N362 Petrophysics for Low Resistivity, Low Contrast Reservoirs

Course Facts

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


This intermediate level practical petrophysics course will provide a proven methodology to identify and evaluate hydrocarbon reservoirs with a particular emphasis on Low Resistivity, Low Contrast (LRLC) pays. Methods to evaluate LRLC pay from both old log suites and the newer generation logging tools will be discussed. Reservoir characterization procedures for creating saturation height models on heterogeneous reservoirs from capillary pressure data will be illustrated with examples. 

Duration and Training Method

A five-day course consisting of a mixture of classroom lectures, spreadsheet calculations and log-based interpretation exercises. Lectures are interspersed with practical exercises (spreadsheet and PC-based interpretation software). Participants are encouraged to bring their own non-proprietary examples for end-of the-day group discussion/evaluation. Computers will be provided.  The ratio of classroom to computer time is approximately 70/30.

Participants will learn to:

  1. Evaluate through logs and core the key petrophysical properties such as Archie parameters, water resistivity and water saturation.
  2. Assess the different modes of shale distribution, estimate shale volume from logs, appraise the different shaly sand interpretation models and understand the difference between effective and total porosity.
  3. Assess possible low resistivity low contrast pay from modern logs in new wells, or as potential bypassed pay from older logs in old wells.
  4. Evaluate the role of clays and conductive minerals, grain size variations and associated capillary properties and their impact on log response.
  5. Judge the appropriate cementation exponents, saturation exponents and water saturation models to use in petrophysical evaluation of these pay sections.
  6. Select appropriate logging tools to evaluate low resistivity low contrast pays.
  7. Assess core data (conventional whole core, sidewall cores and drill cuttings) as a component of a LRLC pay evaluation.
  8. Judge the effectiveness of logging and coring programs designed to evaluate LRLC pay intervals.
  9. Assess the different modes of shale distribution and calculate the net-to-gross of a laminated series from industry crossplot methods.
  10. Estimate the hydrocarbon reserves in a thinly bedded sand-shale sequence.
  11. Evaluate the tool response of multicomponent induction and nuclear magnetic resonance in a thin bedded sand shale sequence.
  12. Judge the advantages and limitations of nuclear magnetic resonance measurements for porosity, saturation and permeability.
  13. Develop a permeability model from nuclear magnetic resonance data by calibrating industry relationships to core data.
  14. Estimate vertical hydrocarbon phase distribution using formation pressure data and gain an understanding of the pressure data quality by integrating other petrophysical data.
  15. Develop a saturation-height model of a heterogeneous reservoir using capillary pressure data and J-functions.

This is an integrated practical petrophysics course and will provide a proven methodology to identify and evaluate LRLC pays as seen in modern wells or as potential bypassed pays in old wells. Topics covered include: physical rock properties, shaly sand analysis, causes of low resistivity pay, evaluation of thinly laminated sand-shale reservoirs, nuclear magnetic resonance interpretation, capillary pressure and saturation height functions.

The application of petrophysical analysis to subsurface projects will be emphasized, and the value of this approach will be illustrated with case studies and exercises.

The course covers:

Petrophysical Properties: Estimation and Interpretation (Logs)
Interpretation principles and workflows; Determination of Rw and Pickett plots, Archie exponents including anomalies, influence of wettability; Archie saturation; Saturationheight

Shaly Sand Analysis
Clay properties, volume of shale from logs; Effective and Total Porosity; Vsh, Double Layer (CEC) and Normalized (Juhasz) models for shaly sand interpretation.

Identifying Low Resistivity Pay from Conventional Log Suites
Tool resolution and responses. Mudlogging specifi cations. Core acquisition. Case studies from Gulf of Mexico.

Geologic Causes of Low Resistivity Pay
Non-Archie type reservoirs. Laminated sand/shale sequences, fresh formation waters, conductive minerals, silt and lower very fi ne sized grains, internal and superfi cial (clay
coats) microporosity.

Shale Distribution in Clastic Reservoirs and Resistivity Anisotropy
Laminar, Dispersed and Structural Shale/Porosity Models, Thomas-Steiber Crossplots, net-to-gross in thin bedded environments, scaler vs. tensor measurements, multicomponent induction tools, interpretation methods.

Theory and Interpretation of Magnetic Resonance (NMR) Data
Measurement principles, porosity and saturation methods and limitations, pore size distribution and permeability models (Coates and SDR), fl uid identifi cation, thin bed
response, T2 measurement on cores, challenges with carbonates.

Using Capillary Pressure Data for Reservoir Models
Air-Hg, Centrifuge and Porous Plate Core Methods, converting lab data to reservoir conditions, Leverett-J cap pressure models, saturation-height models, FWL-OWC

Principles of Dielectric and Spectroscopy Logging

Who should attend

The course targets geoscientists and engineers with four or more years of industry experience who work with petrophysicists in regional evaluations, prospect generation and development studies, as well as petrophysicists with two or more years of experience seeking to enhance their interpretation skills. A major aspect of the course is discussion of petrophysical concepts and how these can be applied.

Prerequisites and linking courses

Participants should have a basic understanding of core properties, logging measurements and petrophysical evaluation, as presented in N083 (Introduction to Petrophysics and Formulation Evaluation), N121 (Modern Petrophysical Well Log Interpretation) or N003 (Geological Interpretation of Well Logs), as well as practical experience working with well logs.

Linking petrophysics courses include N187 (Low Resistivity Low Contrast Pay, US only), N267 (Petrophysics for Shale Gas, US only) and the field course N030 (Rocks and Fluids: Practical Petrophysics, Isle of Wight, UK).

For more advanced treatment of petrophysical topics, consider N314 (Advanced Petrophysics Topics in Conventional Reservoir Evaluation), which builds on the material presented in N054. Related courses at Basic Application Competence Level are N004 (The Essentials of Rock Physics for Seismic Amplitude Interpretation) and N013 (Overpressure in Petroleum Systems and Geopressure Prediction) and at Skilled Application Competence Level courses N032 (Professional Level Rock Physics for Seismic Amplitude Interpretation) and N266 (Stress and Geomechanical Analyses).

Click on a name to learn more about the instructor

David Eickhoff