Formation Evaluation: Recent Advances in Logging France June Petro... · tar heavy intermediate oil...
Transcript of Formation Evaluation: Recent Advances in Logging France June Petro... · tar heavy intermediate oil...
Formation Evaluation: Recent Advances in Logging
Jean-Marc Donadille, Schlumberger
Outline
• Conventional formation evaluation• Porosity• Saturations• Permeability
• Petrophysical challenges: when does conventional interpretation fall short?
• New measurements• Advanced gamma ray induced spectroscopy• Dielectric dispersion• A few NMR applications
• Examples of new formation evaluation
Porosity
(1950’s… Neutron log: 1940’s…)
Saturations+ = Φ
Water saturation: Φ= 𝑆𝑤
Hydrocarbon saturation: Φ= 𝑆ℎ
𝑆𝑤 + 𝑆ℎ = 1
Water is conductiveHydrocarbons are resistive
Resistivity has good sensitivity to saturation
Resistivity log: 1920’s…
Saturations - quantification
Gus Archie (1952): 𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
𝑅𝑤 𝑆𝑎𝑙𝑤, 𝑇
m: pore tortuosity. Original Archie paper: m = 2 for sandstone
n: saturation exponent. Original Archie paper: n= 2 for sandstone
Many extensions to Archie formula many saturation equations, mainly for shale But the principle remains the same…
Impact on oil in place𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
𝑅𝑡 = 20 𝑜ℎ𝑚.𝑚, 𝜙 = 20%
𝑆ℎ = 1 − 𝑆𝑤
Choose nominal values of 𝑆𝑎𝑙𝑤 = 10 𝑝𝑝𝑘,𝑚 = 2, 𝑛 = 2 𝑆𝑤 = 61%, 𝑺𝒉 = 𝟑𝟗%
If instead, choose 𝑆𝑎𝑙𝑤 = 15 𝑝𝑝𝑘,𝑚 = 1.8, 𝑛 = 2… 𝑆𝑤 = 42%, 𝑺𝒉 = 𝟓𝟖%
If instead, choose 𝑆𝑎𝑙𝑤 = 8 𝑝𝑝𝑘,𝑚 = 2.2, 𝑛 = 2.5… 𝑆𝑤 = 86%, 𝑺𝒉 = 𝟏𝟒%
Oil in place increase by 𝟒𝟗%…
Oil in place decrease by 𝟔𝟒%…
Permeability How easily can fluids flow in the system?
Link expected to m and n
Not much to quantify it…
Petrophysical challenges𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
Complex mineralogy
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Bitumen / Kerogen
Permeability
𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
𝑆𝑤𝑛 =
1
𝜙𝑚𝑅𝑤𝑅𝑇
Advanced gamma ray induced spectroscopy
Co
un
ts
Energy
Inelastic
Capture
Neutron source
… …
Advanced spectroscopy answers (from inelastic):
Carbonate: split of calcite (CaCO3) and dolomite (CaMg(CO3)2) (Mg yield)
Shale oil and shale gas clay splitting (Al yield)
ClayQFM
CalciteDolomitePyrite
Unconventionals (kerogen) Total Organic Carbon (C yield)
Petrophysical challenges
Complex mineralogy
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Bitumen / Kerogen
Permeability
Petrophysical challenges
Complex mineralogy
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Bitumen / Kerogen
Permeability
Dielectric dispersionE
E=0
Matrix Oil Water Salt’s ions
Dielectric polarization is sensitive to:
Water-filled porosity: 𝜙𝑤 = 𝜙. 𝑆𝑤
Water salinity: 𝑆𝑎𝑙𝑤
Water phase tortuosity: 𝑀𝑁
Shallow measurement sensitive to the invaded zone.But MN can be used with deep resistivity to estimate oil in place:
𝜙𝑤 =𝑅𝑤𝑅𝑡
1𝑀𝑁
Petrophysical challenges
Complex mineralogy
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Bitumen / Kerogen
Permeability
Petrophysical challenges
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Permeability
Complex mineralogy
Bitumen / Kerogen
NMR applications
𝑇2. 𝑑𝑇2 = 𝜙
Direct correlation between free fluid / bound fluid and permeability:
𝑘 = 𝑎𝜙4𝑓𝑟𝑒𝑒 𝑓𝑙𝑢𝑖𝑑
𝑏𝑜𝑢𝑛𝑑 𝑓𝑙𝑢𝑖𝑑
light
oil
tar heavy
oil
intermediate
oil
Constituent viscosity
Petrophysical challenges
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Permeability
Complex mineralogy
Bitumen / Kerogen
Petrophysical challenges
Fresh water
Unknown / Varying water
Pore tortuosity
Wettability
Permeability
Complex mineralogy
Bitumen / Kerogen
Summary
• Conventional formation evaluation worked fine for easy reservoirs
• Reservoirs currently put on production do not tend to be easy ones…
• Fair progress in interpretation development during the last 10 years to adjust to new challenges
• It should be just a start…
• Keeps petrophysics fun!