N260 Practical Subsurface Mapping

Course Facts

Course Code:
5 days
4.0 Continuing Education Units
40 Professional Development Hours
Certificate Issued Upon Completion


This course provides an introduction to the basic skills and techniques required to generate reliable subsurface maps and volumetric estimates by hand from well and seismic data. Although subsurface interpretation work and contouring is now largely done using computers it remains essential for early career geoscientists and petroleum engineers to understand basic mapping and volumetric concepts and retain control of the critical decisions involved in the process.

Duration and Training Method

A five-day classroom course, comprising lectures, worked exercises and discussions, with at least half of the time devoted to worked examples. Participants will make a variety of hand-contoured maps from both well and seismic data, and understand their significance for estimating volumes of hydrocarbons in place in both exploration and production contexts.

Participants will learn to:

  1. Undertake hand-contouring of posted well and seismic data for structural horizon tops, thicknesses and reservoir properties.
  2. Illustrate fault geometries in section and map view and understand how faults and horizons intersect.
  3. Discuss the use and abuse of statistics and geostatistics in computer mapping.
  4. Appreciate that maps should look good as well as being technically good
  5. Understand the principles of seismic acquisition, processing and interpretation.
  6. Understand the principles of depth conversion and calculate an average velocity map from well tops and seismic times.
  7. Pick formation tops, correlate wireline logs and generate cross sections using good geological principles.
  8. Understand the basics of ‘quick look’ petrophysical analysis.
  9. Analyse subsurface pressure data to constrain fluid contacts and determine lateral and vertical connectivity of reservoir fluids.
  10. Determine volumetric estimates of hydrocarbons in-place using a variety of methods, including assessments of uncertainty.

Subsurface mapping is a critical skill for those involved in describing hydrocarbon reservoirs. It is vital to know how to generate reliable subsurface maps that have internal integrity, honour available data, resolve data conflicts and communicate to decision-makers a realistic representation of the subsurface.

Such maps are used to quantify in-place hydrocarbon volumes and inform all kinds of drilling decisions during prospect evaluation, field appraisal and development and ultimately help to optimise the commercial potential of a project.

The course content is highly practical with several substantial exercises that complement the lecture material, as follows:


Lecture 1: Course overview and objectives

      • Including an introduction to maps and cross-sections
      • Exercise 1: Uncertainty exercises

            Lecture 2: Basics of structural geology

            • Faults and folds
            • Trapping mechanisms
            • Examples of trap geometries
            • Exercise 2: Cross-section skills

                    Lecture 3: Techniques of subsurface mapping, including:

                    • Hand contouring methods for structural and rock property mapping.
                    • Exercise 3: Contouring skills

                            DAY 2

                            Lecture 3: Techniques of subsurface mapping

                            • Use of statistics & geostatistics
                            • Exercise 3: Contouring skills (continued)

                            Lecture 4: Basics of seismic

                            • Introduction to seismic acquisition
                            • Introduction to seismic processing
                            • Introduction to borehole geophysics
                            • Exercise 4: Synthetic seismograms
                            • Introduction to seismic interpretation
                            • Exercise 5: Seismic Interpretation

                            DAY 3

                            Lecture 5: Introduction to depth conversion

                            • Why is it important?
                            • Types of velocities
                            • Approaches to Depth Conversion
                            • Average velocity, layer-cake and Vo-K
                            • Dealing with uplift
                            • Exercise 6: Depth Conversion

                            Lecture 6: Well log data

                            • Overview
                            • Fundamentals of Quantitative Interpretation
                            • Integration with core data
                            • Petrophysical uncertainties
                            • Exercise 7: Taminga Field log analysis & correlation

                            DAYS 3 - 4

                            Lecture 7: Well correlations & well cross-sections

                            • Understanding well depths and thicknesses
                            • Types of stratigraphy
                            • Constructing correlations and cross-sections
                            • Principles of log correlation
                            • Style in log correlation
                            • Exercise 9: Taminga Field mapping (Part 1)

                            Lecture 8: Subsurface pressure data and its value in mapping hydrocarbon distribution, including:

                            • Estimating fluid contents and contacts
                            • Evaluating vertical and lateral continuity
                            • Exercise 8: Using subsurface pressure data to interpret fluid contacts and assess communication

                            DAYS 4 - 5

                            Lecture 9: Calculating volumes of oil and gas in place in exploration and production

                            • The basic equation: gross rock volume, net to gross, porosity, saturation, formation volume factor
                            • Measurement units and abbreviations
                            • Approaches to volumetric calculation – deterministic and probabilistic, paper-based and computer-based.
                            • Assessing and expressing uncertainty
                            • Other things to consider
                            • How to map or estimate net-to-gross, porosity, saturation, Bo and Bg
                            • Exercise 9: Taminga Field mapping (Part 2): Estimating oil in place, and Amazon Field volumetrics.

                            Lecture 10: More advanced volumetric considerations

                            Lecture 11: Volumetrics Checklist

                            Who should attend

                            This course is aimed at early career geologists, geophysicists and reservoir engineers, who want to learn how to make maps that realistically describe hydrocarbon reservoirs and their structural surroundings. It will also be useful for technical assistants involved in subsurface mapping and volumetric estimation.

                            The process of generating subsurface maps provides a technical team with the opportunity to collaborate between subsurface disciplines (geologists, geophysicists, petrophysicists, engineers) and integrate data from a variety of sources (various types of seismic and well data). This course is enriched by attendance of participants with a variety of discipline backgrounds.

                            Prerequisites and linking courses

                            As a foundational course for early career geoscientists and petroleum engineers, no formal pre-requisites exist. Some knowledge of the upstream oil and gas business and some experience using subsurface data will prove helpful, as will a basic awareness of the nature of hydrocarbon reservoirs and their structural settings.

                            After participating in course N260 and developing further experience constructing a variety of subsurface maps, courses N240 (Using Seismic Data from Rank Exploration to Early Field Development), N085 (Introduction to Seismic Interpretation) and N282 (Interpreter’s Guide to Depth Imaging) would be useful follow up courses. These courses address the interpretation and integration of seismic data through lectures and hands on mapping exercises. Further additional courses in related technical topics are V124 (Play Fairway Analysis and Prospect Evaluation: Key Concepts and Techniques), N031 (Prospect Evaluation and Volumetric Methods, Dorset, UK), N087 (Play Fairway Analysis and Exploration Prospecting), N089 (Exploration Risk Analysis: Prospect Quantification, Decision Techniques, Estimating under Uncertainty and Upstream Portfolio Management) and N286 (Seismic Acquisition Principles and Practice).

                            Click on a name to learn more about the instructor

                            Nigel Banks

                            Related Subjects

                            Excellent foundation and great coverage of wide variety of cross-functional topics.