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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
2
Walls, Diaz; Ingrain
CoreHD
Walls, Diaz; Ingrain
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
Walls, Diaz; Ingrain
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
Walls, Diaz; Ingrain
Parasequences Dipping beds, fine laminations
RhoB, Zeff from CT Guides Sampling in Mudstones
Walls, Diaz; Ingrain
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)
Walls, Diaz; Ingrain
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
9
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
Walls, Diaz; Ingrain
Three Classes of Organic Matter Texture
10
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
Walls, Diaz; Ingrain
• 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
12
Walls, Diaz; Ingrain