Relationship of shale porosity-permeability trends to pore type and

organic content

Joel D. Walls, Ingrain Inc.

Elizabeth Diaz, Ingrain Inc.

Denver Well Logging Society

Petrophysics in Tight Oil Workshop

Denver, CO

October 26, 2011

Overview

• Basics of digital rock physics (DRP) in shale

• Integrated shale workflow

• Whole core; 3D whole core imaging and facies analysis

• Plug size samples; organic content and mineralogy

• SCAL; 3D pore scale imaging and computation

• Pore types and organic matter classification

• Porosity-perm trends

• Relative permeability

• Observations

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CoreHD

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Stage 1: CT imaging provides structural and stratigraphic insight (Well B)

Upper Eagle Ford; burrowed, calcareous, pyritic 4

Core is preserved in original aluminum sleeve with rubber end caps. About 500 CT slices/ft

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Stage 1: Whole core density and effective atomic number (Zeff) for facies identification (Well B, +11 ft depth shift)

Green = Higher phi or kero; more qtz

Red = Higher phi or kero; more calcite

Black = Lower phi or kero, less calcite

Blue = Lower phi or kero, more calcite

50% Quartz,

50% Illite

0-20%

Porosity

Dry

98% Calcite

2% Pyrite

0-20% Porosity

Dry

Effective Atomic Number (Zeff)

Rho

B (

g/c

m3

)

RhoB (g/cm3) Eff. Atomic Number (Zeff)

Austin Chalk

Upper E.F.

Lower

Eagle

Ford

Zeff = 10 * (PE)^(1/3.6)

plug sample points

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Parasequences Dipping beds, fine laminations

RhoB, Zeff from CT Guides Sampling in Mudstones

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Eagle Ford shale is laminated at scale of few microns.

a) SEM Image b) X-ray Spectral Map c) Mineral Distribution (% by vol)

Mineralogy by Energy Dispersive Spectral Analysis (EDS)

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3D FIB-SEM Volume with Pore and Kerogen Systems

total porosity = 9.2%, Kh = 4610nd, Kv = 30nd Red: isolated pores Blue: connected pores Green: organic material

Permeability is computed through the pore system using Lattice-Boltzmann method (Tolke, et al, 2010) Walls, Diaz; Ingrain

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Shale Pore Types (after Loucks, et al, 2010)

From Loucks, et al, GCAGS, April 2010

New Albany

Pearsall Shale, S. TX (Loucks, 2010) Haynesville, E.TX

Marcellus

Niobrara

Eagle Ford

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Three Classes of Organic Matter Texture

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spongy

pendular (bubble)

solid

250 nm cube 1 million oil molecules

Two Phase Flow in Shale (gas mobility)

www.ingrainrocks.com 11

30% gas saturation Gas – red Oil - green

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• Density (RhoB) and effective atomic number (Zeff) from X-ray CT scan provide detailed information on shale layering and facies.

• Shales are laminated down to scale of several microns

• Three organic matter forms; solid, spongy, pendular

• Eagle Ford: Pendular organics - oil window Spongy organics - gas/condensate window

• Porosity-permeability trends are affected by pore type and

organic porosity texture.

• Digital rock physics can provide relative perm in shale (not readily available from traditional core analysis labs)

Observations

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