Bond Log Basics and Interpretation

Jul 29, 2024

Bond Log Basics and Interpretation

Introduction

  • Host: Mariam Shreve, Senior Petroleum Engineering student at Lebanese American University
  • Speaker: Engineer Kirk Harris
    • Background: Bachelor’s in Civil Engineering from Purdue University
    • Experience: Halliburton, Occidental Petroleum, Talisman Energy, Repsol
    • Current: Technical Advisor for ThoroughBond LLC
  • Event Host: Arab Oil and Gas Academy
  • Webinar Topic: Bond log basics and interpretation
  • Main Tools Covered: CBL (Cement Bond Log) and Ultrasonic
  • Reminder: Questions through Q&A during the session

Agenda Overview

  1. Basics of CBL and Ultrasonic
  2. Interpretation Techniques (Five C’s)
  3. Practical Bond Log Interpretation

Basics of Cementing

  • Casing and Cementing Steps:
    1. Drill well and run casing
    2. Circulate hole to clean
    3. Pump spacer and drop bottom plug
    4. Pump cement
    5. Drop top plug and displace with fluid
    6. Wait for cement to set (24-72 hours)
    7. Run bond log to evaluate cement
  • Main Equipment: High-pressure cementing unit, cementing head, check valve (float equipment)
  • Goal: Secure wellbore, prevent fluid migration

CBL Basics

  • Tools: Bond log tool with transmitter and receivers (3 ft and 5 ft)
  • Sound Wave Analysis: Ring and resonance
  • Key Elements:
    • Amplitude: Strength of first arrival sound
    • Transit Time: Time for sound to travel from transmitter to receiver
    • VDL (Variable Density Log): Visual representation of sound waves
  • Interpreting VDL:
    • Look for straight lines (bad bond)
    • Curved lines (formation signals)
    • Identify fluid arrivals

Types of Bond Logs

  1. Free Pipe: No cement, straight lines, ringing patterns
  2. Micro Annulus: Weak bond, some casing ring
  3. Channeling: Incomplete cement fill, potential flow paths
  4. Perfect Cement: No straight lines, good formation signals

Ultrasonic Log (USIT)

  • Tool Mechanics: Spinning head, sends and receives sound waves
  • Measurement: Acoustic impedance
  • Log Components: Eccentricity curve, amplitude map, radius, bond index, cement map
  • Use Case: Detect channels, evaluate casing condition, map cement distribution

Five C’s of Interpretation

  1. Construct the Well: Know well details, construction, and cement placement
  2. Compare: Different sections of the log
  3. Correlate: Match changes with formation, casing, etc.
  4. Consider: External factors affecting logs (casing condition, formation type)
  5. Conclusion: Final interpretation based on gathered data

Special Considerations

  • New Casing: Shiny surfaces may lead to poor bond
  • Lightweight Cement: Higher tendency for casing ring
  • Shale Bond: Shale can swell and bond better
  • Pressure Testing: Can break cement bond
  • Formation Effects: Sands and shales bond differently

Interactive Log Interpretation Practice

  1. Construct the Well: Gather all the necessary information
  2. Compare Sections: Identify good vs. bad sections
  3. Correlate: Establish key points and causes
  4. Consider Factors: What could cause discrepancies
  5. Conclusion: Draw conclusions and suggest corrections

Q&A Highlights

  • Calibration of Tools: Function calibration, normalization in free pipe sections
  • Bond Integrity in Washouts: Identifying washout effects on bond
  • Shale vs. Sand Bonding: Strength and formation effect on bond quality

Closing Remarks

  • Recording Available: On Pi Petro’s YouTube channel
  • Upcoming Webinars: Check Arab Oil and Gas Academy Facebook page
  • Final Note: Keep practicing log interpretation for accuracy improvement