Reservoir Engineering

Gas Coning

Gas Coning: A Threat to Oil Production Efficiency

Gas coning is a phenomenon observed in oil reservoirs where a layer of gas trapped above the oil zone moves downward towards producing wells, forming a cone-shaped intrusion. This intrusion can significantly impact oil production efficiency and profitability, posing a serious challenge for oil producers.

Understanding the Phenomenon:

Imagine a layer of oil trapped beneath a layer of gas. When a well is drilled into the oil zone and production begins, the pressure in the reservoir drops. This pressure drop creates a pressure differential between the gas cap and the oil zone, pushing the gas downwards. The downward movement of gas, driven by the pressure difference, takes the shape of a cone, hence the term "gas coning."

Why Gas Coning is a Problem:

  • Reduced Oil Production: As the gas cone advances, it displaces the oil around the wellbore, leading to a decrease in oil production. This is because the produced fluid is increasingly composed of gas, lowering the oil-to-gas ratio.
  • Increased Production Costs: The gas production associated with gas coning necessitates additional processing and separation, increasing production costs.
  • Wellbore Damage: Excessive gas production can lead to wellbore damage, including plugging and erosion, further impacting oil production.

Factors Influencing Gas Coning:

  • Reservoir Characteristics: The size of the gas cap, the thickness of the oil zone, and the permeability of the reservoir rock all influence the development of gas coning.
  • Production Rate: Higher production rates lead to faster pressure depletion and accelerated gas coning.
  • Wellbore Design: The wellbore location, completion design, and the number of perforations can affect the severity of gas coning.

Strategies to Combat Gas Coning:

  • Production Rate Control: Maintaining a sustainable production rate helps to minimize pressure depletion and gas coning.
  • Artificial Lift: Using methods like gas lift or pump jacks can reduce the drawdown pressure and mitigate gas coning.
  • Wellbore Completion Design: Optimizing wellbore completion by using selectively perforated liners and horizontal drilling techniques can minimize gas coning.
  • Water Injection: Injecting water into the reservoir can maintain pressure and minimize the pressure differential that drives gas coning.

Conclusion:

Gas coning is a serious challenge for oil producers, significantly impacting production efficiency and profitability. Understanding the factors that contribute to gas coning and implementing appropriate mitigation strategies are crucial to optimize oil production and maximize reservoir recovery. By employing proactive measures, oil producers can effectively combat gas coning and ensure long-term sustainable production from their oil reservoirs.


Test Your Knowledge

Gas Coning Quiz:

Instructions: Choose the best answer for each question.

1. What is the primary cause of gas coning?

a) Increased oil production b) Pressure difference between gas cap and oil zone c) Water injection into the reservoir d) Wellbore damage

Answer

b) Pressure difference between gas cap and oil zone

2. Which of the following is NOT a consequence of gas coning?

a) Reduced oil production b) Increased reservoir pressure c) Increased production costs d) Wellbore damage

Answer

b) Increased reservoir pressure

3. Which reservoir characteristic contributes to gas coning?

a) Low permeability of reservoir rock b) Thick oil zone c) Small gas cap d) Presence of water injection

Answer

a) Low permeability of reservoir rock

4. What is a common strategy to combat gas coning?

a) Increasing production rate b) Using artificial lift methods c) Reducing the number of wellbore perforations d) Ignoring the issue and letting it continue

Answer

b) Using artificial lift methods

5. Why is water injection a potential solution for gas coning?

a) It decreases reservoir pressure b) It displaces oil in the reservoir c) It increases the pressure differential between the gas cap and oil zone d) It helps maintain reservoir pressure and minimize pressure differential

Answer

d) It helps maintain reservoir pressure and minimize pressure differential

Gas Coning Exercise:

Scenario: An oil producer is experiencing gas coning in a well. The reservoir has a relatively thin oil zone and a large gas cap. The current production rate is high.

Task: Identify two potential strategies the oil producer can implement to mitigate gas coning in this situation. Explain the reasoning behind each strategy.

Exercise Correction

**Strategy 1: Reduce Production Rate:**

Reducing the production rate will decrease the pressure drawdown in the reservoir. This will minimize the pressure differential driving the gas down towards the wellbore, slowing down the advancement of the gas cone and reducing gas production.

**Strategy 2: Implement Artificial Lift:**

Artificial lift methods, such as gas lift or pump jacks, can help to maintain reservoir pressure by assisting in lifting the oil to the surface. This reduces the drawdown pressure at the wellbore, minimizing the pressure differential and consequently reducing gas coning.


Books

  • Petroleum Production Engineering by Tarek Ahmed: This comprehensive textbook covers reservoir engineering principles, including detailed discussions on gas coning.
  • Reservoir Engineering Handbook by J.P. Brill: Offers a thorough treatment of various reservoir engineering concepts, with dedicated sections on gas coning and its impact on oil production.
  • Gas Coning: A Threat to Oil Production Efficiency by R.C. Earlougher Jr. (This is not a book, but a classic article in the field.)

Articles

  • "Gas Coning in Oil Reservoirs" by R.C. Earlougher Jr. - This article, published in the Journal of Petroleum Technology, provides a foundational understanding of gas coning phenomena.
  • "Gas Coning and Its Impact on Oil Production Efficiency" by M.R. Islam et al. - This recent paper, published in the SPE Journal, discusses modern strategies for mitigating gas coning issues in oil production.
  • "A Review of Gas Coning and Its Control in Oil Production" by A.K. Sharma et al. - This review article in the Journal of Petroleum Science and Engineering presents a detailed overview of gas coning and control methods.

Online Resources

  • SPE (Society of Petroleum Engineers) website: The SPE website contains a wealth of information on reservoir engineering, including numerous articles and presentations related to gas coning. You can search for specific keywords like "gas coning," "coning," or "gas cap" to find relevant content.
  • OnePetro: This online platform offers access to a vast collection of technical papers and articles related to petroleum engineering.
  • Schlumberger Oilfield Glossary: This website provides definitions and explanations of various terms used in oil and gas production, including a clear definition of gas coning.

Search Tips

  • Use specific keywords: "Gas coning," "gas cap," "oil production," "reservoir engineering," "production rate," and "wellbore completion" are effective keywords to narrow your search.
  • Include relevant modifiers: Adding modifiers like "mitigation," "control," "strategies," "model," or "simulation" will help you find more targeted results.
  • Explore different file types: Include "pdf," "doc," or "ppt" in your search query to find specific types of documents, such as research papers, presentations, or technical reports.

Techniques

Similar Terms
Reservoir Engineering
Geology & Exploration
Oil & Gas Processing
Drilling & Well Completion
Programmable Logic Controllers (PLC)
HSE Management Systems
Instrumentation & Control Engineering
Asset Integrity Management
Most Viewed

Comments

No Comments
POST COMMENT
captcha
Back