1

Petrophysical Study of Reservoir Rocks:

Use of Image Analysis Software (IAS) and Mercury Injection

Capillary Pressure (MICP) Data

Cristian R. MedinaApril 2015

Acknowledgements

John Rupp, Barb Hill, Carley Gasaway, and Drew Packman (IGS) Steve Greb and Dave Harris (KGS)Ron Riley and Matt Erenpreiss (ODNR)

Source: Archie, 1950

Scale Considerations

6,090 ft.

Why Porosity ()?

Storage Capacity:

Units:

Other geologic aspects where porosity is relevant:• Oil and gas reservoir

• Groundwater• Injection of waste fluids

• Gas storage

Trapping Mechanisms

Source: IPCC, 2005

Pore Characterization: Instrumentation

• Helium porosimetry• Helium/N/CO2 adsorption• Scanning Electron Microscopy (SEM)• (Ultra) Small Angle Neutron Scattering (SANS/USANS)• Optical Microscopy and Image Analysis Software (IAS)• Mercury Injection Capillary Pressure (MICP)

8

Scale and Instruments

SEM images taken by Carley Gasaway

MethodologyImageJ is a public domain image processing program developed at the National Institutes of Health. The source code for ImageJ is freely available.

Porosity (f)• f from core

analysis•Two-Dimensional f

~1 mm

Saturation: 0-255

Saturation: 20-255

Saturation: 40-255

Saturation: 60-255

Saturation: 80-255

Saturation: 100-255

Saturation: 120-255

Adjusting Saturation

Adjusting Saturation

3,465 ft.

Methodology: Thin Sections, Photomicrographs, and Pre-processing

Thin Section (30 mm)1mm=103 microns (mm)

Adjusting Pore Size

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Identifying Micro- Versus Macro-Porosity Using ImageJ

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Optical Microscopy and Image Analysis Software:Visualizing Porosity, Permeability, and Depth in

Sandstones

Petrophysics Study on Carbonates from the Cambro-Ordovician Knox

SupergroupMeasured

depth, Top of Knox (ft)

0

2500

10000

15000

17

Optical Microscopy and Image Analysis Software:Visualizing Porosity and Permeability in

Carbonates

What can we Measure?

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Elements of a Pore Measured on ImageJ

• Area (A)• Perimeter (P)• Major/Minor Axis• Circularity (C)• Aspect ratio (AR)• Roundness (R)

𝐶=4∗𝜋∗𝐴𝑃

𝑅=4∗𝐴

𝜋∗(𝑀𝑎𝑗𝑜𝑟 𝐴𝑥𝑖𝑠)22 mm.

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Results: Porosity from Core Analysis vs. IAS

#1

#2 #3

0.1 1 100

1

10

Sand-stonesCar-bon-ates

Core Porosity (%)

2D P

oros

ity

(All

Pore

s)

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Resolving Discrepancy #1

F = 0.3 F = 1.9

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ID #162029 Depth: 1646 ft

Fcore = 1.4

Resolving Discrepancy #2

Pore Throat Radius (microns)

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Effect of Dual Porosity in Carbonates

Resolving Discrepancy #3

Fcore = 2.6

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Excluding Pixel-Size ‘Pores’

250.1 1 100

1

10

Sand-stones

Core Porosity (%)

2D P

oros

ity

(All

Pore

s)

Results: Porosity from Core Analysis vs. IAS

Porosity from IAS and its Dependency With Pore Size

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Excluding Pixel-Size ‘Pores’

Pore Shape

Relationships

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Mercury Injection Capillary Pressure (MICP)

Source: Crain's petrophysical handbook (www.spec2000.net)

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Data Interpretation and Analysis

Intrusio

n pressure values a

re directly converted

into the corre

sponding pores size by usin

g the

Washburn equation. This is a

straightforward

calculation.

Source: Bliefnick and Kaldi, 1996

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Theory and Key-Parameters

∆ 𝑃=2𝛾 cos𝜃𝑟𝑝𝑜𝑟𝑒

Contact Angle (θ)

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Limitations: It Measures the Largest Entrance Towards a

Pore.

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Results from MICP (Indirect Method)

Pore Size between ~[0.1 - 25] microns

Results from ImageJ (Direct Method)

Pore Size between ~[15 - 300] microns

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Conclusions

• Image Analysis Software provides a good porosity estimator.

• The study of micro- vs. macro- porosity is limited by instrument resolution. Therefore,

multiple techniques should be used in a complementary way.

• Pore shape descriptors and pore size distribution can shed light on reservoir

performance.

• ImageJ measures pores, whereas MICP describes the pore throats.

• Pore systems in carbonates are more complex than those in clastics. Therefore their

characterization is more challenging.

• MICP advantages: rock type, reservoir quality, and pore size distribution.

• Value of a thin section: $30. One MICP test: $500-900.

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Questions?

ReferencesArchie, G.E., 1950, Introduction to petrophysics of reservoir rocks: AAPG Bulletin, v. 34, p. 943-961.

Bliefnick, D.M., and Kaldi, J.G., 1996, Pore geometry; control on reservoir properties, Walker Creek Field, Columbia and Lafayette counties, Arkansas: AAPG Bulletin, v. 80, p. 1027-1044.

Grove, C., and Jerram, D.A., 2011, jPOR: An ImageJ macro to quantify total optical porosity from blue-stained thin sections: Computers & Geosciences, v. 37, p. 1850-1859.

IPCC, 2005, IPCC Special Report on Carbon Dioxide Capture and Storage. Prepared by Working Group III of the Intergovernmental Panel on Climate Change: Cambridge, UK, Cambridge University Press.

Rasband, W.S., ImageJ, US National Institutes of Health, Bethesda, Maryland, USA, http://rsb.info.nih.gov/ij/, 1997–2009.