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Schlum
berger Public
Scintillators for Geophysical Exploration
Markus Berheide and Brad RoscoeSchlumberger-Doll Research
Cambridge, MA
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Talk Outline
• What does an oil well look like?
• What is the well environment?
• What type of measurements are we interested in
• Performance requirements for scintillators
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Surface Seismic
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Drilling
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Logging While Drilling
(LWD)
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Sample Log
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Open-Hole Logging
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Logging Truck
(Land)
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Open-Hole
Logging Tools
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Cementing
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Perforating
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Cased-Hole Logging
or
Reservoir Monitoring
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Measurement Environment
Max
Temperature (oC)
Shock & Vibration
(g’s)
Tool Diameter (in).
Logging While Drilling 150 - 200 1000’s 4-8 but hole in center
Open-Hole Logging 150 - 200 100’s 3.6 – 4.5
Cased-Hole 150 - 200 100’s 1.7-2.4”
Surface Applications 85 N/A N/A
LWD
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Formation Description
φ1 − φ
Matrix Oil
Water
1=Sw+ So+ Sg
Sw
Gas Sg
So
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Measurement Issues
• Source and sensor both in borehole
• Usually want to measure Formation
• Need to make measurement with 1-3 seconds of data
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What do we want?
• Single Well– Formation Evaluation
• Porosity• Presence of hydrocarbons • Fluid identification• Permeability• Lithology
– Production Monitoring• Oil flow rate• Water flow rate• Gas flow rate
– Misc• Cement integrity• Corrosion• Depth• Etc…
• Reservoir– Size– Orientation– Connectivity– Etc…
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Desirable Scintillator Characteristics(Application Dependent)
• High Density, High Z• Good Resolution (all Energies)• High Countrate Capability• Reasonable Size• Non-Hydroscopic • Light Output (350 – 450 nm)• Rugged• Good High Temperature Performance
– Resolution– Wavelength– Decay Time
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τ
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Scintillators Used in the Industry
• NaI
• BGO
• GSO
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Gamma-Ray Measurement
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γγγγ−−−−γγγγ Density
Formation density
Mudcake density
Mud density
(Mudcake thickness or standoff)
Density radial profile
hmc
Source
BS
SS
LS
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Gamma-Ray Spectroscopy
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RSTHardware
RSTHardware
Schlumberger
NearDetector
Shielding
FarDetector
1-11/16 in RST-A
2-1/2 inRST-B
NeutronGenerator** **
Tool OperationTool Operation
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Sigma Modes
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Inelastic-Capture
Mode
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MethodMethod
Schlumberger
C/O SaturationC/O SaturationC/O Yields MethodC/O Yields Method
1 2 3 4 5 6 7 8Energy [MeV]
Oxygen
Silicon
Calcium
Iron
Carbon
RST-B Far Detector Inelastic Standards
ToolBackground
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Importance of Scintillator Characteristics for
Different Logging Applications
High Temperature
Application High
Density, High Z
Good Resolution
Good Resolution
(High Energy)
High Countrate Capability 350-
450 nm Resolution Decay Time
Stability
Natural Gamma Ray High Medium Low Low High Medium Low
Density Measurement High Medium Low Medium High Medium Medium
Gamma-Ray Spectroscopy High High High High High High High
Sigma Medium Medium Low High High Medium High
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Summary
• Match Scintillator Performance to Application
• Always a Trade-Off
• High Temperature Performance Important– Light output
– Decay time
– Resolution
• Ruggedness and Packaging Important
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Nuclear Well LoggingSchlumberger-Doll Research