Upload
hahanh
View
221
Download
1
Embed Size (px)
Citation preview
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
4
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
8
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 – 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