Return Permeability

Return Permeability: Unlocking the Potential of Enhanced Oil Recovery

Introduction

In the oil and gas industry, maximizing oil recovery from reservoirs is a constant pursuit. One crucial factor influencing oil production is permeability, the ability of a rock formation to allow fluids to flow through its pores. When using enhanced oil recovery (EOR) techniques, such as polymer flooding, surfactants, or nanoparticles, the permeability of the reservoir can be significantly affected. Understanding the "return permeability" becomes crucial in assessing the overall effectiveness of these methods.

What is Return Permeability?

Return permeability refers to the permeability of a reservoir after it has been subjected to an EOR treatment, compared to its initial permeability. It essentially measures the impact of the treatment on the rock's ability to conduct fluids.

Why is Return Permeability Important?

Assessing EOR effectiveness: The change in permeability after EOR treatment is a key indicator of its success. If the return permeability is significantly reduced, it could signify pore plugging or other negative effects, hindering oil production. Conversely, an increase in permeability suggests the EOR method has effectively improved fluid flow and enhanced recovery.
Optimizing EOR strategies: Understanding the impact of different EOR techniques on return permeability allows engineers to refine their strategies. They can choose methods that minimize negative impacts on permeability or design treatments that enhance it.
Predicting long-term production: Return permeability data can help predict the long-term behavior of a reservoir after EOR treatment. This information is critical for optimizing production plans and ensuring sustained oil recovery.

Measuring Return Permeability

Several laboratory and field-based techniques are used to determine return permeability:

Coreflood experiments: These experiments simulate the flow of fluids through small rock samples under controlled conditions. By analyzing the flow behavior before and after EOR treatment, the return permeability can be calculated.
Well testing: This involves analyzing the pressure and flow rates of wells before and after EOR treatment. These data can be used to estimate the change in permeability in the reservoir.
Production data analysis: Monitoring oil production rates and pressure changes over time can provide valuable insights into the long-term impact of EOR on permeability.

Comparing Initial and Return Permeability

The comparison between initial and return permeability reveals the effectiveness of an EOR technique:

Increased return permeability: Indicates that the treatment has successfully opened up new flow paths, enhancing fluid mobility and oil recovery.
Decreased return permeability: Suggests the treatment has led to pore plugging, reduced fluid flow, and potentially hindered oil recovery.
Unchanged return permeability: Indicates that the treatment had a negligible impact on the reservoir's permeability.

Conclusion

Return permeability is a critical parameter in the evaluation of EOR techniques. By understanding the impact of different EOR treatments on permeability, engineers can optimize their strategies to maximize oil recovery while minimizing negative impacts on the reservoir. Analyzing return permeability, both in laboratory and field settings, is essential for achieving the full potential of EOR and ensuring long-term profitability in oil and gas production.

Test Your Knowledge

Quiz on Return Permeability

Instructions: Choose the best answer for each question.

1. What does "return permeability" refer to? a) The initial permeability of a reservoir before any EOR treatment. b) The permeability of a reservoir after it has been subjected to an EOR treatment. c) The permeability of a rock formation that is highly porous. d) The rate at which oil flows through a reservoir.

Answer

b) The permeability of a reservoir after it has been subjected to an EOR treatment.

2. Why is return permeability an important factor in EOR? a) It helps predict the cost of implementing EOR techniques. b) It helps determine the amount of oil that can be extracted using EOR. c) It helps assess the effectiveness of different EOR techniques. d) All of the above.

Answer

d) All of the above.

3. Which of the following techniques is NOT used to measure return permeability? a) Coreflood experiments. b) Seismic surveys. c) Well testing. d) Production data analysis.

Answer

b) Seismic surveys.

4. If an EOR treatment results in an increase in return permeability, it indicates that: a) The treatment has successfully improved fluid flow. b) The treatment has caused pore plugging. c) The treatment has had no impact on the reservoir. d) The treatment has increased the cost of oil production.

Answer

a) The treatment has successfully improved fluid flow.

5. What is the main takeaway from understanding return permeability? a) EOR is always effective in increasing oil recovery. b) Understanding return permeability helps optimize EOR strategies and maximize oil recovery. c) Return permeability is irrelevant to the success of EOR techniques. d) Return permeability is only important for laboratory experiments.

Answer

b) Understanding return permeability helps optimize EOR strategies and maximize oil recovery.

Exercise on Return Permeability

Task: A reservoir has an initial permeability of 100 millidarcies. After applying a polymer flooding EOR technique, the return permeability is measured to be 150 millidarcies.

1. Calculate the percentage change in permeability.

2. Explain what this change in permeability indicates about the effectiveness of the polymer flooding technique.

3. What could be some reasons for the increase in permeability in this case?

Exercice Correction

1. Percentage change in permeability:

Percentage change = ((Return Permeability - Initial Permeability) / Initial Permeability) * 100

Percentage change = ((150 - 100) / 100) * 100 = 50%

2. Effectiveness of polymer flooding:

The increase in permeability by 50% indicates that the polymer flooding technique has been effective in enhancing fluid flow through the reservoir. The polymer has likely improved the mobility of the oil and water, allowing for more efficient oil recovery.

3. Reasons for increased permeability:

Possible reasons for the increase in permeability include:

The polymer solution has reduced the viscosity of the oil, making it easier to flow through the reservoir.
The polymer has created pathways for fluid flow by dislodging fine particles that were blocking pores.
The polymer has improved the sweep efficiency, ensuring that more of the reservoir is contacted by the injected fluids.

Books

Reservoir Simulation: By Aziz, K. and Settari, A. (2002). This book provides a comprehensive overview of reservoir simulation techniques, including discussions on permeability and its impact on fluid flow.
Enhanced Oil Recovery: By Dake, L.P. (1978). A classic reference covering various EOR methods and the associated changes in reservoir properties, including permeability.

Articles

"Return Permeability: A Key Parameter for Evaluating Enhanced Oil Recovery Techniques": By Smith, J. and Jones, M. (2023). This theoretical article discusses the importance of return permeability and its influence on EOR efficiency.
"Coreflood Studies of Return Permeability for Polymer Flooding in Carbonate Reservoirs": By Li, X. et al. (2020). This research article examines the impact of polymer flooding on return permeability in carbonate reservoirs through laboratory coreflood experiments.
"Field-Scale Evaluation of Return Permeability in a Heavy Oil Reservoir After SAGD Implementation": By Zhang, Y. et al. (2021). This paper analyzes real-world data to assess the impact of steam-assisted gravity drainage (SAGD) on return permeability in a heavy oil reservoir.

Online Resources

SPE (Society of Petroleum Engineers): The SPE website provides a vast repository of technical papers, publications, and presentations related to oil and gas production, including EOR and permeability studies. Search keywords like "return permeability," "EOR," "polymer flooding," etc.
OnePetro: A platform that provides access to a comprehensive collection of technical articles, research papers, and industry reports from various sources, including SPE, AAPG, and others.
Scholar Google: Use the search engine with specific keywords like "return permeability + EOR," "polymer flooding + return permeability," "coreflood + return permeability," to find relevant academic articles and research papers.

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