Formation Evaluation Course Summary

Introduction to Formation Evaluation

  • Instructor Information
    • Dr. Rita Esuru Okoroafor
    • Assistant Professor, Petroleum Engineering Department, Texas A&M University
    • Ph.D. from Stanford University, B.Eng. from University of Port Harcourt, Nigeria
    • 15 years of industry experience
    • Joined TAMU faculty in August 2022
    • Research focus on sustainable energy and numerical modeling of subsurface systems.

Course Goals

  • Develop knowledge of well-log interpretation techniques.
  • Understand the physics of conventional open-hole well-log measurements including:
    • Density, Neutron Porosity, Photoelectric Factor, Electrical Resistivity, Gamma Ray, Sonic Logs.
  • Estimate petrophysical properties from well logs:
    • Porosity, water saturation, volumetric concentration of shale, permeability.
  • Learn formation evaluation techniques for various formations:
    • Clean sandstone, carbonate, shaly-sand, organic-rich shale formations.
  • Quantify lithology based on well logs data.
  • Identify candidate zones for perforation, stimulation, and fracture treatment.
  • Experience with commercial software for formation evaluation based on multiple wells.

Important Dates

  • Jan 14: 1st day of class
  • Jan 25: No office hours with Dr. Okoroafor
  • Feb 6: Class administered by Teaching Assistant Subhrojit
  • March 6: Midterm Exam
  • April 25: Project Due
  • May 1: Final Exam
  • Weekly quizzes every Thursday except during exams.

Office Hours

  • Instructor: Dr. Rita Okoroafor
    • Office: RICH 501P
    • Office Hours: By appointment, Wednesdays 11 AM-12 PM
  • Teaching Assistant: Subhrojit Mondal
    • Office: RICH 907
    • Office Hours: Mondays 2-3 PM

Grading Policy

  • Grades Breakdown
    • Attendance & Participation: 5%
    • Homework and Lab Assignments: 20%
    • Midterm Exam and Quizzes: 15%
    • Quizzes: 10%
    • Project: 25%
    • Final Exam: 25%

Course Expectations

  • Engage by attending lectures/labs, asking questions, and timely completion of homework.
  • Follow the Aggie Code of Honor.

Additional Information

  • Commitment to equal access to learning opportunities.
  • Mandatory reporter status, providing information for mental health resources and emergency contacts.

The Exploration & Production (E&P) Life Cycle

  • Involves searching for, recovering, and producing crude oil and natural gas.
  • Key phases: Exploration, Appraisal, Development, Production, Enhanced Recovery, Abandonment.
  • Formation Evaluation required at almost all stages in the E&P life cycle.

Formation Evaluation

  • Analysis of subsurface formation characteristics, such as:
    • Lithology, porosity, permeability, saturation.
  • Techniques: Wireline well logging, core analysis.
  • Used to assess a borehole/formation’s ability to produce petroleum.
  • Interchangeably referred to as “petrophysics”, defined as the study of the physical and chemical properties of rocks and their contained fluids.

Petrophysical Data Sources

  • Mud logs, core analysis, open hole logs, cased hole logs, borehole seismic.

Mud Logging

  • One of the first direct evaluation methods during well drilling.
  • Key information includes:
    • Rate of penetration, lithology, hydrocarbon staining, gas percentage, and gas compositions.
  • Monitor bit performance and well position within stratigraphy.
  • Mud Log Accuracy: The lag time between drilling and sampling can vary from 0-2 hours, with an accuracy of ± 5 meters.

Challenges with Data Integration

  • Data may be collected at different times and resolutions.
  • Different measurement scales and quality issues.

Lithology and Reservoir Characteristics

  • Reservoir classification:
    • Simple, Dirty, Complex formations (e.g., Sandstone, Limestone, Shale).
  • Nature of reservoirs is generally complex, heterogeneous, and challenging to evaluate.
  • Reservoir distinction based on porosity, permeability, hydrocarbon saturation, and lithology.

Understanding Well Logs

  • Well logs: Measurements of formation properties as a function of depth.
  • Types of logs include:
    • Spontaneous Potential (SP), Gamma Ray (GR), Density Log, Neutron Log, Sonic Log.
  • Logs are cost-effective for reservoir characterization and are crucial for accurate estimations of rock petrophysical properties.