Workover

Test Your Knowledge

Workover Quiz:

Instructions: Choose the best answer for each question.

1. What is the primary purpose of a workover?

a) To explore for new oil and gas reserves. b) To drill a new well. c) To repair, maintain, or enhance the production of an existing well. d) To transport oil and gas to refineries.

2. Which of these is NOT a common reason for performing a workover?

a) Production decline. b) Equipment failure. c) Wellbore issues. d) Discovering new oil and gas deposits.

3. Which of the following is a common workover operation?

a) Building a new pipeline. b) Well killing. c) Designing a new drilling rig. d) Obtaining permits for exploration.

4. What type of workover focuses primarily on increasing production using techniques like acidizing or fracturing?

a) Minor workover. b) Stimulation workover. c) Recompletion workover. d) Major workover.

5. What is a coiled tubing unit used for?

a) Transporting oil and gas to refineries. b) Drilling new wells. c) Performing workover operations with a flexible tubing string. d) Storing drilling fluids.

Workover Exercise:

Scenario: A well has experienced a significant drop in production due to a buildup of paraffin wax in the wellbore.

Task: Propose a workover plan to address this issue and restore production. Consider the following:

• Typical workover operations: What specific operations would be necessary to remove the paraffin?
• Equipment: What equipment would be required for this workover?
• Safety considerations: What safety precautions need to be taken during the workover?
• Potential challenges: What challenges might arise during the workover process?

Techniques

Workover: The Art of Reviving Dormant Wells

This document expands on the provided text, dividing the information into chapters focusing on Techniques, Models, Software, Best Practices, and Case Studies related to workovers.

Chapter 1: Techniques Used in Workovers

Workover techniques are diverse and chosen based on the specific well issues and desired outcomes. They range from relatively simple repairs to complex interventions requiring specialized equipment and expertise. Key techniques include:

1. Well Killing: This crucial initial step involves safely removing pressure from the wellbore to prevent uncontrolled flow and allow for safe access. Methods include circulating fluids (mud, brine) to displace hydrocarbons and build pressure.

2. Tubing String Operations: This involves removing, inspecting, repairing, or replacing the tubing string, a vital component for transporting produced fluids to the surface. Techniques include pulling the string, running a new string, and performing internal inspections using tools like downhole cameras and caliper logs.

3. Downhole Equipment Installation/Repair: This can involve installing, repairing, or replacing packers (to isolate zones), pumps (artificial lift), valves (control flow), or other downhole components. These operations often require specialized tools and techniques, such as wireline or coiled tubing deployment.

4. Well Stimulation: This aims to enhance production by improving reservoir permeability. Common methods include:

* **Acidizing:** Injecting acid to dissolve formation rock and improve flow paths.  Different acids are used depending on the reservoir lithology.
* **Hydraulic Fracturing (Fracking):** Creating fractures in the formation by injecting high-pressure fluids, often combined with proppants (sand, ceramic beads) to keep the fractures open.
* **Matrix Stimulation:**  Improving flow within the existing pore space of the reservoir rock without creating new fractures.

5. Well Testing: This evaluates well performance after intervention. Tests include:

* **Pressure Build-up Tests (PBU):** Measuring pressure changes after shutting in the well to determine reservoir properties.
* **Production Logging:** Measuring fluid flow rates, pressure, and other parameters along the wellbore.
* **Drill Stem Tests (DST):**  Testing various reservoir zones for their potential productivity.

6. Recompletion: This involves modifying the existing well completion to improve production or target different reservoir zones. This could involve setting new perforations, installing new screens, or changing the tubing configuration.

7. Sand Control: Implementing methods to mitigate sand production, which can damage equipment and reduce production. Techniques include screens, gravel packing, and resin treatments.

Chapter 2: Models Used in Workover Planning and Optimization

Effective workover planning relies on various models to predict outcomes and optimize operations. These models range from simple analytical tools to complex numerical simulations.

1. Reservoir Simulation Models: These models use data on reservoir properties (permeability, porosity, fluid saturation) to predict the impact of workover operations on production. They help determine the optimal stimulation strategy or identify potential problems.

2. Wellbore Simulation Models: These models simulate fluid flow within the wellbore, accounting for factors like friction, pressure drops, and the effects of downhole equipment. This aids in designing efficient workover operations and preventing equipment failure.

3. Production Forecasting Models: These models integrate reservoir and wellbore data to predict future production rates following a workover. They are crucial for economic evaluation and decision-making.

4. Risk Assessment Models: These models assess the potential risks associated with workover operations, including equipment failure, environmental hazards, and well control issues. This helps develop mitigation strategies and improve safety.

5. Cost Estimation Models: These models estimate the costs associated with different workover scenarios, factoring in equipment, personnel, and materials. This allows for efficient resource allocation and cost-benefit analysis.

Chapter 3: Software Used in Workover Operations

Specialized software plays a vital role in planning, executing, and analyzing workover operations.

1. Reservoir Simulation Software: Examples include Eclipse (Schlumberger), CMG (Computer Modelling Group), and INTERSECT (Roxar). These programs simulate reservoir behavior and assist in optimizing stimulation treatments.

2. Wellbore Simulation Software: Software like OLGA (Schlumberger) and Pipesim (Schlumberger) simulates multiphase flow in the wellbore, helping to design efficient lifting systems and predict pressure drops.

3. Drilling and Completion Software: Software packages like Drilling Simulator and WellCAD assist in planning and optimizing well interventions, including workover operations.

4. Data Management and Visualization Software: Software like Petrel (Schlumberger) and Kingdom (IHS Markit) manage and visualize large datasets from various sources, providing a comprehensive overview of well performance and enabling informed decision-making.

5. Real-time Monitoring and Control Systems: These systems provide real-time data on well conditions during workover operations, allowing for adjustments and quick responses to unexpected events.

Chapter 4: Best Practices in Workover Operations

Following best practices is crucial for safe and efficient workover operations.

1. Thorough Planning and Pre-Job Engineering: Detailed planning, including risk assessment, equipment selection, and procedure definition, is essential.

2. Rigorous Safety Procedures: Implementing strict safety protocols, including well control procedures, personal protective equipment, and emergency response plans, is critical.

3. Use of Specialized Equipment and Expertise: Selecting the right equipment and employing qualified personnel with relevant experience is paramount.

4. Data Acquisition and Analysis: Accurate and timely data acquisition and analysis are crucial for assessing workover effectiveness and identifying potential problems.

5. Continuous Improvement: Regularly reviewing workover operations, identifying areas for improvement, and implementing best practices is important for optimizing efficiency and safety.

6. Environmental Protection: Implementing procedures to minimize environmental impact, including waste management and pollution prevention, is crucial.

Chapter 5: Case Studies of Successful Workovers

Case studies showcase successful workovers and highlight the effectiveness of various techniques and technologies. Examples would include:

• Case Study 1: A workover that successfully restored production in a mature oil well through acidizing and selective completion. This case could detail the challenges faced, the techniques used, the results achieved, and the economic benefits.
• Case Study 2: A complex workover involving coiled tubing intervention to repair a downhole pump in a high-pressure gas well. This case would emphasize the use of advanced technology and the safety precautions implemented.
• Case Study 3: A workover that improved production significantly through a recompletion strategy involving the targeting of a previously untapped reservoir zone. This case could highlight the importance of thorough reservoir analysis and advanced completion techniques.

Each case study should include details on the well's initial condition, the problems encountered, the workover techniques applied, the results achieved, and the lessons learned. These examples provide valuable insights into effective workover strategies and the importance of appropriate planning and execution.