TWC (flow path)

Test Your Knowledge

TWC Quiz

Instructions: Choose the best answer for each question.

1. What is the primary purpose of a Two-Way Check (TWC) in oil and gas operations? a) To ensure the flow path is properly isolated and verified. b) To monitor the pressure of fluids in a pipeline. c) To prevent leaks in a wellbore. d) To track the volume of oil and gas produced.

2. Which of the following is NOT a method used to verify the isolation of a flow path in a TWC? a) Physical inspection of valves. b) Pressure testing of the isolated section. c) Flow monitoring with meters. d) Analyzing the chemical composition of the fluid.

3. How does TWC contribute to the safety of oil and gas operations? a) By ensuring the correct flow path, it reduces the risk of spills and explosions. b) By preventing unintended flow, it minimizes the chance of equipment failure. c) By isolating specific sections, it allows for easier maintenance and repair. d) All of the above.

4. Which of the following is NOT a benefit of implementing TWC in oil and gas operations? a) Increased operational efficiency. b) Improved environmental protection. c) Reduced workforce training requirements. d) Enhanced compliance with industry standards.

5. Why is it crucial to verify the isolation of a flow path during a TWC? a) To ensure that the intended path is the only possible route for fluid flow. b) To prevent leaks from occurring in the isolated section. c) To determine the pressure of the fluid in the pipeline. d) To monitor the rate of fluid flow through the system.

TWC Exercise

Scenario: You are working on a well intervention project. Before starting the procedure, you need to perform a TWC on the flow path to isolate the wellbore.

Task: Describe the steps you would take to complete the TWC, including the isolation and verification methods.

Example:

1. Isolation:

   • Close the wellhead valve.
   • Close the flowline valve at the wellhead.
   • Close the isolation valve on the production line.

2. Verification:

   • Physically inspect the closed position of all valves.
   • Perform a pressure test on the isolated wellbore using a pressure gauge.
   • Observe flow meters to confirm that no flow is occurring outside the intended path.

Techniques

Chapter 1: Techniques for TWC (Flow Path) Verification

This chapter delves into the specific techniques used for TWC verification in oil and gas operations.

1.1. Physical Inspection:

• Description: This technique involves manually inspecting the position of valves, blinds, and other isolation devices to confirm their proper closure.
• Advantages: Simple, straightforward, and often the first line of defense in TWC verification.
• Disadvantages: Relies on human observation, prone to errors, and requires physical access to all isolation points.
• Examples: Checking the handle position of a valve, confirming the presence and placement of a blind, visually inspecting a valve for signs of leakage.

1.2. Pressure Testing:

• Description: This technique involves pressurizing a section of the flow path to verify its isolation. Pressure gauges are used to monitor the pressure build-up and potential leakage.
• Advantages: Provides a quantitative measure of isolation, detects leaks that might not be visually apparent.
• Disadvantages: Requires specialized equipment, may not be suitable for all flow paths, and can be time-consuming.
• Examples: Testing a pipeline segment for leakage by pressurizing it with nitrogen, checking the pressure drop across a valve to confirm its proper closure.

1.3. Flow Monitoring:

• Description: This technique utilizes flow meters to directly measure the fluid flow rate within the isolated section. Any non-zero flow reading indicates a failure in the isolation procedure.
• Advantages: Provides real-time confirmation of isolation, highly accurate, and suitable for a wide range of flow paths.
• Disadvantages: Requires installation of flow meters, potentially expensive, and may not be suitable for all flow paths.
• Examples: Using a flow meter to monitor the flow rate in a pipeline during a well intervention, tracking flow through a separator during a shut-in procedure.

1.4. Electronic Verification:

• Description: This technique utilizes electronic sensors and control systems to monitor the status of isolation devices and provide real-time data.
• Advantages: Automated, reduces human error, provides comprehensive data logging, and enables remote monitoring.
• Disadvantages: Requires specialized equipment and expertise, potentially expensive to implement.
• Examples: Using a SCADA (Supervisory Control and Data Acquisition) system to monitor valve positions, integrating smart sensors to track flow rate and pressure changes.

1.5. Combined Techniques:

• Description: In many cases, a combination of techniques is used to achieve robust TWC verification.
• Advantages: Increases confidence in isolation, mitigates the weaknesses of individual techniques, and offers a comprehensive approach.
• Examples: Combining physical inspection with pressure testing to verify the closure of a valve and confirm no leakage, using flow monitoring in conjunction with electronic verification for automated monitoring and data logging.

Conclusion:

The chosen technique for TWC verification should be tailored to the specific flow path, operational context, and desired level of assurance. Each technique offers its own advantages and disadvantages, and using a combination of approaches often leads to more robust verification and increased safety.