PBTD

Test Your Knowledge

PBTD Quiz

Instructions: Choose the best answer for each question.

1. What does PBTD stand for?

(a) Plug Back Total Depth (b) Production Back Total Depth (c) Plugged Back to Depth (d) Partial Back to Depth

2. What is the primary purpose of a plug placed at the PBTD?

(a) To prevent the flow of oil and gas into the wellbore. (b) To isolate a section of the wellbore. (c) To enhance the production rate of the well. (d) To increase the pressure within the wellbore.

3. Which of the following is NOT a benefit of PBTD?

(a) Increased productivity (b) Cost-effective well management (c) Increased environmental impact (d) Reduced environmental impact

4. What is a key factor that determines the PBTD?

(a) The depth of the previous production zone. (b) The depth of the new production zone. (c) The diameter of the wellbore. (d) The type of fluids being produced.

5. Why is PBTD crucial for well abandonment?

(a) It allows for the efficient removal of all equipment from the well. (b) It ensures that the well is permanently sealed and prevents environmental contamination. (c) It enables the well to be reused for other purposes. (d) It helps to reduce the cost of well abandonment.

PBTD Exercise

Scenario:

A well has been drilled to a total depth of 5,000 meters. It has successfully produced hydrocarbons from a zone located at 3,000 meters. The operator decides to re-enter the well and target a new production zone at 2,000 meters.

Task:

1. Determine the PBTD for this scenario.
2. Explain why it is necessary to plug back the well to the PBTD before accessing the new production zone.

Techniques

Chapter 1: Techniques for PBTD

This chapter delves into the various techniques employed to achieve Plug Back Total Depth (PBTD).

1.1 Conventional Plugging Techniques:

• Cementing: This involves placing a cement plug within the wellbore, effectively isolating the targeted section. The cement slurry is pumped down the well and allowed to set, creating a durable barrier.
• Mechanical Plugs: These are pre-designed devices that are lowered into the wellbore and mechanically expanded to create a tight seal. They are often made of materials like steel or elastomers.
• Combination Techniques: Some projects utilize a combination of cementing and mechanical plugs for added security and reliability.

1.2 Advanced Plugging Techniques:

• Expandable Plugs: These plugs are designed to expand radially within the wellbore, ensuring a tight seal even in irregular or damaged sections.
• Squeeze Cementing: This technique involves injecting a specially formulated cement slurry under high pressure, forcing it into the formation and creating a tight seal.
• Injection of Resin: This involves injecting a resin into the wellbore, which hardens and forms a durable plug.

1.3 Selection Criteria for Plugging Techniques:

• Wellbore condition: The presence of damage, corrosion, or irregularities can influence the choice of plugging technique.
• Depth of the PBTD: Deeper PBTDs often require specialized techniques to ensure the plug remains effective.
• Formation characteristics: The properties of the formation, such as porosity and permeability, can impact the efficiency of different plugging methods.
• Environmental regulations: Local regulations may dictate the type of plugging technique employed to minimize environmental impact.

1.4 Conclusion:

Choosing the appropriate PBTD technique is crucial for ensuring the safety and effectiveness of the well abandonment and re-entry process. Understanding the various available options and their suitability for different well conditions and regulatory requirements is essential for successful well management.