Petrophysical Services

Petrophysics

Petrophysics is the study of the physical and chemical properties of rocks and their contained fluids. Petrophysical analysis emphasizes the calculation of reservoir storage and deliverability based on lithology, porosity, thickness, fluid saturation, and permeability. Petrophysics requires the integration of log data with rock data generally in the form of core measurements, routine and/or special core measurements. The purpose of this association is the calibration of log derived reservoir parameters to those same parameters measured in the laboratory. When agreement is reached predictive log based models can be established. These models can now be applied at well locations where no core is available.

Petrophysical Services

Complete petrophysical analysis including the integration of open-hole logging data with conventional (CCA) and special core analysis (SCAL) is provided. Both “deterministic” (backward looking dependencies) and “probabilistic” (response equations) petrophysical approaches are available, log availability and reservoir knowledge will dictate which approach should be applied. Several of the common, dominant reservoir models are:

  • Mineral Modeling
  • Porosity Modeling
  • Water Saturation Modeling
  • TOC Modeling
  • Permeability Modeling
  • Rock Type Modeling

Additional reservoir performance indicators include:

  • Identification of flow units and flow barriers / baffles
  • Characterization of petrophysical properties of each flow unit
  • Fluid saturation height / fluid contacts
  • Flow unit versus facies relationships

Mappable Petrophysical Parameters

The following list details the various mappable parameters associated with the completion of a petrophysical evaluation. These parameters represent the cornerstone of many geologic maps constructed:

  • Thickness (gross, reservoir, pay)
  • Porosity (total, effective)
  • Porosity Thickness
  • Permeability (absolute)
  • Permeability Thickness
  • Water Saturation (total, effective)
  • Hydrocarbon Pore Volume (HCPV)
  • Fluid Interface Contact Depths
  • Mineralogy

Conventional and Special Core Data

When conventional and special core analysis is available it should be included within the petrophysical solution. Conventional laboratory measurements include, porosity, grain density, fluid saturations, permeability (with full diameter core three directions of permeability at ambient conditions result) and lithologic descriptions. Special core analysis provides additional detailed measurements focusing on mineralogy, pore throat dimensions, permeability, diagenesis and carbon content. When applied within the petrophysical model(s) output results are more detailed, more robust, and with increased accuracy. The following lists the various types of SCAL data that can be incorporated:

  • X-Ray Diffraction (XRD) – mineralogy and volume percentages
  • Scanning Electron Microscope (SEM) – pore size, clay/mineral distribution, elemental analysis
  • Mercury Injection Capillary Pressure (MICP) – pore throat size distribution / classification
  • Petrography – mineralogy, diagenetic sequence / texture
  • Tight Rock Analysis (TRA)
  • QEMSCAN – mineralogy
  • Pyrolysis – TOC, S1, S2, S3, HI, OI, PI, vitrinite reflectance

Multi-Well Study Execution

The following provides a detailed flow of events one can follow when engaged in a multi-well analysis.

  1. Database preparation:
    1. Data inventory – review all files, catalog by type and location
    2. Data input – load, digitize, manual entry
    3. Data preparation – depth shifting, normalization, “control well” selection, mapping of normalization, geologic review of normalization
    4. Filtering
    5. Borehole and environmental corrections
    6. True vertical depth corrections (deviated or horizontal wells)
    7. Flow chart for each family of curves
    8. Curve inventory

 

  1. “Preliminary” analysis and parameter selection:
    1. Table of parameters required for each model
    2. Data input – load, digitize, manual entry

 

  1. Key Wells:
    1. Compare core/log correlations
    2. Special core analysis – electrical properties, XRD, MICP, CMS, XRF, petrography,
    3. Sensitivity runs for various parameters
    4. Standard verification format for graphics
    5. Fine tune model parameters
    6. Program algorithms

 

  1. Report Preparation:
    1. Format – separate petrophysical report or integration with geologic and engineering reports
    2. Structure – management summary, discussion of findings, conclusions, recommendations, appendices, future work

 

  1. Database clean-up and archival:
    1. Curve inventory
    2. Back up considerations
    3. Purging of undocumented curve data
    4. Preservation of work files

 

  1. Wrap-up:
    1. Postmortem / Sign-off
    2. Future Phase continuations