Petrophysics Across the Petroleum Industry from a Core to a CEO

Australian Oil and Gas Exhibition and Conference 23 February 2017 Andrew Buffin

What is Petrophysics ?

• Wikipedia: Petrophysics from the Greek

πέτρα (petra) ‘rock’ φύσις (physis) ‘nature’

• The study of physical and chemical rock

properties and their interactions with fluids

• The description of oil and/or gas distributions and production flow capacity of reservoirs, from interpretations of pore systems and fluid interactions using all available downhole data.

A Brief History of Petrophysics

Shell (Interpreted Log Data – Petrophysics) • Archie, G.E. (1942) • An empirical quantitative relationship between porosity,

electrical conductivity, and brine saturation of rocks. • Laid the foundation for modern well log interpretation • Pickett Plot – A graphical representation of Archie Equation

• MH Waxman- LJM Smits (1968) • An equation that relates the electrical conductivity of a

water-saturated shaly sand

Service companies (Acquired Log Data) • Schlumberger founded in 1926 by brothers Conrad and

Marcel Schlumberger and recorded the first-ever electrical resistivity well log in 1927

• Halliburton, Baker Hughes, Weatherford

• Typical logging combo: • 1936/1950s: Spontaneous Potential, Resistivity. • 1950s/60s: Gamma Ray (GR), Neutron, Microlog • 1970s/80s: Sonic, Density, Fluid sampling, Digital data. Data

transmission started • 1990-Today: Logging While Drilling, Down-hole fluid typing,

Nuclear Magnetic Resonance (NMR), Array and Image Data, Data transmission commonplace

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The Petrophysicists Contribution

• More of the parameters used in the calculation of STOIIP are provided by Petrophysics than any other discipline!

Where, STOIIP = Stock tank oil initially in place GRV = Gross rock volume Net = Net Reservoir Gross = Gross Reservoir Ø = Porosity Sw = Water Saturation B0 = Formation Volume Factor

0

1)1(

BS

G

NGRVSTOIIP w

Geophysicist

Geologist

Reservoir Engineer

Petrophysicist

The Basic Role of Petrophysics

• Permeability derived empirically using relationships of log data with core permeability.

• Environment of Deposition

• Lithology • Volume of Shale (Vsh) • Depth and depth of formations • Porosity • Fluid phase, gas, oil, water • Fluid saturations Sw, So, Sg • Moveable Hydrocarbons • Net Sand / Net Pay • Subsurface Pressures • Temperature • Velocity/Time • Seismic responses • Correlation with other wells

The Thin Bed Problem and Solution

• Heterogeneity is common in the rock column

• In rock beds less than 2 feet thick, log resolution is impacted by being strongly influenced by adjacent beds.

• Thinly laminated sand-shale sequences can have clean sands, which are not resolved

• Over thin–bedded and shale intervals, horizontal resistivity is heavily biased toward low–resistivity shale and is less sensitive to the hydrocarbon-bearing sandstone resistivity

• Supressed resistivity data and ‘high’ shale volume result in ‘missed’ hydrocarbons

• An accurate evaluation of low-resistivity pay in thinly bedded or laminated reservoirs, requires an additional vertical resistivity measurement

• This provides much better sensitivity to the presence of hydrocarbons.

• The resistivity is measured in three dimensions and calculates both vertical and horizontal resistivity (Rv and Rh, respectively) from direct induction

• This leads to reliable identification and accurate petrophysical evaluation of low-resistivity pay by determining the Rv, Rh sand fraction and porosity

GR Res

GR Rh Rv

The Complex Lithology Problem and Solution

Probabilistic petrophysics: • Run in complex reservoirs with a variable and mixed mineralogy • Used to solve for multiple clay minerals within the reservoir • To ‘constrain’ the result to a specific outcome, this may be determined from

petrology studies, core analysis, XRD etc. • Solves for volumetric fractions and defines bulk mineralogy, grain matrix density,

porosity and fluid saturations • There is not one unique solution

Pyritic Sand: • High PEF • High Density • High Grain Density • Suppressed Resistivity

Results in: • If D-N log used a high Vsh • Low porosity • High Water Saturation • Potentially “Missed” pay

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Where (do) the Petrophysicists sit (?)

Geologist • Static model input • Porosity &

Permeability • Saturation Height • Net Sand & Pay • Shale volume • Fluid contacts

Commercial (Reserves) • Porosity • Water Saturation • Net Pay

Geophysics • Rock Physics • Gassmann Substitution

Reservoir Engineer • Dynamic model input • Relative Permeability • Saturation Height

Drilling • Pore Pressure • Bit Selection • Lithology

Geomechanics • Core Analysis • Sonic / Density • Rock Strength

Production Technologists • Porosity &

Permeability • Fluid Analysis • Test depths • Perforation Depths Petrophysicist

Service Providers • Data, data and • More Data

Petrophysics from a Core to a CEO

A Core

An Ex-CEO

Petrophysics – State of the Art

The highest level of general development, as of a device, technique, or scientific field achieved at a particular time

• Petrophysical data is used across all the subsurface disciplines – how it’s used is important.

• Are you answering the right questions? • Design your evaluation programme to answer the subsurface

challenges • Data QC & QA with appropriate data editing and corrections • Petrophysical data acquired to identify ‘hidden reserves’ or

‘missed pay’ • Petrophysical techniques and tools developed with demand

from the industry

Petrophysics – The Future

• Artificial Intelligence?

“AI allows a computer to make all the mistakes that humans make – only faster”

Attributed to E. R. (Ross) Crain, a retired Consulting Petrophysicist taken from his web site: Crain's Petrophysical Handbook

• Technology changes in the next few years • Down hole reservoir

engineering laboratory • Down hole core laboratory • Nano-technology • Robotics on fully automated

oil and gas fields • Direct measurement of

permeability • 4 D real time-reservoir

monitoring • Data integration and

interpretation

Thank you andrew.buffin@resevalconsulting.com