Models can assess the potential for fluid loss or wellbore instability during stripping operations.
• Analyzing Stripping Valve Performance: Models can be used to evaluate the performance of stripping valves and identify potential areas for improvement.

2.4 Limitations of Stripping Models:

• Assumptions and Simplifications: Stripping models rely on assumptions about wellbore conditions and fluid properties, which may not always accurately reflect real-world scenarios.
• Data Accuracy: The accuracy of model predictions depends on the quality and completeness of the input data.
• Model Complexity: Developing and calibrating accurate stripping models can be complex and require specialized knowledge and expertise.

2.5 Conclusion:

Mathematical modelling plays a crucial role in optimizing stripping operations and ensuring safety and efficiency during pipe running. By leveraging simulation tools and advanced modelling techniques, operators can make informed decisions and minimize risks associated with this critical wellbore activity.

Chapter 3: Software

Software Tools for Stripping Operations

This chapter highlights the software tools available to assist with stripping operations during pipe running, providing engineers and operators with valuable support for decision-making and optimization.

3.1 Drilling Simulation Software:

• Purpose: Drilling simulation software simulates various aspects of drilling operations, including stripping scenarios. These programs allow users to visualize pressure changes, optimize stripping valve settings, and assess the effectiveness of different stripping techniques.
• Features:
  • Wellbore Modelling: Create detailed models of the wellbore geometry, including depth, diameter, and casing configurations.
  • Fluid Property Input: Define drilling fluid properties like density, viscosity, and compressibility.
  • Pipe Properties: Input pipe weight, diameter, and buoyancy.
  • Stripping Valve Settings: Configure stripping valve characteristics, including flow rate capacity, pressure drop, and opening/closing parameters.
  • Pressure and Flow Simulation: Simulate the pressure and flow behavior during stripping operations under different scenarios.
• Examples:
  • Drilling Simulator by Schlumberger
  • DrillingPro by Drilling Systems Inc.
  • WellPlan by Halliburton

3.2 Finite Element Analysis (FEA) Software:

• Purpose: FEA software focuses on modelling complex fluid flow phenomena within the wellbore. It allows for detailed analysis of pressure distribution, fluid velocities, and interactions between the pipe and the surrounding fluid during stripping operations.
• Features:
  • Mesh Generation: Create a mesh of the wellbore geometry, dividing it into small elements for detailed analysis.
  • Fluid Properties Input: Define fluid properties, including density, viscosity, and compressibility.
  • Boundary Conditions: Specify the boundary conditions for the fluid flow, including the stripping valve settings and other wellbore conditions.
  • Pressure and Velocity Solution: Solve the governing equations of fluid flow to obtain pressure and velocity distributions within the wellbore.
• Examples:
  • ANSYS Fluent
  • COMSOL Multiphysics
  • Abaqus

3.3 Data Acquisition and Monitoring Systems:

• Purpose: Real-time data acquisition and monitoring systems collect and analyze data from the wellhead and downhole sensors. These systems provide vital information on pressure changes, fluid flow rates, and other operational parameters during stripping operations.
• Features:
  • Downhole Sensors: Measure pressure, temperature, and other relevant parameters within the wellbore.
  • Wellhead Sensors: Monitor pressure, flow rates, and stripping valve positions.
  • Data Acquisition Units: Collect and transmit sensor data to a central processing unit.
  • Real-time Monitoring: Display data in real-time on dashboards and provide alerts for critical events.
• Examples:
  • Schlumberger's WellWatcher System
  • Halliburton's WellCube System

3.4 Conclusion:

Specialized software tools provide valuable assistance for engineers and operators involved in stripping operations. These tools enable simulations, analysis, and monitoring of the entire process, leading to better decision-making, optimized stripping strategies, and improved safety during pipe running.

Chapter 4: Best Practices

Best Practices for Stripping Operations

This chapter outlines best practices for conducting stripping operations, ensuring safety, efficiency, and optimal performance during pipe running.

4.1 Pre-Operation Planning:

• Thorough Wellbore Analysis: Understand wellbore geometry, fluid properties, expected pressures, and any potential risks associated with stripping operations.
• Stripping Valve Selection: Choose the appropriate stripping valve based on wellbore depth, fluid volume, and expected pressure gradients.
• Safety Procedures: Develop comprehensive safety procedures for stripping operations, including emergency response plans.
• Training and Certification: Ensure all personnel involved in stripping operations are properly trained and certified.

4.2 Stripping Operation Execution:

• Gradual Pressure Reduction: Reduce pressure gradually during stripping, avoiding sudden changes that can lead to wellbore instability.
• Constant Monitoring: Monitor pressure, flow rates, and valve settings continuously during stripping operations.
• Communication: Maintain clear communication between operators and engineers throughout the stripping process.
• Emergency Response: Be prepared to respond quickly to any unexpected events or emergencies.

4.3 Post-Operation Evaluation:

• Data Review: Analyze pressure and flow data collected during the stripping operation to identify any issues or areas for improvement.
• Equipment Inspection: Inspect and maintain all equipment used during stripping operations to ensure proper functionality.
• Lessons Learned: Document any lessons learned from the stripping operation and share them with the team to improve future operations.

4.4 Stripping Optimization:

• Stripping Valve Calibration: Regularly calibrate stripping valves to ensure accurate flow rate control.
• Fluid Property Monitoring: Continuously monitor fluid properties to ensure that the model assumptions are accurate.
• Optimization Tools: Utilize software tools to simulate and optimize stripping strategies based on real-time data and wellbore conditions.

4.5 Safety Considerations:

• Blowout Prevention: Implement strict measures to prevent blowouts during stripping operations, including adequate wellhead equipment and safety procedures.
• Fluid Loss Control: Minimize fluid loss into the formation during stripping to maintain wellbore stability and prevent environmental contamination.
• Personnel Safety: Ensure the safety of all personnel involved in stripping operations by adhering to proper safety procedures, using appropriate personal protective equipment, and conducting regular safety inspections.

4.6 Conclusion:

By adhering to best practices, engineers and operators can conduct safe, efficient, and optimal stripping operations during pipe running. This ensures a smooth wellbore operation, minimizes risks, and enhances the overall success of oil and gas production projects.

Chapter 5: Case Studies

Case Studies in Stripping Operations

This chapter presents real-world examples of stripping operations, highlighting the challenges faced, the techniques employed, and the lessons learned.

5.1 Case Study 1: Deepwater Well Stripping:

Scenario: A deepwater well in the Gulf of Mexico encountered high pressure and fluid loss during pipe running.

Challenges:

• Extreme depth and high pressure.
• Risk of wellbore instability and fluid loss.
• Limited space and accessibility on the rig.

Techniques:

• Automated stripping system with multiple stripping valves.
• Partial stripping with carefully controlled fluid flow rates.
• Frequent pressure monitoring and adjustments.
• Wellbore integrity analysis using FEA software.

Lessons Learned:

• Automated stripping systems offer greater control and efficiency in deepwater wells.
• Careful pressure management and wellbore stability monitoring are crucial.
• Optimization tools can enhance stripping operations in challenging environments.

5.2 Case Study 2: Casing Running in High-Pressure Reservoir:

Scenario: Casing running in a high-pressure gas reservoir.

Challenges:

• Risk of blowouts due to high reservoir pressure.
• Potential for casing sticking and difficulties during lowering.
• Limited access to the wellhead during casing running.

Techniques:

• Full stripping with a large stripping valve to manage high pressure.
• Careful weight management of the casing string.
• Frequent pressure monitoring and adjustments.
• Real-time data acquisition and monitoring systems to track the operation.

Lessons Learned:

• Proper stripping valve selection and operation are critical for high-pressure wells.
• Rigorous weight management and real-time monitoring are essential to prevent sticking and other complications.
• Safety procedures should be strictly followed to prevent blowouts during casing running.

5.3 Case Study 3: Stripping in Horizontal Well:

Scenario: Running pipe in a horizontal well with complex geometry.

Challenges:

• Complex wellbore geometry and multiple bends.
• Potential for pipe sticking due to friction and tight spots.
• Difficulty in accurately modelling fluid flow in the wellbore.

Techniques:

• Partial stripping with precise fluid flow control.
• Use of specialized pipe running tools and techniques.
• Simulation software to analyze fluid flow and optimize stripping strategies.
• Real-time monitoring of wellbore conditions to detect potential issues.

Lessons Learned:

• Specialized tools and techniques are required for stripping operations in horizontal wells.
• Accurate modelling of fluid flow is essential for optimizing stripping strategies.
• Continuous monitoring and adjustments are critical for ensuring a successful operation.

5.4 Conclusion:

Case studies illustrate the diverse challenges and solutions associated with stripping operations in various wellbore environments. By sharing experiences and analyzing successes and failures, the oil and gas industry can continuously improve its approach to stripping operations, ensuring safety, efficiency, and optimal production from its wells.