Application of Mechanical and Mineralogical Rock Properties to Identify Fracture Fabrics in the

Devonian Duvernay Formation in Alberta

Presented by

Mehrdad Soltanzadeh, Ph.D., P.Eng.

Duvernay Project,Study Area and Geology

Study Area

(Source: Switzer et al., 1994)

Study

Area

Geology

900 m of Detailed Core Description for 29 Wells

(Source: Switzer et al., 1994)

Core-based Stratigraphy

(Source: Switzer et al., 1994)

Idealized Core-based Parasequence/TR Cycle in the Upper Duvernay Shale

Stratigraphic Depositional Model

Observed Fractures in Duvernay

(a) (b) (d)

(h)(e) (f) (g)

(c)

Examples of fracture fabrics observed in the Duvernay Formation cores: (a) subvertical fracture, (b) parallel set of subvertical fractures, (c) conjugate set of sub-vertical planar fractures (arrows) on bedding plane, (d) hackle plume on fracture surface, (e) polished slip faces (PSF), (f) bedding–plane fragments of core in Figure 4e showing indistinct PSF surfaces with striae, (g) cleavage lineation on bedding-parallel core surface with oblique calcite-cemented microfracture (arrow), (h) bed-parallel parting (BPP) or core disking.

Fractures and Geomechanics

Mechanical Rock PropertiesLab Tests• Uniaxial/Triaxial• Hardness• Multi-stage• Multi-stress• Ultrasonic• Brazilian

Mechanical Properties• Static/Dynamic

Properties• Strength

Properties• Anisotropy• Tensile Strength

Logs

• Sonic/Dipole Sonic

• Cross-dipole Sonic

• Density

Mechanical Properties

• Dynamic Elastic Properties

• Strength Properties

• Anisotropy

Log-based Elastic Properties

Dynamic Poisson’s Ratio Dynamic Young’s Modulus (GPa)

Ireton F

Ireton F

Ireton D

Ireton C

Ireton B

Ireton A

Duvernay C5

Duvernay C4

Duvernay C3

Duvernay C2

Duvernay C1

Duvernay B

Duvernay A

0.10 0.15 0.20 0.25 0.30 0.35 0.40 20 30 40 50 60 70 80

(a) (b)

Lab-based Elastic Properties

Static Poisson’s Ratio Dynamic Poisson’s Ratio

Effect of Fluid Type and Pressure?

Duvernay

Ireton

Poisson’s Ratio

Fre

qu

en

cy

Static vs. DynamicDepth

(m)

Petrophysics

Calculated Quartz Volume (V/V)

Qu

artz

Vo

lum

e fr

om

XR

D (%

)

(a)

Calculated TOC (%)

TOC

from

SR

A (%

)

(b)

Mineralogy and Mechanical Properties

Data from a key wellData from 16 wells

Investigating Brittleness• So-called ‘Brittleness Index’ suppose to help with

identifying brittle rock from ductile rock. This is anambiguous definition with different interpretations.

• Both science and experience confirm that fracturingbehaviour cannot be limited to a small number ofattributes such as elastic properties.

• However, it may be possible to integrate these datawith other information and come up with some‘locally-defined’ parameters that act as proxies foridentifying the ‘fraccability’ of the rock.

Trying Different Indices• Mineralogical Brittleness Indices:

• Mechanical Brittleness Indices:

𝐵𝑅𝐷𝑜𝑙𝑜𝑚𝑖𝑡𝑒 =𝐷𝑜𝑙𝑜𝑚𝑖𝑡𝑒[+𝑄𝑢𝑎𝑟𝑡𝑧]

𝐴𝑙𝑙 𝑀𝑖𝑛𝑒𝑟𝑎𝑙𝑠× 100 Commonly-used Parameter

𝐵𝑅𝐶𝑙𝑎𝑦 = 1 −𝐶𝑙𝑎𝑦 [+𝑇𝑂𝐶]

𝐴𝑙𝑙 𝑀𝑖𝑛𝑒𝑟𝑎𝑙𝑠 × 100 Used in This Study

𝐵𝑅𝑅𝑖𝑐𝑘𝑚𝑎𝑛 =1

2

𝐸 − 𝐸𝑚𝑖𝑛

𝐸𝑚𝑎𝑥 − 𝐸𝑚𝑖𝑛+

𝜈𝑚𝑎𝑥 − 𝜈

𝜈𝑚𝑎𝑥 − 𝜈𝑚𝑖𝑛 × 100

𝐸𝑝𝑠 =𝐸

1 − 𝜈2=

2𝐺

1 − 𝜈 Used in This Study

Commonly-used Parameter

Eps Comes from Fracture Mechanics

• Fracture Geometry

• Stress Profile

PKN Fracture Model

Comparison of Different Indices

Rickman’s Brittleness Index (%)

80 10 20 30 40 50 60 70

(c)Ireton F

Ireton F

Ireton D

Ireton C

Ireton B

Ireton A

Duvernay C5

Duvernay C4

Duvernay C3

Duvernay C2

Duvernay C1

Duvernay B

Duvernay A

(a)

Plane-strain Young’s Modulus (GPa)

20 30 40 50 60 70 80

(d)Ireton F

Ireton F

Ireton D

Ireton C

Ireton B

Ireton A

Duvernay C5

Duvernay C4

Duvernay C3

Duvernay C2

Duvernay C1

Duvernay B

Duvernay A

(b)Ireton F

Ireton F

Ireton D

Ireton C

Ireton B

Ireton A

Duvernay C5

Duvernay C4

Duvernay C3

Duvernay C2

Duvernay C1

Duvernay B

Duvernay A

0 20 40 60 80 100

Brittleness Index based on Dolomite and Quartz (%)

(c) (d)

Brittleness Index based on Clay (%)

30 40 50 60 70 80 90 100

El Diablo

The best correlation exists between these

two parameters.

Eps vs. BRClay

Effective Porosity

Fractures on Cores and Image LogsPS-YM

BRClay

BRRickman

YM

PRGamma

Logs Image Log Graphic Core Description

Fractures and Rock Properties

Fraccablity

Range

Fracture Types and Rock Properties

Sonic PR YM BR SP. GR Hardness

Rock Properties Core Description

Identifying Fracture Types

(a) (b)

Hardness vs. Log-based Properties

Conclusions• Shale behaviour in the field is strongly affected by in-situ

conditions, so, integrating field and lab measurements needs to be performed with extreme caution.

• Different plays may need to be treated differently as shown for the brittleness index.

• Observed fractures on the core and image logs are probably one of the most trustworthy criteria to determine rock’s fraccability.

• Rock properties, along with stresses, have identifiable effects on the formation of different fracture fabrics.

• Data integration in unconventional plays can help with more precise characterization of the play behaviour and provides opportunities for application of more efficient approaches for development of these plays.

Acknowledgments

Co-authors:• Graham David, Graham Davies Geological Consulting Ltd.

• Amy Fox, Canadian Discovery Ltd.

• David Hum, Core Laboratories LP

• Nasir Rahim, Canadian Discovery Ltd.

Trican Geological Solutions Ltd.• Albert Cui, Ken Glover.

Canadian Discovery Ltd.• Sarah Hawkes, Ching Zhu, Leydy Garcia, Susan Wang, Suzie Jia.

Seven Generations Energy Ltd.