Diverter (acidizing)

Test Your Knowledge

Quiz: Diverters in Acidizing

Instructions: Choose the best answer for each question.

1. What is the primary function of diverters in acidizing? a) To increase the viscosity of the acid.

2. What is the main principle behind viscosity-based diverters? a) Creating a filter cake to block acid flow.

3. Which of the following is NOT an advantage of using diverters in acidizing? a) Reduced risk of formation damage.

4. What is a critical factor to consider when selecting a diverter? a) The type of drilling rig used.

5. What is the primary purpose of a filter cake in acidizing? a) To increase the viscosity of the acid.

Exercise: Diverter Selection

Scenario: You are working on an acidizing treatment in a reservoir with two zones:

• Zone A: High permeability, desired stimulation target.
• Zone B: Low permeability, undesired zone.

Task: Choose the appropriate diverter type for this scenario and explain your reasoning:

• Viscosity-based diverter
• Filter cake diverter

Techniques

Chapter 1: Techniques for Diverter Application in Acidizing

This chapter delves into the practical methods employed to implement diverter technology in acidizing treatments. Understanding these techniques is crucial for effectively steering acid to the desired zones and maximizing treatment efficiency.

1.1 Viscosity-Based Diverters:

• Gel Placement:
  • This technique involves injecting a high-viscosity gel, typically a cross-linked polymer solution, into the wellbore.
  • The gel's high viscosity preferentially flows into the higher permeability zone, creating a path for subsequent acid injection.
  • This method is particularly effective for targeting zones with significant permeability contrasts.
• Pre-flush Diverters:
  • This method uses a pre-flush fluid, usually a high-viscosity polymer solution, to create a diversion path in the wellbore.
  • The pre-flush fluid is injected before the acid, creating a pathway that directs the acid to the desired zone.
  • This technique is often combined with other diversion methods to enhance effectiveness.
• Delayed-Break Diverters:
  • These diverters utilize fluids that initially exhibit high viscosity but break down over time, allowing acid to flow through the diverted path.
  • This technique allows for controlled acid delivery, gradually shifting the acid flow to the desired zone.

1.2 Filter Cake Diverters:

• Proppant-Based Diverters:
  • In this method, a mixture of proppants and acid are injected into the wellbore.
  • The proppants, typically sand or ceramic beads, form a filter cake at the desired zone's entrance, preventing acid from entering other zones.
  • Proppant size and concentration are crucial factors influencing filter cake formation and effectiveness.
• Resin-Based Diverters:
  • These diverters utilize resin materials that react with the acid to form a cohesive filter cake.
  • Resin-based diverters offer the advantage of forming a strong and durable filter cake, effectively blocking acid flow into unwanted zones.
  • This method is particularly useful for applications requiring long-term diversion.

1.3 Combination Diverters:

• Combined Viscosity and Filter Cake Diversion:
  • This approach combines the advantages of both techniques, utilizing a high-viscosity fluid to create a diversion path and a filter cake to further seal the undesired zones.
  • This combination offers a robust and versatile solution for complex wellbore geometries and challenging reservoir conditions.

1.4 Considerations for Diverter Selection:

• Formation Characteristics: Permeability, porosity, and heterogeneity play a major role in determining the appropriate diverter technique.
• Acid Type and Concentration: The reactivity and viscosity of the acid must be compatible with the chosen diverter material.
• Wellbore Conditions: Injection pressure, temperature, and flow rate significantly influence diverter performance.

Chapter 2: Models for Predicting Diverter Performance

Predicting the performance of diverters in acidizing is crucial for designing effective treatment plans and optimizing well productivity. This chapter explores various models and techniques used to simulate and predict diverter behavior.

2.1 Flow Simulation Models:

• Numerical Models: These models use sophisticated algorithms to simulate fluid flow in complex wellbore geometries.
• Analytical Models: These models simplify flow behavior and provide approximate solutions for diverter performance.
• Field Data Analysis: Historical data from previous acidizing treatments can be analyzed to calibrate and validate models.

2.2 Factors Influencing Diverter Performance:

• Fluid Properties: Viscosity, density, and interfacial tension of fluids involved in the treatment.
• Formation Characteristics: Permeability, porosity, and heterogeneity of the reservoir.
• Wellbore Geometry: Wellbore size, shape, and completion design.
• Operational Parameters: Injection pressure, flow rate, and temperature.

2.3 Applications of Diverter Models:

• Treatment Optimization: Identifying the optimal diverter technique and parameters for a specific well.
• Risk Assessment: Estimating the likelihood of success and potential risks associated with diverter application.
• Cost Optimization: Determining the most cost-effective diverter strategy for a given scenario.

2.4 Limitations of Models:

• Assumptions and Simplifications: Models often rely on simplifying assumptions and may not capture all complexities of real-world scenarios.
• Data Availability: Accurate model input requires reliable data, which may not always be readily available.

Chapter 3: Software for Diverter Design and Simulation

Software tools play a crucial role in designing, simulating, and analyzing diverter treatments. This chapter highlights various software applications used in the industry for diverter analysis and optimization.

3.1 Commercial Software Packages:

• Reservoir Simulation Software: These packages offer sophisticated capabilities for modeling fluid flow in reservoirs, including diverter behavior.
• Wellbore Simulation Software: This software focuses on simulating fluid flow in wellbores, providing detailed insights into diverter performance.
• Specialized Diverter Design Software: Some software programs are specifically designed for designing and analyzing diverter treatments, offering dedicated tools for specific applications.

3.2 Open-Source Software:

• Open-Source Reservoir Simulators: Several open-source software projects provide free and accessible tools for reservoir simulation, including diverter functionality.
• Programming Libraries: Libraries such as Python and MATLAB allow users to develop custom scripts and algorithms for diverter analysis.

3.3 Software Features:

• Fluid Property Input: Software allows users to define the properties of fluids involved in the treatment.
• Formation Characterization: Users can specify reservoir properties, including permeability, porosity, and heterogeneity.
• Wellbore Geometry Definition: Software supports the input of wellbore design and completion details.
• Diverter Simulation: Software simulates diverter behavior, predicting acid flow patterns and treatment effectiveness.
• Results Visualization: Software provides graphical representations of simulation results, facilitating interpretation and analysis.

Chapter 4: Best Practices for Diverter Implementation in Acidizing

This chapter outlines essential guidelines and best practices for successful implementation of diverter technology in acidizing treatments. Adhering to these practices ensures optimal results and minimizes potential complications.

4.1 Planning and Design:

• Thorough Reservoir Characterization: Accurate understanding of reservoir properties is crucial for selecting appropriate diverter technology.
• Wellbore Condition Assessment: Careful evaluation of wellbore geometry, completion design, and potential issues.
• Diverter Type Selection: Choosing the most suitable diverter technique based on reservoir characteristics, acid type, and wellbore conditions.
• Treatment Optimization: Determining optimal injection parameters, including pressure, flow rate, and volume.

4.2 Execution and Monitoring:

• Proper Equipment and Materials: Using high-quality equipment and materials ensures reliable diverter performance.
• Rigorous Injection Control: Monitoring and adjusting injection parameters to maintain desired flow patterns.
• Real-Time Monitoring and Data Acquisition: Collecting data during the treatment to assess diverter effectiveness and identify any anomalies.

4.3 Post-Treatment Evaluation:

• Well Performance Monitoring: Assessing the effectiveness of the diverter treatment through post-treatment production data analysis.
• Analysis of Production Logs: Examining production logs to identify any changes in production behavior attributed to the diverter treatment.
• Evaluation of Treatment Success: Determining whether the diverter effectively achieved its intended goals.

4.4 Best Practice Examples:

• Careful Pre-Treatment Planning: Thorough analysis of reservoir and wellbore conditions before selecting a diverter technique.
• Effective Communication: Clear communication between engineering teams, field personnel, and operations teams.
• Continuous Improvement: Analyzing past experiences and implementing improvements in diverter selection and treatment design.

Chapter 5: Case Studies of Diverter Applications in Acidizing

This chapter presents real-world examples showcasing the successful implementation of diverter technology in acidizing treatments. These case studies highlight the benefits of diverter application and demonstrate the practical application of the concepts discussed in previous chapters.

5.1 Case Study 1: Targeted Stimulation of a Low-Permeability Zone:

• Description: An oil well with a low-permeability zone in the middle of the reservoir required targeted stimulation to improve production.
• Diverter Technique: A viscosity-based diverter using a gel solution was employed to direct the acid to the low-permeability zone.
• Results: The diverter successfully targeted the desired zone, increasing production rates and improving well performance.

5.2 Case Study 2: Prevention of Acid Leak-off in a Fractured Formation:

• Description: An acidizing treatment in a fractured formation required a diversion technique to prevent acid leak-off into the fractures.
• Diverter Technique: A filter cake diverter using proppants was used to create a barrier and minimize acid loss.
• Results: The diverter successfully controlled acid leak-off, ensuring effective acid placement in the desired zones.

5.3 Case Study 3: Combined Diverter Approach for Complex Wellbore:

• Description: A complex wellbore with multiple zones required a multi-stage acidizing treatment with diversion in each stage.
• Diverter Technique: A combined viscosity and filter cake diverter approach was employed to achieve targeted stimulation in each zone.
• Results: The combined technique effectively diverted acid to the desired zones, leading to significant production improvements.

5.4 Analysis of Case Study Results:

• Production Increases: Case studies demonstrate the potential for significant production increases through effective diverter application.
• Reduced Operational Costs: Diverters can minimize acid consumption and reduce the overall cost of acidizing treatments.
• Improved Well Life: Targeted stimulation and minimized formation damage contribute to longer well life and sustained production.

These case studies provide valuable insights into the practical application of diverter technology in acidizing treatments, demonstrating its effectiveness in improving well performance and maximizing hydrocarbon recovery.