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Line 190:
Line 190: − + − ! Vertical Resolution − ! Radius of Investigation − ! Applications − ! Limitations − + − − − − − + − − − − − + − − − − − + − − − − − + − − − − | — − + − + − + − + − +
→Porosity
|+ {{table number|4}}Resolution and application of porosity and lithology devices
|+ {{table number|4}}Resolution and application of porosity and lithology devices
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! Tool
! Tool || Vertical Resolution || Radius of Investigation || Applications || Limitations
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| Compensated density
| Compensated density || 18 in. || 8 in. || Estimate porosity || Pad contact device
| 18 in.
| 8 in.
| Estimate porosity
| Pad contact device
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|-
| Compensated neutron
| Compensated neutron || 2 ft || 10 in. || Estimate porosity and identify presence of gas || Needs environmental corrections; sensitive to standoff from wall
| 2 ft
| 10 in.
| Estimate porosity and identify presence of gas
| Needs environmental corrections; sensitive to standoff from wall
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| Sonic
| IPL* (Integrated Porosity Lithology) || 1 ft || -- || Estimate porosity and identify presence of gas, thin bed evaluation, shalt sand evaluation || Needs environmental corrections; sensitive to standoff from wall
| 2 ft
| Typically 6 in.
| Measure compressional velocity and estimate porosity
| Sensitive to compressibility
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| FWS (monopole)
| Sonic || 2 ft || Typically 6 in. || Measure compressional velocity and estimate porosity || Sensitive to compressibility
| 4 ft
| Typically 6 in.
| Measure compressional and shear velocities and estimate porosity
| Cannot measure shear velocity when shear velocity > mud velocity
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| Dipole sonic
| FWS (monopole) || 4 ft || Typically 6 in. || Measure compressional and shear velocities and estimate porosity || Cannot measure shear velocity when shear velocity > mud velocity
| 4 ft
| Typically 12 in.
| Measure shear velocity
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| Photoelectrical effect (Pe)
| Dipole sonic || 4 ft || Typically 12 in. || Measure shear velocity || —
| 2 in.
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| 2 in.
| CMR* (Combinable Magnetic Resonance) || 6 in. || 1 in. || Porosity, pore size distribution, permeability || Minimum 6.5 in. wellbore
| Identify lithology and correlation
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| Does not work in barite mud and pad contact tool
| Photoelectrical effect (Pe) || 2 in. || 2 in. || Identify lithology and correlation || Does not work in barite mud and pad contact tool
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