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Glossary of Technical Terms Used in Drilling & Well Completion: Deflection

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Deflection

Deflection in Oil & Gas: Navigating the Curves of Wellbores

In the oil and gas industry, drilling straight down isn't always the most efficient or effective way to reach the target reservoir. That's where deflection comes into play.

Deflection in oil and gas terminology refers to the total change in angle of a wellbore in a given distance. It's essentially the amount the wellbore deviates from a straight vertical path. This deviation is measured in degrees, and the distance over which it occurs is measured in feet.

Why is Deflection Necessary?

Deflection is used for a variety of reasons, including:

  • Reaching Targets: Horizontal or angled wells can access reservoirs that are inaccessible from a straight vertical well.
  • Optimizing Production: Deflection can be used to target specific areas within a reservoir to maximize production.
  • Avoiding Obstacles: Wells can be deflected to avoid geological formations, water-bearing zones, or other obstacles.
  • Accessing Multiple Reservoirs: A single well can be deflected to access multiple reservoirs at different depths.

Types of Deflection:

There are two main types of deflection:

  • Planned Deflection: This is when the wellbore is intentionally deflected to achieve a specific objective. This can be done using specialized drilling tools and techniques.
  • Unplanned Deflection: This is when the wellbore deviates from the intended path due to unexpected geological conditions, such as faults or rock formations.

Measuring and Controlling Deflection:

  • Measurement: Deflection is measured using specialized surveying tools, like gyroscopes and magnetic sensors. These tools provide data on the wellbore's position and orientation in real-time.

  • Control: Drilling engineers and directional drillers use various techniques to control deflection, including:

    • Steering tools: These tools allow for adjustments to the wellbore trajectory while drilling.
    • Mud weight: The weight of the drilling mud can help to control the wellbore's trajectory.
    • Bit design: Different bit designs can influence how the wellbore is deflected.

Deflection: A Crucial Element of Oil and Gas Exploration

Deflection is a fundamental concept in oil and gas exploration and production. Understanding how to measure, control, and utilize deflection allows engineers to optimize drilling operations, reach targeted reservoirs, and ultimately maximize production efficiency. By skillfully navigating the curves of wellbores, the industry can effectively extract valuable resources from challenging locations.

Test Your Knowledge

Quiz: Deflection in Oil & Gas

Instructions: Choose the best answer for each question.

1. What does "deflection" refer to in oil and gas terminology? a) The total length of a wellbore. b) The amount of pressure applied during drilling. c) The total change in angle of a wellbore in a given distance. d) The type of drilling fluid used.

Answer

c) The total change in angle of a wellbore in a given distance.

2. Which of the following is NOT a reason for using deflection in drilling? a) Reaching targets that are inaccessible from a straight vertical well. b) Optimizing production by targeting specific areas within a reservoir. c) Avoiding geological formations and obstacles. d) Maximizing the drilling time required to reach the target.

Answer

d) Maximizing the drilling time required to reach the target.

3. What is the difference between "planned deflection" and "unplanned deflection"? a) Planned deflection is intentional, while unplanned deflection is caused by unexpected geological conditions. b) Planned deflection is measured using gyroscopes, while unplanned deflection is measured using magnetic sensors. c) Planned deflection uses steering tools, while unplanned deflection uses mud weight. d) Planned deflection is more common than unplanned deflection.

Answer

a) Planned deflection is intentional, while unplanned deflection is caused by unexpected geological conditions.

4. Which of the following is NOT a technique used to control deflection? a) Steering tools. b) Mud weight. c) Bit design. d) Using a larger drilling rig.

Answer

d) Using a larger drilling rig.

5. Why is understanding deflection crucial in oil and gas exploration? a) It allows engineers to estimate the total cost of drilling. b) It helps to determine the type of drilling fluid to use. c) It enables engineers to optimize drilling operations, reach target reservoirs, and maximize production efficiency. d) It is used to calculate the volume of oil and gas reserves.

Answer

c) It enables engineers to optimize drilling operations, reach target reservoirs, and maximize production efficiency.

Exercise: Deflection Calculation

Instructions: A wellbore is drilled vertically for 1000 feet. Then, it is deflected at a constant rate of 3 degrees per 100 feet for the next 500 feet. Calculate the total angle of deflection at the end of the 1500 feet.

Exercice Correction

Here's the solution:

The wellbore is deflected for 500 feet at a rate of 3 degrees per 100 feet.

Total deflection = (Deflection rate per 100 feet) * (Total deflected distance / 100 feet)

Total deflection = 3 degrees/100 feet * 500 feet / 100 feet = 15 degrees.

Therefore, the total angle of deflection at the end of 1500 feet is 15 degrees.

Books

  • Petroleum Engineering Handbook: This comprehensive handbook covers various aspects of oil and gas engineering, including directional drilling and wellbore trajectory control. It's a great source for understanding the fundamentals of deflection.
  • Directional Drilling: An Introduction to the Fundamentals of Drilling Deviated and Horizontal Wells: This book provides a thorough overview of directional drilling techniques, focusing on the planning, execution, and control of wellbore deflection.
  • Drilling Engineering: This book by John Lee covers a wide range of drilling engineering principles, including the physics of wellbore deflection, measurement methods, and steering techniques.

Articles

  • "Directional Drilling: A Guide for Wellbore Trajectory Control" by SPE (Society of Petroleum Engineers): This article provides a detailed explanation of directional drilling principles, including deflection, and the role of technology in optimizing wellbore trajectories.
  • "The Importance of Wellbore Trajectory Control in Horizontal Wells" by Oil and Gas Journal: This article discusses the significance of wellbore deflection in horizontal wells, particularly for maximizing production and accessing unconventional reservoirs.
  • "Advanced Wellbore Trajectory Control Techniques for Complex Reservoirs" by Schlumberger: This article highlights advanced technologies and techniques used for controlling wellbore deflection in complex geological formations.

Online Resources

  • Society of Petroleum Engineers (SPE) website: This website offers a wealth of resources on various topics related to the oil and gas industry, including drilling engineering, directional drilling, and wellbore trajectory control.
  • Schlumberger Oilfield Glossary: This online glossary provides definitions and explanations of various technical terms related to the oil and gas industry, including deflection and directional drilling.
  • Baker Hughes Directional Drilling website: This website offers information on Baker Hughes' directional drilling services and technologies, including steering tools, measurement instruments, and wellbore trajectory control solutions.

Search Tips

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  • Search for specific publications: Use "site:spe.org" or "site:slb.com" to search for relevant content within specific websites.
  • Use quotation marks: Enclose keywords in quotation marks to find exact matches, such as "wellbore trajectory control".
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