Plugging back is a common practice in drilling and well completion, often employed to optimize production and manage reservoir fluids. It involves placing a barrier, typically cement, in a wellbore to isolate different zones or formations. This versatile technique allows operators to achieve several objectives, including:
1. Excluding Bottom Water:
2. Sidetracking:
3. Producing from a Higher Formation:
Methods of Plugging Back:
Plugging back can be achieved using various methods, each suited to specific circumstances:
Advantages of Plugging Back:
Considerations:
Conclusion:
Plugging back is a versatile and valuable technique in drilling and well completion. It allows for optimal production, improves wellbore integrity, and extends the life of wells. By carefully planning and executing plugging back operations, operators can optimize their field development strategy and maximize resource recovery.
Instructions: Choose the best answer for each question.
1. What is the primary purpose of plugging back in drilling and well completion?
a) To permanently seal off a wellbore. b) To enhance production by isolating zones or formations. c) To increase the diameter of the wellbore. d) To prevent blowouts during drilling.
b) To enhance production by isolating zones or formations.
2. What is the most common method used for plugging back?
a) Mechanical plugs. b) Cementing. c) Gravel packing. d) Acidizing.
b) Cementing.
3. Which of the following is NOT a potential advantage of plugging back?
a) Increased production. b) Improved wellbore integrity. c) Reduced drilling time. d) Cost-effective solution.
c) Reduced drilling time.
4. What is a potential problem that can be addressed by plugging back?
a) Excessive production from a target formation. b) Water influx from a lower formation. c) Formation of a gas cap in the reservoir. d) Insufficient drilling mud weight.
b) Water influx from a lower formation.
5. Which of the following is an important consideration when planning plugging back operations?
a) Proper drilling fluid selection. b) Availability of specialized drilling equipment. c) Environmental impact and regulatory compliance. d) Adequate wellbore casing pressure.
c) Environmental impact and regulatory compliance.
Scenario:
An oil well is producing from a target formation at 10,000 feet depth. However, a water-bearing zone is encountered at 9,000 feet, significantly impacting oil production. The operator decides to plug back to isolate the water zone and continue production from the target formation.
Task:
**1. Steps Involved in Plugging Back:** * **Wellbore Preparation:** The well would be cleaned and prepared for cementing. * **Cementing:** Cement slurry would be pumped through the drill pipe to a depth just above the water-bearing zone (9,000 feet). * **Cement Setting:** The cement would be allowed to set, creating a solid barrier. * **Wellbore Testing:** The cemented section would be tested to ensure proper isolation. * **Production Restoration:** The well would be re-completed and production resumed from the target formation. **2. Addressing Water Influx:** Plugging back by cementing a barrier above the water-bearing zone would effectively isolate the water-producing formation. This would prevent water from entering the production string and contaminating the oil production. **3. Advantages of Plugging Back:** * **Increased Oil Production:** By isolating the water zone, oil production would be significantly enhanced. * **Extended Well Life:** Plugging back can extend the life of a well by preventing premature abandonment due to water influx.
Comments