Minh Tran

Tapan Mukerji

Energy Resources Engineering Department

Stanford University, CA, USA

Petrophysical Study of Shale

Properties in Alaska North Slope

Region of Interest

20 miles

1.5 miles

Stratigraphic Column

Motivation

Characterize elastic properties of different North Alaskan

shale lithofacies.

Validate existing rock physics models in the literature by

comparing to other shale plays in the United States.

Integrate geochemical analysis into quantitative seismic

interpretation.

Quantify seismic signature to evaluate source rock potential

in the region of interest.

Quantitative Seismic Interpretation Workflow

Acoustic Impedance: AI=Vp*Density

Elastic Impedance: EI=Function (Vp, Vs, Density, Angle)

Statistical Classification

Post-processing Seismic Data

(partial or full pre-stack)

Inverted Seismic Data of

Elastic Properties (AI, EI, AVO cube)

Source Rock

Properties (TOC, HI, Ro)

Well Log, Core,

Thin Section

Training Data of

Each Lithofacies (Vp, Vs, Density)

Geochemical Analysis

Rock physics model

Evaluation of source rock potential in terms of Geochemical and

Petrophysical Properties

Facies-dependent Relationship between Elastic

and Geochemical Properties

Calibration of multi-scale data

Scope of Research

Build a reliable training data set of elastic properties (Vp, Vs,

density) of different shale units in Alaska North Slope

(Hue/HRZ, Pebble, Kingak, Shublik) based on log analysis.

Measure shale elastic properties (Vp, Vs) of core plugs in

laboratory to calibrate logging measurements and characterize

shale anisotropy in terms of wave propagation.

Establish relationship between elastic properties and source rock

credentials (Total Organic Content, Hydrogen Index, thermal

maturity).

Available Data

Log suite of Alcor and Merak:

Gamma Ray tool.

Density tools,

Acoustic tools.

Cored interval:

Alcor 1: 117 feet (Hue, Shublik)

Merak 1: 398 feet (Hue, HRZ, Kingak, Shublik)

Core plug measurement:

Intervals of interest: 8500-11000 feet MD in each well.

Purpose: to delineate different lithofacies in terms of

petrophysical and elastic properties.

Methodology: crossplot of different properties to separate

clusters of data of each lithofacies.

Petrophysical Diagnostics by Well Log Analysis

Petrophysical Diagnostics

HRZ

SHUBLIK

HUE

KINGAK

PEBBLE

Merak

HUE/HRZ

Lithofacies Definition

SHUBLIK

SHUBLIK

KINGAK & pebble

SHUBLIK & HUE HUE

HRZ

pebble

KINGAK

SHUBLIK

SHUBLIK

Lithofacies Definition

HUE

HRZ

KINGAK & pebble

HUE

HRZ

pebble

KINGAK

SHUBLIK

SHUBLIK

Lithofacies Definition

HUE

KINGAK & pebble

HUE

HRZ

pebble

KINGAK SHUBLIK

SHUBLIK

Lithofacies Definition

HUE

KINGAK, HRZ & pebble

HUE

HRZ

pebble

KINGAK

SHUBLIK

Shale Anisotropy

Property depends on direction.

Seismic wave sees shale anisotropy:

Direction of propagation (P and S-wave)

Direction of polarization (within S-wave: SH and SV).

Defined at the scale of the measurement (core plugs or log).

Affects seismic signature (amplitude) of multi-azimuth seismic

data.

Make use of Amplitude-versus-offset seismic data.

Shear wave polarization

(Hyperphysics.edu)

Direction of propagation

Shear Splitting in Sonic Logs

MERAK HUE

Core Selection

• At least one plug per lithofacies.

• Avoid undesirable lithology (calcite bands, pyrite inclusion…).

• Avoid visible fracture.

• 3 different directions at each selected depth (horizontal, vertical and 45º to the

bedding plane) if possible

• Similar texture and depth.

Elastic Properties vs Geochemical Properties

Prasad et al. 2009

SHUBLIK

HRZ

KINGAK HUE

Correlation with other Geochemical Properties

Correlation with Geochemical Properties

(Alfred and Vernik 2012)

SHUBLIK

KINGAK & HRZ

Summary

Different shale lithofacies in North Alaska System can be

qualitatively delineated in terms of elastic and petrophysical

properties.

Alaskan North Slope shale anisotropy is apparent in sonic log but

needs to be verified by core measurements.

Crossplots between elastic properties and TOC or HI show good

separation of different lithofacies.

Existing petrophysical model for shale can be applied if properly

calibrated.

Future Work

Perform velocity measurement (bench-top and varying confining

pressure) on Stanford core set.

Update geochemical data with GeoMark data.

Calibrate the log-derived training data set from core

measurements.

Expand training dataset by using existing rock physics model for

shale (fluid substitution).

Build quantitative rock physics model for Alaska North Slope

shale.

22 Basin and Petroleum System Modeling Industrial Affiliates Program

Questions?

References

Passey, Q.R., Creaney, S., Kulla, J.B., Moretti, F.J. & Stroud,

J.D., 1990, A practical model for organic richness from

porosity and resisitivity logs: American Association of

Petroleum Geologists Bulletin 74(12), 1777-1794.

Alfred, D. & Vernik, L, 2012, A new petrophysical model for

organic shales: Society of Petrophysicists and Well Log

Analysis.

Prasad, M., Kenechukwu, C., McEvoy, E. & Batzle M.L.,

2009, Maturity and impedance analysis of organic-rich shales:

SPE 123531.