N267 Petrophysics for Shale Gas Reservoirs

Course Facts

Course Code:
N267
Duration:
3 days
Type:
Classroom
CEU:
2.4 Continuing Education Units
PDH:
24 Professional Development Hours
Certificate:
Certificate Issued Upon Completion

Summary

The petrophysical evaluation of mudstones presents challenges because of complex mineralogy, high organic content, proportion of adsorbed versus free gas and very low permeabilities. This course explores how the physical and chemical nature of shale gas constrain our petrophysical approach and how core measurements integrated with log analysis can help develop an appropriate petrophysical model. The course focuses on shale gas, although liquids are briefly considered.

Duration and Training Method

A three-day seminar-style course in the classroom comprising of a mixture of lectures, discussions, break-out groups, and short exercises using calculators and Excel.

Participants will learn to:

  1. Characterise the geologic nature of shale reservoirs, and how the geological environment and history affect the physical and chemical properties.
  2. Assess the effect of the variability of the physical and chemical properties on the petrophysical properties of shale gas.
  3. Assess how the petrophysical analysis of conventional reservoirs applies to unconventional shale gas, and judge those components of the analysis that may be applied and those that require modification.
  4. Assess the range of core analyses that can be applied to shale gas and the importance of the outputs from these measurements, including an estimation of any uncertainties in the data.
  5. Assess the range of open hole and LWD log measurements that can be applied to shale gas and the importance of the outputs from these measurements, including an estimation of any uncertainties in the data.
  6. Evaluate both core and log data in an integrated approach to optimise the petrophysical interpretation in a shale gas reservoir.
  7. Estimate the gas in place in a shale gas reservoir, separating out free and adsorbed gas components.
  8. Consider at an elementary level the geomechanical properties of a shale gas play and how they may be quantified from core and log data.

Shale gas reservoirs present a significant petrophysical challenge compared to conventional oil and gas reservoirs. The basis of petrophysical evaluation in conventional reservoirs involves the simple separation of solids and fluids but is problematic when considering fine grained successions of mudstones, or shale gas plays.  Core analyses must be adapted for these low permeability formations, while traditional logs are best supplemented by more recently developed measurements.

This seminar-style course will present an overview of mudstones, and how in shale gas plays the physical and chemical properties are central to any petrophysical evaluation. The course starts from the conventional petrophysics viewpoint, considers the nature of mudstone systems, and then uses a variety of approaches appropriate for evaluating shale gas using core and log data within a geological framework. 

The course will cover the following items:

Day 1: Introduction to shale gas reservoirs and petrophysical models for shale gas; case study 1.

  1. Introduction: Shale gas resources and shale gas petrophysics.
  2. Shale gas reservoirs. Mudstones: what do we mean by the term shale? Grain size, shape, mineralogy, pore sizes and shapes. Depositional environments, compaction, dewatering, diagenesis, temperature and pressure. TOC, kerogen, organic maturity, chemical and physical properties.
  3. Petrophysical models for shale gas. Introduction to shale gas petrophysics. Adsorption and desorption. Mineralogy, chemistry and physical properties. Calculating gas in place.
  4. Shale gas: case study 1.

Day 2: Review of petrophysics and introduction to shale gas core analysis.

  1. Review of petrophysics as applied to conventional reservoirs. Petrophysical properties; porosity, saturation, density, permeability, capillary pressure; gross, net and pay. Review of core analysis procedures. Review of geophysics and petrophysical relationships. Review of downhole logs.
  2. Shale gas core analysis. Coring, core handling and core preservation. Porosity, permeability and saturation. Core sub-sampling. Desorption tests. Langmuir isotherms. Total organic carbon, kerogen, thermal maturity, gas analysis. Geomechanical properties.

Day 3: Shale gas log analysis, petrophysical models revisited, geomechanical properties, and an integrated workflow.

  1. Routine log analysis and new approaches (e.g. induced gamma ray spectroscopy, NMR, imaging, stress and dielectric measurements). TOC from logs. Density and porosity. Saturation from Archie, from shaly sand resistivity models and from mineral models. Integrated analysis of core and log data.
  2. Worked example: case study 2.
  3. Petrophysical models revisited; shale gas in place calculations.
  4. Geomechanical properties.
  5. Integrated workflow. Review of possible steps, problems, pitfalls, and future directions. Summary of how shale gas varies from conventional reservoirs, and how the variable nature determines the petrophysical approach.

Who should attend

Anyone involved in shale gas petrophysics, including geologists, geophysicists, petrophysicists and engineers. The course aims to review shale gas petrophysics and provide an awareness of the complexities faced in developing appropriate shale gas petrophysical models.

Prerequisites and linking courses

Prerequisites – Participants should have a basic understanding of petrophysical evaluation, as presented in Basic level N083 (Petrophysics and Formation Evaluation: Principles and Practice) or N121 (Modern Petrophysical Well Log Interpretation), as well as practical experience working with well logs.

Linking Skilled level petrophysics courses include N054 (Intermediate Petrophysics for Conventional Reservoirs), N187 (Low Resistivity Low Contrast Pay) and the field course N030 (Rocks and Fluids: Practical Petrophysics, Isle of Wight, UK).

Linking Unconventional Resource Basic level classes include N313 (Evaluating Resource Plays) and N259 (From Outcrop to Subsurface: Understanding and Evaluating Shale Resource Plays, Alberta, Canada); at a Skilled level consider N364 (Fracture Architecture, Sedimentology and Diagenesis of Organic-rich Mudstones of Ancient Upwelling Zones with Application to Naturally Fractured Reservoirs (California, USA) and N250 (Evaluation Methods for Shale Reservoirs).

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Mike Lovell

Very good introduction to petrophysics of unconventionals!!