Reservoir Characteristics & Geological Controls on

Permeability of the Triassic Doig-Montney Shales of NEBC

Gareth Chalmers, Marc Bustin & Amanda Bustin

Earth and Ocean Sciences University of British Columbia

- Comparison with the Devonian Horn River Shale

Presentation Outline • Introduction • Triassic Rocks

• Mineralogy, texture and fabric • Organic geochemistry • Porosity distribution • Geological controls on pore size distribution & K

• Comparison between Triassic and Devonian Rocks • Mineralogy, fabric versus K • PSD versus K

• Pore Models and Conclusions

Introduction • Large TCF gas-in-place estimates for unconventional

reservoirs • What controls the fluid flow?

• Fracture porosity is important BUT so is matrix flow • Porosity models include

• Dual porosity model • Coal – micropores (<2nm)1 & cleat fractures (Lu and

Connell, 2007) • Triple porosity model (Wei & Zhang, 2010)

• Coal and shale reservoirs • Micropores, mesopores1 and macropores (>50nm)1

1 International Union of Pure and Applied Chemistry (IUPAC) pore classification (Rouquerol et al., 1994).

Introduction: street-map-pore analogy

Woodford Shale: FE-SEM micrograph

100 nm

Fracture Plane mesopores

Google Maps 2012.

Geological Setting Summary • Triassic Montney-Doig-Halfway Fms

• Westward thickening, siliciclastic prograding wedge in a passive margin setting (Edwards et al., 1994; Davies 1997; Walsh et al., 2006; Dixon, 2009a and b).

• 2 of 3 T-R cycles

• Devonian Horn River Basin Fms • Reef-dominated shale basin (Kent, 1994)

• Shales & carbonates deposited within a embayments (shale rich) & salients (carbonate platforms) due to faulting & unconformity development (Morrow et al., 2002).

Devonian Shale - Liard (LB) and Horn River (HRB) Basins

Facies from Ross (2008) PhD Thesis, UBC.

Study Areas Triassic Doig-Montney Shales

Palaeogeog. by Kent (1994)

Stratigraphy - Triassic DOIG-MONTNEY SHALES

2.5 cm

Stratigraphy - Devonian

Liard Basin Deeper target Shallower target

Bovie Fault

Ferri et al., (2011)

More siliceous

Horn River Basin East West

Geological parameters studied

• Mineralogy – XRD & Rietveld, EDX + petrology • TOC Content – Rock Eval II + organic petrology • Porosity – He Pycnometry & Hg Porosimetry • Pore Size Distribution (PSD) – Hg porosimetry & low P gas adsorption analyses • Matrix Permeability – pulse decay permeameter • Texture and fabric – qualitative, thin sections & back scatter electron microscopy (BSEM)

• Future use of EBSD analysis

EBSD Boudier et al, (2009)

http://www.ingrainrocks.com/shale/

Mineralogy

• Poor to moderate clay in both Devonian and Triassic rocks

• Vary between high and low quartz, carbonates (feldspar is important Triassic) Triassic Doig/Montney Shales

Devonian LB/HRB Shales

Mineralogy, Texture & Fabric of Triassic shales

Doig Mineralogical Trends

• Doig A (Phosphate Zone) is carbonate rich; highly variable mineralogy

• Quartz increases upwards • Clay conc. in finer sections • Feldspars conc. in Doig A and B • Apatite highest in Doig A

Doig/ Halfway Petrology

125 µm

Doig “A” Textural Analysis – BSEM

Darker mins = quartz+dolomite Lighter mins = calcite+feldspar+muscovite

Montney Mineralogical Trends

• Carbonate, quartz & feldspar are significant • Illite < 20% • Carbonate & Qtz are highly variable • Apatite locally significant

Montney Textural Analysis - BSEM

5 cm apart

100 µm

Mod clay/qtz/CaCO3

Anisotropic;11-7-34 Mod Qtz/CaCO3 Isotropic;11-7-16

Fabric – Degree of anisotropy • qualitative measurement of the degree of crystal/clast

alignment • Controlled by mineralogy & paragenesis

• Clay-rich samples are more anisotropic than quartz & carbonate rich samples

Bedding

Direction

Mineralogy, fabric & texture summary

• 3 coarsening upward packages for Montney-Doig-Halfway

• Mineralogy, texture & fabric varies significantly within the Doig A (phosphate zone) and in parts of the Montney

• Higher carbonate or higher quartz contents reduce gamma log response

• Carbonate in the form of cement or detrital grains • Apatite locally important coating grains, cement or

nodule

Organic geochemistry of Triassic Shales

Organic Geochemistry of Doig Shale

• Kerogen is carbon rich • Reflectance & Tmax

indicate maturity is beyond oil window

• Majority have low HI and OI; due to either primary kerogen type &/or maturity

Tmax, Reflectance & HCs generation

• Averaged pyrobitumen equivalent* %Ro is 2.058 (dry gas)

• S2 peak too low for most sample for Tmax value

• Tmax = 457°C; wet to dry gas generation

y = 955.4x + 752.96 R² = 0.9036

1800

2000

2200

2400

2600

2800

3000

3200

34001.0 1.5 2.0 2.5 3.0

Dept

h (m

)

Vitrinite Reflectance (%) *Schoenherr et al. (2007)

Doig TOC Distribution • Large, abrupt TOC changes

in Doig A • Sampling resolution • Primary deposition

• TOC vs pyrite & quartz

R² = 0.5862

012345678

0 2 4 6

TOC

Cont

ent (

%)

Pyrite Content (%)

012345678

0 20 40 60 80

TOC

Cont

ent (

%)

Quartz Content (%)

Doig Organic Petrology 41 µm

Doig Organic Petrology

41 µm

11-7-32

11-7-33

11-7-34

Montney Organic Petrology

41 µm

HC generation summary

• From observations, kerogen has been converted to bitumen (oil) • Flow textures • Oil migration (Riediger et al., 1990)

• Inefficient oil migration resulted in secondary cracking of remaining bitumen to pyrobitumen • No fluorescence • degassing (macro) pores • Increasing TOC maturity =

increasing micropores & storage of methane (Chalmers & Bustin, 2008)

Porosity Distribution of Triassic Rocks

100 nm

Porosity Measurements

• 2 porosity methods • Hg Porosimetry – measures greater than 3 nm • He pycnometry – measures greater than 0.26 nm

• Any difference between measurements highlights pore

sizes between 0.26 – 3.0 nm (mostly micropores)

Porosity distribution

Measured difference between porosity methods is 3 to 0.3 nm

Geological Controls on Pore Size Distribution & Permeability for Triassic Rocks

Geological Controls on Pore Size Distribution (PSD)

• Combination of: •Mineralogy •TOC content •Texture and fabric •Degree of anisotropy

Pore Size Distribution by porosimetry

0.E+00

5.E-04

1.E-03

2.E-03

2.E-03

3.E-03

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

Incr

emen

tal p

ore

volu

me

(mL/

g)

Pore Diameter (nm)

PSD for Doig A Samples

11-7-19.11-7-16.

mesopores macropores

Why are mesopores & micropores important?

0.E+00

5.E-04

1.E-03

2.E-03

2.E-03

3.E-03

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

Incr

emen

tal p

ore

volu

me

(mL/

g)

Pore Diameter (nm)

PSD for Doig A Samples

11-7-19.11-7-16.

mesopores macropores

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 10 100 1000 10000 100000 1000000

Incr

emen

tal S

urfa

ce A

rea

(m2 /

g)

Pore Diameter (nm)

P.S.D for Doig A Samples

11-7-19.

11-7-16.

GREATER AMOUNT OF SMALLER PORES = GREATER SURFACE AREA Greater surface area = greater sorbed methane = greater GIP

Why are mesopores & micropores important? • Surface area/storage sites important for continuous HC reservoirs

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100 1000

CO2 a

nd N

2 Gas

Sat

urat

ion

(%)

Pore Diameter (nm)

11-7-19.

11-7-16.

ID

CO2 Surface Area (m2/g)

(DR)

N2 Surface Area (m2/g)

(BET)

11-7-19 20.4 2.7

11-7-16 5.2 1.0

macropores

micropores mesopores

PSD and Clay + TOC Contents

Matrix permeability

• No visible fractures in core & partially submerged in alcohol after analyses

• Confined to 4000 PSI (28 MPa) • Pore P = 500 PSI • Methane gas used

• Corrected for sorption • Cui et al., 2009*

* Geofluids, vol. 9, p 208-223, 2009.

Down-hole profile of K

Highly Variable K

Low K due to calcite cement

Mineralogy & fabric vs Permeability for Triassic and Devonian Rocks

Variability of Matrix Permeability

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 20 40 60 80 100

Met

hane

Per

mea

bilit

y, co

rrec

ted

(mD

)

Quartz+Feldspar Content

LB/HRBDoig/MontneyHorn River

Comparing High & Low K – Triassic

Mod Qtz/clay/CaCO3 11-7-34

250 µm

High K (>1E-04 mD) Low K (< 1E-5 mD)

Mod Qtz/CaCO3 11-7-16

250 µm

Mod Qtz/CaCO3 11-7-19

250 µm

Mod Qtz/CaCO3 11-7-45

500 µm

Bedding

Direction

11-7-34

50 µm

11-7-19

50 µm

11-7-16

500 µm

Calcite cemented

Calcite cemented

less cemented

Comparing High & Low K – Devonian • Mineralogy is not the sole cause of permeability differences

Quartz-rich MK1

250 µm

CaC03-rich EV2

500 µm

Low K ( <1E-5 mD) High K (>1E- 4 mD)

250 µm

Qtz-rich MK4

250 µm

CaCO3-rich EV6

EV6

100 µm

Mod Qtz/clay/CaCO3 OP1

250 µm

MK1 25 µm

EV2 100 µm

OP1 10 µm

Bedding

Direction MK4

25 µm

Mineralogy, fabric vs K Sensitivity

OP1: anisotropic, clay rich, sensitive EV6: isotropic, carbonate rich, less sensitive

y = 7E-07e7E-06x

y = 0.4101e-8E-04x

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2000 4000 6000 8000

Mat

rix P

erm

eabi

lity

(mD)

Effective Pressure (PSI)

EV6

OP1

Ø = 1.5% Ø = 2.5%

10 µm 10 µm

bedding

direction

Bedding

Direction

Fabric vs K - summary

• Anisotropic • Greater content of clay, kerogen,

long axis of elliptical clasts parallel with lamination

• High K • K more sensitive to varying E.P.

• Isotropic – High proportion of equant

grains – calcite or quartz – High or low K – Less sensitive

100 µm

87% carbonate Mod clay/qtz/CaCO3

Doig:11-7-34 Muskwa: MK5 200 µm

bedding

direction

Bedding

Direction

PSD vs Permeability

Hg intrusion curves and K

• PSD by incremental pore volume

0

0.0005

0.001

0.0015

0.002

0.0025

1 10 100 1000 10000 100000 1000000

Incr

emen

tal p

ore

volu

me

(mL/

g)

Pore Diameter (nm)

P.S.D for Doig A Samples

11-7-19.

11-7-16.

mesopores macropores

K = 2.5E-4 mD K = 6.5E-6 mD

better communication

poorer communication

PSD by Gas Adsorption

Ratio of Micro-, meso-, macropore:

DOIG/Montney

Horn River Doig 38: 22: 40

HRB 45: 25: 30

Higher K samples have similar ratio & shape

* = high K

Balanced ratio

Pore Model

• Moderate, more balanced ratio of pore sizes (model #1) • Increases connectedness &

flow • Greatest surface area is within

micropores • Surface area stores HCs

Conclusions: Controls on Matrix Permeability

• PSD controls permeability • PSD

• Mineralogy • TOC content • Texture • Fabric and degree of

anisotropy

Google Maps 2012.

Conclusions • Triassic rocks show small scaled heterogeneity in TOC

and mineralogy and PSD • Increases the reservoir’s complexity with respect to

storage of methane and permeability • Kerogen (TOC) distribution due to deposition &

conversion of bitumen to pyrobitumen has produced gas & storage site within reservoir

• Although Devonian rocks differ from Triassic rocks, higher K values have similar PSD • More balanced ratios of micro-, meso and macropores

Acknowledgements

• Geosciences BC • Shell Oil Company • CBM Solutions & Trican • “Your name here” • “Geological Controls on Permeability of the Devonian Horn River Shales”

• In review, International Journal of Coal Geology, special issue of gas shales

• “Geological Controls on Permeability of Triassic Doig/Montney Shales” • In review, Journal of Marine and Petroleum Geology