BUR in Drilling: Understanding Build-Up Rate and its Impact on Well Trajectory
In the world of drilling and well completion, the term "BUR" stands for Build-Up Rate. It refers to the rate at which the inclination of a wellbore increases during the drilling process. Understanding BUR is crucial for managing well trajectory, optimizing drilling operations, and ensuring wellbore stability.
What is Build-Up Rate?
Imagine a wellbore being drilled vertically. As the drilling progresses, the wellbore may start to deviate from its vertical path, gradually tilting towards a specific direction. This deviation is known as the wellbore inclination, and the rate at which this inclination increases is the Build-Up Rate (BUR).
Factors Influencing Build-Up Rate:
- Drilling Parameters: The BUR is directly influenced by drilling parameters such as weight on bit (WOB), rotary speed, and mud weight. Higher WOB and rotary speed can lead to higher BUR, while increased mud weight can help reduce it.
- Formation Properties: The geological formations being drilled through significantly impact BUR. Formations with weaker rocks and high pore pressure tend to exhibit higher BUR.
- Drilling Tools and Techniques: The type of drilling tools used, such as drill bits and mud motors, and the drilling techniques employed, can influence the BUR.
- Wellbore Design: The planned wellbore trajectory, including the target inclination and azimuth, plays a crucial role in determining the BUR.
Importance of Managing Build-Up Rate:
- Wellbore Stability: Uncontrolled BUR can lead to wellbore instability, causing problems like wellbore collapse, stuck pipe, and loss of circulation.
- Trajectory Control: Accurate BUR management is crucial for achieving the desired wellbore trajectory, ensuring that the well reaches its target zone effectively.
- Drilling Efficiency: Controlling BUR helps optimize drilling operations by minimizing time spent correcting deviations and avoiding complications.
- Drilling Costs: Uncontrolled BUR can lead to costly rework and delays, impacting overall drilling costs.
Managing Build-Up Rate:
- Real-time Monitoring: Using downhole tools like MWD (Measurement While Drilling) and LWD (Logging While Drilling) enables continuous monitoring of BUR and wellbore inclination.
- Adjusting Drilling Parameters: Based on real-time data, drilling parameters like WOB, rotary speed, and mud weight can be adjusted to control BUR and maintain the desired trajectory.
- Directional Drilling Techniques: Techniques like "whipping" or "walking" the wellbore can be used to control and manipulate the BUR during drilling.
Conclusion:
Build-Up Rate (BUR) is a critical parameter in drilling operations, directly impacting wellbore stability, trajectory control, efficiency, and costs. Understanding the factors influencing BUR and employing effective management strategies are crucial for successful and cost-effective drilling projects. By carefully monitoring, controlling, and optimizing BUR, drilling teams can ensure that wells are drilled safely, efficiently, and with the desired trajectory.
Test Your Knowledge
BUR Quiz: Build-Up Rate in Drilling
Instructions: Choose the best answer for each question.
1. What does BUR stand for in drilling?
a) Bit Uplift Rate b) Build-Up Rate c) Bottom Up Rate d) Borehole Uplift Rate
Answer
b) Build-Up Rate
2. Which of the following factors does NOT directly influence Build-Up Rate?
a) Mud weight b) Formation properties c) Ambient temperature d) Rotary speed
Answer
c) Ambient temperature
3. What is a potential consequence of uncontrolled Build-Up Rate?
a) Increased wellbore stability b) Reduced drilling costs c) Wellbore collapse d) Improved trajectory accuracy
Answer
c) Wellbore collapse
4. Which technology allows for real-time monitoring of Build-Up Rate?
a) Mud logging b) Wireline logging c) MWD (Measurement While Drilling) d) Seismic surveys
Answer
c) MWD (Measurement While Drilling)
5. Adjusting which drilling parameter can help control Build-Up Rate?
a) Mud density b) Drilling depth c) Rig horsepower d) Drilling fluid viscosity
Answer
a) Mud density
BUR Exercise:
Scenario:
A wellbore is being drilled with the following parameters:
- Weight on Bit (WOB): 40,000 lbs
- Rotary Speed: 100 RPM
- Mud Weight: 12.5 ppg
The wellbore is currently at an inclination of 30 degrees. The drilling engineer observes that the Build-Up Rate is 1 degree per 100 feet drilled.
Task:
- Calculate the expected inclination of the wellbore after drilling 500 feet.
- Analyze the potential consequences of this BUR for the wellbore stability and trajectory.
- Suggest two possible actions the drilling engineer can take to control the BUR and achieve the desired trajectory.
Exercice Correction
1. Expected Inclination:
- BUR = 1 degree per 100 feet
- Distance drilled = 500 feet
- Total inclination increase = (1 degree/100 feet) * 500 feet = 5 degrees
- Expected inclination after 500 feet = Initial inclination + Inclination increase = 30 degrees + 5 degrees = 35 degrees
2. Potential Consequences:
- Wellbore Stability: The relatively high BUR (1 degree per 100 feet) suggests the formation may be relatively weak or have high pore pressure. This could lead to potential issues like wellbore collapse, stuck pipe, and loss of circulation if not managed effectively.
- Trajectory: The BUR exceeding the planned trajectory can result in the well deviating from its target zone, potentially impacting reservoir access and production.
3. Actions to Control BUR:
- Reduce WOB: Decreasing the weight on the bit can reduce the stress on the formation, potentially lowering the BUR.
- Increase Mud Weight: Increasing mud weight can provide better wellbore support and counter the formation pressure, helping to minimize the BUR.
Books
- "Drilling Engineering" by Bourgoyne, Millheim, Chenevert, and Economides: This comprehensive textbook covers various drilling aspects, including wellbore trajectory control and BUR.
- "Directional Drilling Manual" by John C. Haas: This manual focuses on directional drilling practices and includes sections on BUR analysis and management.
- "Petroleum Engineering Handbook" by Society of Petroleum Engineers: This handbook provides an extensive overview of petroleum engineering, with sections on drilling and wellbore stability that may include BUR information.
Articles
- "Build-Up Rate Control in Directional Drilling" by SPE: Search the Society of Petroleum Engineers (SPE) website for articles related to BUR, particularly those focusing on control methods and best practices.
- "Factors Influencing Build-Up Rate in Horizontal Wells" by Journal of Petroleum Technology: Look for articles in reputable drilling and petroleum journals that explore the relationship between BUR and drilling parameters, formation properties, and wellbore design.
Online Resources
- SPE website (www.spe.org): The SPE website offers a vast library of technical papers, articles, and presentations on various drilling topics.
- ONEPetro (www.onepetro.org): This platform houses a wealth of technical content from multiple industry organizations, including SPE publications.
- DrillingInfo (www.drillinginfo.com): DrillingInfo offers data and analytics for the oil and gas industry. They may have resources specifically related to BUR and wellbore stability.
Search Tips
- Use specific keywords: When searching for BUR information, try terms like "build-up rate drilling," "build-up rate control," "directional drilling build-up rate," or "wellbore stability build-up rate."
- Combine with other terms: Use keywords related to your specific area of interest, such as "build-up rate shale formations" or "build-up rate horizontal wells."
- Filter your results: Use advanced search operators in Google, like "site:" to specify a particular website (e.g., site:spe.org build-up rate).
- Explore related topics: Look for content related to wellbore stability, directional drilling, drilling parameters, and formation properties.
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